Added hello world project

2018-09-25 18:31:29 +02:00 · 2018-09-25 18:31:29 +02:00 · 3512206d77
commit 3512206d77
parent 215767a724
70 changed files with 4835 additions and 5 deletions
--- a/.gitignore
+++ b/.gitignore
@ -148,7 +148,6 @@ CMakeCache.txt
 CMakeFiles
 CMakeScripts
 Testing
-Makefile
 cmake_install.cmake
 install_manifest.txt
 compile_commands.json
--- a/hello-world/Makefile
+++ b/hello-world/Makefile
@ -0,0 +1,14 @@
+
+TARGET = hello
+C_SRCS += $(wildcard *.c) 
+#CFLAGS += -O2 
+#-fno-builtin-printf
+
+BOARD=freedom-e300-hifive1
+LINK_TARGET=link
+RISCV_ARCH=rv32imac
+RISCV_ABI=ilp32
+
+TOOL_DIR?=/opt/riscv/FreedomStudio/20180122/SiFive/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6/bin
+BSP_BASE = ./bsp
+include $(BSP_BASE)/env/common.mk
--- a/hello-world/bsp/drivers/fe300prci/fe300prci_driver.c
+++ b/hello-world/bsp/drivers/fe300prci/fe300prci_driver.c
@ -0,0 +1,252 @@
+// See LICENSE file for license details
+
+#include "platform.h"
+
+#ifdef PRCI_BASE_ADDR
+#include "fe300prci/fe300prci_driver.h"
+#include <unistd.h>
+
+#define rdmcycle(x)  {				       \
+    uint32_t lo, hi, hi2;			       \
+    __asm__ __volatile__ ("1:\n\t"		       \
+			  "csrr %0, mcycleh\n\t"       \
+			  "csrr %1, mcycle\n\t"	       \
+			  "csrr %2, mcycleh\n\t"		\
+			  "bne  %0, %2, 1b\n\t"			\
+			  : "=r" (hi), "=r" (lo), "=r" (hi2)) ;	\
+    *(x) = lo | ((uint64_t) hi << 32); 				\
+  }
+
+uint32_t PRCI_measure_mcycle_freq(uint32_t mtime_ticks, uint32_t mtime_freq)
+{
+
+  uint32_t start_mtime = CLINT_REG(CLINT_MTIME);
+  uint32_t end_mtime = start_mtime + mtime_ticks + 1;
+
+  // Make sure we won't get rollover.
+  while (end_mtime < start_mtime){
+    start_mtime = CLINT_REG(CLINT_MTIME);
+    end_mtime = start_mtime + mtime_ticks + 1;
+  }
+
+  // Don't start measuring until mtime edge.
+  uint32_t tmp = start_mtime;
+  do {
+    start_mtime = CLINT_REG(CLINT_MTIME);
+  } while (start_mtime == tmp);
+  
+  uint64_t start_mcycle;
+  rdmcycle(&start_mcycle);
+  
+  while (CLINT_REG(CLINT_MTIME) < end_mtime) ;
+  
+  uint64_t end_mcycle;
+  rdmcycle(&end_mcycle);
+  uint32_t difference = (uint32_t) (end_mcycle - start_mcycle);
+
+  uint64_t freq = ((uint64_t) difference * mtime_freq) / mtime_ticks;
+  return (uint32_t) freq & 0xFFFFFFFF;
+  
+}
+ 
+
+void PRCI_use_hfrosc(int div, int trim)
+{
+  // Make sure the HFROSC is running at its default setting
+  // It is OK to change this even if we are running off of it.
+  
+  PRCI_REG(PRCI_HFROSCCFG) = (ROSC_DIV(div) | ROSC_TRIM(trim) | ROSC_EN(1));
+
+  while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0);
+  
+  PRCI_REG(PRCI_PLLCFG) &= ~PLL_SEL(1);
+}
+
+void PRCI_use_pll(int refsel, int bypass,
+			 int r, int f, int q, int finaldiv,
+			 int hfroscdiv, int hfrosctrim)
+{
+  // Ensure that we aren't running off the PLL before we mess with it.
+  if (PRCI_REG(PRCI_PLLCFG) & PLL_SEL(1)) {
+    // Make sure the HFROSC is running at its default setting
+    PRCI_use_hfrosc(4, 16);
+  }
+  
+  // Set PLL Source to be HFXOSC if desired.
+  uint32_t config_value = 0;
+
+  config_value |= PLL_REFSEL(refsel);
+  
+  if (bypass) {
+    // Bypass
+    config_value |= PLL_BYPASS(1);
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // If we don't have an HFXTAL, this doesn't really matter.
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+  } else {
+  
+    // To overclock, use the hfrosc
+    if (hfrosctrim >= 0 && hfroscdiv >= 0) {
+      PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
+    }
+    
+    // Set DIV Settings for PLL
+    
+    // (Legal values of f_REF are 6-48MHz)
+
+    // Set DIVR to divide-by-2 to get 8MHz frequency
+    // (legal values of f_R are 6-12 MHz)
+
+    config_value |= PLL_BYPASS(1);
+    config_value |= PLL_R(r);
+
+    // Set DIVF to get 512Mhz frequncy
+    // There is an implied multiply-by-2, 16Mhz.
+    // So need to write 32-1
+    // (legal values of f_F are 384-768 MHz)
+    config_value |= PLL_F(f);
+
+    // Set DIVQ to divide-by-2 to get 256 MHz frequency
+    // (legal values of f_Q are 50-400Mhz)
+    config_value |= PLL_Q(q);
+
+    // Set our Final output divide to divide-by-1:
+    if (finaldiv == 1){
+      PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+    } else {
+      PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV(finaldiv-1));
+    }
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // Un-Bypass the PLL.
+    PRCI_REG(PRCI_PLLCFG) &= ~PLL_BYPASS(1);
+
+    // Wait for PLL Lock
+    // Note that the Lock signal can be glitchy.
+    // Need to wait 100 us
+    // RTC is running at 32kHz.
+    // So wait 4 ticks of RTC.
+    uint32_t now = CLINT_REG(CLINT_MTIME);
+    while (CLINT_REG(CLINT_MTIME) - now < 4) ;
+    
+    // Now it is safe to check for PLL Lock
+    while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0);
+
+  }
+
+  // Switch over to PLL Clock source
+  PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
+
+  // If we're running off HFXOSC, turn off the HFROSC to
+  // save power.
+  if (refsel) {
+    PRCI_REG(PRCI_HFROSCCFG) &= ~ROSC_EN(1);
+  }
+  
+}
+
+void PRCI_use_default_clocks()
+{
+  // Turn off the LFROSC
+  AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
+
+  // Use HFROSC
+  PRCI_use_hfrosc(4, 16);
+}
+
+void PRCI_use_hfxosc(uint32_t finaldiv)
+{
+  
+  PRCI_use_pll(1, // Use HFXTAL
+	       1, // Bypass = 1
+	       0, // PLL settings don't matter
+	       0, // PLL settings don't matter
+	       0, // PLL settings don't matter
+	       finaldiv,
+	       -1,
+	       -1);
+}
+
+// This is a generic function, which
+// doesn't span the entire range of HFROSC settings.
+// It only adjusts the trim, which can span a hundred MHz or so.
+// This function does not check the legality of the PLL settings
+// at all, and it is quite possible to configure invalid PLL settings
+// this way.
+// It returns the actual measured CPU frequency.
+
+uint32_t PRCI_set_hfrosctrim_for_f_cpu(uint32_t f_cpu, PRCI_freq_target target )
+{
+
+  uint32_t hfrosctrim = 0;
+  uint32_t hfroscdiv = 4;
+  uint32_t prev_trim = 0;
+
+  // In this function we use PLL settings which
+  // will give us a 32x multiplier from the output
+  // of the HFROSC source to the output of the
+  // PLL. We first measure our HFROSC to get the
+  // right trim, then finally use it as the PLL source.
+  // We should really check here that the f_cpu
+  // requested is something in the limit of the PLL. For
+  // now that is up to the user.
+
+  // This will undershoot for frequencies not divisible by 16.
+  uint32_t desired_hfrosc_freq = (f_cpu/ 16);
+
+  PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
+  
+  // Ignore the first run (for icache reasons)
+  uint32_t cpu_freq = PRCI_measure_mcycle_freq(3000, RTC_FREQ);
+
+  cpu_freq = PRCI_measure_mcycle_freq(3000, RTC_FREQ);
+  uint32_t prev_freq = cpu_freq;
+  
+  while ((cpu_freq < desired_hfrosc_freq) && (hfrosctrim < 0x1F)){
+    prev_trim = hfrosctrim;
+    prev_freq = cpu_freq;
+    hfrosctrim ++;
+    PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
+    cpu_freq = PRCI_measure_mcycle_freq(3000, RTC_FREQ);
+  } 
+
+  // We couldn't go low enough
+  if (prev_freq > desired_hfrosc_freq){
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
+    return cpu_freq;
+  }
+  
+  // We couldn't go high enough
+  if (cpu_freq < desired_hfrosc_freq){
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
+    return cpu_freq;
+  }
+
+  // Check for over/undershoot
+  switch(target) {
+  case(PRCI_FREQ_CLOSEST):
+    if ((desired_hfrosc_freq - prev_freq) < (cpu_freq - desired_hfrosc_freq)) {
+      PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    } else {
+      PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, hfrosctrim);
+    }
+    break;
+  case(PRCI_FREQ_UNDERSHOOT):
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    break;
+  default:
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, hfrosctrim);
+  }
+
+  cpu_freq =  PRCI_measure_mcycle_freq(1000, RTC_FREQ);
+  return cpu_freq;
+
+}
+
+#endif
--- a/hello-world/bsp/drivers/fe300prci/fe300prci_driver.h
+++ b/hello-world/bsp/drivers/fe300prci/fe300prci_driver.h
@ -0,0 +1,79 @@
+// See LICENSE file for license details
+
+#ifndef _FE300PRCI_DRIVER_H_
+#define _FE300PRCI_DRIVER_H_
+
+__BEGIN_DECLS
+
+#include <unistd.h>
+
+typedef enum prci_freq_target {
+  
+  PRCI_FREQ_OVERSHOOT,
+  PRCI_FREQ_CLOSEST,
+  PRCI_FREQ_UNDERSHOOT
+
+} PRCI_freq_target;
+
+/* Measure and return the approximate frequency of the 
+ * CPU, as given by measuring the mcycle counter against 
+ * the mtime ticks.
+ */
+uint32_t PRCI_measure_mcycle_freq(uint32_t mtime_ticks, uint32_t mtime_freq);
+
+/* Safely switch over to the HFROSC using the given div
+ * and trim settings.
+ */
+void PRCI_use_hfrosc(int div, int trim);
+
+/* Safely switch over to the 16MHz HFXOSC,
+ * applying the finaldiv clock divider (1 is the lowest
+ * legal value).
+ */
+void PRCI_use_hfxosc(uint32_t finaldiv);
+
+/* Safely switch over to the PLL using the given
+ * settings.
+ * 
+ * Note that not all combinations of the inputs are actually
+ * legal, and this function does not check for their
+ * legality ("safely" means that this function won't turn off
+ * or glitch the clock the CPU is actually running off, but
+ * doesn't protect against you making it too fast or slow.)
+ */
+
+void PRCI_use_pll(int refsel, int bypass,
+			 int r, int f, int q, int finaldiv,
+			 int hfroscdiv, int hfrosctrim);
+
+/* Use the default clocks configured at reset.
+ * This is ~16Mhz HFROSC and turns off the LFROSC
+ * (on the current FE310 Dev Platforms, an external LFROSC is 
+ * used as it is more power efficient).
+ */
+void PRCI_use_default_clocks();
+
+/* This routine will adjust the HFROSC trim
+ * while using HFROSC as the clock source, 
+ * measure the resulting frequency, then
+ * use it as the PLL clock source, 
+ * in an attempt to get over, under, or close to the 
+ * requested frequency. It returns the actual measured 
+ * frequency. 
+ *
+ * Note that the requested frequency must be within the 
+ * range supported by the PLL so not all values are 
+ * achievable with this function, and not all 
+ * are guaranteed to actually work. The PLL
+ * is rated higher than the hardware.
+ * 
+ * There is no check on the desired f_cpu frequency, it
+ * is up to the user to specify something reasonable.
+ */
+
+uint32_t PRCI_set_hfrosctrim_for_f_cpu(uint32_t f_cpu, PRCI_freq_target target);
+
+__END_DECLS
+
+#endif
+  
--- a/hello-world/bsp/drivers/plic/plic_driver.c
+++ b/hello-world/bsp/drivers/plic/plic_driver.c
@ -0,0 +1,127 @@
+// See LICENSE for license details.
+
+#include "sifive/devices/plic.h"
+#include "plic/plic_driver.h"
+#include "platform.h"
+#include "encoding.h"
+#include <string.h>
+
+
+// Note that there are no assertions or bounds checking on these
+// parameter values.
+
+void volatile_memzero(uint8_t * base, unsigned int size)
+{
+  volatile uint8_t * ptr;
+  for (ptr = base; ptr < (base + size); ptr++){
+    *ptr = 0;
+  }
+}
+
+void PLIC_init (
+                plic_instance_t * this_plic,
+                uintptr_t         base_addr,
+                uint32_t num_sources,
+                uint32_t num_priorities
+                )
+{
+  
+  this_plic->base_addr = base_addr;
+  this_plic->num_sources = num_sources;
+  this_plic->num_priorities = num_priorities;
+  
+  // Disable all interrupts (don't assume that these registers are reset).
+  unsigned long hart_id = read_csr(mhartid);
+  volatile_memzero((uint8_t*) (this_plic->base_addr +
+                               PLIC_ENABLE_OFFSET +
+                               (hart_id << PLIC_ENABLE_SHIFT_PER_TARGET)),
+                   (num_sources + 8) / 8);
+  
+  // Set all priorities to 0 (equal priority -- don't assume that these are reset).
+  volatile_memzero ((uint8_t *)(this_plic->base_addr +
+                                PLIC_PRIORITY_OFFSET),
+                    (num_sources + 1) << PLIC_PRIORITY_SHIFT_PER_SOURCE);
+
+  // Set the threshold to 0.
+  volatile plic_threshold* threshold = (plic_threshold*)
+    (this_plic->base_addr +
+     PLIC_THRESHOLD_OFFSET +
+     (hart_id << PLIC_THRESHOLD_SHIFT_PER_TARGET));
+
+  *threshold = 0;
+  
+}
+
+void PLIC_set_threshold (plic_instance_t * this_plic,
+			 plic_threshold threshold){
+
+  unsigned long hart_id = read_csr(mhartid);  
+  volatile plic_threshold* threshold_ptr = (plic_threshold*) (this_plic->base_addr +
+                                                              PLIC_THRESHOLD_OFFSET +
+                                                              (hart_id << PLIC_THRESHOLD_SHIFT_PER_TARGET));
+
+  *threshold_ptr = threshold;
+
+}
+  
+
+void PLIC_enable_interrupt (plic_instance_t * this_plic, plic_source source){
+
+  unsigned long hart_id = read_csr(mhartid);
+  volatile uint8_t * current_ptr = (volatile uint8_t *)(this_plic->base_addr +
+                                                        PLIC_ENABLE_OFFSET +
+                                                        (hart_id << PLIC_ENABLE_SHIFT_PER_TARGET) +
+                                                        (source >> 3));
+  uint8_t current = *current_ptr;
+  current = current | ( 1 << (source & 0x7));
+  *current_ptr = current;
+
+}
+
+void PLIC_disable_interrupt (plic_instance_t * this_plic, plic_source source){
+  
+  unsigned long hart_id = read_csr(mhartid);
+  volatile uint8_t * current_ptr = (volatile uint8_t *) (this_plic->base_addr +
+                                                         PLIC_ENABLE_OFFSET +
+                                                         (hart_id << PLIC_ENABLE_SHIFT_PER_TARGET) +
+                                                         (source >> 3));
+  uint8_t current = *current_ptr;
+  current = current & ~(( 1 << (source & 0x7)));
+  *current_ptr = current;
+  
+}
+
+void PLIC_set_priority (plic_instance_t * this_plic, plic_source source, plic_priority priority){
+
+  if (this_plic->num_priorities > 0) {
+    volatile plic_priority * priority_ptr = (volatile plic_priority *)
+      (this_plic->base_addr +
+       PLIC_PRIORITY_OFFSET +
+       (source << PLIC_PRIORITY_SHIFT_PER_SOURCE));
+    *priority_ptr = priority;
+  }
+}
+
+plic_source PLIC_claim_interrupt(plic_instance_t * this_plic){
+  
+  unsigned long hart_id = read_csr(mhartid);
+
+  volatile plic_source * claim_addr = (volatile plic_source * )
+    (this_plic->base_addr +
+     PLIC_CLAIM_OFFSET +
+     (hart_id << PLIC_CLAIM_SHIFT_PER_TARGET));
+
+  return  *claim_addr;
+  
+}
+
+void PLIC_complete_interrupt(plic_instance_t * this_plic, plic_source source){
+  
+  unsigned long hart_id = read_csr(mhartid);
+  volatile plic_source * claim_addr = (volatile plic_source *) (this_plic->base_addr +
+                                                                PLIC_CLAIM_OFFSET +
+                                                                (hart_id << PLIC_CLAIM_SHIFT_PER_TARGET));
+  *claim_addr = source;
+  
+}
+
--- a/hello-world/bsp/drivers/plic/plic_driver.h
+++ b/hello-world/bsp/drivers/plic/plic_driver.h
@ -0,0 +1,51 @@
+// See LICENSE file for licence details
+
+#ifndef PLIC_DRIVER_H
+#define PLIC_DRIVER_H
+
+
+__BEGIN_DECLS
+
+#include "platform.h"
+
+typedef struct __plic_instance_t
+{
+  uintptr_t base_addr;
+
+  uint32_t num_sources;
+  uint32_t num_priorities;
+  
+} plic_instance_t;
+
+typedef uint32_t plic_source;
+typedef uint32_t plic_priority;
+typedef uint32_t plic_threshold;
+
+void PLIC_init (
+                plic_instance_t * this_plic,
+                uintptr_t         base_addr,
+                uint32_t num_sources,
+                uint32_t num_priorities
+                );
+
+void PLIC_set_threshold (plic_instance_t * this_plic,
+			 plic_threshold threshold);
+  
+void PLIC_enable_interrupt (plic_instance_t * this_plic,
+			    plic_source source);
+
+void PLIC_disable_interrupt (plic_instance_t * this_plic,
+			     plic_source source);
+  
+void PLIC_set_priority (plic_instance_t * this_plic,
+			plic_source source,
+			plic_priority priority);
+
+plic_source PLIC_claim_interrupt(plic_instance_t * this_plic);
+
+void PLIC_complete_interrupt(plic_instance_t * this_plic,
+			     plic_source source);
+
+__END_DECLS
+
+#endif
--- a/hello-world/bsp/env/common.mk
+++ b/hello-world/bsp/env/common.mk
@ -0,0 +1,65 @@
+# See LICENSE for license details.
+
+ifndef _SIFIVE_MK_COMMON
+_SIFIVE_MK_COMMON := # defined
+
+.PHONY: all
+all: $(TARGET)
+
+include $(BSP_BASE)/libwrap/libwrap.mk
+
+ENV_DIR = $(BSP_BASE)/env
+PLATFORM_DIR = $(ENV_DIR)/$(BOARD)
+
+ASM_SRCS += $(ENV_DIR)/start.S
+ASM_SRCS += $(ENV_DIR)/entry.S
+C_SRCS += $(PLATFORM_DIR)/init.c
+
+LINKER_SCRIPT := $(PLATFORM_DIR)/$(LINK_TARGET).lds
+
+INCLUDES += -I$(BSP_BASE)/include
+INCLUDES += -I$(BSP_BASE)/drivers/
+INCLUDES += -I$(ENV_DIR)
+INCLUDES += -I$(PLATFORM_DIR)
+
+TOOL_DIR ?= $(BSP_BASE)/../toolchain/bin
+
+LDFLAGS += -T $(LINKER_SCRIPT) -nostartfiles
+LDFLAGS += -L$(ENV_DIR) --specs=nano.specs
+
+ASM_OBJS := $(ASM_SRCS:.S=.o)
+C_OBJS   := $(C_SRCS:.c=.o)
+CXX_OBJS := $(CXX_SRCS:.cpp=.o)
+
+LINK_OBJS += $(ASM_OBJS) $(C_OBJS) $(CXX_OBJS)
+LINK_DEPS += $(LINKER_SCRIPT)
+
+CLEAN_OBJS += $(TARGET) $(LINK_OBJS)
+
+CFLAGS += -march=$(RISCV_ARCH)
+CFLAGS += -mabi=$(RISCV_ABI)
+CFLAGS += -mcmodel=medany
+
+TRIPLET?=riscv64-unknown-elf
+CXX=$(TOOL_DIR)/$(TRIPLET)-c++
+CC=$(TOOL_DIR)/$(TRIPLET)-gcc
+LD=$(TOOL_DIR)/$(TRIPLET)-gcc
+
+
+$(TARGET): $(LINK_OBJS) $(LINK_DEPS)
+	$(LD) $(LINK_OBJS) $(LDFLAGS) $(LIBWRAP) -o $@
+	
+$(ASM_OBJS): %.o: %.S $(HEADERS)
+	$(CC) $(CFLAGS) $(INCLUDES) -c -o $@ $<
+
+$(C_OBJS): %.o: %.c $(HEADERS)
+	$(CC) $(CFLAGS) $(INCLUDES) -include sys/cdefs.h -c -o $@ $<
+
+$(CXX_OBJS): %.o: %.cpp $(HEADERS)
+	$(CXX) $(CFLAGS) $(CXXFLAGS) $(INCLUDES) -include sys/cdefs.h -c -o $@ $<
+
+.PHONY: clean
+clean:
+	rm -f $(CLEAN_OBJS)
+
+endif # _SIFIVE_MK_COMMON
--- a/hello-world/bsp/env/encoding.h
+++ b/hello-world/bsp/env/encoding.h
--- a/hello-world/bsp/env/entry.S
+++ b/hello-world/bsp/env/entry.S
@ -0,0 +1,97 @@
+// See LICENSE for license details
+
+#ifndef ENTRY_S
+#define ENTRY_S
+
+#include "encoding.h"
+#include "sifive/bits.h"
+
+  .section      .text.entry	
+  .align 2
+  .global trap_entry
+trap_entry:
+  addi sp, sp, -32*REGBYTES
+
+  STORE x1, 1*REGBYTES(sp)
+  STORE x2, 2*REGBYTES(sp)
+  STORE x3, 3*REGBYTES(sp)
+  STORE x4, 4*REGBYTES(sp)
+  STORE x5, 5*REGBYTES(sp)
+  STORE x6, 6*REGBYTES(sp)
+  STORE x7, 7*REGBYTES(sp)
+  STORE x8, 8*REGBYTES(sp)
+  STORE x9, 9*REGBYTES(sp)
+  STORE x10, 10*REGBYTES(sp)
+  STORE x11, 11*REGBYTES(sp)
+  STORE x12, 12*REGBYTES(sp)
+  STORE x13, 13*REGBYTES(sp)
+  STORE x14, 14*REGBYTES(sp)
+  STORE x15, 15*REGBYTES(sp)
+  STORE x16, 16*REGBYTES(sp)
+  STORE x17, 17*REGBYTES(sp)
+  STORE x18, 18*REGBYTES(sp)
+  STORE x19, 19*REGBYTES(sp)
+  STORE x20, 20*REGBYTES(sp)
+  STORE x21, 21*REGBYTES(sp)
+  STORE x22, 22*REGBYTES(sp)
+  STORE x23, 23*REGBYTES(sp)
+  STORE x24, 24*REGBYTES(sp)
+  STORE x25, 25*REGBYTES(sp)
+  STORE x26, 26*REGBYTES(sp)
+  STORE x27, 27*REGBYTES(sp)
+  STORE x28, 28*REGBYTES(sp)
+  STORE x29, 29*REGBYTES(sp)
+  STORE x30, 30*REGBYTES(sp)
+  STORE x31, 31*REGBYTES(sp)
+
+  csrr a0, mcause
+  csrr a1, mepc
+  mv a2, sp
+  call handle_trap
+  csrw mepc, a0
+
+  # Remain in M-mode after mret
+  li t0, MSTATUS_MPP
+  csrs mstatus, t0
+
+  LOAD x1, 1*REGBYTES(sp)
+  LOAD x2, 2*REGBYTES(sp)
+  LOAD x3, 3*REGBYTES(sp)
+  LOAD x4, 4*REGBYTES(sp)
+  LOAD x5, 5*REGBYTES(sp)
+  LOAD x6, 6*REGBYTES(sp)
+  LOAD x7, 7*REGBYTES(sp)
+  LOAD x8, 8*REGBYTES(sp)
+  LOAD x9, 9*REGBYTES(sp)
+  LOAD x10, 10*REGBYTES(sp)
+  LOAD x11, 11*REGBYTES(sp)
+  LOAD x12, 12*REGBYTES(sp)
+  LOAD x13, 13*REGBYTES(sp)
+  LOAD x14, 14*REGBYTES(sp)
+  LOAD x15, 15*REGBYTES(sp)
+  LOAD x16, 16*REGBYTES(sp)
+  LOAD x17, 17*REGBYTES(sp)
+  LOAD x18, 18*REGBYTES(sp)
+  LOAD x19, 19*REGBYTES(sp)
+  LOAD x20, 20*REGBYTES(sp)
+  LOAD x21, 21*REGBYTES(sp)
+  LOAD x22, 22*REGBYTES(sp)
+  LOAD x23, 23*REGBYTES(sp)
+  LOAD x24, 24*REGBYTES(sp)
+  LOAD x25, 25*REGBYTES(sp)
+  LOAD x26, 26*REGBYTES(sp)
+  LOAD x27, 27*REGBYTES(sp)
+  LOAD x28, 28*REGBYTES(sp)
+  LOAD x29, 29*REGBYTES(sp)
+  LOAD x30, 30*REGBYTES(sp)
+  LOAD x31, 31*REGBYTES(sp)
+
+  addi sp, sp, 32*REGBYTES
+  mret
+
+.weak handle_trap
+handle_trap:
+1:
+  j 1b
+	
+#endif
--- a/hello-world/bsp/env/freedom-e300-arty/init.c
+++ b/hello-world/bsp/env/freedom-e300-arty/init.c
@ -0,0 +1,87 @@
+//See LICENSE for license details.
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "platform.h"
+#include "encoding.h"
+
+extern int main(int argc, char** argv);
+extern void trap_entry();
+
+static unsigned long get_cpu_freq()
+{
+  return 65000000;
+}
+
+unsigned long get_timer_freq()
+{
+  return get_cpu_freq();
+}
+
+uint64_t get_timer_value()
+{
+#if __riscv_xlen == 32
+  while (1) {
+    uint32_t hi = read_csr(mcycleh);
+    uint32_t lo = read_csr(mcycle);
+    if (hi == read_csr(mcycleh))
+      return ((uint64_t)hi << 32) | lo;
+  }
+#else
+  return read_csr(mcycle);
+#endif
+}
+
+static void uart_init(size_t baud_rate)
+{
+  GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
+  GPIO_REG(GPIO_IOF_EN) |= IOF0_UART0_MASK;
+  UART0_REG(UART_REG_DIV) = get_cpu_freq() / baud_rate - 1;
+  UART0_REG(UART_REG_TXCTRL) |= UART_TXEN;
+}
+
+
+#ifdef USE_PLIC
+extern void handle_m_ext_interrupt();
+#endif
+
+#ifdef USE_M_TIME
+extern void handle_m_time_interrupt();
+#endif
+
+uintptr_t handle_trap(uintptr_t mcause, uintptr_t epc)
+{
+  if (0){
+#ifdef USE_PLIC
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
+    handle_m_ext_interrupt();
+#endif
+#ifdef USE_M_TIME
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
+    handle_m_time_interrupt();
+#endif
+  }
+  else {
+    write(1, "Unhandled Trap:\n", 16);
+    _exit(1 + mcause);
+  }
+  return epc;
+}
+
+void _init()
+{
+  #ifndef NO_INIT
+  uart_init(115200);
+
+  printf("core freq at %d Hz\n", get_cpu_freq());
+
+  write_csr(mtvec, &trap_entry);
+  #endif
+}
+
+void _fini()
+{
+}
--- a/hello-world/bsp/env/freedom-e300-arty/link.lds
+++ b/hello-world/bsp/env/freedom-e300-arty/link.lds
@ -0,0 +1,167 @@
+OUTPUT_ARCH( "riscv" )
+
+ENTRY( _start )
+
+MEMORY
+{
+  flash (rxai!w) : ORIGIN = 0x20400000, LENGTH = 512M
+  ram (wxa!ri) : ORIGIN = 0x80000000, LENGTH = 16K
+}
+
+PHDRS
+{
+  flash PT_LOAD;
+  ram_init PT_LOAD;
+  ram PT_NULL;
+}
+
+SECTIONS
+{
+  __stack_size = DEFINED(__stack_size) ? __stack_size : 2K;
+
+  .init           :
+  {
+    KEEP (*(SORT_NONE(.init)))
+  } >flash AT>flash :flash
+
+  .text           :
+  {
+    *(.text.unlikely .text.unlikely.*)
+    *(.text.startup .text.startup.*)
+    *(.text .text.*)
+    *(.gnu.linkonce.t.*)
+  } >flash AT>flash :flash
+
+  .fini           :
+  {
+    KEEP (*(SORT_NONE(.fini)))
+  } >flash AT>flash :flash
+
+  PROVIDE (__etext = .);
+  PROVIDE (_etext = .);
+  PROVIDE (etext = .);
+
+  .rodata         :
+  {
+    *(.rdata)
+    *(.rodata .rodata.*)
+    *(.gnu.linkonce.r.*)
+  } >flash AT>flash :flash
+
+  . = ALIGN(4);
+
+  .preinit_array  :
+  {
+    PROVIDE_HIDDEN (__preinit_array_start = .);
+    KEEP (*(.preinit_array))
+    PROVIDE_HIDDEN (__preinit_array_end = .);
+  } >flash AT>flash :flash
+
+  .init_array     :
+  {
+    PROVIDE_HIDDEN (__init_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
+    KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors))
+    PROVIDE_HIDDEN (__init_array_end = .);
+  } >flash AT>flash :flash
+
+  .fini_array     :
+  {
+    PROVIDE_HIDDEN (__fini_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
+    KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors))
+    PROVIDE_HIDDEN (__fini_array_end = .);
+  } >flash AT>flash :flash
+
+  .ctors          :
+  {
+    /* gcc uses crtbegin.o to find the start of
+       the constructors, so we make sure it is
+       first.  Because this is a wildcard, it
+       doesn't matter if the user does not
+       actually link against crtbegin.o; the
+       linker won't look for a file to match a
+       wildcard.  The wildcard also means that it
+       doesn't matter which directory crtbegin.o
+       is in.  */
+    KEEP (*crtbegin.o(.ctors))
+    KEEP (*crtbegin?.o(.ctors))
+    /* We don't want to include the .ctor section from
+       the crtend.o file until after the sorted ctors.
+       The .ctor section from the crtend file contains the
+       end of ctors marker and it must be last */
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+  } >flash AT>flash :flash
+
+  .dtors          :
+  {
+    KEEP (*crtbegin.o(.dtors))
+    KEEP (*crtbegin?.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+  } >flash AT>flash :flash
+
+  .lalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data_lma = . );
+  } >flash AT>flash :flash
+
+  .dalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data = . );
+  } >ram AT>flash :ram_init
+
+  .data          :
+  {
+    *(.data .data.*)
+    *(.gnu.linkonce.d.*)
+  } >ram AT>flash :ram_init
+
+  .srodata        :
+  {
+    PROVIDE( _gp = . + 0x800 );
+    *(.srodata.cst16)
+    *(.srodata.cst8)
+    *(.srodata.cst4)
+    *(.srodata.cst2)
+    *(.srodata .srodata.*)
+  } >ram AT>flash :ram_init
+
+  .sdata          :
+  {
+    *(.sdata .sdata.*)
+    *(.gnu.linkonce.s.*)
+  } >ram AT>flash :ram_init
+
+  . = ALIGN(4);
+  PROVIDE( _edata = . );
+  PROVIDE( edata = . );
+
+  PROVIDE( _fbss = . );
+  PROVIDE( __bss_start = . );
+  .bss            :
+  {
+    *(.sbss*)
+    *(.gnu.linkonce.sb.*)
+    *(.bss .bss.*)
+    *(.gnu.linkonce.b.*)
+    *(COMMON)
+    . = ALIGN(4);
+  } >ram AT>ram :ram
+
+  . = ALIGN(8);
+  PROVIDE( _end = . );
+  PROVIDE( end = . );
+
+  .stack ORIGIN(ram) + LENGTH(ram) - __stack_size :
+  {
+    PROVIDE( _heap_end = . );
+    . = __stack_size;
+    PROVIDE( _sp = . );
+  } >ram AT>ram :ram
+}
--- a/hello-world/bsp/env/freedom-e300-arty/openocd.cfg
+++ b/hello-world/bsp/env/freedom-e300-arty/openocd.cfg
@ -0,0 +1,30 @@
+adapter_khz     10000
+
+#source [find interface/ftdi/olimex-arm-usb-tiny-h.cfg]
+
+interface ftdi
+ftdi_device_desc "Olimex OpenOCD JTAG ARM-USB-TINY-H"
+ftdi_vid_pid 0x15ba 0x002a
+
+ftdi_layout_init 0x0808 0x0a1b
+ftdi_layout_signal nSRST -oe 0x0200
+ftdi_layout_signal nTRST -data 0x0100 -oe 0x0100
+ftdi_layout_signal LED -data 0x0800
+#
+
+set _CHIPNAME riscv
+jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x10e31913
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME riscv -chain-position $_TARGETNAME
+$_TARGETNAME configure -work-area-phys 0x80000000 -work-area-size 10000 -work-area-backup 1
+
+flash bank my_first_flash fespi 0x20000000 0 0 0 $_TARGETNAME
+init
+#reset
+if {[ info exists pulse_srst]} {
+  ftdi_set_signal nSRST 0
+  ftdi_set_signal nSRST z
+}
+halt
+#flash protect 0 64 last off
--- a/hello-world/bsp/env/freedom-e300-arty/platform.h
+++ b/hello-world/bsp/env/freedom-e300-arty/platform.h
@ -0,0 +1,125 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_PLATFORM_H
+#define _SIFIVE_PLATFORM_H
+
+// Some things missing from the official encoding.h
+#define MCAUSE_INT         0x80000000
+#define MCAUSE_CAUSE       0x7FFFFFFF
+
+#include "sifive/const.h"
+#include "sifive/devices/aon.h"
+#include "sifive/devices/clint.h"
+#include "sifive/devices/gpio.h"
+#include "sifive/devices/plic.h"
+#include "sifive/devices/pwm.h"
+#include "sifive/devices/spi.h"
+#include "sifive/devices/uart.h"
+
+/****************************************************************************
+ * Platform definitions
+ *****************************************************************************/
+
+#define TRAPVEC_TABLE_BASE_ADDR _AC(0x00001010,UL)
+#define CLINT_BASE_ADDR _AC(0x02000000,UL)
+#define PLIC_BASE_ADDR _AC(0x0C000000,UL)
+#define AON_BASE_ADDR _AC(0x10000000,UL)
+#define GPIO_BASE_ADDR _AC(0x10012000,UL)
+#define UART0_BASE_ADDR _AC(0x10013000,UL)
+#define SPI0_BASE_ADDR _AC(0x10014000,UL)
+#define PWM0_BASE_ADDR _AC(0x10015000,UL)
+#define UART1_BASE_ADDR _AC(0x10023000,UL)
+#define SPI1_BASE_ADDR _AC(0x10024000,UL)
+#define PWM1_BASE_ADDR _AC(0x10025000,UL)
+#define SPI2_BASE_ADDR _AC(0x10034000,UL)
+#define PWM2_BASE_ADDR _AC(0x10035000,UL)
+#define SPI0_MMAP_ADDR _AC(0x20000000,UL)
+#define MEM_BASE_ADDR _AC(0x80000000,UL)
+
+// IOF Mappings
+#define IOF0_SPI1_MASK          _AC(0x000007FC,UL)
+#define SPI11_NUM_SS     (4)
+#define IOF_SPI1_SS0          (2u)
+#define IOF_SPI1_SS1          (8u)
+#define IOF_SPI1_SS2          (9u)
+#define IOF_SPI1_SS3          (10u)
+#define IOF_SPI1_MOSI         (3u)
+#define IOF_SPI1_MISO         (4u)
+#define IOF_SPI1_SCK          (5u)
+#define IOF_SPI1_DQ0          (3u)
+#define IOF_SPI1_DQ1          (4u)
+#define IOF_SPI1_DQ2          (6u)
+#define IOF_SPI1_DQ3          (7u)
+
+#define IOF0_SPI2_MASK          _AC(0xFC000000,UL)
+#define SPI2_NUM_SS       (1)
+#define IOF_SPI2_SS0          (26u)
+#define IOF_SPI2_MOSI         (27u)
+#define IOF_SPI2_MISO         (28u)
+#define IOF_SPI2_SCK          (29u)
+#define IOF_SPI2_DQ0          (27u)
+#define IOF_SPI2_DQ1          (28u)
+#define IOF_SPI2_DQ2          (30u)
+#define IOF_SPI2_DQ3          (31u)
+
+#define IOF0_UART0_MASK         _AC(0x00030000, UL)
+#define IOF_UART0_RX   (16u)
+#define IOF_UART0_TX   (17u)
+
+#define IOF0_UART1_MASK         _AC(0x03000000, UL)
+#define IOF_UART1_RX (24u)
+#define IOF_UART1_TX (25u)
+
+#define IOF1_PWM0_MASK          _AC(0x0000000F, UL)
+#define IOF1_PWM1_MASK          _AC(0x00780000, UL)
+#define IOF1_PWM2_MASK          _AC(0x00003C00, UL)
+
+// Interrupt Numbers
+#define INT_RESERVED 0
+#define INT_WDOGCMP 1
+#define INT_RTCCMP 2
+#define INT_UART0_BASE 3
+#define INT_UART1_BASE 4
+#define INT_SPI0_BASE 5
+#define INT_SPI1_BASE 6
+#define INT_SPI2_BASE 7
+#define INT_GPIO_BASE 8
+#define INT_PWM0_BASE 40
+#define INT_PWM1_BASE 44
+#define INT_PWM2_BASE 48
+
+// Helper functions
+#define _REG32(p, i) (*(volatile uint32_t *) ((p) + (i)))
+#define _REG32P(p, i) ((volatile uint32_t *) ((p) + (i)))
+#define AON_REG(offset) _REG32(AON_BASE_ADDR, offset)
+#define CLINT_REG(offset) _REG32(CLINT_BASE_ADDR, offset)
+#define GPIO_REG(offset) _REG32(GPIO_BASE_ADDR, offset)
+#define OTP_REG(offset)  _REG32(OTP_BASE_ADDR, offset)
+#define PLIC_REG(offset) _REG32(PLIC_BASE_ADDR, offset)
+#define PRCI_REG(offset) _REG32(PRCI_BASE_ADDR, offset)
+#define PWM0_REG(offset) _REG32(PWM0_BASE_ADDR, offset)
+#define PWM1_REG(offset) _REG32(PWM1_BASE_ADDR, offset)
+#define PWM2_REG(offset) _REG32(PWM2_BASE_ADDR, offset)
+#define SPI0_REG(offset) _REG32(SPI0_BASE_ADDR, offset)
+#define SPI1_REG(offset) _REG32(SPI1_BASE_ADDR, offset)
+#define SPI2_REG(offset) _REG32(SPI2_BASE_ADDR, offset)
+#define UART0_REG(offset) _REG32(UART0_BASE_ADDR, offset)
+#define UART1_REG(offset) _REG32(UART1_BASE_ADDR, offset)
+
+// Misc
+
+#include <stdint.h>
+
+
+#define NUM_GPIO 32
+
+#define PLIC_NUM_INTERRUPTS 52
+#define PLIC_NUM_PRIORITIES 7
+
+#define HAS_BOARD_BUTTONS
+#include "hifive1.h"
+
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
+#endif /* _SIFIVE_PLATFORM_H */
--- a/hello-world/bsp/env/freedom-e300-hifive1/init.c
+++ b/hello-world/bsp/env/freedom-e300-hifive1/init.c
@ -0,0 +1,238 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "platform.h"
+#include "encoding.h"
+
+extern int main(int argc, char** argv);
+extern void trap_entry();
+
+static unsigned long mtime_lo(void)
+{
+  return *(volatile unsigned long *)(CLINT_BASE_ADDR + CLINT_MTIME);
+}
+
+#ifdef __riscv32
+
+static uint32_t mtime_hi(void)
+{
+  return *(volatile uint32_t *)(CLINT_BASE_ADDR + CLINT_MTIME + 4);
+}
+
+uint64_t get_timer_value()
+{
+  while (1) {
+    uint32_t hi = mtime_hi();
+    uint32_t lo = mtime_lo();
+    if (hi == mtime_hi())
+      return ((uint64_t)hi << 32) | lo;
+  }
+}
+
+#else /* __riscv32 */
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
+{
+  return 32768;
+}
+
+static void use_hfrosc(int div, int trim)
+{
+  // Make sure the HFROSC is running at its default setting
+  PRCI_REG(PRCI_HFROSCCFG) = (ROSC_DIV(div) | ROSC_TRIM(trim) | ROSC_EN(1));
+  while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0) ;
+  PRCI_REG(PRCI_PLLCFG) &= ~PLL_SEL(1);
+}
+
+static void use_pll(int refsel, int bypass, int r, int f, int q)
+{
+  // Ensure that we aren't running off the PLL before we mess with it.
+  if (PRCI_REG(PRCI_PLLCFG) & PLL_SEL(1)) {
+    // Make sure the HFROSC is running at its default setting
+    use_hfrosc(4, 16);
+  }
+
+  // Set PLL Source to be HFXOSC if available.
+  uint32_t config_value = 0;
+
+  config_value |= PLL_REFSEL(refsel);
+
+  if (bypass) {
+    // Bypass
+    config_value |= PLL_BYPASS(1);
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // If we don't have an HFXTAL, this doesn't really matter.
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+  } else {
+    // In case we are executing from QSPI,
+    // (which is quite likely) we need to
+    // set the QSPI clock divider appropriately
+    // before boosting the clock frequency.
+
+    // Div = f_sck/2
+    SPI0_REG(SPI_REG_SCKDIV) = 8;
+
+    // Set DIV Settings for PLL
+    // Both HFROSC and HFXOSC are modeled as ideal
+    // 16MHz sources (assuming dividers are set properly for
+    // HFROSC).
+    // (Legal values of f_REF are 6-48MHz)
+
+    // Set DIVR to divide-by-2 to get 8MHz frequency
+    // (legal values of f_R are 6-12 MHz)
+
+    config_value |= PLL_BYPASS(1);
+    config_value |= PLL_R(r);
+
+    // Set DIVF to get 512Mhz frequncy
+    // There is an implied multiply-by-2, 16Mhz.
+    // So need to write 32-1
+    // (legal values of f_F are 384-768 MHz)
+    config_value |= PLL_F(f);
+
+    // Set DIVQ to divide-by-2 to get 256 MHz frequency
+    // (legal values of f_Q are 50-400Mhz)
+    config_value |= PLL_Q(q);
+
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // Un-Bypass the PLL.
+    PRCI_REG(PRCI_PLLCFG) &= ~PLL_BYPASS(1);
+
+    // Wait for PLL Lock
+    // Note that the Lock signal can be glitchy.
+    // Need to wait 100 us
+    // RTC is running at 32kHz.
+    // So wait 4 ticks of RTC.
+    uint32_t now = mtime_lo();
+    while (mtime_lo() - now < 4) ;
+
+    // Now it is safe to check for PLL Lock
+    while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0) ;
+  }
+
+  // Switch over to PLL Clock source
+  PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
+}
+
+static void use_default_clocks()
+{
+  // Turn off the LFROSC
+  AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
+
+  // Use HFROSC
+  use_hfrosc(4, 16);
+}
+
+static unsigned long __attribute__((noinline)) measure_cpu_freq(size_t n)
+{
+  unsigned long start_mtime, delta_mtime;
+  unsigned long mtime_freq = get_timer_freq();
+
+  // Don't start measuruing until we see an mtime tick
+  unsigned long tmp = mtime_lo();
+  do {
+    start_mtime = mtime_lo();
+  } while (start_mtime == tmp);
+
+  unsigned long start_mcycle = read_csr(mcycle);
+
+  do {
+    delta_mtime = mtime_lo() - start_mtime;
+  } while (delta_mtime < n);
+
+  unsigned long delta_mcycle = read_csr(mcycle) - start_mcycle;
+
+  return (delta_mcycle / delta_mtime) * mtime_freq
+         + ((delta_mcycle % delta_mtime) * mtime_freq) / delta_mtime;
+}
+
+unsigned long get_cpu_freq()
+{
+  static uint32_t cpu_freq;
+
+  if (!cpu_freq) {
+    // warm up I$
+    measure_cpu_freq(1);
+    // measure for real
+    cpu_freq = measure_cpu_freq(10);
+  }
+
+  return cpu_freq;
+}
+
+static void uart_init(size_t baud_rate)
+{
+  GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
+  GPIO_REG(GPIO_IOF_EN) |= IOF0_UART0_MASK;
+  UART0_REG(UART_REG_DIV) = get_cpu_freq() / baud_rate - 1;
+  UART0_REG(UART_REG_TXCTRL) |= UART_TXEN;
+}
+
+
+
+#ifdef USE_PLIC
+extern void handle_m_ext_interrupt();
+#endif
+
+#ifdef USE_M_TIME
+extern void handle_m_time_interrupt();
+#endif
+
+uintptr_t handle_trap(uintptr_t mcause, uintptr_t epc)
+{
+  if (0){
+#ifdef USE_PLIC
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
+    handle_m_ext_interrupt();
+#endif
+#ifdef USE_M_TIME
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
+    handle_m_time_interrupt();
+#endif
+  }
+  else {
+    write(1, "trap\n", 5);
+    _exit(1 + mcause);
+  }
+  return epc;
+}
+
+void _init()
+{
+  
+  #ifndef NO_INIT
+  use_default_clocks();
+  use_pll(0, 0, 1, 31, 1);
+  uart_init(115200);
+
+  printf("core freq at %d Hz\n", get_cpu_freq());
+
+  write_csr(mtvec, &trap_entry);
+  if (read_csr(misa) & (1 << ('F' - 'A'))) { // if F extension is present
+    write_csr(mstatus, MSTATUS_FS); // allow FPU instructions without trapping
+    write_csr(fcsr, 0); // initialize rounding mode, undefined at reset
+  }
+  #endif
+  
+}
+
+void _fini()
+{
+}
--- a/hello-world/bsp/env/freedom-e300-hifive1/link.lds
+++ b/hello-world/bsp/env/freedom-e300-hifive1/link.lds
@ -0,0 +1,167 @@
+OUTPUT_ARCH( "riscv" )
+
+ENTRY( _start )
+
+MEMORY
+{
+  flash (rxai!w) : ORIGIN = 0x20400000, LENGTH = 512M
+  ram (wxa!ri) : ORIGIN = 0x80000000, LENGTH = 16K
+}
+
+PHDRS
+{
+  flash PT_LOAD;
+  ram_init PT_LOAD;
+  ram PT_NULL;
+}
+
+SECTIONS
+{
+  __stack_size = DEFINED(__stack_size) ? __stack_size : 2K;
+
+  .init           :
+  {
+    KEEP (*(SORT_NONE(.init)))
+  } >flash AT>flash :flash
+
+  .text           :
+  {
+    *(.text.unlikely .text.unlikely.*)
+    *(.text.startup .text.startup.*)
+    *(.text .text.*)
+    *(.gnu.linkonce.t.*)
+  } >flash AT>flash :flash
+
+  .fini           :
+  {
+    KEEP (*(SORT_NONE(.fini)))
+  } >flash AT>flash :flash
+
+  PROVIDE (__etext = .);
+  PROVIDE (_etext = .);
+  PROVIDE (etext = .);
+
+  .rodata         :
+  {
+    *(.rdata)
+    *(.rodata .rodata.*)
+    *(.gnu.linkonce.r.*)
+  } >flash AT>flash :flash
+
+  . = ALIGN(4);
+
+  .preinit_array  :
+  {
+    PROVIDE_HIDDEN (__preinit_array_start = .);
+    KEEP (*(.preinit_array))
+    PROVIDE_HIDDEN (__preinit_array_end = .);
+  } >flash AT>flash :flash
+
+  .init_array     :
+  {
+    PROVIDE_HIDDEN (__init_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
+    KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors))
+    PROVIDE_HIDDEN (__init_array_end = .);
+  } >flash AT>flash :flash
+
+  .fini_array     :
+  {
+    PROVIDE_HIDDEN (__fini_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
+    KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors))
+    PROVIDE_HIDDEN (__fini_array_end = .);
+  } >flash AT>flash :flash
+
+  .ctors          :
+  {
+    /* gcc uses crtbegin.o to find the start of
+       the constructors, so we make sure it is
+       first.  Because this is a wildcard, it
+       doesn't matter if the user does not
+       actually link against crtbegin.o; the
+       linker won't look for a file to match a
+       wildcard.  The wildcard also means that it
+       doesn't matter which directory crtbegin.o
+       is in.  */
+    KEEP (*crtbegin.o(.ctors))
+    KEEP (*crtbegin?.o(.ctors))
+    /* We don't want to include the .ctor section from
+       the crtend.o file until after the sorted ctors.
+       The .ctor section from the crtend file contains the
+       end of ctors marker and it must be last */
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+  } >flash AT>flash :flash
+
+  .dtors          :
+  {
+    KEEP (*crtbegin.o(.dtors))
+    KEEP (*crtbegin?.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+  } >flash AT>flash :flash
+
+  .lalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data_lma = . );
+  } >flash AT>flash :flash
+
+  .dalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data = . );
+  } >ram AT>flash :ram_init
+
+  .data          :
+  {
+    *(.data .data.*)
+    *(.gnu.linkonce.d.*)
+  } >ram AT>flash :ram_init
+
+  .srodata        :
+  {
+    PROVIDE( _gp = . + 0x800 );
+    *(.srodata.cst16)
+    *(.srodata.cst8)
+    *(.srodata.cst4)
+    *(.srodata.cst2)
+    *(.srodata .srodata.*)
+  } >ram AT>flash :ram_init
+
+  .sdata          :
+  {
+    *(.sdata .sdata.*)
+    *(.gnu.linkonce.s.*)
+  } >ram AT>flash :ram_init
+
+  . = ALIGN(4);
+  PROVIDE( _edata = . );
+  PROVIDE( edata = . );
+
+  PROVIDE( _fbss = . );
+  PROVIDE( __bss_start = . );
+  .bss            :
+  {
+    *(.sbss*)
+    *(.gnu.linkonce.sb.*)
+    *(.bss .bss.*)
+    *(.gnu.linkonce.b.*)
+    *(COMMON)
+    . = ALIGN(4);
+  } >ram AT>ram :ram
+
+  . = ALIGN(8);
+  PROVIDE( _end = . );
+  PROVIDE( end = . );
+
+  .stack ORIGIN(ram) + LENGTH(ram) - __stack_size :
+  {
+    PROVIDE( _heap_end = . );
+    . = __stack_size;
+    PROVIDE( _sp = . );
+  } >ram AT>ram :ram
+}
--- a/hello-world/bsp/env/freedom-e300-hifive1/openocd.cfg
+++ b/hello-world/bsp/env/freedom-e300-hifive1/openocd.cfg
@ -0,0 +1,34 @@
+adapter_khz     10000
+
+interface ftdi
+ftdi_device_desc "Dual RS232-HS"
+ftdi_vid_pid 0x0403 0x6010
+
+ftdi_layout_init 0x0008 0x001b
+ftdi_layout_signal nSRST -oe 0x0020 -data 0x0020
+
+#Reset Stretcher logic on FE310 is ~1 second long
+#This doesn't apply if you use
+# ftdi_set_signal, but still good to document
+#adapter_nsrst_delay 1500
+
+set _CHIPNAME riscv
+jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x10e31913
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME riscv -chain-position $_TARGETNAME
+$_TARGETNAME configure -work-area-phys 0x80000000 -work-area-size 10000 -work-area-backup 1
+
+flash bank onboard_spi_flash fespi 0x20000000 0 0 0 $_TARGETNAME
+init
+#reset -- This type of reset is not implemented yet
+if {[ info exists pulse_srst]} {
+  ftdi_set_signal nSRST 0
+  ftdi_set_signal nSRST z
+  #Wait for the reset stretcher
+  #It will work without this, but
+  #will incur lots of delays for later commands.
+  sleep 1500
+}	
+halt
+#flash protect 0 64 last off
--- a/hello-world/bsp/env/freedom-e300-hifive1/platform.h
+++ b/hello-world/bsp/env/freedom-e300-hifive1/platform.h
@ -0,0 +1,133 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_PLATFORM_H
+#define _SIFIVE_PLATFORM_H
+
+// Some things missing from the official encoding.h
+#define MCAUSE_INT         0x80000000
+#define MCAUSE_CAUSE       0x7FFFFFFF
+
+#include "sifive/const.h"
+#include "sifive/devices/aon.h"
+#include "sifive/devices/clint.h"
+#include "sifive/devices/gpio.h"
+#include "sifive/devices/otp.h"
+#include "sifive/devices/plic.h"
+#include "sifive/devices/prci.h"
+#include "sifive/devices/pwm.h"
+#include "sifive/devices/spi.h"
+#include "sifive/devices/uart.h"
+
+/****************************************************************************
+ * Platform definitions
+ *****************************************************************************/
+
+// Memory map
+#define MASKROM_BASE_ADDR _AC(0x00001000,UL)
+#define TRAPVEC_TABLE_BASE_ADDR _AC(0x00001010,UL)
+#define OTP_MMAP_ADDR _AC(0x00020000,UL)
+#define CLINT_BASE_ADDR _AC(0x02000000,UL)
+#define PLIC_BASE_ADDR _AC(0x0C000000,UL)
+#define AON_BASE_ADDR _AC(0x10000000,UL)
+#define PRCI_BASE_ADDR _AC(0x10008000,UL)
+#define OTP_BASE_ADDR _AC(0x10010000,UL)
+#define GPIO_BASE_ADDR _AC(0x10012000,UL)
+#define UART0_BASE_ADDR _AC(0x10013000,UL)
+#define SPI0_BASE_ADDR _AC(0x10014000,UL)
+#define PWM0_BASE_ADDR _AC(0x10015000,UL)
+#define UART1_BASE_ADDR _AC(0x10023000,UL)
+#define SPI1_BASE_ADDR _AC(0x10024000,UL)
+#define PWM1_BASE_ADDR _AC(0x10025000,UL)
+#define SPI2_BASE_ADDR _AC(0x10034000,UL)
+#define PWM2_BASE_ADDR _AC(0x10035000,UL)
+#define SPI0_MMAP_ADDR _AC(0x20000000,UL)
+#define MEM_BASE_ADDR _AC(0x80000000,UL)
+
+// IOF masks
+#define IOF0_SPI1_MASK          _AC(0x000007FC,UL)
+#define SPI11_NUM_SS     (4)
+#define IOF_SPI1_SS0          (2u)
+#define IOF_SPI1_SS1          (8u)
+#define IOF_SPI1_SS2          (9u)
+#define IOF_SPI1_SS3          (10u)
+#define IOF_SPI1_MOSI         (3u)
+#define IOF_SPI1_MISO         (4u)
+#define IOF_SPI1_SCK          (5u)
+#define IOF_SPI1_DQ0          (3u)
+#define IOF_SPI1_DQ1          (4u)
+#define IOF_SPI1_DQ2          (6u)
+#define IOF_SPI1_DQ3          (7u)
+
+#define IOF0_SPI2_MASK          _AC(0xFC000000,UL)
+#define SPI2_NUM_SS       (1)
+#define IOF_SPI2_SS0          (26u)
+#define IOF_SPI2_MOSI         (27u)
+#define IOF_SPI2_MISO         (28u)
+#define IOF_SPI2_SCK          (29u)
+#define IOF_SPI2_DQ0          (27u)
+#define IOF_SPI2_DQ1          (28u)
+#define IOF_SPI2_DQ2          (30u)
+#define IOF_SPI2_DQ3          (31u)
+
+//#define IOF0_I2C_MASK          _AC(0x00003000,UL)
+
+#define IOF0_UART0_MASK         _AC(0x00030000, UL)
+#define IOF_UART0_RX   (16u)
+#define IOF_UART0_TX   (17u)
+
+#define IOF0_UART1_MASK         _AC(0x03000000, UL)
+#define IOF_UART1_RX (24u)
+#define IOF_UART1_TX (25u)
+
+#define IOF1_PWM0_MASK          _AC(0x0000000F, UL)
+#define IOF1_PWM1_MASK          _AC(0x00780000, UL)
+#define IOF1_PWM2_MASK          _AC(0x00003C00, UL)
+
+// Interrupt numbers
+#define INT_RESERVED 0
+#define INT_WDOGCMP 1
+#define INT_RTCCMP 2
+#define INT_UART0_BASE 3
+#define INT_UART1_BASE 4
+#define INT_SPI0_BASE 5
+#define INT_SPI1_BASE 6
+#define INT_SPI2_BASE 7
+#define INT_GPIO_BASE 8
+#define INT_PWM0_BASE 40
+#define INT_PWM1_BASE 44
+#define INT_PWM2_BASE 48
+
+// Helper functions
+#define _REG32(p, i) (*(volatile uint32_t *) ((p) + (i)))
+#define _REG32P(p, i) ((volatile uint32_t *) ((p) + (i)))
+#define AON_REG(offset) _REG32(AON_BASE_ADDR, offset)
+#define CLINT_REG(offset) _REG32(CLINT_BASE_ADDR, offset)
+#define GPIO_REG(offset) _REG32(GPIO_BASE_ADDR, offset)
+#define OTP_REG(offset)  _REG32(OTP_BASE_ADDR, offset)
+#define PLIC_REG(offset) _REG32(PLIC_BASE_ADDR, offset)
+#define PRCI_REG(offset) _REG32(PRCI_BASE_ADDR, offset)
+#define PWM0_REG(offset) _REG32(PWM0_BASE_ADDR, offset)
+#define PWM1_REG(offset) _REG32(PWM1_BASE_ADDR, offset)
+#define PWM2_REG(offset) _REG32(PWM2_BASE_ADDR, offset)
+#define SPI0_REG(offset) _REG32(SPI0_BASE_ADDR, offset)
+#define SPI1_REG(offset) _REG32(SPI1_BASE_ADDR, offset)
+#define SPI2_REG(offset) _REG32(SPI2_BASE_ADDR, offset)
+#define UART0_REG(offset) _REG32(UART0_BASE_ADDR, offset)
+#define UART1_REG(offset) _REG32(UART1_BASE_ADDR, offset)
+
+// Misc
+
+#include <stdint.h>
+
+#define NUM_GPIO 32
+
+#define PLIC_NUM_INTERRUPTS 52
+#define PLIC_NUM_PRIORITIES 7
+
+#include "hifive1.h"
+
+unsigned long get_cpu_freq(void);
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
+#endif /* _SIFIVE_PLATFORM_H */
--- a/hello-world/bsp/env/hifive1.h
+++ b/hello-world/bsp/env/hifive1.h
@ -0,0 +1,81 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_HIFIVE1_H
+#define _SIFIVE_HIFIVE1_H
+
+#include <stdint.h>
+
+/****************************************************************************
+ * GPIO Connections
+ *****************************************************************************/
+
+// These are the GPIO bit offsets for the RGB LED on HiFive1 Board.
+// These are also mapped to RGB LEDs on the Freedom E300 Arty
+// FPGA
+// Dev Kit.
+
+#define RED_LED_OFFSET   22
+#define GREEN_LED_OFFSET 19
+#define BLUE_LED_OFFSET  21
+
+// These are the GPIO bit offsets for the differen digital pins
+// on the headers for both the HiFive1 Board and the Freedom E300 Arty FPGA Dev Kit.
+#define PIN_0_OFFSET 16
+#define PIN_1_OFFSET 17
+#define PIN_2_OFFSET 18
+#define PIN_3_OFFSET 19
+#define PIN_4_OFFSET 20
+#define PIN_5_OFFSET 21
+#define PIN_6_OFFSET 22
+#define PIN_7_OFFSET 23
+#define PIN_8_OFFSET 0
+#define PIN_9_OFFSET 1
+#define PIN_10_OFFSET 2
+#define PIN_11_OFFSET 3
+#define PIN_12_OFFSET 4
+#define PIN_13_OFFSET 5
+//#define PIN_14_OFFSET 8 //This pin is not connected on either board.
+#define PIN_15_OFFSET 9
+#define PIN_16_OFFSET 10
+#define PIN_17_OFFSET 11
+#define PIN_18_OFFSET 12
+#define PIN_19_OFFSET 13
+
+// These are *PIN* numbers, not
+// GPIO Offset Numbers.
+#define PIN_SPI1_SCK    (13u)
+#define PIN_SPI1_MISO   (12u)
+#define PIN_SPI1_MOSI   (11u)
+#define PIN_SPI1_SS0    (10u)
+#define PIN_SPI1_SS1    (14u) 
+#define PIN_SPI1_SS2    (15u)
+#define PIN_SPI1_SS3    (16u)
+
+#define SS_PIN_TO_CS_ID(x) \
+  ((x==PIN_SPI1_SS0 ? 0 :		 \
+    (x==PIN_SPI1_SS1 ? 1 :		 \
+     (x==PIN_SPI1_SS2 ? 2 :		 \
+      (x==PIN_SPI1_SS3 ? 3 :		 \
+       -1))))) 
+
+
+// These buttons are present only on the Freedom E300 Arty Dev Kit.
+#ifdef HAS_BOARD_BUTTONS
+#define BUTTON_0_OFFSET 15
+#define BUTTON_1_OFFSET 30
+#define BUTTON_2_OFFSET 31
+
+#define INT_DEVICE_BUTTON_0 (INT_GPIO_BASE + BUTTON_0_OFFSET)
+#define INT_DEVICE_BUTTON_1 (INT_GPIO_BASE + BUTTON_1_OFFSET)
+#define INT_DEVICE_BUTTON_2 (INT_GPIO_BASE + BUTTON_2_OFFSET)
+
+#endif
+
+#define HAS_HFXOSC 1
+#define HAS_LFROSC_BYPASS 1
+
+#define RTC_FREQ 32768
+
+void write_hex(int fd, uint32_t hex);
+
+#endif /* _SIFIVE_HIFIVE1_H */
--- a/hello-world/bsp/env/iss/init.c
+++ b/hello-world/bsp/env/iss/init.c
@ -0,0 +1,238 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "platform.h"
+#include "encoding.h"
+
+extern int main(int argc, char** argv);
+extern void trap_entry();
+
+static unsigned long mtime_lo(void)
+{
+  return *(volatile unsigned long *)(CLINT_BASE_ADDR + CLINT_MTIME);
+}
+
+#ifdef __riscv32
+
+static uint32_t mtime_hi(void)
+{
+  return *(volatile uint32_t *)(CLINT_BASE_ADDR + CLINT_MTIME + 4);
+}
+
+uint64_t get_timer_value()
+{
+  while (1) {
+    uint32_t hi = mtime_hi();
+    uint32_t lo = mtime_lo();
+    if (hi == mtime_hi())
+      return ((uint64_t)hi << 32) | lo;
+  }
+}
+
+#else /* __riscv32 */
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
+{
+  return 32768;
+}
+
+static void use_hfrosc(int div, int trim)
+{
+  // Make sure the HFROSC is running at its default setting
+  PRCI_REG(PRCI_HFROSCCFG) = (ROSC_DIV(div) | ROSC_TRIM(trim) | ROSC_EN(1));
+  while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0) ;
+  PRCI_REG(PRCI_PLLCFG) &= ~PLL_SEL(1);
+}
+
+static void use_pll(int refsel, int bypass, int r, int f, int q)
+{
+  // Ensure that we aren't running off the PLL before we mess with it.
+  if (PRCI_REG(PRCI_PLLCFG) & PLL_SEL(1)) {
+    // Make sure the HFROSC is running at its default setting
+    use_hfrosc(4, 16);
+  }
+
+  // Set PLL Source to be HFXOSC if available.
+  uint32_t config_value = 0;
+
+  config_value |= PLL_REFSEL(refsel);
+
+  if (bypass) {
+    // Bypass
+    config_value |= PLL_BYPASS(1);
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // If we don't have an HFXTAL, this doesn't really matter.
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+  } else {
+    // In case we are executing from QSPI,
+    // (which is quite likely) we need to
+    // set the QSPI clock divider appropriately
+    // before boosting the clock frequency.
+
+    // Div = f_sck/2
+    SPI0_REG(SPI_REG_SCKDIV) = 8;
+
+    // Set DIV Settings for PLL
+    // Both HFROSC and HFXOSC are modeled as ideal
+    // 16MHz sources (assuming dividers are set properly for
+    // HFROSC).
+    // (Legal values of f_REF are 6-48MHz)
+
+    // Set DIVR to divide-by-2 to get 8MHz frequency
+    // (legal values of f_R are 6-12 MHz)
+
+    config_value |= PLL_BYPASS(1);
+    config_value |= PLL_R(r);
+
+    // Set DIVF to get 512Mhz frequncy
+    // There is an implied multiply-by-2, 16Mhz.
+    // So need to write 32-1
+    // (legal values of f_F are 384-768 MHz)
+    config_value |= PLL_F(f);
+
+    // Set DIVQ to divide-by-2 to get 256 MHz frequency
+    // (legal values of f_Q are 50-400Mhz)
+    config_value |= PLL_Q(q);
+
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // Un-Bypass the PLL.
+    PRCI_REG(PRCI_PLLCFG) &= ~PLL_BYPASS(1);
+
+    // Wait for PLL Lock
+    // Note that the Lock signal can be glitchy.
+    // Need to wait 100 us
+    // RTC is running at 32kHz.
+    // So wait 4 ticks of RTC.
+    uint32_t now = mtime_lo();
+    while (mtime_lo() - now < 4) ;
+
+    // Now it is safe to check for PLL Lock
+    while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0) ;
+  }
+
+  // Switch over to PLL Clock source
+  PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
+}
+
+static void use_default_clocks()
+{
+  // Turn off the LFROSC
+  AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
+
+  // Use HFROSC
+  use_hfrosc(4, 16);
+}
+
+static unsigned long __attribute__((noinline)) measure_cpu_freq(size_t n)
+{
+  unsigned long start_mtime, delta_mtime;
+  unsigned long mtime_freq = get_timer_freq();
+
+  // Don't start measuruing until we see an mtime tick
+  unsigned long tmp = mtime_lo();
+  do {
+    start_mtime = mtime_lo();
+  } while (start_mtime == tmp);
+
+  unsigned long start_mcycle = read_csr(mcycle);
+
+  do {
+    delta_mtime = mtime_lo() - start_mtime;
+  } while (delta_mtime < n);
+
+  unsigned long delta_mcycle = read_csr(mcycle) - start_mcycle;
+
+  return (delta_mcycle / delta_mtime) * mtime_freq
+         + ((delta_mcycle % delta_mtime) * mtime_freq) / delta_mtime;
+}
+
+unsigned long get_cpu_freq()
+{
+  static uint32_t cpu_freq;
+
+  if (!cpu_freq) {
+    // warm up I$
+    measure_cpu_freq(1);
+    // measure for real
+    cpu_freq = measure_cpu_freq(10);
+  }
+
+  return cpu_freq;
+}
+
+static void uart_init(size_t baud_rate)
+{
+  GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
+  GPIO_REG(GPIO_IOF_EN) |= IOF0_UART0_MASK;
+  UART0_REG(UART_REG_DIV) = get_cpu_freq() / baud_rate - 1;
+  UART0_REG(UART_REG_TXCTRL) |= UART_TXEN;
+}
+
+
+
+#ifdef USE_PLIC
+extern void handle_m_ext_interrupt();
+#endif
+
+#ifdef USE_M_TIME
+extern void handle_m_time_interrupt();
+#endif
+
+uintptr_t handle_trap(uintptr_t mcause, uintptr_t epc)
+{
+  if (0){
+#ifdef USE_PLIC
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
+    handle_m_ext_interrupt();
+#endif
+#ifdef USE_M_TIME
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
+    handle_m_time_interrupt();
+#endif
+  }
+  else {
+    write(1, "trap\n", 5);
+    _exit(1 + mcause);
+  }
+  return epc;
+}
+
+void _init()
+{
+  
+  #ifndef NO_INIT
+  use_default_clocks();
+  use_pll(0, 0, 1, 31, 1);
+  uart_init(115200);
+
+  printf("core freq at %d Hz\n", get_cpu_freq());
+
+  write_csr(mtvec, &trap_entry);
+  if (read_csr(misa) & (1 << ('F' - 'A'))) { // if F extension is present
+    write_csr(mstatus, MSTATUS_FS); // allow FPU instructions without trapping
+    write_csr(fcsr, 0); // initialize rounding mode, undefined at reset
+  }
+  #endif
+  
+}
+
+void _fini()
+{
+}
--- a/hello-world/bsp/env/iss/link.lds
+++ b/hello-world/bsp/env/iss/link.lds
@ -0,0 +1,168 @@
+OUTPUT_ARCH( "riscv" )
+
+ENTRY( _start )
+
+MEMORY
+{
+  /*flash (rxai!w) : ORIGIN = 0x00000000, LENGTH = 1M*/
+  flash (rxai!w) : ORIGIN = 0x20400000, LENGTH = 512M
+  ram (wxa!ri) :   ORIGIN = 0x80000000, LENGTH = 16K
+}
+
+PHDRS
+{
+  flash PT_LOAD;
+  ram_init PT_LOAD;
+  ram PT_NULL;
+}
+
+SECTIONS
+{
+  __stack_size = DEFINED(__stack_size) ? __stack_size : 2K;
+
+  .init           :
+  {
+    KEEP (*(SORT_NONE(.init)))
+  } >flash AT>flash :flash
+
+  .text           :
+  {
+    *(.text.unlikely .text.unlikely.*)
+    *(.text.startup .text.startup.*)
+    *(.text .text.*)
+    *(.gnu.linkonce.t.*)
+  } >flash AT>flash :flash
+
+  .fini           :
+  {
+    KEEP (*(SORT_NONE(.fini)))
+  } >flash AT>flash :flash
+
+  PROVIDE (__etext = .);
+  PROVIDE (_etext = .);
+  PROVIDE (etext = .);
+
+  .rodata         :
+  {
+    *(.rdata)
+    *(.rodata .rodata.*)
+    *(.gnu.linkonce.r.*)
+  } >flash AT>flash :flash
+
+  . = ALIGN(4);
+
+  .preinit_array  :
+  {
+    PROVIDE_HIDDEN (__preinit_array_start = .);
+    KEEP (*(.preinit_array))
+    PROVIDE_HIDDEN (__preinit_array_end = .);
+  } >flash AT>flash :flash
+
+  .init_array     :
+  {
+    PROVIDE_HIDDEN (__init_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
+    KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors))
+    PROVIDE_HIDDEN (__init_array_end = .);
+  } >flash AT>flash :flash
+
+  .fini_array     :
+  {
+    PROVIDE_HIDDEN (__fini_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
+    KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors))
+    PROVIDE_HIDDEN (__fini_array_end = .);
+  } >flash AT>flash :flash
+
+  .ctors          :
+  {
+    /* gcc uses crtbegin.o to find the start of
+       the constructors, so we make sure it is
+       first.  Because this is a wildcard, it
+       doesn't matter if the user does not
+       actually link against crtbegin.o; the
+       linker won't look for a file to match a
+       wildcard.  The wildcard also means that it
+       doesn't matter which directory crtbegin.o
+       is in.  */
+    KEEP (*crtbegin.o(.ctors))
+    KEEP (*crtbegin?.o(.ctors))
+    /* We don't want to include the .ctor section from
+       the crtend.o file until after the sorted ctors.
+       The .ctor section from the crtend file contains the
+       end of ctors marker and it must be last */
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+  } >flash AT>flash :flash
+
+  .dtors          :
+  {
+    KEEP (*crtbegin.o(.dtors))
+    KEEP (*crtbegin?.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+  } >flash AT>flash :flash
+
+  .lalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data_lma = . );
+  } >flash AT>flash :flash
+
+  .dalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data = . );
+  } >ram AT>flash :ram_init
+
+  .data          :
+  {
+    *(.data .data.*)
+    *(.gnu.linkonce.d.*)
+  } >ram AT>flash :ram_init
+
+  .srodata        :
+  {
+    PROVIDE( _gp = . + 0x800 );
+    *(.srodata.cst16)
+    *(.srodata.cst8)
+    *(.srodata.cst4)
+    *(.srodata.cst2)
+    *(.srodata .srodata.*)
+  } >ram AT>flash :ram_init
+
+  .sdata          :
+  {
+    *(.sdata .sdata.*)
+    *(.gnu.linkonce.s.*)
+  } >ram AT>flash :ram_init
+
+  . = ALIGN(4);
+  PROVIDE( _edata = . );
+  PROVIDE( edata = . );
+
+  PROVIDE( _fbss = . );
+  PROVIDE( __bss_start = . );
+  .bss            :
+  {
+    *(.sbss*)
+    *(.gnu.linkonce.sb.*)
+    *(.bss .bss.*)
+    *(.gnu.linkonce.b.*)
+    *(COMMON)
+    . = ALIGN(4);
+  } >ram AT>ram :ram
+
+  . = ALIGN(8);
+  PROVIDE( _end = . );
+  PROVIDE( end = . );
+
+  .stack ORIGIN(ram) + LENGTH(ram) - __stack_size :
+  {
+    PROVIDE( _heap_end = . );
+    . = __stack_size;
+    PROVIDE( _sp = . );
+  } >ram AT>ram :ram
+}
--- a/hello-world/bsp/env/iss/openocd.cfg
+++ b/hello-world/bsp/env/iss/openocd.cfg
@ -0,0 +1,34 @@
+adapter_khz     10000
+
+interface ftdi
+ftdi_device_desc "Dual RS232-HS"
+ftdi_vid_pid 0x0403 0x6010
+
+ftdi_layout_init 0x0008 0x001b
+ftdi_layout_signal nSRST -oe 0x0020 -data 0x0020
+
+#Reset Stretcher logic on FE310 is ~1 second long
+#This doesn't apply if you use
+# ftdi_set_signal, but still good to document
+#adapter_nsrst_delay 1500
+
+set _CHIPNAME riscv
+jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x10e31913
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME riscv -chain-position $_TARGETNAME
+$_TARGETNAME configure -work-area-phys 0x80000000 -work-area-size 10000 -work-area-backup 1
+
+flash bank onboard_spi_flash fespi 0x20000000 0 0 0 $_TARGETNAME
+init
+#reset -- This type of reset is not implemented yet
+if {[ info exists pulse_srst]} {
+  ftdi_set_signal nSRST 0
+  ftdi_set_signal nSRST z
+  #Wait for the reset stretcher
+  #It will work without this, but
+  #will incur lots of delays for later commands.
+  sleep 1500
+}	
+halt
+#flash protect 0 64 last off
--- a/hello-world/bsp/env/iss/platform.h
+++ b/hello-world/bsp/env/iss/platform.h
@ -0,0 +1,133 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_PLATFORM_H
+#define _SIFIVE_PLATFORM_H
+
+// Some things missing from the official encoding.h
+#define MCAUSE_INT         0x80000000
+#define MCAUSE_CAUSE       0x7FFFFFFF
+
+#include "sifive/const.h"
+#include "sifive/devices/aon.h"
+#include "sifive/devices/clint.h"
+#include "sifive/devices/gpio.h"
+#include "sifive/devices/otp.h"
+#include "sifive/devices/plic.h"
+#include "sifive/devices/prci.h"
+#include "sifive/devices/pwm.h"
+#include "sifive/devices/spi.h"
+#include "sifive/devices/uart.h"
+
+/****************************************************************************
+ * Platform definitions
+ *****************************************************************************/
+
+// Memory map
+#define MASKROM_BASE_ADDR _AC(0x00001000,UL)
+#define TRAPVEC_TABLE_BASE_ADDR _AC(0x00001010,UL)
+#define OTP_MMAP_ADDR _AC(0x00020000,UL)
+#define CLINT_BASE_ADDR _AC(0x02000000,UL)
+#define PLIC_BASE_ADDR _AC(0x0C000000,UL)
+#define AON_BASE_ADDR _AC(0x10000000,UL)
+#define PRCI_BASE_ADDR _AC(0x10008000,UL)
+#define OTP_BASE_ADDR _AC(0x10010000,UL)
+#define GPIO_BASE_ADDR _AC(0x10012000,UL)
+#define UART0_BASE_ADDR _AC(0x10013000,UL)
+#define SPI0_BASE_ADDR _AC(0x10014000,UL)
+#define PWM0_BASE_ADDR _AC(0x10015000,UL)
+#define UART1_BASE_ADDR _AC(0x10023000,UL)
+#define SPI1_BASE_ADDR _AC(0x10024000,UL)
+#define PWM1_BASE_ADDR _AC(0x10025000,UL)
+#define SPI2_BASE_ADDR _AC(0x10034000,UL)
+#define PWM2_BASE_ADDR _AC(0x10035000,UL)
+#define SPI0_MMAP_ADDR _AC(0x20000000,UL)
+#define MEM_BASE_ADDR _AC(0x80000000,UL)
+
+// IOF masks
+#define IOF0_SPI1_MASK          _AC(0x000007FC,UL)
+#define SPI11_NUM_SS     (4)
+#define IOF_SPI1_SS0          (2u)
+#define IOF_SPI1_SS1          (8u)
+#define IOF_SPI1_SS2          (9u)
+#define IOF_SPI1_SS3          (10u)
+#define IOF_SPI1_MOSI         (3u)
+#define IOF_SPI1_MISO         (4u)
+#define IOF_SPI1_SCK          (5u)
+#define IOF_SPI1_DQ0          (3u)
+#define IOF_SPI1_DQ1          (4u)
+#define IOF_SPI1_DQ2          (6u)
+#define IOF_SPI1_DQ3          (7u)
+
+#define IOF0_SPI2_MASK          _AC(0xFC000000,UL)
+#define SPI2_NUM_SS       (1)
+#define IOF_SPI2_SS0          (26u)
+#define IOF_SPI2_MOSI         (27u)
+#define IOF_SPI2_MISO         (28u)
+#define IOF_SPI2_SCK          (29u)
+#define IOF_SPI2_DQ0          (27u)
+#define IOF_SPI2_DQ1          (28u)
+#define IOF_SPI2_DQ2          (30u)
+#define IOF_SPI2_DQ3          (31u)
+
+//#define IOF0_I2C_MASK          _AC(0x00003000,UL)
+
+#define IOF0_UART0_MASK         _AC(0x00030000, UL)
+#define IOF_UART0_RX   (16u)
+#define IOF_UART0_TX   (17u)
+
+#define IOF0_UART1_MASK         _AC(0x03000000, UL)
+#define IOF_UART1_RX (24u)
+#define IOF_UART1_TX (25u)
+
+#define IOF1_PWM0_MASK          _AC(0x0000000F, UL)
+#define IOF1_PWM1_MASK          _AC(0x00780000, UL)
+#define IOF1_PWM2_MASK          _AC(0x00003C00, UL)
+
+// Interrupt numbers
+#define INT_RESERVED 0
+#define INT_WDOGCMP 1
+#define INT_RTCCMP 2
+#define INT_UART0_BASE 3
+#define INT_UART1_BASE 4
+#define INT_SPI0_BASE 5
+#define INT_SPI1_BASE 6
+#define INT_SPI2_BASE 7
+#define INT_GPIO_BASE 8
+#define INT_PWM0_BASE 40
+#define INT_PWM1_BASE 44
+#define INT_PWM2_BASE 48
+
+// Helper functions
+#define _REG32(p, i) (*(volatile uint32_t *) ((p) + (i)))
+#define _REG32P(p, i) ((volatile uint32_t *) ((p) + (i)))
+#define AON_REG(offset) _REG32(AON_BASE_ADDR, offset)
+#define CLINT_REG(offset) _REG32(CLINT_BASE_ADDR, offset)
+#define GPIO_REG(offset) _REG32(GPIO_BASE_ADDR, offset)
+#define OTP_REG(offset)  _REG32(OTP_BASE_ADDR, offset)
+#define PLIC_REG(offset) _REG32(PLIC_BASE_ADDR, offset)
+#define PRCI_REG(offset) _REG32(PRCI_BASE_ADDR, offset)
+#define PWM0_REG(offset) _REG32(PWM0_BASE_ADDR, offset)
+#define PWM1_REG(offset) _REG32(PWM1_BASE_ADDR, offset)
+#define PWM2_REG(offset) _REG32(PWM2_BASE_ADDR, offset)
+#define SPI0_REG(offset) _REG32(SPI0_BASE_ADDR, offset)
+#define SPI1_REG(offset) _REG32(SPI1_BASE_ADDR, offset)
+#define SPI2_REG(offset) _REG32(SPI2_BASE_ADDR, offset)
+#define UART0_REG(offset) _REG32(UART0_BASE_ADDR, offset)
+#define UART1_REG(offset) _REG32(UART1_BASE_ADDR, offset)
+
+// Misc
+
+#include <stdint.h>
+
+#define NUM_GPIO 32
+
+#define PLIC_NUM_INTERRUPTS 52
+#define PLIC_NUM_PRIORITIES 7
+
+#include "hifive1.h"
+
+unsigned long get_cpu_freq(void);
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
+#endif /* _SIFIVE_PLATFORM_H */
--- a/hello-world/bsp/env/start.S
+++ b/hello-world/bsp/env/start.S
@ -0,0 +1,54 @@
+// See LICENSE for license details.
+
+	.section .init
+	.globl _start
+	.type _start,@function
+
+_start:
+	la gp, _gp
+	la sp, _sp
+
+	/* Load data section */
+	la a0, _data_lma
+	la a1, _data
+	la a2, _edata
+	bgeu a1, a2, 2f
+1:
+	lw t0, (a0)
+	sw t0, (a1)
+	addi a0, a0, 4
+	addi a1, a1, 4
+	bltu a1, a2, 1b
+2:
+
+	/* Clear bss section */
+	la a0, __bss_start
+	la a1, _end
+	bgeu a0, a1, 2f
+1:
+	sw zero, (a0)
+	addi a0, a0, 4
+	bltu a0, a1, 1b
+2:
+
+	/* Call global constructors */
+	la a0, __libc_fini_array
+	call atexit
+	call __libc_init_array
+
+#ifndef __riscv_float_abi_soft
+	/* Enable FPU */
+	li t0, MSTATUS_FS
+	csrs mstatus, t0
+	csrr t1, mstatus
+	and t1, t1, t0
+	beqz t1, 1f
+	fssr x0
+1:
+#endif
+
+	/* argc = argv = 0 */
+	li a0, 0
+	li a1, 0
+	call main
+	tail exit
--- a/hello-world/bsp/include/sifive/bits.h
+++ b/hello-world/bsp/include/sifive/bits.h
@ -0,0 +1,35 @@
+#ifndef _RISCV_BITS_H
+#define _RISCV_BITS_H
+
+#define likely(x) __builtin_expect((x), 1)
+#define unlikely(x) __builtin_expect((x), 0)
+
+#define ROUNDUP(a, b) ((((a)-1)/(b)+1)*(b))
+#define ROUNDDOWN(a, b) ((a)/(b)*(b))
+
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define CLAMP(a, lo, hi) MIN(MAX(a, lo), hi)
+
+#define EXTRACT_FIELD(val, which) (((val) & (which)) / ((which) & ~((which)-1)))
+#define INSERT_FIELD(val, which, fieldval) (((val) & ~(which)) | ((fieldval) * ((which) & ~((which)-1))))
+
+#define STR(x) XSTR(x)
+#define XSTR(x) #x
+
+#ifdef __riscv64
+# define SLL32    sllw
+# define STORE    sd
+# define LOAD     ld
+# define LWU      lwu
+# define LOG_REGBYTES 3
+#else
+# define SLL32    sll
+# define STORE    sw
+# define LOAD     lw
+# define LWU      lw
+# define LOG_REGBYTES 2
+#endif
+#define REGBYTES (1 << LOG_REGBYTES)
+
+#endif
--- a/hello-world/bsp/include/sifive/const.h
+++ b/hello-world/bsp/include/sifive/const.h
@ -0,0 +1,17 @@
+/* Derived from <linux/const.h> */
+
+#ifndef _SIFIVE_CONST_H
+#define _SIFIVE_CONST_H
+
+#ifdef __ASSEMBLER__
+#define _AC(X,Y)        X
+#define _AT(T,X)        X
+#else
+#define _AC(X,Y)        (X##Y)
+#define _AT(T,X)        ((T)(X))
+#endif /* !__ASSEMBLER__*/
+
+#define _BITUL(x)       (_AC(1,UL) << (x))
+#define _BITULL(x)      (_AC(1,ULL) << (x))
+
+#endif /* _SIFIVE_CONST_H */
--- a/hello-world/bsp/include/sifive/devices/aon.h
+++ b/hello-world/bsp/include/sifive/devices/aon.h
@ -0,0 +1,88 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_AON_H
+#define _SIFIVE_AON_H
+
+/* Register offsets */
+
+#define AON_WDOGCFG     0x000
+#define AON_WDOGCOUNT   0x008
+#define AON_WDOGS       0x010
+#define AON_WDOGFEED    0x018
+#define AON_WDOGKEY     0x01C
+#define AON_WDOGCMP     0x020
+
+#define AON_RTCCFG      0x040
+#define AON_RTCLO       0x048
+#define AON_RTCHI       0x04C
+#define AON_RTCS        0x050
+#define AON_RTCCMP      0x060
+
+#define AON_BACKUP0     0x080
+#define AON_BACKUP1     0x084
+#define AON_BACKUP2     0x088
+#define AON_BACKUP3     0x08C
+#define AON_BACKUP4     0x090
+#define AON_BACKUP5     0x094
+#define AON_BACKUP6     0x098
+#define AON_BACKUP7     0x09C
+#define AON_BACKUP8     0x0A0
+#define AON_BACKUP9     0x0A4
+#define AON_BACKUP10    0x0A8
+#define AON_BACKUP11    0x0AC
+#define AON_BACKUP12    0x0B0
+#define AON_BACKUP13    0x0B4
+#define AON_BACKUP14    0x0B8
+#define AON_BACKUP15    0x0BC
+
+#define AON_PMUWAKEUPI0 0x100
+#define AON_PMUWAKEUPI1 0x104
+#define AON_PMUWAKEUPI2 0x108
+#define AON_PMUWAKEUPI3 0x10C
+#define AON_PMUWAKEUPI4 0x110
+#define AON_PMUWAKEUPI5 0x114
+#define AON_PMUWAKEUPI6 0x118
+#define AON_PMUWAKEUPI7 0x11C
+#define AON_PMUSLEEPI0  0x120
+#define AON_PMUSLEEPI1  0x124
+#define AON_PMUSLEEPI2  0x128
+#define AON_PMUSLEEPI3  0x12C
+#define AON_PMUSLEEPI4  0x130
+#define AON_PMUSLEEPI5  0x134
+#define AON_PMUSLEEPI6  0x138
+#define AON_PMUSLEEPI7  0x13C
+#define AON_PMUIE       0x140
+#define AON_PMUCAUSE    0x144
+#define AON_PMUSLEEP    0x148
+#define AON_PMUKEY      0x14C
+
+#define AON_LFROSC      0x070
+/* Constants */
+
+#define AON_WDOGKEY_VALUE  0x51F15E
+#define AON_WDOGFEED_VALUE 0xD09F00D
+
+#define AON_WDOGCFG_SCALE       0x0000000F
+#define AON_WDOGCFG_RSTEN       0x00000100
+#define AON_WDOGCFG_ZEROCMP     0x00000200
+#define AON_WDOGCFG_ENALWAYS    0x00001000
+#define AON_WDOGCFG_ENCOREAWAKE 0x00002000
+#define AON_WDOGCFG_CMPIP       0x10000000
+
+#define AON_RTCCFG_SCALE     0x0000000F
+#define AON_RTCCFG_ENALWAYS  0x00001000
+#define AON_RTCCFG_CMPIP     0x10000000
+
+#define AON_WAKEUPCAUSE_RESET   0x00
+#define AON_WAKEUPCAUSE_RTC     0x01
+#define AON_WAKEUPCAUSE_DWAKEUP 0x02
+#define AON_WAKEUPCAUSE_AWAKEUP 0x03
+
+#define AON_RESETCAUSE_POWERON  0x0000
+#define AON_RESETCAUSE_EXTERNAL 0x0100
+#define AON_RESETCAUSE_WATCHDOG 0x0200
+
+#define AON_PMUCAUSE_WAKEUPCAUSE 0x00FF
+#define AON_PMUCAUSE_RESETCAUSE  0xFF00
+
+#endif /* _SIFIVE_AON_H */
--- a/hello-world/bsp/include/sifive/devices/clint.h
+++ b/hello-world/bsp/include/sifive/devices/clint.h
@ -0,0 +1,14 @@
+// See LICENSE for license details
+
+#ifndef _SIFIVE_CLINT_H
+#define _SIFIVE_CLINT_H
+
+
+#define CLINT_MSIP 0x0000
+#define CLINT_MSIP_size   0x4
+#define CLINT_MTIMECMP 0x4000
+#define CLINT_MTIMECMP_size 0x8
+#define CLINT_MTIME 0xBFF8
+#define CLINT_MTIME_size 0x8
+
+#endif /* _SIFIVE_CLINT_H */ 
--- a/hello-world/bsp/include/sifive/devices/gpio.h
+++ b/hello-world/bsp/include/sifive/devices/gpio.h
@ -0,0 +1,24 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_GPIO_H
+#define _SIFIVE_GPIO_H
+
+#define GPIO_INPUT_VAL  (0x00)
+#define GPIO_INPUT_EN   (0x04)
+#define GPIO_OUTPUT_EN  (0x08)
+#define GPIO_OUTPUT_VAL (0x0C)
+#define GPIO_PULLUP_EN  (0x10)
+#define GPIO_DRIVE      (0x14)
+#define GPIO_RISE_IE    (0x18)
+#define GPIO_RISE_IP    (0x1C)
+#define GPIO_FALL_IE    (0x20)
+#define GPIO_FALL_IP    (0x24)
+#define GPIO_HIGH_IE    (0x28)
+#define GPIO_HIGH_IP    (0x2C)
+#define GPIO_LOW_IE     (0x30)
+#define GPIO_LOW_IP     (0x34)
+#define GPIO_IOF_EN     (0x38)
+#define GPIO_IOF_SEL    (0x3C)
+#define GPIO_OUTPUT_XOR    (0x40)
+
+#endif /* _SIFIVE_GPIO_H */
--- a/hello-world/bsp/include/sifive/devices/otp.h
+++ b/hello-world/bsp/include/sifive/devices/otp.h
@ -0,0 +1,23 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_OTP_H
+#define _SIFIVE_OTP_H
+
+/* Register offsets */
+
+#define OTP_LOCK         0x00
+#define OTP_CK           0x04
+#define OTP_OE           0x08
+#define OTP_SEL          0x0C
+#define OTP_WE           0x10
+#define OTP_MR           0x14
+#define OTP_MRR          0x18
+#define OTP_MPP          0x1C
+#define OTP_VRREN        0x20
+#define OTP_VPPEN        0x24
+#define OTP_A            0x28
+#define OTP_D            0x2C
+#define OTP_Q            0x30
+#define OTP_READ_TIMINGS 0x34
+
+#endif
--- a/hello-world/bsp/include/sifive/devices/plic.h
+++ b/hello-world/bsp/include/sifive/devices/plic.h
@ -0,0 +1,31 @@
+// See LICENSE for license details.
+
+#ifndef PLIC_H
+#define PLIC_H
+
+#include <sifive/const.h>
+
+// 32 bits per source
+#define PLIC_PRIORITY_OFFSET            _AC(0x0000,UL)
+#define PLIC_PRIORITY_SHIFT_PER_SOURCE  2
+// 1 bit per source (1 address)
+#define PLIC_PENDING_OFFSET             _AC(0x1000,UL)
+#define PLIC_PENDING_SHIFT_PER_SOURCE   0
+
+//0x80 per target
+#define PLIC_ENABLE_OFFSET              _AC(0x2000,UL)
+#define PLIC_ENABLE_SHIFT_PER_TARGET    7
+
+
+#define PLIC_THRESHOLD_OFFSET           _AC(0x200000,UL)
+#define PLIC_CLAIM_OFFSET               _AC(0x200004,UL)
+#define PLIC_THRESHOLD_SHIFT_PER_TARGET 12
+#define PLIC_CLAIM_SHIFT_PER_TARGET     12
+
+#define PLIC_MAX_SOURCE                 1023
+#define PLIC_SOURCE_MASK                0x3FF
+
+#define PLIC_MAX_TARGET                 15871
+#define PLIC_TARGET_MASK                0x3FFF
+
+#endif /* PLIC_H */
--- a/hello-world/bsp/include/sifive/devices/prci.h
+++ b/hello-world/bsp/include/sifive/devices/prci.h
@ -0,0 +1,56 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_PRCI_H
+#define _SIFIVE_PRCI_H
+
+/* Register offsets */
+
+#define PRCI_HFROSCCFG   (0x0000)
+#define PRCI_HFXOSCCFG   (0x0004)
+#define PRCI_PLLCFG      (0x0008)
+#define PRCI_PLLDIV      (0x000C)
+#define PRCI_PROCMONCFG  (0x00F0)
+
+/* Fields */
+#define ROSC_DIV(x)    (((x) & 0x2F) << 0 ) 
+#define ROSC_TRIM(x)   (((x) & 0x1F) << 16)
+#define ROSC_EN(x)     (((x) & 0x1 ) << 30) 
+#define ROSC_RDY(x)    (((x) & 0x1 ) << 31)
+
+#define XOSC_EN(x)     (((x) & 0x1) << 30)
+#define XOSC_RDY(x)    (((x) & 0x1) << 31)
+
+#define PLL_R(x)       (((x) & 0x7)  << 0)
+// single reserved bit for F LSB.
+#define PLL_F(x)       (((x) & 0x3F) << 4)
+#define PLL_Q(x)       (((x) & 0x3)  << 10)
+#define PLL_SEL(x)     (((x) & 0x1)  << 16)
+#define PLL_REFSEL(x)  (((x) & 0x1)  << 17)
+#define PLL_BYPASS(x)  (((x) & 0x1)  << 18)
+#define PLL_LOCK(x)    (((x) & 0x1)  << 31)
+
+#define PLL_R_default 0x1
+#define PLL_F_default 0x1F
+#define PLL_Q_default 0x3
+
+#define PLL_REFSEL_HFROSC 0x0
+#define PLL_REFSEL_HFXOSC 0x1
+
+#define PLL_SEL_HFROSC 0x0
+#define PLL_SEL_PLL    0x1
+
+#define PLL_FINAL_DIV(x)      (((x) & 0x3F) << 0)
+#define PLL_FINAL_DIV_BY_1(x) (((x) & 0x1 ) << 8)
+
+#define PROCMON_DIV(x)   (((x) & 0x1F) << 0)
+#define PROCMON_TRIM(x)  (((x) & 0x1F) << 8)
+#define PROCMON_EN(x)    (((x) & 0x1)  << 16)
+#define PROCMON_SEL(x)   (((x) & 0x3)  << 24)
+#define PROCMON_NT_EN(x) (((x) & 0x1)  << 28)
+
+#define PROCMON_SEL_HFCLK     0
+#define PROCMON_SEL_HFXOSCIN  1
+#define PROCMON_SEL_PLLOUTDIV 2
+#define PROCMON_SEL_PROCMON   3
+
+#endif // _SIFIVE_PRCI_H
--- a/hello-world/bsp/include/sifive/devices/pwm.h
+++ b/hello-world/bsp/include/sifive/devices/pwm.h
@ -0,0 +1,37 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_PWM_H
+#define _SIFIVE_PWM_H
+
+/* Register offsets */
+
+#define PWM_CFG   0x00
+#define PWM_COUNT 0x08
+#define PWM_S     0x10
+#define PWM_CMP0  0x20
+#define PWM_CMP1  0x24
+#define PWM_CMP2  0x28
+#define PWM_CMP3  0x2C
+
+/* Constants */
+
+#define PWM_CFG_SCALE       0x0000000F
+#define PWM_CFG_STICKY      0x00000100
+#define PWM_CFG_ZEROCMP     0x00000200
+#define PWM_CFG_DEGLITCH    0x00000400
+#define PWM_CFG_ENALWAYS    0x00001000
+#define PWM_CFG_ONESHOT     0x00002000
+#define PWM_CFG_CMP0CENTER  0x00010000
+#define PWM_CFG_CMP1CENTER  0x00020000
+#define PWM_CFG_CMP2CENTER  0x00040000
+#define PWM_CFG_CMP3CENTER  0x00080000
+#define PWM_CFG_CMP0GANG    0x01000000
+#define PWM_CFG_CMP1GANG    0x02000000
+#define PWM_CFG_CMP2GANG    0x04000000
+#define PWM_CFG_CMP3GANG    0x08000000
+#define PWM_CFG_CMP0IP      0x10000000
+#define PWM_CFG_CMP1IP      0x20000000
+#define PWM_CFG_CMP2IP      0x40000000
+#define PWM_CFG_CMP3IP      0x80000000
+
+#endif /* _SIFIVE_PWM_H */
--- a/hello-world/bsp/include/sifive/devices/spi.h
+++ b/hello-world/bsp/include/sifive/devices/spi.h
@ -0,0 +1,80 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_SPI_H
+#define _SIFIVE_SPI_H
+
+/* Register offsets */
+
+#define SPI_REG_SCKDIV          0x00
+#define SPI_REG_SCKMODE         0x04
+#define SPI_REG_CSID            0x10
+#define SPI_REG_CSDEF           0x14
+#define SPI_REG_CSMODE          0x18
+
+#define SPI_REG_DCSSCK          0x28
+#define SPI_REG_DSCKCS          0x2a
+#define SPI_REG_DINTERCS        0x2c
+#define SPI_REG_DINTERXFR       0x2e
+
+#define SPI_REG_FMT             0x40
+#define SPI_REG_TXFIFO          0x48
+#define SPI_REG_RXFIFO          0x4c
+#define SPI_REG_TXCTRL          0x50
+#define SPI_REG_RXCTRL          0x54
+
+#define SPI_REG_FCTRL           0x60
+#define SPI_REG_FFMT            0x64
+
+#define SPI_REG_IE              0x70
+#define SPI_REG_IP              0x74
+
+/* Fields */
+
+#define SPI_SCK_POL             0x1
+#define SPI_SCK_PHA             0x2
+
+#define SPI_FMT_PROTO(x)        ((x) & 0x3)
+#define SPI_FMT_ENDIAN(x)       (((x) & 0x1) << 2)
+#define SPI_FMT_DIR(x)          (((x) & 0x1) << 3)
+#define SPI_FMT_LEN(x)          (((x) & 0xf) << 16)
+
+/* TXCTRL register */
+#define SPI_TXWM(x)             ((x) & 0xffff)
+/* RXCTRL register */
+#define SPI_RXWM(x)             ((x) & 0xffff)
+
+#define SPI_IP_TXWM             0x1
+#define SPI_IP_RXWM             0x2
+
+#define SPI_FCTRL_EN            0x1
+
+#define SPI_INSN_CMD_EN         0x1
+#define SPI_INSN_ADDR_LEN(x)    (((x) & 0x7) << 1)
+#define SPI_INSN_PAD_CNT(x)     (((x) & 0xf) << 4)
+#define SPI_INSN_CMD_PROTO(x)   (((x) & 0x3) << 8)
+#define SPI_INSN_ADDR_PROTO(x)  (((x) & 0x3) << 10)
+#define SPI_INSN_DATA_PROTO(x)  (((x) & 0x3) << 12)
+#define SPI_INSN_CMD_CODE(x)    (((x) & 0xff) << 16)
+#define SPI_INSN_PAD_CODE(x)    (((x) & 0xff) << 24)
+
+#define SPI_TXFIFO_FULL  (1 << 31)   
+#define SPI_RXFIFO_EMPTY (1 << 31)   
+
+/* Values */
+
+#define SPI_CSMODE_AUTO         0
+#define SPI_CSMODE_HOLD         2
+#define SPI_CSMODE_OFF          3
+
+#define SPI_DIR_RX              0
+#define SPI_DIR_TX              1
+
+#define SPI_PROTO_S             0
+#define SPI_PROTO_D             1
+#define SPI_PROTO_Q             2
+
+#define SPI_ENDIAN_MSB          0
+#define SPI_ENDIAN_LSB          1
+
+
+#endif /* _SIFIVE_SPI_H */
--- a/hello-world/bsp/include/sifive/devices/uart.h
+++ b/hello-world/bsp/include/sifive/devices/uart.h
@ -0,0 +1,27 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_UART_H
+#define _SIFIVE_UART_H
+
+/* Register offsets */
+#define UART_REG_TXFIFO         0x00
+#define UART_REG_RXFIFO         0x04
+#define UART_REG_TXCTRL         0x08
+#define UART_REG_RXCTRL         0x0c
+#define UART_REG_IE             0x10
+#define UART_REG_IP             0x14
+#define UART_REG_DIV            0x18
+
+/* TXCTRL register */
+#define UART_TXEN               0x1
+#define UART_TXWM(x)            (((x) & 0xffff) << 16)
+
+/* RXCTRL register */
+#define UART_RXEN               0x1
+#define UART_RXWM(x)            (((x) & 0xffff) << 16)
+
+/* IP register */
+#define UART_IP_TXWM            0x1
+#define UART_IP_RXWM            0x2
+
+#endif /* _SIFIVE_UART_H */
--- a/hello-world/bsp/include/sifive/sections.h
+++ b/hello-world/bsp/include/sifive/sections.h
@ -0,0 +1,16 @@
+#ifndef _SECTIONS_H
+#define _SECTIONS_H
+
+extern unsigned char _rom[];
+extern unsigned char _rom_end[];
+
+extern unsigned char _ram[];
+extern unsigned char _ram_end[];
+
+extern unsigned char _ftext[];
+extern unsigned char _etext[];
+extern unsigned char _fbss[];
+extern unsigned char _ebss[];
+extern unsigned char _end[];
+
+#endif /* _SECTIONS_H */
--- a/hello-world/bsp/libwrap/libwrap.mk
+++ b/hello-world/bsp/libwrap/libwrap.mk
@ -0,0 +1,54 @@
+# See LICENSE for license details.
+
+ifndef _SIFIVE_MK_LIBWRAP
+_SIFIVE_MK_LIBWRAP := # defined
+
+LIBWRAP_DIR := $(dir $(lastword $(MAKEFILE_LIST)))
+LIBWRAP_DIR := $(LIBWRAP_DIR:/=)
+
+LIBWRAP_SRCS := \
+	stdlib/malloc.c \
+	sys/open.c \
+	sys/lseek.c \
+	sys/read.c \
+	sys/write.c \
+	sys/fstat.c \
+	sys/stat.c \
+	sys/close.c \
+	sys/link.c \
+	sys/unlink.c \
+	sys/execve.c \
+	sys/fork.c \
+	sys/getpid.c \
+	sys/kill.c \
+	sys/wait.c \
+	sys/isatty.c \
+	sys/times.c \
+	sys/sbrk.c \
+	sys/_exit.c \
+	misc/write_hex.c
+
+LIBWRAP_SRCS := $(foreach f,$(LIBWRAP_SRCS),$(LIBWRAP_DIR)/$(f))
+LIBWRAP_OBJS := $(LIBWRAP_SRCS:.c=.o)
+
+LIBWRAP_SYMS := malloc free \
+	open lseek read write fstat stat close link unlink \
+	execve fork getpid kill wait \
+	isatty times sbrk _exit
+
+LIBWRAP := libwrap.a
+
+LINK_DEPS += $(LIBWRAP)
+
+LDFLAGS += $(foreach s,$(LIBWRAP_SYMS),-Wl,--wrap=$(s))
+LDFLAGS += -L. -Wl,--start-group -lwrap -lc -Wl,--end-group
+
+CLEAN_OBJS += $(LIBWRAP_OBJS)
+
+$(LIBWRAP_OBJS): %.o: %.c $(HEADERS)
+	$(CC) $(CFLAGS) $(INCLUDES) -c -o $@ $<
+
+$(LIBWRAP): $(LIBWRAP_OBJS)
+	$(AR) rcs $@ $^
+
+endif # _SIFIVE_MK_LIBWRAP
--- a/hello-world/bsp/libwrap/misc/write_hex.c
+++ b/hello-world/bsp/libwrap/misc/write_hex.c
@ -0,0 +1,19 @@
+/* See LICENSE of license details. */
+
+#include <stdint.h>
+#include <unistd.h>
+#include "platform.h"
+
+void write_hex(int fd, uint32_t hex)
+{
+  uint8_t ii;
+  uint8_t jj;
+  char towrite;
+  write(fd , "0x", 2);
+  for (ii = 8 ; ii > 0; ii--) {
+    jj = ii - 1;
+    uint8_t digit = ((hex & (0xF << (jj*4))) >> (jj*4));
+    towrite = digit < 0xA ? ('0' + digit) : ('A' +  (digit - 0xA));
+    write(fd, &towrite, 1);
+  }
+}
--- a/hello-world/bsp/libwrap/stdlib/malloc.c
+++ b/hello-world/bsp/libwrap/stdlib/malloc.c
@ -0,0 +1,17 @@
+/* See LICENSE for license details. */
+
+/* These functions are intended for embedded RV32 systems and are
+   obviously incorrect in general. */
+
+void* __wrap_malloc(unsigned long sz)
+{
+  extern void* sbrk(long);
+  void* res = sbrk(sz);
+  if ((long)res == -1)
+    return 0;
+  return res;
+}
+
+void __wrap_free(void* ptr)
+{
+}
--- a/hello-world/bsp/libwrap/sys/_exit.c
+++ b/hello-world/bsp/libwrap/sys/_exit.c
@ -0,0 +1,17 @@
+/* See LICENSE of license details. */
+
+#include <unistd.h>
+#include "platform.h"
+
+void __wrap__exit(int code)
+{
+//volatile uint32_t* leds = (uint32_t*) (GPIO_BASE_ADDR + GPIO_OUT_OFFSET);
+  const char message[] = "\nProgam has exited with code:";
+//*leds = (~(code));
+
+  write(STDERR_FILENO, message, sizeof(message) - 1);
+  write_hex(STDERR_FILENO, code);
+  write(STDERR_FILENO, "\n", 1);
+
+  for (;;);
+}
--- a/hello-world/bsp/libwrap/sys/close.c
+++ b/hello-world/bsp/libwrap/sys/close.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_close(int fd)
+{
+  return _stub(EBADF);
+}
--- a/hello-world/bsp/libwrap/sys/execve.c
+++ b/hello-world/bsp/libwrap/sys/execve.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_execve(const char* name, char* const argv[], char* const env[])
+{
+  return _stub(ENOMEM);
+}
--- a/hello-world/bsp/libwrap/sys/fork.c
+++ b/hello-world/bsp/libwrap/sys/fork.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int fork(void)
+{
+  return _stub(EAGAIN);
+}
--- a/hello-world/bsp/libwrap/sys/fstat.c
+++ b/hello-world/bsp/libwrap/sys/fstat.c
@ -0,0 +1,16 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include "stub.h"
+
+int __wrap_fstat(int fd, struct stat* st)
+{
+  if (isatty(fd)) {
+    st->st_mode = S_IFCHR;
+    return 0;
+  }
+
+  return _stub(EBADF);
+}
--- a/hello-world/bsp/libwrap/sys/getpid.c
+++ b/hello-world/bsp/libwrap/sys/getpid.c
@ -0,0 +1,6 @@
+/* See LICENSE of license details. */
+
+int __wrap_getpid(void)
+{
+  return 1;
+}
--- a/hello-world/bsp/libwrap/sys/isatty.c
+++ b/hello-world/bsp/libwrap/sys/isatty.c
@ -0,0 +1,11 @@
+/* See LICENSE of license details. */
+
+#include <unistd.h>
+
+int __wrap_isatty(int fd)
+{
+  if (fd == STDOUT_FILENO || fd == STDERR_FILENO)
+    return 1;
+
+  return 0;
+}
--- a/hello-world/bsp/libwrap/sys/kill.c
+++ b/hello-world/bsp/libwrap/sys/kill.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_kill(int pid, int sig)
+{
+  return _stub(EINVAL);
+}
--- a/hello-world/bsp/libwrap/sys/link.c
+++ b/hello-world/bsp/libwrap/sys/link.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_link(const char *old_name, const char *new_name)
+{
+  return _stub(EMLINK);
+}
--- a/hello-world/bsp/libwrap/sys/lseek.c
+++ b/hello-world/bsp/libwrap/sys/lseek.c
@ -0,0 +1,14 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "stub.h"
+
+off_t __wrap_lseek(int fd, off_t ptr, int dir)
+{
+  if (isatty(fd))
+    return 0;
+
+  return _stub(EBADF);
+}
--- a/hello-world/bsp/libwrap/sys/open.c
+++ b/hello-world/bsp/libwrap/sys/open.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_open(const char* name, int flags, int mode)
+{
+  return _stub(ENOENT);
+}
--- a/hello-world/bsp/libwrap/sys/openat.c
+++ b/hello-world/bsp/libwrap/sys/openat.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_openat(int dirfd, const char* name, int flags, int mode)
+{
+  return _stub(ENOENT);
+}
--- a/hello-world/bsp/libwrap/sys/read.c
+++ b/hello-world/bsp/libwrap/sys/read.c
@ -0,0 +1,30 @@
+/* See LICENSE of license details. */
+
+#include <stdint.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#include "platform.h"
+#include "stub.h"
+
+ssize_t __wrap_read(int fd, void* ptr, size_t len)
+{
+  uint8_t * current = (uint8_t *)ptr;
+  volatile uint32_t * uart_rx = (uint32_t *)(UART0_BASE_ADDR + UART_REG_RXFIFO);
+  volatile uint8_t * uart_rx_cnt = (uint8_t *)(UART0_BASE_ADDR + UART_REG_RXCTRL + 2);
+
+  ssize_t result = 0;
+
+  if (isatty(fd)) {
+    for (current = (uint8_t *)ptr;
+        (current < ((uint8_t *)ptr) + len) && (*uart_rx_cnt > 0);
+        current ++) {
+      *current = *uart_rx;
+      result++;
+    }
+    return result;
+  }
+
+  return _stub(EBADF);
+}
--- a/hello-world/bsp/libwrap/sys/sbrk.c
+++ b/hello-world/bsp/libwrap/sys/sbrk.c
@ -0,0 +1,16 @@
+/* See LICENSE of license details. */
+
+#include <stddef.h>
+
+void *__wrap_sbrk(ptrdiff_t incr)
+{
+  extern char _end[];
+  extern char _heap_end[];
+  static char *curbrk = _end;
+
+  if ((curbrk + incr < _end) || (curbrk + incr > _heap_end))
+    return NULL - 1;
+
+  curbrk += incr;
+  return curbrk - incr;
+}
--- a/hello-world/bsp/libwrap/sys/stat.c
+++ b/hello-world/bsp/libwrap/sys/stat.c
@ -0,0 +1,10 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <sys/stat.h>
+#include "stub.h"
+
+int __wrap_stat(const char* file, struct stat* st)
+{
+  return _stub(EACCES);
+}
--- a/hello-world/bsp/libwrap/sys/stub.h
+++ b/hello-world/bsp/libwrap/sys/stub.h
@ -0,0 +1,10 @@
+/* See LICENSE of license details. */
+#ifndef _SIFIVE_SYS_STUB_H
+#define _SIFIVE_SYS_STUB_H
+
+static inline int _stub(int err)
+{
+  return -1;
+}
+
+#endif /* _SIFIVE_SYS_STUB_H */
--- a/hello-world/bsp/libwrap/sys/times.c
+++ b/hello-world/bsp/libwrap/sys/times.c
@ -0,0 +1,10 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <sys/times.h>
+#include "stub.h"
+
+clock_t __wrap_times(struct tms* buf)
+{
+  return _stub(EACCES);
+}
--- a/hello-world/bsp/libwrap/sys/unlink.c
+++ b/hello-world/bsp/libwrap/sys/unlink.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_unlink(const char* name)
+{
+  return _stub(ENOENT);
+}
--- a/hello-world/bsp/libwrap/sys/wait.c
+++ b/hello-world/bsp/libwrap/sys/wait.c
@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int wait(int* status)
+{
+  return _stub(ECHILD);
+}
--- a/hello-world/bsp/libwrap/sys/write.c
+++ b/hello-world/bsp/libwrap/sys/write.c
@ -0,0 +1,29 @@
+/* See LICENSE of license details. */
+
+#include <stdint.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#include "platform.h"
+#include "stub.h"
+
+ssize_t __wrap_write(int fd, const void* ptr, size_t len)
+{
+  const uint8_t * current = (const char *)ptr;
+
+  if (isatty(fd)) {
+    for (size_t jj = 0; jj < len; jj++) {
+      while (UART0_REG(UART_REG_TXFIFO) & 0x80000000) ;
+      UART0_REG(UART_REG_TXFIFO) = current[jj];
+
+      if (current[jj] == '\n') {
+        while (UART0_REG(UART_REG_TXFIFO) & 0x80000000) ;
+        UART0_REG(UART_REG_TXFIFO) = '\r';
+      }
+    }
+    return len;
+  }
+
+  return _stub(EBADF);
+}
--- a/hello-world/hello
+++ b/hello-world/hello
--- a/hello-world/hello.c
+++ b/hello-world/hello.c
@ -0,0 +1,32 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "platform.h"
+#include "encoding.h"
+
+int factorial(int i){
+
+	volatile int result = 1;
+	for (int ii = 1; ii <= i; ii++) {
+		result = result * ii;
+	}
+	return result;
+
+}
+
+int main()
+{
+	FILE * out = fdopen(STDOUT_FILENO, "w");
+	int value=0;
+	int res = read(STDIN_FILENO, &value, 1);
+//    FILE * inp = fdopen(STDIN_FILENO, "r");
+	//fprintf(out, "hello world!\n");
+//	int value = 0;
+//    int res = fscanf(inp, "%d", value);
+//	int res = scanf("%d", value);
+	volatile int result = factorial (10);
+	fprintf(out, "Factorial is %d\n", result);
+	printf("End of execution");
+	return 0;
+}
--- a/hello-world/wrap_printf.c
+++ b/hello-world/wrap_printf.c
@ -0,0 +1,271 @@
+/* The functions in this file are only meant to support Dhrystone on an
+ * embedded RV32 system and are obviously incorrect in general. */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+
+#undef putchar
+int putchar(int ch)
+{
+  return write(STDOUT_FILENO, &ch, 1) == 1 ? ch : -1;
+}
+
+static void sprintf_putch(int ch, void** data)
+{
+  char** pstr = (char**)data;
+  **pstr = ch;
+  (*pstr)++;
+}
+
+static unsigned long getuint(va_list *ap, int lflag)
+{
+  if (lflag)
+    return va_arg(*ap, unsigned long);
+  else
+    return va_arg(*ap, unsigned int);
+}
+
+static long getint(va_list *ap, int lflag)
+{
+  if (lflag)
+    return va_arg(*ap, long);
+  else
+    return va_arg(*ap, int);
+}
+
+static inline void printnum(void (*putch)(int, void**), void **putdat,
+                    unsigned long num, unsigned base, int width, int padc)
+{
+  unsigned digs[sizeof(num)*8];
+  int pos = 0;
+
+  while (1)
+  {
+    digs[pos++] = num % base;
+    if (num < base)
+      break;
+    num /= base;
+  }
+
+  while (width-- > pos)
+    putch(padc, putdat);
+
+  while (pos-- > 0)
+    putch(digs[pos] + (digs[pos] >= 10 ? 'a' - 10 : '0'), putdat);
+}
+
+static inline void print_double(void (*putch)(int, void**), void **putdat,
+                                double num, int width, int prec)
+{
+  union {
+    double d;
+    uint64_t u;
+  } u;
+  u.d = num;
+
+  if (u.u & (1ULL << 63)) {
+    putch('-', putdat);
+    u.u &= ~(1ULL << 63);
+  }
+
+  for (int i = 0; i < prec; i++)
+    u.d *= 10;
+
+  char buf[32], *pbuf = buf;
+  printnum(sprintf_putch, (void**)&pbuf, (unsigned long)u.d, 10, 0, 0);
+  if (prec > 0) {
+    for (int i = 0; i < prec; i++) {
+      pbuf[-i] = pbuf[-i-1];
+    }
+    pbuf[-prec] = '.';
+    pbuf++;
+  }
+
+  for (char* p = buf; p < pbuf; p++)
+    putch(*p, putdat);
+}
+
+static void vprintfmt(void (*putch)(int, void**), void **putdat, const char *fmt, va_list ap)
+{
+  register const char* p;
+  const char* last_fmt;
+  register int ch, err;
+  unsigned long num;
+  int base, lflag, width, precision, altflag;
+  char padc;
+
+  while (1) {
+    while ((ch = *(unsigned char *) fmt) != '%') {
+      if (ch == '\0')
+        return;
+      fmt++;
+      putch(ch, putdat);
+    }
+    fmt++;
+
+    // Process a %-escape sequence
+    last_fmt = fmt;
+    padc = ' ';
+    width = -1;
+    precision = -1;
+    lflag = 0;
+    altflag = 0;
+  reswitch:
+    switch (ch = *(unsigned char *) fmt++) {
+
+    // flag to pad on the right
+    case '-':
+      padc = '-';
+      goto reswitch;
+      
+    // flag to pad with 0's instead of spaces
+    case '0':
+      padc = '0';
+      goto reswitch;
+
+    // width field
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+      for (precision = 0; ; ++fmt) {
+        precision = precision * 10 + ch - '0';
+        ch = *fmt;
+        if (ch < '0' || ch > '9')
+          break;
+      }
+      goto process_precision;
+
+    case '*':
+      precision = va_arg(ap, int);
+      goto process_precision;
+
+    case '.':
+      if (width < 0)
+        width = 0;
+      goto reswitch;
+
+    case '#':
+      altflag = 1;
+      goto reswitch;
+
+    process_precision:
+      if (width < 0)
+        width = precision, precision = -1;
+      goto reswitch;
+
+    // long flag
+    case 'l':
+      if (lflag)
+        goto bad;
+      goto reswitch;
+
+    // character
+    case 'c':
+      putch(va_arg(ap, int), putdat);
+      break;
+
+    // double
+    case 'f':
+      print_double(putch, putdat, va_arg(ap, double), width, precision);
+      break;
+
+    // string
+    case 's':
+      if ((p = va_arg(ap, char *)) == NULL)
+        p = "(null)";
+      if (width > 0 && padc != '-')
+        for (width -= strnlen(p, precision); width > 0; width--)
+          putch(padc, putdat);
+      for (; (ch = *p) != '\0' && (precision < 0 || --precision >= 0); width--) {
+        putch(ch, putdat);
+        p++;
+      }
+      for (; width > 0; width--)
+        putch(' ', putdat);
+      break;
+
+    // (signed) decimal
+    case 'd':
+      num = getint(&ap, lflag);
+      if ((long) num < 0) {
+        putch('-', putdat);
+        num = -(long) num;
+      }
+      base = 10;
+      goto signed_number;
+
+    // unsigned decimal
+    case 'u':
+      base = 10;
+      goto unsigned_number;
+
+    // (unsigned) octal
+    case 'o':
+      // should do something with padding so it's always 3 octits
+      base = 8;
+      goto unsigned_number;
+
+    // pointer
+    case 'p':
+      lflag = 1;
+      putch('0', putdat);
+      putch('x', putdat);
+      /* fall through to 'x' */
+
+    // (unsigned) hexadecimal
+    case 'x':
+      base = 16;
+    unsigned_number:
+      num = getuint(&ap, lflag);
+    signed_number:
+      printnum(putch, putdat, num, base, width, padc);
+      break;
+
+    // escaped '%' character
+    case '%':
+      putch(ch, putdat);
+      break;
+      
+    // unrecognized escape sequence - just print it literally
+    default:
+    bad:
+      putch('%', putdat);
+      fmt = last_fmt;
+      break;
+    }
+  }
+}
+
+int __wrap_printf(const char* fmt, ...)
+{
+  va_list ap;
+  va_start(ap, fmt);
+
+  vprintfmt((void*)putchar, 0, fmt, ap);
+
+  va_end(ap);
+  return 0; // incorrect return value, but who cares, anyway?
+}
+
+int __wrap_sprintf(char* str, const char* fmt, ...)
+{
+  va_list ap;
+  char* str0 = str;
+  va_start(ap, fmt);
+
+  vprintfmt(sprintf_putch, (void**)&str, fmt, ap);
+  *str = 0;
+
+  va_end(ap);
+  return str - str0;
+}
--- a/hello-world/wrap_stubs.c
+++ b/hello-world/wrap_stubs.c
@ -0,0 +1,15 @@
+#include "platform.h"
+
+/* The functions in this file are only meant to support Dhrystone on an
+ * embedded RV32 system and are obviously incorrect in general. */
+
+long time(void)
+{
+  return get_timer_value() / get_timer_freq();
+}
+
+// set the number of dhrystone iterations
+void __wrap_scanf(const char* fmt, int* n)
+{
+  *n = 100000000;
+}
--- a/riscv-bldc-forced-commutation/Makefile
+++ b/riscv-bldc-forced-commutation/Makefile
@ -0,0 +1,28 @@
+
+TARGET    = riscv-bldc
+C_SRCS    = $(wildcard src/*.c)  $(BSP_BASE)/drivers/fe300prci/fe300prci_driver.c $(BSP_BASE)/drivers/plic/plic_driver.c
+CXX_SRCS  = $(wildcard src/*.cpp) 
+HEADERS   = $(wildcard src/*.h)
+CFLAGS    = -g 
+CFLAGS   += -fno-builtin-printf -DUSE_PLIC -DUSE_M_TIME -DNO_INIT -I./src
+CXXFLAGS  = -fno-use-cxa-atexit
+LDFLAGS   = -Wl,--wrap=printf
+LDFLAGS  += -g -lstdc++ -fno-use-cxa-atexit -march=$(RISCV_ARCH) -mabi=$(RISCV_ABI) -mcmodel=medany
+
+
+BOARD=freedom-e300-hifive1
+LINK_TARGET=flash
+RISCV_ARCH=rv32imac
+RISCV_ABI=ilp32
+
+TOOL_DIR?=/opt/riscv/FreedomStudio/20180122/SiFive/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6/bin
+BSP_BASE = ./bsp
+include $(BSP_BASE)/env/common.mk
+
+.PHONY: all
+all: $(TARGET).dump
+
+$(TARGET).dump: $(TARGET)
+	$(TOOL_DIR)/$(TRIPLET)-objdump -d -S -C $< > $@
+
+	
--- a/riscv-bldc-forced-commutation/bsp/env/common.mk
+++ b/riscv-bldc-forced-commutation/bsp/env/common.mk
@ -28,9 +28,10 @@ LDFLAGS += -T $(LINKER_SCRIPT) -nostartfiles
 LDFLAGS += -L$(ENV_DIR) --specs=nano.specs

 ASM_OBJS := $(ASM_SRCS:.S=.o)
-C_OBJS := $(C_SRCS:.c=.o)
+C_OBJS   := $(C_SRCS:.c=.o)
+CXX_OBJS := $(CXX_SRCS:.cpp=.o)

-LINK_OBJS += $(ASM_OBJS) $(C_OBJS)
+LINK_OBJS += $(ASM_OBJS) $(C_OBJS) $(CXX_OBJS)
 LINK_DEPS += $(LINKER_SCRIPT)

 CLEAN_OBJS += $(TARGET) $(LINK_OBJS)
@ -39,15 +40,24 @@ CFLAGS += -march=$(RISCV_ARCH)
 CFLAGS += -mabi=$(RISCV_ABI)
 CFLAGS += -mcmodel=medany

-$(TARGET): $(LINK_OBJS) $(LINK_DEPS)
-	$(CC) $(CFLAGS) $(INCLUDES) $(LINK_OBJS) -o $@ $(LDFLAGS)
+TRIPLET?=riscv64-unknown-elf
+CXX=$(TOOL_DIR)/$(TRIPLET)-c++
+CC=$(TOOL_DIR)/$(TRIPLET)-gcc
+LD=$(TOOL_DIR)/$(TRIPLET)-gcc

+
+$(TARGET): $(LINK_OBJS) $(LINK_DEPS)
+	$(LD) $(LINK_OBJS) $(LDFLAGS) $(LIBWRAP) -o $@
+	
 $(ASM_OBJS): %.o: %.S $(HEADERS)
 	$(CC) $(CFLAGS) $(INCLUDES) -c -o $@ $<

 $(C_OBJS): %.o: %.c $(HEADERS)
 	$(CC) $(CFLAGS) $(INCLUDES) -include sys/cdefs.h -c -o $@ $<

+$(CXX_OBJS): %.o: %.cpp $(HEADERS)
+	$(CXX) $(CFLAGS) $(CXXFLAGS) $(INCLUDES) -include sys/cdefs.h -c -o $@ $<
+
 .PHONY: clean
 clean:
 	rm -f $(CLEAN_OBJS)
--- a/riscv-bldc-forced-commutation/src/peripherals.cpp
+++ b/riscv-bldc-forced-commutation/src/peripherals.cpp
--- a/riscv-bldc-forced-commutation/src/peripherals.h
+++ b/riscv-bldc-forced-commutation/src/peripherals.h
--- a/riscv-bldc-forced-commutation/src/io/gpio.h
+++ b/riscv-bldc-forced-commutation/src/io/gpio.h
--- a/riscv-bldc-forced-commutation/src/io/pwm.h
+++ b/riscv-bldc-forced-commutation/src/io/pwm.h
--- a/riscv-bldc-forced-commutation/src/io/spi.h
+++ b/riscv-bldc-forced-commutation/src/io/spi.h
--- a/riscv-bldc-forced-commutation/src/io/uart.h
+++ b/riscv-bldc-forced-commutation/src/io/uart.h