From 06532a6743d83fac4b79389fc8c86c88cb4e3302 Mon Sep 17 00:00:00 2001 From: "K.Prasad" Date: Tue, 15 Jun 2010 11:35:41 +0530 Subject: [PATCH] powerpc, hw_breakpoint: Enable hw-breakpoints while handling intervening signals A signal delivered between a hw_breakpoint_handler() and the single_step_dabr_instruction() will not have the breakpoint active while the signal handler is running -- the signal delivery will set up a new MSR value which will not have MSR_SE set, so we won't get the signal step interrupt until and unless the signal handler returns (which it may never do). To fix this, we restore the breakpoint when delivering a signal -- we clear the MSR_SE bit and set the DABR again. If the signal handler returns, the DABR interrupt will occur again when the instruction that we were originally trying to single-step gets re-executed. [Paul Mackerras pointed out the need to do this.] Signed-off-by: K.Prasad Signed-off-by: Paul Mackerras --- arch/powerpc/include/asm/hw_breakpoint.h | 3 +++ arch/powerpc/kernel/hw_breakpoint.c | 18 ++++++++++++++++++ arch/powerpc/kernel/signal.c | 3 +++ 3 files changed, 24 insertions(+) diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h index b111713b593..6576bad1069 100644 --- a/arch/powerpc/include/asm/hw_breakpoint.h +++ b/arch/powerpc/include/asm/hw_breakpoint.h @@ -65,9 +65,12 @@ static inline void hw_breakpoint_disable(void) { set_dabr(0); } +extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs); #else /* CONFIG_HAVE_HW_BREAKPOINT */ static inline void hw_breakpoint_disable(void) { } +static inline void thread_change_pc(struct task_struct *tsk, + struct pt_regs *regs) { } #endif /* CONFIG_HAVE_HW_BREAKPOINT */ #endif /* __KERNEL__ */ #endif /* _PPC_BOOK3S_64_HW_BREAKPOINT_H */ diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index 7a2ad5e84c1..7bd01a56d19 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -174,6 +174,24 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp) return 0; } +/* + * Restores the breakpoint on the debug registers. + * Invoke this function if it is known that the execution context is + * about to change to cause loss of MSR_SE settings. + */ +void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs) +{ + struct arch_hw_breakpoint *info; + + if (likely(!tsk->thread.last_hit_ubp)) + return; + + info = counter_arch_bp(tsk->thread.last_hit_ubp); + regs->msr &= ~MSR_SE; + set_dabr(info->address | info->type | DABR_TRANSLATION); + tsk->thread.last_hit_ubp = NULL; +} + /* * Handle debug exception notifications. */ diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c index a0afb555a7c..7109f5b1baa 100644 --- a/arch/powerpc/kernel/signal.c +++ b/arch/powerpc/kernel/signal.c @@ -11,6 +11,7 @@ #include #include +#include #include #include @@ -149,6 +150,8 @@ static int do_signal_pending(sigset_t *oldset, struct pt_regs *regs) if (current->thread.dabr) set_dabr(current->thread.dabr); #endif + /* Re-enable the breakpoints for the signal stack */ + thread_change_pc(current, regs); if (is32) { if (ka.sa.sa_flags & SA_SIGINFO) -- 2.46.0