From b5908548537ccd3ada258ca5348df7ffc93e5a06 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 10 Nov 2010 22:29:49 -0500 Subject: tracing: Force arch_local_irq_* notrace for paravirt When running ktest.pl randconfig tests, I would sometimes trigger a lockdep annotation bug (possible reason: unannotated irqs-on). This triggering happened right after function tracer self test was executed. After doing a config bisect I found that this was caused with having function tracer, paravirt guest, prove locking, and rcu torture all enabled. The rcu torture just enhanced the likelyhood of triggering the bug. Prove locking was needed, since it was the thing that was bugging. Function tracer would trace and disable interrupts in all sorts of funny places. paravirt guest would turn arch_local_irq_* into functions that would be traced. Besides the fact that tracing arch_local_irq_* is just a bad idea, this is what is happening. The bug happened simply in the local_irq_restore() code: if (raw_irqs_disabled_flags(flags)) { \ raw_local_irq_restore(flags); \ trace_hardirqs_off(); \ } else { \ trace_hardirqs_on(); \ raw_local_irq_restore(flags); \ } \ The raw_local_irq_restore() was defined as arch_local_irq_restore(). Now imagine, we are about to enable interrupts. We go into the else case and call trace_hardirqs_on() which tells lockdep that we are enabling interrupts, so it sets the current->hardirqs_enabled = 1. Then we call raw_local_irq_restore() which calls arch_local_irq_restore() which gets traced! Now in the function tracer we disable interrupts with local_irq_save(). This is fine, but flags is stored that we have interrupts disabled. When the function tracer calls local_irq_restore() it does it, but this time with flags set as disabled, so we go into the if () path. This keeps interrupts disabled and calls trace_hardirqs_off() which sets current->hardirqs_enabled = 0. When the tracer is finished and proceeds with the original code, we enable interrupts but leave current->hardirqs_enabled as 0. Which now breaks lockdeps internal processing. Cc: Thomas Gleixner Signed-off-by: Steven Rostedt --- arch/x86/include/asm/paravirt.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 18e3b8a8709f..ef9975812c77 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -824,27 +824,27 @@ static __always_inline void arch_spin_unlock(struct arch_spinlock *lock) #define __PV_IS_CALLEE_SAVE(func) \ ((struct paravirt_callee_save) { func }) -static inline unsigned long arch_local_save_flags(void) +static inline notrace unsigned long arch_local_save_flags(void) { return PVOP_CALLEE0(unsigned long, pv_irq_ops.save_fl); } -static inline void arch_local_irq_restore(unsigned long f) +static inline notrace void arch_local_irq_restore(unsigned long f) { PVOP_VCALLEE1(pv_irq_ops.restore_fl, f); } -static inline void arch_local_irq_disable(void) +static inline notrace void arch_local_irq_disable(void) { PVOP_VCALLEE0(pv_irq_ops.irq_disable); } -static inline void arch_local_irq_enable(void) +static inline notrace void arch_local_irq_enable(void) { PVOP_VCALLEE0(pv_irq_ops.irq_enable); } -static inline unsigned long arch_local_irq_save(void) +static inline notrace unsigned long arch_local_irq_save(void) { unsigned long f; -- cgit v1.2.3 From 6c0aca288e726405b01dacb12cac556454d34b2a Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 11 Nov 2010 21:18:43 +0100 Subject: x86: Ignore trap bits on single step exceptions When a single step exception fires, the trap bits, used to signal hardware breakpoints, are in a random state. These trap bits might be set if another exception will follow, like a breakpoint in the next instruction, or a watchpoint in the previous one. Or there can be any junk there. So if we handle these trap bits during the single step exception, we are going to handle an exception twice, or we are going to handle junk. Just ignore them in this case. This fixes https://bugzilla.kernel.org/show_bug.cgi?id=21332 Reported-by: Michael Stefaniuc Signed-off-by: Frederic Weisbecker Cc: Rafael J. Wysocki Cc: Maciej Rutecki Cc: Alexandre Julliard Cc: Jason Wessel Cc: All since 2.6.33.x --- arch/x86/kernel/hw_breakpoint.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch') diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index ff15c9dcc25d..42c594254507 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -433,6 +433,10 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args) dr6_p = (unsigned long *)ERR_PTR(args->err); dr6 = *dr6_p; + /* If it's a single step, TRAP bits are random */ + if (dr6 & DR_STEP) + return NOTIFY_DONE; + /* Do an early return if no trap bits are set in DR6 */ if ((dr6 & DR_TRAP_BITS) == 0) return NOTIFY_DONE; -- cgit v1.2.3 From 0e2af2a9abf94b408ff70679b692a8644fed4aab Mon Sep 17 00:00:00 2001 From: Rakib Mullick Date: Fri, 12 Nov 2010 09:50:54 -0500 Subject: x86, hw_nmi: Move backtrace_mask declaration under ARCH_HAS_NMI_WATCHDOG MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit backtrace_mask has been used under the code context of ARCH_HAS_NMI_WATCHDOG. So put it into that context. We were warned by the following warning: arch/x86/kernel/apic/hw_nmi.c:21: warning: ‘backtrace_mask’ defined but not used Signed-off-by: Rakib Mullick Signed-off-by: Don Zickus LKML-Reference: <1289573455-3410-2-git-send-email-dzickus@redhat.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic/hw_nmi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index cefd6942f0e9..62f6e1e55b90 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -17,15 +17,16 @@ #include #include -/* For reliability, we're prepared to waste bits here. */ -static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; - u64 hw_nmi_get_sample_period(void) { return (u64)(cpu_khz) * 1000 * 60; } #ifdef ARCH_HAS_NMI_WATCHDOG + +/* For reliability, we're prepared to waste bits here. */ +static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; + void arch_trigger_all_cpu_backtrace(void) { int i; -- cgit v1.2.3 From de31ec8a31046111befd16a7083e3bdda2ff42cf Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 18 Nov 2010 19:16:55 +0900 Subject: x86/kprobes: Prevent kprobes to probe on save_args() Prevent kprobes to probe on save_args() since this function will be called from breakpoint exception handler. That will cause infinit loop on breakpoint handling. Signed-off-by: Masami Hiramatsu Cc: 2nddept-manager@sdl.hitachi.co.jp Cc: Ananth N Mavinakayanahalli LKML-Reference: <20101118101655.2779.2816.stgit@ltc236.sdl.hitachi.co.jp> Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch') diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index fe2690d71c0c..e3ba417e8697 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -295,6 +295,7 @@ ENDPROC(native_usergs_sysret64) .endm /* save partial stack frame */ + .pushsection .kprobes.text, "ax" ENTRY(save_args) XCPT_FRAME cld @@ -334,6 +335,7 @@ ENTRY(save_args) ret CFI_ENDPROC END(save_args) + .popsection ENTRY(save_rest) PARTIAL_FRAME 1 REST_SKIP+8 -- cgit v1.2.3