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selftests/x86: Add a test for vDSO unwinding

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While the kernel itself doesn't use DWARF unwinding, user code
expects to be able to unwind the vDSO.  The vsyscall
(AT_SYSINFO) entry is manually CFI-annotated, and this tests
that it unwinds correctly.

I tested the test by incorrectly annotating __kernel_vsyscall,
and the test indeed fails if I do that.

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>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/8bf736d1925cdd165c0f980156a4248e55af47a1.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-10-05 17:47:51 -07:00 committed by Ingo Molnar
parent 7e0f51cb44
commit 3b56aae34b
2 changed files with 210 additions and 1 deletions
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2
tools/testing/selftests/x86/Makefile
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@ -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 ldt_gdt syscall_nt
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso unwind_vdso
TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)

209
tools/testing/selftests/x86/unwind_vdso.c Normal file
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@ -0,0 +1,209 @@
/*
* unwind_vdso.c - tests unwind info for AT_SYSINFO in the vDSO
* Copyright (c) 2014-2015 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 tests __kernel_vsyscall's unwind info.
*/
#define _GNU_SOURCE
#include <features.h>
#include <stdio.h>
#if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16
int main()
{
/* We need getauxval(). */
printf("[SKIP]\tGLIBC before 2.16 cannot compile this test\n");
return 0;
}
#else
#include <sys/time.h>
#include <stdlib.h>
#include <syscall.h>
#include <unistd.h>
#include <string.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <signal.h>
#include <sys/ucontext.h>
#include <err.h>
#include <stddef.h>
#include <stdbool.h>
#include <sys/ptrace.h>
#include <sys/user.h>
#include <sys/ucontext.h>
#include <link.h>
#include <sys/auxv.h>
#include <dlfcn.h>
#include <unwind.h>
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
#ifdef __x86_64__
# define WIDTH "q"
#else
# define WIDTH "l"
#endif
static unsigned long get_eflags(void)
{
unsigned long eflags;
asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
return eflags;
}
static void set_eflags(unsigned long eflags)
{
asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
: : "rm" (eflags) : "flags");
}
#define X86_EFLAGS_TF (1UL << 8)
static volatile sig_atomic_t nerrs;
static unsigned long sysinfo;
static bool got_sysinfo = false;
static unsigned long return_address;
struct unwind_state {
unsigned long ip; /* trap source */
int depth; /* -1 until we hit the trap source */
};
_Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
{
struct unwind_state *state = opaque;
unsigned long ip = _Unwind_GetIP(ctx);
if (state->depth == -1) {
if (ip == state->ip)
state->depth = 0;
else
return _URC_NO_REASON; /* Not there yet */
}
printf("\t 0x%lx\n", ip);
if (ip == return_address) {
/* Here we are. */
unsigned long eax = _Unwind_GetGR(ctx, 0);
unsigned long ecx = _Unwind_GetGR(ctx, 1);
unsigned long edx = _Unwind_GetGR(ctx, 2);
unsigned long ebx = _Unwind_GetGR(ctx, 3);
unsigned long ebp = _Unwind_GetGR(ctx, 5);
unsigned long esi = _Unwind_GetGR(ctx, 6);
unsigned long edi = _Unwind_GetGR(ctx, 7);
bool ok = (eax == SYS_getpid || eax == getpid()) &&
ebx == 1 && ecx == 2 && edx == 3 &&
esi == 4 && edi == 5 && ebp == 6;
if (!ok)
nerrs++;
printf("[%s]\t NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
(ok ? "OK" : "FAIL"),
eax, ebx, ecx, edx, esi, edi, ebp);
return _URC_NORMAL_STOP;
} else {
state->depth++;
return _URC_NO_REASON;
}
}
static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t*)ctx_void;
struct unwind_state state;
unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
if (!got_sysinfo && ip == sysinfo) {
got_sysinfo = true;
/* Find the return address. */
return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
ip, return_address);
}
if (!got_sysinfo)
return; /* Not there yet */
if (ip == return_address) {
ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
printf("\tVsyscall is done\n");
return;
}
printf("\tSIGTRAP at 0x%lx\n", ip);
state.ip = ip;
state.depth = -1;
_Unwind_Backtrace(trace_fn, &state);
}
int main()
{
sysinfo = getauxval(AT_SYSINFO);
printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
Dl_info info;
if (!dladdr((void *)sysinfo, &info)) {
printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
} else {
printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
info.dli_fname, info.dli_fbase);
}
sethandler(SIGTRAP, sigtrap, 0);
syscall(SYS_getpid); /* Force symbol binding without TF set. */
printf("[RUN]\tSet TF and check a fast syscall\n");
set_eflags(get_eflags() | X86_EFLAGS_TF);
syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
if (!got_sysinfo) {
set_eflags(get_eflags() & ~X86_EFLAGS_TF);
/*
* The most likely cause of this is that you're on Debian or
* a Debian-based distro, you're missing libc6-i686, and you're
* affected by libc/19006 (https://sourceware.org/PR19006).
*/
printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
} if (get_eflags() & X86_EFLAGS_TF) {
printf("[FAIL]\tTF is still set\n");
nerrs++;
}
if (nerrs) {
printf("[FAIL]\tThere were errors\n");
return 1;
} else {
printf("[OK]\tAll is well\n");
return 0;
}
}
#endif /* New enough libc */