From 2f0993e0fb663c49e4d1e02654f6203246be4817 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 5 Dec 2009 07:06:10 +0100 Subject: hw-breakpoints: Drop callback and task parameters from modify helper Drop the callback and task parameters from modify_user_hw_breakpoint(). For now we have no user that need to modify a breakpoint to the point of changing its handler or its task context. Signed-off-by: Frederic Weisbecker Cc: "K. Prasad" --- include/linux/hw_breakpoint.h | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) (limited to 'include/linux/hw_breakpoint.h') diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index a03daed08c5..d33096e0dbd 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -57,10 +57,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr, /* FIXME: only change from the attr, and don't unregister */ extern struct perf_event * -modify_user_hw_breakpoint(struct perf_event *bp, - struct perf_event_attr *attr, - perf_callback_t triggered, - struct task_struct *tsk); +modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr); /* * Kernel breakpoints are not associated with any particular thread. @@ -97,9 +94,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr, struct task_struct *tsk) { return NULL; } static inline struct perf_event * modify_user_hw_breakpoint(struct perf_event *bp, - struct perf_event_attr *attr, - perf_callback_t triggered, - struct task_struct *tsk) { return NULL; } + struct perf_event_attr *attr) { return NULL; } static inline struct perf_event * register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr, perf_callback_t triggered, -- cgit From b326e9560a28fc3e950637ef51847ed8f05c1335 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 5 Dec 2009 09:44:31 +0100 Subject: hw-breakpoints: Use overflow handler instead of the event callback struct perf_event::event callback was called when a breakpoint triggers. But this is a rather opaque callback, pretty tied-only to the breakpoint API and not really integrated into perf as it triggers even when we don't overflow. We prefer to use overflow_handler() as it fits into the perf events rules, being called only when we overflow. Reported-by: Peter Zijlstra Signed-off-by: Frederic Weisbecker Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: "K. Prasad" --- include/linux/hw_breakpoint.h | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-) (limited to 'include/linux/hw_breakpoint.h') diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index d33096e0dbd..4d14a384a01 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -20,19 +20,16 @@ enum { #ifdef CONFIG_HAVE_HW_BREAKPOINT -/* As it's for in-kernel or ptrace use, we want it to be pinned */ -#define DEFINE_BREAKPOINT_ATTR(name) \ -struct perf_event_attr name = { \ - .type = PERF_TYPE_BREAKPOINT, \ - .size = sizeof(name), \ - .pinned = 1, \ -}; - static inline void hw_breakpoint_init(struct perf_event_attr *attr) { attr->type = PERF_TYPE_BREAKPOINT; attr->size = sizeof(*attr); + /* + * As it's for in-kernel or ptrace use, we want it to be pinned + * and to call its callback every hits. + */ attr->pinned = 1; + attr->sample_period = 1; } static inline unsigned long hw_breakpoint_addr(struct perf_event *bp) @@ -52,7 +49,7 @@ static inline int hw_breakpoint_len(struct perf_event *bp) extern struct perf_event * register_user_hw_breakpoint(struct perf_event_attr *attr, - perf_callback_t triggered, + perf_overflow_handler_t triggered, struct task_struct *tsk); /* FIXME: only change from the attr, and don't unregister */ @@ -64,12 +61,12 @@ modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr); */ extern struct perf_event * register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr, - perf_callback_t triggered, + perf_overflow_handler_t triggered, int cpu); extern struct perf_event ** register_wide_hw_breakpoint(struct perf_event_attr *attr, - perf_callback_t triggered); + perf_overflow_handler_t triggered); extern int register_perf_hw_breakpoint(struct perf_event *bp); extern int __register_perf_hw_breakpoint(struct perf_event *bp); @@ -90,18 +87,18 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp) static inline struct perf_event * register_user_hw_breakpoint(struct perf_event_attr *attr, - perf_callback_t triggered, + perf_overflow_handler_t triggered, struct task_struct *tsk) { return NULL; } static inline struct perf_event * modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) { return NULL; } static inline struct perf_event * register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr, - perf_callback_t triggered, + perf_overflow_handler_t triggered, int cpu) { return NULL; } static inline struct perf_event ** register_wide_hw_breakpoint(struct perf_event_attr *attr, - perf_callback_t triggered) { return NULL; } + perf_overflow_handler_t triggered) { return NULL; } static inline int register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; } static inline int -- cgit From ed872d09effd54aa8ecb4ceedbc4dbab9592f337 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 7 Dec 2009 03:14:17 +0100 Subject: hw-breakpoints: Zeroe the breakpoint attrs on initialization The perf attrs used to set up breakpoint parameters are often allocated in the stack and not zeroed out before calling hw_breakpoint_init(). Handle it from this helper to avoid random attributes set by the stack. Signed-off-by: Frederic Weisbecker Cc: Prasad --- include/linux/hw_breakpoint.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/hw_breakpoint.h') diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index 4d14a384a01..42da1ce19ec 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -22,6 +22,8 @@ enum { static inline void hw_breakpoint_init(struct perf_event_attr *attr) { + memset(attr, 0, sizeof(*attr)); + attr->type = PERF_TYPE_BREAKPOINT; attr->size = sizeof(*attr); /* -- cgit From 44234adcdce38f83c56e05f808ce656175b4beeb Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 9 Dec 2009 09:25:48 +0100 Subject: hw-breakpoints: Modify breakpoints without unregistering them Currently, when ptrace needs to modify a breakpoint, like disabling it, changing its address, type or len, it calls modify_user_hw_breakpoint(). This latter will perform the heavy and racy task of unregistering the old breakpoint and registering a new one. This is racy as someone else might steal the reserved breakpoint slot under us, which is undesired as the breakpoint is only supposed to be modified, sometimes in the middle of a debugging workflow. We don't want our slot to be stolen in the middle. So instead of unregistering/registering the breakpoint, just disable it while we modify its breakpoint fields and re-enable it after if necessary. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Prasad LKML-Reference: <1260347148-5519-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- include/linux/hw_breakpoint.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/hw_breakpoint.h') diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index 42da1ce19ec..69f07a9f127 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -55,7 +55,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr, struct task_struct *tsk); /* FIXME: only change from the attr, and don't unregister */ -extern struct perf_event * +extern int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr); /* @@ -91,7 +91,7 @@ static inline struct perf_event * register_user_hw_breakpoint(struct perf_event_attr *attr, perf_overflow_handler_t triggered, struct task_struct *tsk) { return NULL; } -static inline struct perf_event * +static inline int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) { return NULL; } static inline struct perf_event * -- cgit From 99ac64c826e62a07e5818cfde620be4d524f1edf Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 11 Dec 2009 11:58:42 +0100 Subject: hw-breakpoints: Handle bad modify_user_hw_breakpoint off-case return value While converting modify_user_hw_breakpoint() return value, we forgot to handle the off-case. It's not returning a pointer anymore. This solves the build warning reported by Stephen Rothwell against linux-next. Reported-by: Stephen Rothwell Signed-off-by: Frederic Weisbecker Cc: Prasad LKML-Reference: <1260529122-6260-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar Cc: Prasad --- include/linux/hw_breakpoint.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/hw_breakpoint.h') diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index 69f07a9f127..41235c93e4e 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -93,7 +93,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr, struct task_struct *tsk) { return NULL; } static inline int modify_user_hw_breakpoint(struct perf_event *bp, - struct perf_event_attr *attr) { return NULL; } + struct perf_event_attr *attr) { return -ENOSYS; } static inline struct perf_event * register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr, perf_overflow_handler_t triggered, -- cgit From 5352ae638e2d7d5c9b2e4d528676bbf2af6fd6f3 Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Thu, 28 Jan 2010 17:04:43 -0600 Subject: perf, hw_breakpoint, kgdb: Do not take mutex for kernel debugger This patch fixes the regression in functionality where the kernel debugger and the perf API do not nicely share hw breakpoint reservations. The kernel debugger cannot use any mutex_lock() calls because it can start the kernel running from an invalid context. A mutex free version of the reservation API needed to get created for the kernel debugger to safely update hw breakpoint reservations. The possibility for a breakpoint reservation to be concurrently processed at the time that kgdb interrupts the system is improbable. Should this corner case occur the end user is warned, and the kernel debugger will prohibit updating the hardware breakpoint reservations. Any time the kernel debugger reserves a hardware breakpoint it will be a system wide reservation. Signed-off-by: Jason Wessel Acked-by: Frederic Weisbecker Cc: kgdb-bugreport@lists.sourceforge.net Cc: K.Prasad Cc: Peter Zijlstra Cc: Alan Stern Cc: torvalds@linux-foundation.org LKML-Reference: <1264719883-7285-3-git-send-email-jason.wessel@windriver.com> Signed-off-by: Ingo Molnar --- include/linux/hw_breakpoint.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/hw_breakpoint.h') diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index 41235c93e4e..070ba062173 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -75,6 +75,8 @@ extern int __register_perf_hw_breakpoint(struct perf_event *bp); extern void unregister_hw_breakpoint(struct perf_event *bp); extern void unregister_wide_hw_breakpoint(struct perf_event **cpu_events); +extern int dbg_reserve_bp_slot(struct perf_event *bp); +extern int dbg_release_bp_slot(struct perf_event *bp); extern int reserve_bp_slot(struct perf_event *bp); extern void release_bp_slot(struct perf_event *bp); -- cgit