127 lines
2.6 KiB
C
127 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* vdso_test.c: Sample code to test parse_vdso.c on x86
|
|
* Copyright (c) 2011-2014 Andy Lutomirski
|
|
*
|
|
* You can amuse yourself by compiling with:
|
|
* gcc -std=gnu99 -nostdlib
|
|
* -Os -fno-asynchronous-unwind-tables -flto -lgcc_s
|
|
* vdso_standalone_test_x86.c parse_vdso.c
|
|
* to generate a small binary. On x86_64, you can omit -lgcc_s
|
|
* if you want the binary to be completely standalone.
|
|
*/
|
|
|
|
#include <sys/syscall.h>
|
|
#include <sys/time.h>
|
|
#include <unistd.h>
|
|
#include <stdint.h>
|
|
|
|
#include "parse_vdso.h"
|
|
|
|
/* We need a libc functions... */
|
|
int strcmp(const char *a, const char *b)
|
|
{
|
|
/* This implementation is buggy: it never returns -1. */
|
|
while (*a || *b) {
|
|
if (*a != *b)
|
|
return 1;
|
|
if (*a == 0 || *b == 0)
|
|
return 1;
|
|
a++;
|
|
b++;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* ...and two syscalls. This is x86-specific. */
|
|
static inline long x86_syscall3(long nr, long a0, long a1, long a2)
|
|
{
|
|
long ret;
|
|
#ifdef __x86_64__
|
|
asm volatile ("syscall" : "=a" (ret) : "a" (nr),
|
|
"D" (a0), "S" (a1), "d" (a2) :
|
|
"cc", "memory", "rcx",
|
|
"r8", "r9", "r10", "r11" );
|
|
#else
|
|
asm volatile ("int $0x80" : "=a" (ret) : "a" (nr),
|
|
"b" (a0), "c" (a1), "d" (a2) :
|
|
"cc", "memory" );
|
|
#endif
|
|
return ret;
|
|
}
|
|
|
|
static inline long linux_write(int fd, const void *data, size_t len)
|
|
{
|
|
return x86_syscall3(__NR_write, fd, (long)data, (long)len);
|
|
}
|
|
|
|
static inline void linux_exit(int code)
|
|
{
|
|
x86_syscall3(__NR_exit, code, 0, 0);
|
|
}
|
|
|
|
void to_base10(char *lastdig, time_t n)
|
|
{
|
|
while (n) {
|
|
*lastdig = (n % 10) + '0';
|
|
n /= 10;
|
|
lastdig--;
|
|
}
|
|
}
|
|
|
|
__attribute__((externally_visible)) void c_main(void **stack)
|
|
{
|
|
/* Parse the stack */
|
|
long argc = (long)*stack;
|
|
stack += argc + 2;
|
|
|
|
/* Now we're pointing at the environment. Skip it. */
|
|
while(*stack)
|
|
stack++;
|
|
stack++;
|
|
|
|
/* Now we're pointing at auxv. Initialize the vDSO parser. */
|
|
vdso_init_from_auxv((void *)stack);
|
|
|
|
/* Find gettimeofday. */
|
|
typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
|
|
gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
|
|
|
|
if (!gtod)
|
|
linux_exit(1);
|
|
|
|
struct timeval tv;
|
|
long ret = gtod(&tv, 0);
|
|
|
|
if (ret == 0) {
|
|
char buf[] = "The time is .000000\n";
|
|
to_base10(buf + 31, tv.tv_sec);
|
|
to_base10(buf + 38, tv.tv_usec);
|
|
linux_write(1, buf, sizeof(buf) - 1);
|
|
} else {
|
|
linux_exit(ret);
|
|
}
|
|
|
|
linux_exit(0);
|
|
}
|
|
|
|
/*
|
|
* This is the real entry point. It passes the initial stack into
|
|
* the C entry point.
|
|
*/
|
|
asm (
|
|
".text\n"
|
|
".global _start\n"
|
|
".type _start,@function\n"
|
|
"_start:\n\t"
|
|
#ifdef __x86_64__
|
|
"mov %rsp,%rdi\n\t"
|
|
"jmp c_main"
|
|
#else
|
|
"push %esp\n\t"
|
|
"call c_main\n\t"
|
|
"int $3"
|
|
#endif
|
|
);
|