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 } 107