[GIT PULL] x86 fixes

Ingo Molnar
2015-04-18T15:26:21Z

Linus,

Please pull the latest x86-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

# HEAD: a6dfa128ce5c414ab46b1d690f7a1b8decb8526d config: Enable NEED_DMA_MAP_STATE by default when SWIOTLB is selected

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

out-of-topic modifications in x86-urgent-for-linus:
-----------------------------------------------------
tools/testing/selftests/x86/Makefile# 0a15584d7276: x86, selftests: Add single_s
tools/testing/selftests/x86/run_x86_tests.sh# 0a15584d7276: x86, selftests: Add single_s
tools/testing/selftests/x86/single_step_syscall.c# 0a15584d7276: x86, selftests: Add single_s

Thanks,

Ingo

------------------>
Andy Lutomirski (1):
x86, selftests: Add single_step_syscall test

Borislav Petkov (1):
x86/fpu: Load xsave pointer *after* initialization

Konrad Rzeszutek Wilk (1):
config: Enable NEED_DMA_MAP_STATE by default when SWIOTLB is selected

Oleg Nesterov (1):
x86/ptrace: Fix the TIF_FORCED_TF logic in handle_signal()

arch/x86/Kconfig | 2 +-
arch/x86/kernel/i387.c | 8 +-
arch/x86/kernel/signal.c | 22 +--
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/run_x86_tests.sh | 2 +
tools/testing/selftests/x86/single_step_syscall.c | 181 ++++++++++++++++++++++
6 files changed, 202 insertions(+), 15 deletions(-)
create mode 100644 tools/testing/selftests/x86/single_step_syscall.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index faff6934c05a..eb79036e3503 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -177,7 +177,7 @@ 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
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 367f39d35e9c..009183276bb7 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -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.
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 3e581865c8e2..d185bdd95a4b 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -630,7 +630,8 @@ 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.. */
@@ -654,12 +655,13 @@ 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) {
@@ -670,10 +672,8 @@ 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);
/*
@@ -682,7 +682,7 @@ 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
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index f0a7918178dd..ddf63569df5a 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -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)
diff --git a/tools/testing/selftests/x86/run_x86_tests.sh b/tools/testing/selftests/x86/run_x86_tests.sh
index 3d3ec65f3e7c..3fc19b376812 100644
--- a/tools/testing/selftests/x86/run_x86_tests.sh
+++ b/tools/testing/selftests/x86/run_x86_tests.sh
@@ -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
diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c
new file mode 100644
index 000000000000..50c26358e8b7
--- /dev/null
+++ b/tools/testing/selftests/x86/single_step_syscall.c
@@ -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;
+}