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 #include <stdbool.h> 18 19 #include <sys/mman.h> 20 #include <sys/auxv.h> 21 #include <sys/syscall.h> 22 #include <sys/wait.h> 23 #include "../kselftest.h" 24 25 #define PAGE_SIZE 4096 26 27 static int try_to_remap(void *vdso_addr, unsigned long size) 28 { 29 void *dest_addr, *new_addr; 30 31 /* Searching for memory location where to remap */ 32 dest_addr = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); 33 if (dest_addr == MAP_FAILED) { 34 ksft_print_msg("WARN: mmap failed (%d): %m\n", errno); 35 return 0; 36 } 37 38 ksft_print_msg("Moving vDSO: [%p, %#lx] -> [%p, %#lx]\n", 39 vdso_addr, (unsigned long)vdso_addr + size, 40 dest_addr, (unsigned long)dest_addr + size); 41 fflush(stdout); 42 43 new_addr = mremap(vdso_addr, size, size, 44 MREMAP_FIXED|MREMAP_MAYMOVE, dest_addr); 45 if ((unsigned long)new_addr == (unsigned long)-1) { 46 munmap(dest_addr, size); 47 if (errno == EINVAL) { 48 ksft_print_msg("vDSO partial move failed, will try with bigger size\n"); 49 return -1; /* Retry with larger */ 50 } 51 ksft_print_msg("[FAIL]\tmremap failed (%d): %m\n", errno); 52 return 1; 53 } 54 55 return 0; 56 57 } 58 59 #define VDSO_NAME "[vdso]" 60 #define VMFLAGS "VmFlags:" 61 #define MSEAL_FLAGS "sl" 62 #define MAX_LINE_LEN 512 63 64 bool vdso_sealed(FILE *maps) 65 { 66 char line[MAX_LINE_LEN]; 67 bool has_vdso = false; 68 69 while (fgets(line, sizeof(line), maps)) { 70 if (strstr(line, VDSO_NAME)) 71 has_vdso = true; 72 73 if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) { 74 if (strstr(line, MSEAL_FLAGS)) 75 return true; 76 77 return false; 78 } 79 } 80 81 return false; 82 } 83 84 int main(int argc, char **argv, char **envp) 85 { 86 pid_t child; 87 FILE *maps; 88 89 ksft_print_header(); 90 ksft_set_plan(1); 91 92 maps = fopen("/proc/self/smaps", "r"); 93 if (!maps) { 94 ksft_test_result_skip( 95 "Could not open /proc/self/smaps, errno=%d\n", 96 errno); 97 98 return 0; 99 } 100 101 if (vdso_sealed(maps)) { 102 ksft_test_result_skip("vdso is sealed\n"); 103 return 0; 104 } 105 106 fclose(maps); 107 108 child = fork(); 109 if (child == -1) 110 ksft_exit_fail_msg("failed to fork (%d): %m\n", errno); 111 112 if (child == 0) { 113 unsigned long vdso_size = PAGE_SIZE; 114 unsigned long auxval; 115 int ret = -1; 116 117 auxval = getauxval(AT_SYSINFO_EHDR); 118 ksft_print_msg("AT_SYSINFO_EHDR is %#lx\n", auxval); 119 if (!auxval || auxval == -ENOENT) { 120 ksft_print_msg("WARN: getauxval failed\n"); 121 return 0; 122 } 123 124 /* Simpler than parsing ELF header */ 125 while (ret < 0) { 126 ret = try_to_remap((void *)auxval, vdso_size); 127 vdso_size += PAGE_SIZE; 128 } 129 130 #ifdef __i386__ 131 /* Glibc is likely to explode now - exit with raw syscall */ 132 asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret)); 133 #else /* __x86_64__ */ 134 syscall(SYS_exit, ret); 135 #endif 136 } else { 137 int status; 138 139 if (waitpid(child, &status, 0) != child || 140 !WIFEXITED(status)) 141 ksft_test_result_fail("mremap() of the vDSO does not work on this kernel!\n"); 142 else if (WEXITSTATUS(status) != 0) 143 ksft_test_result_fail("Child failed with %d\n", WEXITSTATUS(status)); 144 else 145 ksft_test_result_pass("%s\n", __func__); 146 } 147 148 ksft_finished(); 149 } 150