On Mon, Apr 18, 2016 at 6:43 AM, Dmitry Safonov <dsafonov@xxxxxxxxxxxxx> wrote:
> Should print on success:
> [root@localhost ~]# ./test_mremap_vdso_32
> AT_SYSINFO_EHDR is 0xf773f000
> [NOTE] Moving vDSO: [f773f000, f7740000] -> [a000000, a001000]
> [OK]
> Or segfault if landing was bad (before patches):
> [root@localhost ~]# ./test_mremap_vdso_32
> AT_SYSINFO_EHDR is 0xf774f000
> [NOTE] Moving vDSO: [f774f000, f7750000] -> [a000000, a001000]
> Segmentation fault (core dumped)
>
> Cc: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
> Cc: linux-kselftest@xxxxxxxxxxxxxxx
> Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
> Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
> ---
> v5: initial version
>
> tools/testing/selftests/x86/Makefile | 2 +-
> tools/testing/selftests/x86/test_mremap_vdso.c | 72 ++++++++++++++++++++++++++
> 2 files changed, 73 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/x86/test_mremap_vdso.c
>
> diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
> index b47ebd170690..c7162b511ab0 100644
> --- a/tools/testing/selftests/x86/Makefile
> +++ b/tools/testing/selftests/x86/Makefile
> @@ -7,7 +7,7 @@ include ../lib.mk
> TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
> check_initial_reg_state sigreturn ldt_gdt iopl
> TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
> - test_FCMOV test_FCOMI test_FISTTP \
> + test_FCMOV test_FCOMI test_FISTTP test_mremap_vdso \
> vdso_restorer
>
> TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
> 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 000000000000..a470790e2118
> --- /dev/null
> +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> @@ -0,0 +1,72 @@
> +/*
> + * 32-bit test to check vdso mremap.
> + *
> + * Copyright (c) 2016 Dmitry Safonov
> + * Suggested-by: Andrew Lutomirski
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */
> +/*
> + * 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>
> +
> +#if !defined(__i386__)
> +int main(int argc, char **argv, char **envp)
> +{
> + printf("[SKIP]\tNot a 32-bit x86 userspace\n");
> + return 0;
What's wrong with testing on 64-bit systems?
> +}
> +#else
> +
> +#define PAGE_SIZE 4096
> +#define VDSO_SIZE PAGE_SIZE
The vdso is frequently bigger than a page.
> +
> +int main(int argc, char **argv, char **envp)
> +{
> + unsigned long vdso_addr, dest_addr;
> + void *new_addr;
> + const char *ok_string = "[OK]\n";
> +
> + vdso_addr = getauxval(AT_SYSINFO_EHDR);
> + printf("\tAT_SYSINFO_EHDR is 0x%lx\n", vdso_addr);
> + if (!vdso_addr || vdso_addr == -ENOENT) {
> + printf("[FAIL]\tgetauxval failed\n");
> + return 1;
Let's make this [WARN] and return 0. The vdso is optional, and
getauxval is missing on many systems.
> + }
> +
> + /* to low for stack, to high for lib/data/code mappings */
> + dest_addr = 0x0a000000;
This could be make reliable -- map a big enough area PROT_NONE and use
that address.
> + printf("[NOTE]\tMoving vDSO: [%lx, %lx] -> [%lx, %lx]\n",
> + vdso_addr, vdso_addr + VDSO_SIZE,
> + dest_addr, dest_addr + VDSO_SIZE);
fflush(stdout), please, for the benefit of test harnesses that use pipes.
--Andy
> + new_addr = mremap((void *)vdso_addr, VDSO_SIZE, VDSO_SIZE,
> + MREMAP_FIXED|MREMAP_MAYMOVE, dest_addr);
> + if ((unsigned long)new_addr == (unsigned long)-1) {
> + printf("[FAIL]\tmremap failed (%d): %m\n", errno);
> + return 1;
> + }
> +
> + asm volatile ("int $0x80" : : "a" (__NR_write), "b" (STDOUT_FILENO),
> + "c" (ok_string), "d" (strlen(ok_string)));
> + asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (0));
> +
> + return 0;
> +}
> +#endif
> --
> 2.8.0
>
--
Andy Lutomirski
AMA Capital Management, LLC
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