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Diffstat (limited to '')
-rw-r--r-- | tools/testing/selftests/x86/test_mremap_vdso.c | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c new file mode 100644 index 000000000..f0d876d48 --- /dev/null +++ b/tools/testing/selftests/x86/test_mremap_vdso.c @@ -0,0 +1,107 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 32-bit test to check vDSO mremap. + * + * Copyright (c) 2016 Dmitry Safonov + * Suggested-by: Andrew Lutomirski + */ +/* + * Can be built statically: + * gcc -Os -Wall -static -m32 test_mremap_vdso.c + */ +#define _GNU_SOURCE +#include <stdio.h> +#include <errno.h> +#include <unistd.h> +#include <string.h> + +#include <sys/mman.h> +#include <sys/auxv.h> +#include <sys/syscall.h> +#include <sys/wait.h> + +#define PAGE_SIZE 4096 + +static int try_to_remap(void *vdso_addr, unsigned long size) +{ + void *dest_addr, *new_addr; + + /* Searching for memory location where to remap */ + dest_addr = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); + if (dest_addr == MAP_FAILED) { + printf("[WARN]\tmmap failed (%d): %m\n", errno); + return 0; + } + + printf("[NOTE]\tMoving vDSO: [%p, %#lx] -> [%p, %#lx]\n", + vdso_addr, (unsigned long)vdso_addr + size, + dest_addr, (unsigned long)dest_addr + size); + fflush(stdout); + + new_addr = mremap(vdso_addr, size, size, + MREMAP_FIXED|MREMAP_MAYMOVE, dest_addr); + if ((unsigned long)new_addr == (unsigned long)-1) { + munmap(dest_addr, size); + if (errno == EINVAL) { + printf("[NOTE]\tvDSO partial move failed, will try with bigger size\n"); + return -1; /* Retry with larger */ + } + printf("[FAIL]\tmremap failed (%d): %m\n", errno); + return 1; + } + + return 0; + +} + +int main(int argc, char **argv, char **envp) +{ + pid_t child; + + child = fork(); + if (child == -1) { + printf("[WARN]\tfailed to fork (%d): %m\n", errno); + return 1; + } + + if (child == 0) { + unsigned long vdso_size = PAGE_SIZE; + unsigned long auxval; + int ret = -1; + + auxval = getauxval(AT_SYSINFO_EHDR); + printf("\tAT_SYSINFO_EHDR is %#lx\n", auxval); + if (!auxval || auxval == -ENOENT) { + printf("[WARN]\tgetauxval failed\n"); + return 0; + } + + /* Simpler than parsing ELF header */ + while (ret < 0) { + ret = try_to_remap((void *)auxval, vdso_size); + vdso_size += PAGE_SIZE; + } + +#ifdef __i386__ + /* Glibc is likely to explode now - exit with raw syscall */ + asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret)); +#else /* __x86_64__ */ + syscall(SYS_exit, ret); +#endif + } else { + int status; + + if (waitpid(child, &status, 0) != child || + !WIFEXITED(status)) { + printf("[FAIL]\tmremap() of the vDSO does not work on this kernel!\n"); + return 1; + } else if (WEXITSTATUS(status) != 0) { + printf("[FAIL]\tChild failed with %d\n", + WEXITSTATUS(status)); + return 1; + } + printf("[OK]\n"); + } + + return 0; +} |