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 <pra...@linux.vnet.ibm.com> --- 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 <linux/tracehook.h> #include <linux/signal.h> +#include <asm/hw_breakpoint.h> #include <asm/uaccess.h> #include <asm/unistd.h> @@ -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 <asm/cacheflush.h> #include <asm/syscalls.h> #include <asm/vdso.h> +#include <asm/hw_breakpoint.h> #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 =================================================================== --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal_32.c +++ linux-2.6.ppc64_test/arch/powerpc/kernel/signal_32.c @@ -42,6 +42,7 @@ #include <asm/syscalls.h> #include <asm/sigcontext.h> #include <asm/vdso.h> +#include <asm/hw_breakpoint.h> #ifdef CONFIG_PPC64 #include "ppc32.h" #include <asm/unistd.h> @@ -996,6 +997,9 @@ long sys_swapcontext(struct ucontext __u || put_sigset_t(&old_ctx->uc_sigmask, ¤t->blocked) || __put_user(to_user_ptr(mctx), &old_ctx->uc_regs)) return -EFAULT; +#ifdef CONFIG_HAVE_HW_BREAKPOINT + thread_change_pc(current, new_msr); +#endif /* CONFIG_HAVE_HW_BREAKPOINT */ } if (new_ctx == NULL) return 0; @@ -1034,6 +1038,9 @@ long sys_rt_sigreturn(int r3, int r4, in (regs->gpr[1] + __SIGNAL_FRAMESIZE + 16); if (!access_ok(VERIFY_READ, rt_sf, sizeof(*rt_sf))) goto bad; +#ifdef CONFIG_HAVE_HW_BREAKPOINT + sigreturn_uninstall_bp(current); +#endif /* CONFIG_HAVE_HW_BREAKPOINT */ if (do_setcontext(&rt_sf->uc, regs, 1)) goto bad; @@ -1279,6 +1286,9 @@ long sys_sigreturn(int r3, int r4, int r #endif restore_sigmask(&set); +#ifdef CONFIG_HAVE_HW_BREAKPOINT + sigreturn_uninstall_bp(current); +#endif /* CONFIG_HAVE_HW_BREAKPOINT */ sr = (struct mcontext __user *)from_user_ptr(sigctx.regs); addr = sr; if (!access_ok(VERIFY_READ, sr, sizeof(*sr)) _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev