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selftests/x86: Test __kernel_sigreturn and __kernel_rt_sigreturn 

The vdso-based sigreturn mechanism is fragile and isn't used by
modern glibc so, if we break it, we'll only notice when someone
tests an unusual libc.

Add an explicit selftest.

[ I wrote this while debugging a Bionic breakage -- my first guess
  was that I had somehow messed up sigreturn.  I've caused problems in
  that code before, and it's really easy to fail to notice it because
  there's nothing on a modern distro that needs vdso-based sigreturn. ]

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/32946d714156879cd8e5d8eab044cd07557ed558.1452628504.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-01-12 11:56:15 -08:00 committed by Ingo Molnar
parent 2f0c0b2d96
commit 65cacec1ba
2 changed files with 90 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
tools/testing/selftests/x86/Makefile
View File

@ -7,7 +7,8 @@ include ../lib.mk
TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
ldt_gdt
ldt_gdt \
vdso_restorer
TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)

88
tools/testing/selftests/x86/vdso_restorer.c Normal file
View File

@ -0,0 +1,88 @@
/*
* vdso_restorer.c - tests vDSO-based signal restore
* Copyright (c) 2015 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.
*
* This makes sure that sa_restorer == NULL keeps working on 32-bit
* configurations. Modern glibc doesn't use it under any circumstances,
* so it's easy to overlook breakage.
*
* 64-bit userspace has never supported sa_restorer == NULL, so this is
* 32-bit only.
*/
#define _GNU_SOURCE
#include <err.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <syscall.h>
#include <sys/syscall.h>
/* Open-code this -- the headers are too messy to easily use them. */
struct real_sigaction {
void *handler;
unsigned long flags;
void *restorer;
unsigned int mask[2];
};
static volatile sig_atomic_t handler_called;
static void handler_with_siginfo(int sig, siginfo_t *info, void *ctx_void)
{
handler_called = 1;
}
static void handler_without_siginfo(int sig)
{
handler_called = 1;
}
int main()
{
int nerrs = 0;
struct real_sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.handler = handler_with_siginfo;
sa.flags = SA_SIGINFO;
sa.restorer = NULL; /* request kernel-provided restorer */
if (syscall(SYS_rt_sigaction, SIGUSR1, &sa, NULL, 8) != 0)
err(1, "raw rt_sigaction syscall");
raise(SIGUSR1);
if (handler_called) {
printf("[OK]\tSA_SIGINFO handler returned successfully\n");
} else {
printf("[FAIL]\tSA_SIGINFO handler was not called\n");
nerrs++;
}
sa.flags = 0;
sa.handler = handler_without_siginfo;
if (syscall(SYS_sigaction, SIGUSR1, &sa, 0) != 0)
err(1, "raw sigaction syscall");
handler_called = 0;
raise(SIGUSR1);
if (handler_called) {
printf("[OK]\t!SA_SIGINFO handler returned successfully\n");
} else {
printf("[FAIL]\t!SA_SIGINFO handler was not called\n");
nerrs++;
}
}