rework structure

bare-metal-bsp/env/.gitignore

@@ -0,0 +1 @@
+/*.o

bare-metal-bsp/env/common-clang.mk

@@ -0,0 +1,72 @@
+# 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=$(RISCV_ABI)
+CFLAGS += -mcmodel=medany
+
+TRIPLET?=riscv32
+CXX=$(LLVM_TOOL_DIR)clang++ --target=$(TRIPLET) -isystem $(TOOL_DIR)/../$(TRIPLET)/include
+CC=$(LLVM_TOOL_DIR)clang --target=$(TRIPLET) -isystem $(TOOL_DIR)/../$(TRIPLET)/include
+LD=$(TOOL_DIR)$(TRIPLET)-gcc
+AR=$(TOOL_DIR)$(TRIPLET)-ar
+OBJDUMP := $(TOOL_DIR)/$(TRIPLET)-objdump
+
+
+$(TARGET): $(LINK_OBJS) $(LINK_DEPS)
+	$(LD) $(LINK_OBJS) $(LDFLAGS) $(LIBWRAP) -o $@
+	$(OBJDUMP) -d -S $(TARGET) > $(TARGET).dis
+	
+$(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 $(TARGET) $(LINK_OBJS)
+
+.PHONY: clean-all
+clean-all:
+	rm -f $(CLEAN_OBJS) $(LIBWRAP)
+
+endif

bare-metal-bsp/env/common-gcc.mk

@@ -0,0 +1,74 @@
+ifndef _MK_COMMON
+_MK_COMMON := # defined
+
+.PHONY: all
+all: $(TARGET)
+
+include $(BSP_BASE)/libwrap/libwrap.mk
+
+BOARD?=iss
+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 ?= $(BSP_BASE)/../toolchain/bin/
+
+LDFLAGS += -march=$(RISCV_ARCH) -mabi=$(RISCV_ABI)
+LDFLAGS += -T $(LINKER_SCRIPT) -Wl,-Map=$(TARGET).map  -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)
+
+GCCVERSION = $(shell $(CC) --version | grep gcc | awk '{print($NF);}')
+ifeq ($(GCCVERSION),9.2)
+  CFLAGS += -march=$(RISCV_ARCH)
+else
+  CFLAGS += -march=$(RISCV_ARCH)_zicsr_zifencei
+endif
+CFLAGS += -mabi=$(RISCV_ABI)
+CFLAGS += -mcmodel=medany
+
+TRIPLET?=riscv64-unknown-elf
+CXX=$(TOOL_DIR)$(TRIPLET)-c++
+CC=$(TOOL_DIR)$(TRIPLET)-gcc
+LD=$(TOOL_DIR)$(TRIPLET)-gcc
+AR=$(TOOL_DIR)$(TRIPLET)-ar
+OBJDUMP := $(TOOL_DIR)$(TRIPLET)-objdump
+
+
+$(TARGET): $(LINK_OBJS) $(LINK_DEPS)
+	$(LD) $(LINK_OBJS) $(LDFLAGS) $(LIBWRAP) -o $@
+	$(OBJDUMP) -d -S $(TARGET) > $(TARGET).dis
+	
+$(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) $(LIBWRAP)
+
+endif

bare-metal-bsp/env/entry.S

@@ -0,0 +1,99 @@
+// See LICENSE for license details
+
+#ifndef ENTRY_S
+#define ENTRY_S
+
+#include "encoding.h"
+#include "rtl/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)
+#ifndef __riscv_abi_rve
+  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)
+#endif
+  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)
+#ifndef __riscv_abi_rve
+  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)
+#endif
+  addi sp, sp, 32*REGBYTES
+  mret
+
+.weak handle_trap
+handle_trap:
+1:
+  j 1b
+	
+#endif

bare-metal-bsp/env/iss/.gitignore

@@ -0,0 +1 @@
+/*.o

bare-metal-bsp/env/iss/init.c

@@ -0,0 +1,107 @@
+#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)
+{
+    unsigned long ret;
+    __asm volatile("rdtime %0":"=r"(ret));
+    return ret;
+}
+
+
+#if __riscv_xlen==32
+
+static uint32_t mtime_hi(void)
+{
+    unsigned long ret;
+    __asm volatile("rdtimeh %0":"=r"(ret));
+    return ret;
+}
+
+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;
+  }
+}
+
+#elif __riscv_xlen==64
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
+{
+  return 32768;
+}
+
+unsigned long get_cpu_freq()
+{
+  return 10000000;
+}
+
+void init_pll(void){
+
+}
+
+#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
+  init_pll();
+  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()
+{
+}

bare-metal-bsp/env/iss/link.lds

@@ -0,0 +1,174 @@
+OUTPUT_ARCH( "riscv" )
+
+ENTRY( _start )
+
+MEMORY
+{
+  flash (rxai!w) : ORIGIN = 0x00000020, LENGTH = 1M
+  ram (wxa!ri) :   ORIGIN = 0x10000000, LENGTH = 16K
+}
+
+PHDRS
+{
+  flash PT_LOAD;
+  ram_init PT_LOAD;
+  ram PT_NULL;
+}
+
+SECTIONS
+{
+  __stack_size = DEFINED(__stack_size) ? __stack_size : 2K;
+
+  .init ORIGIN(flash)        :
+  {
+    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_BEGIN__ = .;
+    *(.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_BEGIN__ = .;
+    *(.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);
+  __BSS_END__ = .;
+  __global_pointer$ = MIN(__SDATA_BEGIN__ + 0x800,  MAX(__DATA_BEGIN__ + 0x800, __BSS_END__ - 0x800));
+  PROVIDE( _end = . );
+  PROVIDE( end = . );
+
+  .stack ORIGIN(ram) + LENGTH(ram) - __stack_size :
+  {
+    PROVIDE( _heap_end = . );
+    . = __stack_size;
+    PROVIDE( _sp = . );
+  } >ram AT>ram :ram
+
+  PROVIDE( tohost = 0xfffffff0 );
+  PROVIDE( fromhost = 0xfffffff8 );
+}

bare-metal-bsp/env/iss/platform.h

@@ -0,0 +1,30 @@
+// See LICENSE for license details.
+
+#ifndef _ISS_PLATFORM_H
+#define _ISS_PLATFORM_H
+
+// Some things missing from the official encoding.h
+#define MCAUSE_INT         0x80000000
+#define MCAUSE_CAUSE       0x7FFFFFFF
+
+#include "rtl/const.h"
+/****************************************************************************
+ * Platform definitions
+ *****************************************************************************/
+
+#define MEM_BASE_ADDR _AC(0x00000000,UL)
+
+// Helper functions
+#define _REG32(p, i) (*(volatile uint32_t *) ((p) + (i)))
+#define _REG32P(p, i) ((volatile uint32_t *) ((p) + (i)))
+
+// Misc
+
+#include <stdint.h>
+
+void init_pll(void);
+unsigned long get_cpu_freq(void);
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
+#endif /* _ISS_PLATFORM_H */

bare-metal-bsp/env/rtl/.gitignore

@@ -0,0 +1 @@
+/*.o

bare-metal-bsp/env/rtl/init.c

@@ -0,0 +1,107 @@
+#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)
+{
+    unsigned long ret;
+    __asm volatile("rdtime %0":"=r"(ret));
+    return ret;
+}
+
+
+#if __riscv_xlen==32
+
+static uint32_t mtime_hi(void)
+{
+    unsigned long ret;
+    __asm volatile("rdtimeh %0":"=r"(ret));
+    return ret;
+}
+
+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;
+  }
+}
+
+#elif __riscv_xlen==64
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
+{
+  return 32768;
+}
+
+unsigned long get_cpu_freq()
+{
+  return 10000000;
+}
+
+void init_pll(void){
+
+}
+
+#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
+  init_pll();
+  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()
+{
+}

bare-metal-bsp/env/rtl/link.lds

@@ -0,0 +1,170 @@
+OUTPUT_ARCH( "riscv" )
+
+ENTRY( _start )
+
+MEMORY
+{
+  flash (rxai!w) : ORIGIN = 0x00000000, LENGTH = 1M
+  ram (wxa!ri) :   ORIGIN = 0x10000000, LENGTH = 16K
+}
+
+PHDRS
+{
+  flash PT_LOAD;
+  ram_init PT_LOAD;
+  ram PT_NULL;
+}
+
+SECTIONS
+{
+  __stack_size = DEFINED(__stack_size) ? __stack_size : 2K;
+
+  .init ORIGIN(flash)        :
+  {
+    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
+
+  PROVIDE( tohost = 0x00018000 );
+  PROVIDE( fromhost = 0xfffffff8 );
+}

bare-metal-bsp/env/rtl/platform.h

@@ -0,0 +1,30 @@
+// See LICENSE for license details.
+
+#ifndef _ISS_PLATFORM_H
+#define _ISS_PLATFORM_H
+
+// Some things missing from the official encoding.h
+#define MCAUSE_INT         0x80000000
+#define MCAUSE_CAUSE       0x7FFFFFFF
+
+#include "rtl/const.h"
+/****************************************************************************
+ * Platform definitions
+ *****************************************************************************/
+
+#define MEM_BASE_ADDR _AC(0x00000000,UL)
+
+// Helper functions
+#define _REG32(p, i) (*(volatile uint32_t *) ((p) + (i)))
+#define _REG32P(p, i) ((volatile uint32_t *) ((p) + (i)))
+
+// Misc
+
+#include <stdint.h>
+
+void init_pll(void);
+unsigned long get_cpu_freq(void);
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
+#endif /* _ISS_PLATFORM_H */

bare-metal-bsp/env/start.S

@@ -0,0 +1,58 @@
+// See LICENSE for license details.
+
+	.section .init
+	.globl _start
+	.type _start,@function
+
+_start:
+.option push
+.option norelax
+    la gp, __global_pointer$
+.option pop
+	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 */
+#ifdef HAVE_INIT_FINI
+	la a0, __libc_fini_array
+	call atexit
+	call __libc_init_array
+#endif
+#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