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struct syscall_result {
long val;
int errno;
};
static struct syscall_result syscall_return(long result)
{
struct syscall_result res;
if (((unsigned long)result) >= ((unsigned long)-125)) {
res.errno = - result;
res.val = -1;
} else {
res.errno = 0;
res.val = result;
}
return res;
}
static struct syscall_result syscall1(unsigned long nr, unsigned long arg1)
{
long res;
asm volatile(
"int $0x80"
: "=a" (res)
: "a" (nr), "b" (arg1));
return syscall_return(res);
}
static struct syscall_result syscall3(unsigned long nr, unsigned long arg1, unsigned long arg2,
unsigned long arg3)
{
long res;
asm volatile(
"int $0x80"
: "=a" (res)
: "a" (nr), "b" (arg1), "c" (arg2), "d" (arg3));
return syscall_return(res);
}
#define NR_exit 1
#define NR_write 4
/* Standard file descriptors */
#define STDIN_FILENO 0 /* Standard input */
#define STDOUT_FILENO 1 /* Standard output */
#define STDERR_FILENO 2 /* Standard error output */
typedef long ssize_t;
typedef unsigned long size_t;
static ssize_t write(int fd, const void *buf, size_t count)
{
struct syscall_result res;
res = syscall3(NR_write, fd, (unsigned long)buf, count);
return res.val;
}
static void _exit(int status)
{
struct syscall_result res;
res = syscall1(NR_exit, status);
}
static void main(void)
{
static const char msg[] = "hello world\r\n";
write(STDOUT_FILENO, msg, sizeof(msg));
_exit(0);
}
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