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// An extremely minimalist syscalls.c for newlib
// Based on riscv newlib libgloss/riscv/machine/syscall.h
// Written by Clifford Wolf.
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#define UNIMPL_FUNC(_f) ".globl " #_f "\n.type " #_f ", @function\n" #_f ":\n"
asm (
".text\n"
".align 2\n"
UNIMPL_FUNC(_open)
UNIMPL_FUNC(_openat)
UNIMPL_FUNC(_lseek)
UNIMPL_FUNC(_stat)
UNIMPL_FUNC(_lstat)
UNIMPL_FUNC(_fstatat)
UNIMPL_FUNC(_isatty)
UNIMPL_FUNC(_access)
UNIMPL_FUNC(_faccessat)
UNIMPL_FUNC(_link)
UNIMPL_FUNC(_unlink)
UNIMPL_FUNC(_execve)
UNIMPL_FUNC(_getpid)
UNIMPL_FUNC(_fork)
UNIMPL_FUNC(_kill)
UNIMPL_FUNC(_wait)
UNIMPL_FUNC(_times)
UNIMPL_FUNC(_gettimeofday)
UNIMPL_FUNC(_ftime)
UNIMPL_FUNC(_utime)
UNIMPL_FUNC(_chown)
UNIMPL_FUNC(_chmod)
UNIMPL_FUNC(_chdir)
UNIMPL_FUNC(_getcwd)
UNIMPL_FUNC(_sysconf)
"j unimplemented_syscall\n"
);
void unimplemented_syscall()
{
const char *p = "Unimplemented system call called!\n";
while (*p)
*(volatile int*)0x10000000 = *(p++);
asm volatile ("sbreak");
__builtin_unreachable();
}
ssize_t _read(int file, void *ptr, size_t len)
{
// All reads read from console
unsigned char *p = ptr;
for (int i = 0; i < len;) {
int v = *(volatile int*)0x30000000;
if (v >= 0)
p[i++] = v;
else if (i)
return i;
}
return len;
}
ssize_t _write(int file, const void *ptr, size_t len)
{
// All writes go to console
const unsigned char *p = ptr;
for (int i = 0; i < len; i++)
*(volatile int*)0x30000000 = p[i];
return len;
}
int _close(int file)
{
// close is called before _exit()
return 0;
}
int _fstat(int file, struct stat *st)
{
// fstat is called during libc startup
errno = ENOENT;
return -1;
}
void *_sbrk(ptrdiff_t incr)
{
extern unsigned char _end[]; // Defined by linker
static unsigned long heap_end;
if (heap_end == 0)
heap_end = (long)_end;
heap_end += incr;
return (void *)(heap_end - incr);
}
void _exit(int exit_status)
{
asm volatile ("sbreak");
__builtin_unreachable();
}