tools/testing/selftests/x86/test_mremap_vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * 32-bit test to check vDSO mremap.
   4  *
   5  * Copyright (c) 2016 Dmitry Safonov
   6  * Suggested-by: Andrew Lutomirski
   7  */
   8 /*
   9  * Can be built statically:
  10  * gcc -Os -Wall -static -m32 test_mremap_vdso.c
  11  */
  12 #define _GNU_SOURCE
  13 #include <stdio.h>
  14 #include <errno.h>
  15 #include <unistd.h>
  16 #include <string.h>
  17
  18 #include <sys/mman.h>
  19 #include <sys/auxv.h>
  20 #include <sys/syscall.h>
  21 #include <sys/wait.h>
  22 #include "../kselftest.h"
  23
  24 #define PAGE_SIZE       4096
  25
  26 static int try_to_remap(void *vdso_addr, unsigned long size)
  27 {
  28         void *dest_addr, *new_addr;
  29
  30         /* Searching for memory location where to remap */
  31         dest_addr = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
  32         if (dest_addr == MAP_FAILED) {
  33                 ksft_print_msg("WARN: mmap failed (%d): %m\n", errno);
  34                 return 0;
  35         }
  36
  37         ksft_print_msg("Moving vDSO: [%p, %#lx] -> [%p, %#lx]\n",
  38                        vdso_addr, (unsigned long)vdso_addr + size,
  39                        dest_addr, (unsigned long)dest_addr + size);
  40         fflush(stdout);
  41
  42         new_addr = mremap(vdso_addr, size, size,
  43                         MREMAP_FIXED|MREMAP_MAYMOVE, dest_addr);
  44         if ((unsigned long)new_addr == (unsigned long)-1) {
  45                 munmap(dest_addr, size);
  46                 if (errno == EINVAL) {
  47                         ksft_print_msg("vDSO partial move failed, will try with bigger size\n");
  48                         return -1; /* Retry with larger */
  49                 }
  50                 ksft_print_msg("[FAIL]\tmremap failed (%d): %m\n", errno);
  51                 return 1;
  52         }
  53
  54         return 0;
  55
  56 }
  57
  58 int main(int argc, char **argv, char **envp)
  59 {
  60         pid_t child;
  61
  62         ksft_print_header();
  63         ksft_set_plan(1);
  64
  65         child = fork();
  66         if (child == -1)
  67                 ksft_exit_fail_msg("failed to fork (%d): %m\n", errno);
  68
  69         if (child == 0) {
  70                 unsigned long vdso_size = PAGE_SIZE;
  71                 unsigned long auxval;
  72                 int ret = -1;
  73
  74                 auxval = getauxval(AT_SYSINFO_EHDR);
  75                 ksft_print_msg("AT_SYSINFO_EHDR is %#lx\n", auxval);
  76                 if (!auxval || auxval == -ENOENT) {
  77                         ksft_print_msg("WARN: getauxval failed\n");
  78                         return 0;
  79                 }
  80
  81                 /* Simpler than parsing ELF header */
  82                 while (ret < 0) {
  83                         ret = try_to_remap((void *)auxval, vdso_size);
  84                         vdso_size += PAGE_SIZE;
  85                 }
  86
  87 #ifdef __i386__
  88                 /* Glibc is likely to explode now - exit with raw syscall */
  89                 asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret));
  90 #else /* __x86_64__ */
  91                 syscall(SYS_exit, ret);
  92 #endif
  93         } else {
  94                 int status;
  95
  96                 if (waitpid(child, &status, 0) != child ||
  97                         !WIFEXITED(status))
  98                         ksft_test_result_fail("mremap() of the vDSO does not work on this kernel!\n");
  99                 else if (WEXITSTATUS(status) != 0)
 100                         ksft_test_result_fail("Child failed with %d\n", WEXITSTATUS(status));
 101                 else
 102                         ksft_test_result_pass("%s\n", __func__);
 103         }
 104
 105         ksft_finished();
 106 }