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Message-ID: <tip-65cacec1ba908a153cfb19c4de596a108f95970c@git.kernel.org>
Date: Wed, 13 Jan 2016 01:37:04 -0800
From: tip-bot for Andy Lutomirski <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: hpa@...or.com, bp@...en8.de, shuahkh@....samsung.com,
linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
tglx@...utronix.de, mingo@...nel.org, luto@...nel.org,
dvlasenk@...hat.com, luto@...capital.net, peterz@...radead.org,
brgerst@...il.com
Subject: [tip:x86/urgent] selftests/x86:
Test __kernel_sigreturn and __kernel_rt_sigreturn
Commit-ID: 65cacec1ba908a153cfb19c4de596a108f95970c
Gitweb: http://git.kernel.org/tip/65cacec1ba908a153cfb19c4de596a108f95970c
Author: Andy Lutomirski <luto@...nel.org>
AuthorDate: Tue, 12 Jan 2016 11:56:15 -0800
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 13 Jan 2016 10:34:40 +0100
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@...nel.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Shuah Khan <shuahkh@....samsung.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/32946d714156879cd8e5d8eab044cd07557ed558.1452628504.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
tools/testing/selftests/x86/Makefile | 3 +-
tools/testing/selftests/x86/vdso_restorer.c | 88 +++++++++++++++++++++++++++++
2 files changed, 90 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 398bb0e..d0c473f 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -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)
diff --git a/tools/testing/selftests/x86/vdso_restorer.c b/tools/testing/selftests/x86/vdso_restorer.c
new file mode 100644
index 0000000..cb03842
--- /dev/null
+++ b/tools/testing/selftests/x86/vdso_restorer.c
@@ -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++;
+ }
+}
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