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Date: Fri, 22 Apr 2016 14:34:23 +0300
From: Dmitry Safonov <dsafonov@...tuozzo.com>
To: Andy Lutomirski <luto@...capital.net>
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: [PATCHv5 3/3] selftest/x86: add mremap vdso 32-bit test
On 04/21/2016 11:01 PM, Andy Lutomirski wrote:
> On Mon, Apr 18, 2016 at 6:43 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)
>>
>> 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>
>> ---
>> 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?
Ok, will drop this.
>> +}
>> +#else
>> +
>> +#define PAGE_SIZE 4096
>> +#define VDSO_SIZE PAGE_SIZE
> The vdso is frequently bigger than a page.
Ok, will enlarge this. Are two pages big enough?
>> +
>> +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.
Ok
>> + }
>> +
>> + /* 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.
Oh, that's good, will do.
>> + 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.
Will add.
>> + 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
>>
>
>
--
Regards,
Dmitry Safonov
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