cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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vdso_standalone_test_x86.c (2698B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * vdso_test.c: Sample code to test parse_vdso.c on x86
      4 * Copyright (c) 2011-2014 Andy Lutomirski
      5 *
      6 * You can amuse yourself by compiling with:
      7 * gcc -std=gnu99 -nostdlib
      8 *     -Os -fno-asynchronous-unwind-tables -flto -lgcc_s
      9 *      vdso_standalone_test_x86.c parse_vdso.c
     10 * to generate a small binary.  On x86_64, you can omit -lgcc_s
     11 * if you want the binary to be completely standalone.
     12 */
     13
     14#include <sys/syscall.h>
     15#include <sys/time.h>
     16#include <unistd.h>
     17#include <stdint.h>
     18
     19#include "parse_vdso.h"
     20
     21/* We need a libc functions... */
     22int strcmp(const char *a, const char *b)
     23{
     24	/* This implementation is buggy: it never returns -1. */
     25	while (*a || *b) {
     26		if (*a != *b)
     27			return 1;
     28		if (*a == 0 || *b == 0)
     29			return 1;
     30		a++;
     31		b++;
     32	}
     33
     34	return 0;
     35}
     36
     37/* ...and two syscalls.  This is x86-specific. */
     38static inline long x86_syscall3(long nr, long a0, long a1, long a2)
     39{
     40	long ret;
     41#ifdef __x86_64__
     42	asm volatile ("syscall" : "=a" (ret) : "a" (nr),
     43		      "D" (a0), "S" (a1), "d" (a2) :
     44		      "cc", "memory", "rcx",
     45		      "r8", "r9", "r10", "r11" );
     46#else
     47	asm volatile ("int $0x80" : "=a" (ret) : "a" (nr),
     48		      "b" (a0), "c" (a1), "d" (a2) :
     49		      "cc", "memory" );
     50#endif
     51	return ret;
     52}
     53
     54static inline long linux_write(int fd, const void *data, size_t len)
     55{
     56	return x86_syscall3(__NR_write, fd, (long)data, (long)len);
     57}
     58
     59static inline void linux_exit(int code)
     60{
     61	x86_syscall3(__NR_exit, code, 0, 0);
     62}
     63
     64void to_base10(char *lastdig, time_t n)
     65{
     66	while (n) {
     67		*lastdig = (n % 10) + '0';
     68		n /= 10;
     69		lastdig--;
     70	}
     71}
     72
     73__attribute__((externally_visible)) void c_main(void **stack)
     74{
     75	/* Parse the stack */
     76	long argc = (long)*stack;
     77	stack += argc + 2;
     78
     79	/* Now we're pointing at the environment.  Skip it. */
     80	while(*stack)
     81		stack++;
     82	stack++;
     83
     84	/* Now we're pointing at auxv.  Initialize the vDSO parser. */
     85	vdso_init_from_auxv((void *)stack);
     86
     87	/* Find gettimeofday. */
     88	typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
     89	gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
     90
     91	if (!gtod)
     92		linux_exit(1);
     93
     94	struct timeval tv;
     95	long ret = gtod(&tv, 0);
     96
     97	if (ret == 0) {
     98		char buf[] = "The time is                     .000000\n";
     99		to_base10(buf + 31, tv.tv_sec);
    100		to_base10(buf + 38, tv.tv_usec);
    101		linux_write(1, buf, sizeof(buf) - 1);
    102	} else {
    103		linux_exit(ret);
    104	}
    105
    106	linux_exit(0);
    107}
    108
    109/*
    110 * This is the real entry point.  It passes the initial stack into
    111 * the C entry point.
    112 */
    113asm (
    114	".text\n"
    115	".global _start\n"
    116	".type _start,@function\n"
    117	"_start:\n\t"
    118#ifdef __x86_64__
    119	"mov %rsp,%rdi\n\t"
    120	"jmp c_main"
    121#else
    122	"push %esp\n\t"
    123	"call c_main\n\t"
    124	"int $3"
    125#endif
    126	);