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Date: Mon, 25 Apr 2016 14:39:31 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Dmitry Safonov <dsafonov@...tuozzo.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Dmitry Safonov <0x7f454c46@...il.com>,
Shuah Khan <shuahkh@....samsung.com>,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCHv8 2/2] selftest/x86: add mremap vdso test
On Mon, Apr 25, 2016 at 4:37 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
> Should print on success:
> [root@...alhost ~]# ./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@...alhost ~]# ./test_mremap_vdso_32
> AT_SYSINFO_EHDR is 0xf774f000
> [NOTE] Moving vDSO: [f774f000, f7750000] -> [a000000, a001000]
> Segmentation fault (core dumped)
Acked-by: Andy Lutomirski <luto@...capital.net>
Ingo, can you apply this?
>
> Cc: Shuah Khan <shuahkh@....samsung.com>
> Cc: linux-kselftest@...r.kernel.org
> Suggested-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.com>
> ---
> v8: run test for x86_64 too;
> removed fixed VDSO_SIZE - check EINVAL mremap return for partial remapping
> v5: initial version
>
> tools/testing/selftests/x86/Makefile | 2 +-
> tools/testing/selftests/x86/test_mremap_vdso.c | 99 ++++++++++++++++++++++++++
> 2 files changed, 100 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..ba865f2efcce 100644
> --- a/tools/testing/selftests/x86/Makefile
> +++ b/tools/testing/selftests/x86/Makefile
> @@ -5,7 +5,7 @@ include ../lib.mk
> .PHONY: all all_32 all_64 warn_32bit_failure clean
>
> TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
> - check_initial_reg_state sigreturn ldt_gdt iopl
> + check_initial_reg_state sigreturn ldt_gdt iopl test_mremap_vdso
> TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
> test_FCMOV test_FCOMI test_FISTTP \
> vdso_restorer
> 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..831e2e0107d9
> --- /dev/null
> +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> @@ -0,0 +1,99 @@
> +/*
> + * 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>
> +
> +#define PAGE_SIZE 4096
> +
> +static int try_to_remap(void *vdso_addr, unsigned long size)
> +{
> + void *dest_addr, *new_addr;
> +
> + 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)
> +{
> + unsigned long auxval;
> + const char *ok_string = "[OK]\n";
> + int ret = -1;
> + unsigned long vdso_size = PAGE_SIZE;
> +
> + 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;
> + }
> +
> + if (!ret)
> +#if defined(__i386__)
> + 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" (!!ret));
> +#else
> + asm volatile ("syscall" : :
> + "a" (__NR_write), "D" (STDOUT_FILENO),
> + "S" (ok_string), "d" (strlen(ok_string)));
> +
> + asm volatile ("syscall" : : "a" (__NR_exit), "D" (!!ret));
> +#endif
> +
> + return 0;
> +}
> --
> 2.8.0
>
--
Andy Lutomirski
AMA Capital Management, LLC
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