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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * 32-bit test to check vDSO mremap.4 *5 * Copyright (c) 2016 Dmitry Safonov6 * Suggested-by: Andrew Lutomirski7 */8/*9 * Can be built statically:10 * gcc -Os -Wall -static -m32 test_mremap_vdso.c11 */12#define _GNU_SOURCE13#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 409625 26static 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 58int 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#endif93 } 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 else102 ksft_test_result_pass("%s\n", __func__);103 }104 105 ksft_finished();106}107