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Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse Source 
Pull x86 fixes from Ingo Molnar:
 "This tree includes:

   - an FPU related crash fix

   - a ptrace fix (with matching testcase in tools/testing/selftests/)

   - an x86 Kconfig DMA-config defaults tweak to better avoid
     non-working drivers"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  config: Enable NEED_DMA_MAP_STATE by default when SWIOTLB is selected
  x86/fpu: Load xsave pointer *after* initialization
  x86/ptrace: Fix the TIF_FORCED_TF logic in handle_signal()
  x86, selftests: Add single_step_syscall test
This commit is contained in:
Linus Torvalds 2015-04-18 11:31:11 -04:00
commit 90d1c08786
6 changed files with 202 additions and 15 deletions
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2
arch/x86/Kconfig
View File

@ -178,7 +178,7 @@ config SBUS
config NEED_DMA_MAP_STATE
def_bool y
depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG
depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
config NEED_SG_DMA_LENGTH
def_bool y

8
arch/x86/kernel/i387.c
View File

@ -341,7 +341,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
void *kbuf, void __user *ubuf)
{
struct xsave_struct *xsave = &target->thread.fpu.state->xsave;
struct xsave_struct *xsave;
int ret;
if (!cpu_has_xsave)
@ -351,6 +351,8 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
if (ret)
return ret;
xsave = &target->thread.fpu.state->xsave;
/*
* Copy the 48bytes defined by the software first into the xstate
* memory layout in the thread struct, so that we can copy the entire
@ -369,7 +371,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
struct xsave_struct *xsave = &target->thread.fpu.state->xsave;
struct xsave_struct *xsave;
int ret;
if (!cpu_has_xsave)
@ -379,6 +381,8 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
if (ret)
return ret;
xsave = &target->thread.fpu.state->xsave;
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
/*
* mxcsr reserved bits must be masked to zero for security reasons.

22
arch/x86/kernel/signal.c
View File

@ -616,7 +616,8 @@ setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
bool failed;
bool stepping, failed;
/* Are we from a system call? */
if (syscall_get_nr(current, regs) >= 0) {
/* If so, check system call restarting.. */
@ -640,12 +641,13 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
}
/*
* If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
* flag so that register information in the sigcontext is correct.
* If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
* so that register information in the sigcontext is correct and
* then notify the tracer before entering the signal handler.
*/
if (unlikely(regs->flags & X86_EFLAGS_TF) &&
likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
regs->flags &= ~X86_EFLAGS_TF;
stepping = test_thread_flag(TIF_SINGLESTEP);
if (stepping)
user_disable_single_step(current);
failed = (setup_rt_frame(ksig, regs) < 0);
if (!failed) {
@ -656,10 +658,8 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
* it might disable possible debug exception from the
* signal handler.
*
* Clear TF when entering the signal handler, but
* notify any tracer that was single-stepping it.
* The tracer may want to single-step inside the
* handler too.
* Clear TF for the case when it wasn't set by debugger to
* avoid the recursive send_sigtrap() in SIGTRAP handler.
*/
regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
/*
@ -668,7 +668,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
if (used_math())
fpu_reset_state(current);
}
signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));
signal_setup_done(failed, ksig, stepping);
}
#ifdef CONFIG_X86_32

2
tools/testing/selftests/x86/Makefile
View File

@ -1,6 +1,6 @@
.PHONY: all all_32 all_64 check_build32 clean run_tests
TARGETS_C_BOTHBITS := sigreturn
TARGETS_C_BOTHBITS := sigreturn single_step_syscall
BINARIES_32 := $(TARGETS_C_BOTHBITS:%=%_32)
BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64)

2
tools/testing/selftests/x86/run_x86_tests.sh
View File

@ -3,9 +3,11 @@
# This is deliberately minimal. IMO kselftests should provide a standard
# script here.
./sigreturn_32 || exit 1
./single_step_syscall_32 || exit 1
if [[ "$uname -p" -eq "x86_64" ]]; then
./sigreturn_64 || exit 1
./single_step_syscall_64 || exit 1
fi
exit 0

181
tools/testing/selftests/x86/single_step_syscall.c Normal file
View File

@ -0,0 +1,181 @@
/*
* single_step_syscall.c - single-steps various x86 syscalls
* 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 is a very simple series of tests that makes system calls with
* the TF flag set. This exercises some nasty kernel code in the
* SYSENTER case: SYSENTER does not clear TF, so SYSENTER with TF set
* immediately issues #DB from CPL 0. This requires special handling in
* the kernel.
*/
#define _GNU_SOURCE
#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <sys/signal.h>
#include <sys/ucontext.h>
#include <asm/ldt.h>
#include <err.h>
#include <setjmp.h>
#include <stddef.h>
#include <stdbool.h>
#include <sys/ptrace.h>
#include <sys/user.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");
}
static volatile sig_atomic_t sig_traps;
#ifdef __x86_64__
# define REG_IP REG_RIP
# define WIDTH "q"
#else
# define REG_IP REG_EIP
# 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 void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t*)ctx_void;
if (get_eflags() & X86_EFLAGS_TF) {
set_eflags(get_eflags() & ~X86_EFLAGS_TF);
printf("[WARN]\tSIGTRAP handler had TF set\n");
_exit(1);
}
sig_traps++;
if (sig_traps == 10000 || sig_traps == 10001) {
printf("[WARN]\tHit %d SIGTRAPs with si_addr 0x%lx, ip 0x%lx\n",
(int)sig_traps,
(unsigned long)info->si_addr,
(unsigned long)ctx->uc_mcontext.gregs[REG_IP]);
}
}
static void check_result(void)
{
unsigned long new_eflags = get_eflags();
set_eflags(new_eflags & ~X86_EFLAGS_TF);
if (!sig_traps) {
printf("[FAIL]\tNo SIGTRAP\n");
exit(1);
}
if (!(new_eflags & X86_EFLAGS_TF)) {
printf("[FAIL]\tTF was cleared\n");
exit(1);
}
printf("[OK]\tSurvived with TF set and %d traps\n", (int)sig_traps);
sig_traps = 0;
}
int main()
{
int tmp;
sethandler(SIGTRAP, sigtrap, 0);
printf("[RUN]\tSet TF and check nop\n");
set_eflags(get_eflags() | X86_EFLAGS_TF);
asm volatile ("nop");
check_result();
#ifdef __x86_64__
printf("[RUN]\tSet TF and check syscall-less opportunistic sysret\n");
set_eflags(get_eflags() | X86_EFLAGS_TF);
extern unsigned char post_nop[];
asm volatile ("pushf" WIDTH "\n\t"
"pop" WIDTH " %%r11\n\t"
"nop\n\t"
"post_nop:"
: : "c" (post_nop) : "r11");
check_result();
#endif
printf("[RUN]\tSet TF and check int80\n");
set_eflags(get_eflags() | X86_EFLAGS_TF);
asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid));
check_result();
/*
* This test is particularly interesting if fast syscalls use
* SYSENTER: it triggers a nasty design flaw in SYSENTER.
* Specifically, SYSENTER does not clear TF, so either SYSENTER
* or the next instruction traps at CPL0. (Of course, Intel
* mostly forgot to document exactly what happens here.) So we
* get a CPL0 fault with usergs (on 64-bit kernels) and possibly
* no stack. The only sane way the kernel can possibly handle
* it is to clear TF on return from the #DB handler, but this
* happens way too early to set TF in the saved pt_regs, so the
* kernel has to do something clever to avoid losing track of
* the TF bit.
*
* Needless to say, we've had bugs in this area.
*/
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);
check_result();
/* Now make sure that another fast syscall doesn't set TF again. */
printf("[RUN]\tFast syscall with TF cleared\n");
fflush(stdout); /* Force a syscall */
if (get_eflags() & X86_EFLAGS_TF) {
printf("[FAIL]\tTF is now set\n");
exit(1);
}
if (sig_traps) {
printf("[FAIL]\tGot SIGTRAP\n");
exit(1);
}
printf("[OK]\tNothing unexpected happened\n");
return 0;
}