first semihosting integration

This commit is contained in:
gabriel 2024-02-26 20:41:15 +01:00
parent 532f7e9bb8
commit 39ee91af7d
5 changed files with 219 additions and 1 deletions

2
env/entry.S vendored
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@ -41,7 +41,7 @@ trap_entry:
csrr a0, mcause
csrr a1, mepc
mv a2, sp
call handle_trap
call trap
csrw mepc, a0
#ifndef __riscv_abi_rve
addi sp, sp, -8*REGBYTES

54
libwrap/CMakeLists.txt Normal file
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@ -0,0 +1,54 @@
IF(NOT DEFINED _MK_LIBWRAP)
SET(_MK_LIBWRAP TRUE)
SET(LIBWRAP_DIR ${CMAKE_CURRENT_LIST_DIR})
SET(LIBWRAP_SRCS
${LIBWRAP_DIR}/stdlib/malloc.c
${LIBWRAP_DIR}/sys/open.c
${LIBWRAP_DIR}/sys/lseek.c
${LIBWRAP_DIR}/sys/read.c
${LIBWRAP_DIR}/sys/write.c
${LIBWRAP_DIR}/sys/fstat.c
${LIBWRAP_DIR}/sys/stat.c
${LIBWRAP_DIR}/sys/close.c
${LIBWRAP_DIR}/sys/link.c
${LIBWRAP_DIR}/sys/unlink.c
${LIBWRAP_DIR}/sys/execve.c
${LIBWRAP_DIR}/sys/fork.c
${LIBWRAP_DIR}/sys/getpid.c
${LIBWRAP_DIR}/sys/kill.c
${LIBWRAP_DIR}/sys/wait.c
${LIBWRAP_DIR}/sys/isatty.c
${LIBWRAP_DIR}/sys/times.c
${LIBWRAP_DIR}/sys/sbrk.c
${LIBWRAP_DIR}/sys/_exit.c
${LIBWRAP_DIR}/misc/write_hex.c
${LIBWRAP_DIR}/sys/printf.c
)
IF(${SEMIHOSTING})
SET(LIBWRAP_SRCS ${LIBWRAP_SRCS} ${LIBWRAP_DIR}/semihosting/semihosting.c ${LIBWRAP_DIR}/semihosting/trap.c)
ENDIF()
SET(LIBWRAP_SYMS malloc free open lseek read write fstat stat close link unlink execve fork getpid jukk wait isatty times sbrk _exit printf puts)
# Includes
INCLUDE_DIRECTORIES(
${LIBWRAP_DIR}
${LIBWRAP_DIR}/../include
${LIBWRAP_DIR}/../drivers
${LIBWRAP_DIR}/../env
${LIBWRAP_DIR}/../env/iss
)
ADD_LIBRARY(LIBWRAP_TGC STATIC ${LIBWRAP_SRCS})
TARGET_COMPILE_OPTIONS(LIBWRAP_TGC PRIVATE -march=${RISCV_ARCH}_zicsr_zifencei -mabi=${RISCV_ABI} "-DBOARD_${BOARD}")
FOREACH(SYM ${LIBWRAP_SYMS})
LIST(APPEND WRAP_LDFLAGS "-Wl,--wrap=${SYM}")
ENDFOREACH()
SET(LIBWRAP_TGC_LDFLAGS ${WRAP_LDFLAGS} "-Wl,--start-group" "-Wl,--end-group")
ENDIF(NOT DEFINED _MK_LIBWRAP)

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@ -0,0 +1,90 @@
#include <stdint.h>
#include <stdarg.h>
#include <stddef.h>
#include "semihosting.h"
#define SEMIHOSTING_SYS_OPEN 0x01
#define SEMIHOSTING_SYS_CLOSE 0x02
#define SEMIHOSTING_SYS_WRITEC 0x03
#define SEMIHOSTING_SYS_WRITE0 0x04
#define SEMIHOSTING_SYS_WRITE 0x05
#define SEMIHOSTING_SYS_READ 0x06
#define SEMIHOSTING_SYS_READC 0x07
#define SEMIHOSTING_SYS_ISERROR 0x08
#define SEMIHOSTING_SYS_ISTTY 0x09
#define SEMIHOSTING_SYS_SEEK 0x0A
#define SEMIHOSTING_SYS_FLEN 0x0C
#define SEMIHOSTING_SYS_TMPNAM 0x0D
#define SEMIHOSTING_SYS_REMOVE 0x0E
#define SEMIHOSTING_SYS_RENAME 0x0F
#define SEMIHOSTING_SYS_CLOCK 0x10
#define SEMIHOSTING_SYS_TIME 0x11
#define SEMIHOSTING_SYS_SYSTEM 0x12
#define SEMIHOSTING_SYS_ERRNO 0x13
#define SEMIHOSTING_SYS_GET_CMDLINE 0x15
#define SEMIHOSTING_SYS_HEAPINFO 0x16
#define SEMIHOSTING_EnterSVC 0x17
#define SEMIHOSTING_ReportException 0x18
#define SEMIHOSTING_SYS_ELAPSED 0x30
#define SEMIHOSTING_SYS_TICKFREQ 0x31
#define RISCV_SEMIHOSTING_CALL_NUMBER 7
static inline int __attribute__ ((always_inline)) call_host(int reason, void* arg) {
#if 1
// This must always be set back to 0 to cover the case where a host wasn't
// initially present, but only connected while the program was already up and
// running. In that case, trap() suddenly won't be called anymore, so we have to
// clear this variable *before* EBREAK is called.
sh_missing_host = 0;
register int value asm ("a0") = reason;
register void* ptr asm ("a1") = arg;
asm volatile (
// Workaround for RISC-V lack of multiple EBREAKs.
" .option push \n"
" .option norvc \n"
// Force 16-byte alignment to make sure that the 3 instruction fall
// within the same virtual page. If you the instruction straddle a page boundary
// the debugger fetching the instructions could lead to a page fault.
// Note: align 4 means, align by 2 to the power of 4!
" .align 4 \n"
" slli x0, x0, 0x1f \n"
" ebreak \n"
" srai x0, x0, 0x07 \n"
" .option pop \n"
: "=r" (value) /* Outputs */
: "0" (value), "r" (ptr), [swi] "i" (RISCV_SEMIHOSTING_CALL_NUMBER) /* Inputs */
: "memory" /* Clobbers */
);
return value;
#else
return 0;
#endif
}
void sh_write0(const char* buf)
{
// Print zero-terminated string
call_host(SEMIHOSTING_SYS_WRITE0, (void*) buf);
}
void sh_writec(char c)
{
// Print single character
call_host(SEMIHOSTING_SYS_WRITEC, (void*)&c);
}
char sh_readc(void)
{
// Read character from keyboard. (Blocking operation!)
char c = call_host(SEMIHOSTING_SYS_READC, (void*)NULL);
if (sh_missing_host)
return 0;
else
return c;
}

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@ -0,0 +1,14 @@
#ifndef SEMIHOSTING_H
#define SEMIHOSTING_H
//int32_t trace_write(const char* buf, uint32_t nbyte);
void sh_write0(const char* buf);
void sh_writec(char c);
char sh_readc(void);
int getchar(void);
extern int sh_missing_host;
#endif

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@ -0,0 +1,60 @@
#include <stdint.h>
#include <stdlib.h>
#include <math.h>
#include "encoding.h"
#define EBREAK_OPCODE 0x00100073
#define EBREAK_MCAUSE 0x00000003
#define SLLI_X0_X0_0X1F_OPCODE 0x01f01013
#define SRAI_X0_X0_0X07_OPCODE 0x40705013
int sh_missing_host = 0;
void trap()
{
uint32_t mepc = read_csr(0x341); // Address of trap
uint32_t mtval = read_csr(0x343); // Instruction value of trap
uint32_t mcause = read_csr(0x342); // Reason for the trap
if (mcause == EBREAK_MCAUSE && mtval == EBREAK_OPCODE){
// This trap was caused by an EBREAK...
int aligned = ((mepc-4) & 0x0f) == 0;
if (aligned
&& *(uint32_t *)mepc == EBREAK_OPCODE
&& *(uint32_t *)(mepc-4) == SLLI_X0_X0_0X1F_OPCODE
&& *(uint32_t *)(mepc+4) == SRAI_X0_X0_0X07_OPCODE)
{
// The EBREAK was part of the semihosting call. (See semihosting.c)
//
// If a debugger were connected, this would have resulted in a CPU halt,
// and the debugger would have serviced the the semihosting call.
//
// However, the semihosting function was called without a debugger being
// attached. The best course of action is to simply return from the trap
// and let the semihosting function continue after the call to EBREAK to
// prevent the CPU from hanging in the trap handler.
write_csr(mepc, mepc+4);
// Set a global variable to tell the semihosting code the the semihosting
// call
// didn't execute on the host.
sh_missing_host = 1;
return;
}
// EBREAK was not part of a semihosting call. This should not have happened.
// Hang forever.
while(1)
;
}
// Trap was issued for another reason than an EBREAK.
// Replace the code below with whatever trap handler you'd normally use. (e.g. interrupt
// processing.)
while(1)
;
}