From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp07.in.ibm.com (e28smtp07.in.ibm.com [122.248.162.7]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e28smtp07.in.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id A2A9DB7D1D for ; Mon, 24 May 2010 23:47:22 +1000 (EST) Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by e28smtp07.in.ibm.com (8.14.3/8.13.1) with ESMTP id o4ODjCZX012000 for ; Mon, 24 May 2010 19:17:07 +0530 Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o4OAYo333559518 for ; Mon, 24 May 2010 16:04:58 +0530 Received: from d28av05.in.ibm.com (loopback [127.0.0.1]) by d28av05.in.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o4OAYnNw027642 for ; Mon, 24 May 2010 20:34:49 +1000 Date: Mon, 24 May 2010 16:04:19 +0530 From: "K.Prasad" To: "linuxppc-dev@ozlabs.org" , Paul Mackerras Subject: [Patch 4/4] PPC64-HWBKPT: Enable hw-breakpoints while handling intervening signals Message-ID: <20100524103419.GE8131@in.ibm.com> References: <20100524102614.040177456@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Michael Neuling , Benjamin Herrenschmidt , shaggy@linux.vnet.ibm.com, Frederic Weisbecker , David Gibson , Alan Stern , "K.Prasad" , Roland McGrath List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 @@ -175,6 +175,34 @@ 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 =================================================================== --- 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 #include #include +#include #ifdef CONFIG_PPC64 #include "ppc32.h" #include @@ -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))