[Patch 4/5] PPC64-HWBKPT: 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 during signal handling (since breakpoint will not be restored through single-stepping due to absence of MSR_SE bit on the signal frame). Enable breakpoints before signal delivery. Restore hw-breakpoints if the user-context is altered in the signal handler. [With inputs from Paul Mackerras which helped identify a need to restore breakpoints before handling a signal delivered in certain cases] Signed-off-by: K.Prasad --- 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(+) Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h === --- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/hw_breakpoint.h +++ linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h @@ -65,9 +65,12 @@ static inline void hw_breakpoint_disable { 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 */ Index: linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/hw_breakpoint.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c @@ -174,6 +174,24 @@ int arch_validate_hwbkpt_settings(struct } /* + * 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. */ int __kprobes hw_breakpoint_handler(struct die_args *args) Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal.c +++ linux-2.6.ppc64_test/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 *o 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) ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[Patch 4/5] PPC64-HWBKPT: 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 during signal handling (since breakpoint will not be restored through single-stepping due to absence of MSR_SE bit on the signal frame). Enable breakpoints before signal delivery. Restore hw-breakpoints if the user-context is altered in the signal handler. Signed-off-by: K.Prasad --- 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(+) Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h === --- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/hw_breakpoint.h +++ linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h @@ -65,9 +65,12 @@ static inline void hw_breakpoint_disable { 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 */ Index: linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/hw_breakpoint.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c @@ -174,6 +174,24 @@ int arch_validate_hwbkpt_settings(struct } /* + * 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. */ int __kprobes hw_breakpoint_handler(struct die_args *args) Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal.c +++ linux-2.6.ppc64_test/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 *o 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) ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[Patch 4/5] PPC64-HWBKPT: 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 during signal handling (since breakpoint will not be restored through single-stepping due to absence of MSR_SE bit on the signal frame). Enable breakpoints before signal delivery. Restore hw-breakpoints if the user-context is altered in the signal handler. Signed-off-by: K.Prasad --- 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(+) Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h === --- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/hw_breakpoint.h +++ linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h @@ -65,9 +65,12 @@ static inline void hw_breakpoint_disable { 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 */ Index: linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/hw_breakpoint.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c @@ -176,6 +176,24 @@ int arch_validate_hwbkpt_settings(struct } /* + * 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. */ int __kprobes hw_breakpoint_handler(struct die_args *args) Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal.c +++ linux-2.6.ppc64_test/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 *o 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) ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[RFC Patch 4/5] PPC64-HWBKPT: 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 during signal handling (since breakpoint will not be restored through single-stepping due to absence of MSR_SE bit on the signal frame). Enable breakpoints before signal delivery and clear them during sigreturn() syscall. Limitation: Nested hw-breakpoint exceptions (where second exception is raised inside signal context) will cause a 'double-hit' i.e. the first breakpoint exception will be taken twice. Restore hw-breakpoints if the user-context is altered in the signal handler (causing loss of MSR_SE). Side-effect: 'Double-hit' of breakpoint if the instruction pointer is unaltered in the new context. Signed-off-by: K.Prasad --- arch/powerpc/include/asm/hw_breakpoint.h |3 +++ arch/powerpc/kernel/hw_breakpoint.c | 28 arch/powerpc/kernel/signal.c |8 arch/powerpc/kernel/signal_32.c | 10 ++ arch/powerpc/kernel/signal_64.c |7 +++ 5 files changed, 56 insertions(+) Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h === --- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/hw_breakpoint.h +++ linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h @@ -43,6 +43,9 @@ static inline void hw_breakpoint_disable { set_dabr(0); } +extern void sighandler_install_bp(struct task_struct *tsk); +extern void sigreturn_uninstall_bp(struct task_struct *tsk); +extern void thread_change_pc(struct task_struct *tsk, unsigned long msr); #endif /* CONFIG_HAVE_HW_BREAKPOINT */ #endif /* __KERNEL__ */ Index: linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/hw_breakpoint.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c @@ -188,6 +188,34 @@ int arch_validate_hwbkpt_settings(struct return 0; } +void sighandler_install_bp(struct task_struct *tsk) +{ + struct arch_hw_breakpoint *info; + + if (likely(!tsk->thread.last_hit_ubp)) + return; + + info = counter_arch_bp(tsk->thread.last_hit_ubp); + set_dabr(info->address | info->type | DABR_TRANSLATION); +} + +void sigreturn_uninstall_bp(struct task_struct *tsk) +{ + if (unlikely(tsk->thread.last_hit_ubp)) + set_dabr(0); +} + +void thread_change_pc(struct task_struct *tsk, unsigned long new_msr) +{ + /* +* Do not bother to restore breakpoints if single-stepping is not +* cleared. single_step_dabr_instruction() will handle it if MSR_SE +* is set. +*/ + if (!(new_msr & MSR_SE)) + sighandler_install_bp(tsk); +} + /* * Handle debug exception notifications. */ Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c @@ -11,6 +11,7 @@ #include #include +#include #include #include @@ -149,6 +150,13 @@ static int do_signal_pending(sigset_t *o if (current->thread.dabr) set_dabr(current->thread.dabr); #endif +#ifdef CONFIG_HAVE_HW_BREAKPOINT + /* +* Re-enable the breakpoints (if it was previously cleared in +* hw_breakpoint_handler()) for the signal stack. +*/ + sighandler_install_bp(current); +#endif /* CONFIG_HAVE_HW_BREAKPOINT */ if (is32) { if (ka.sa.sa_flags & SA_SIGINFO) Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal_64.c === --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal_64.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/signal_64.c @@ -33,6 +33,7 @@ #include #include #include +#include #include "signal.h" @@ -312,6 +313,9 @@ int sys_swapcontext(struct ucontext __us || __copy_to_user(&old_ctx->uc_sigmask, ¤t->blocked, sizeof(sigset_t))) return -EFAULT; +#ifdef CONFIG_HAVE_HW_BREAKPOINT + thread_change_pc(current, new_msr); +#endif /* CONFIG_HAVE_HW_BREAKPOINT */ } if (new_ctx == NULL) return 0; @@ -364,6 +368,9 @@ int sys_rt_sigreturn(unsigned long r3, u if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set))) goto badframe; restore_sigmask(&set); +#ifdef CONFIG_HAVE_HW_BREAKPOINT + sigreturn_uninstall_bp(current); +#endif /* CONFIG_HAVE_HW_BREAKPOINT */ if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext)) goto badframe; Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal_32.c =