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