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Peter Anvin" , x86@kernel.org, Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Mathieu Desnoyers , David Hildenbrand , Jonathan Corbet , Matthew Wilcox , Alan Stern , Randy Dunlap , Alexander Potapenko , Marco Elver , Mike Rapoport , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-doc@vger.kernel.org, Jinchao Wang Subject: [RFC PATCH v2 04/13] HWBP: Add modify_wide_hw_breakpoint_local() API Date: Fri, 17 Jul 2026 09:03:40 -0400 Message-ID: <20260717130340.1902076-1-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260717125023.1895892-1-wangjinchao600@gmail.com> References: <20260717125023.1895892-1-wangjinchao600@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Masami Hiramatsu (Google)" Add modify_wide_hw_breakpoint_local() arch-wide interface which allows hwbp users to update watch address on-line. This is available if the arch supports CONFIG_HAVE_REINSTALL_HW_BREAKPOINT. Note that this allows to change the type only for compatible types, because it does not release and reserve the hwbp slot based on type. For instance, you can not change HW_BREAKPOINT_W to HW_BREAKPOINT_X. Assisted-by: Antigravity:gemini-3.5-flash Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Jinchao Wang --- include/linux/hw_breakpoint.h | 6 +++++ kernel/events/hw_breakpoint.c | 43 +++++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+) diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index db199d653dd1..6754ffbee9ed 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -81,6 +81,9 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr, perf_overflow_handler_t triggered, void *context); +extern int modify_wide_hw_breakpoint_local(struct perf_event *bp, + struct perf_event_attr *attr); + 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 * __percpu *cpu_events); @@ -124,6 +127,9 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr, perf_overflow_handler_t triggered, void *context) { return NULL; } static inline int +modify_wide_hw_breakpoint_local(struct perf_event *bp, + struct perf_event_attr *attr) { return -EOPNOTSUPP; } +static inline int register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; } static inline void unregister_hw_breakpoint(struct perf_event *bp) { } static inline void diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index 789add0c185a..f4709c892d67 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -888,6 +888,49 @@ void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events) } EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint); +/** + * modify_wide_hw_breakpoint_local - update breakpoint config for local CPU + * @bp: the hwbp perf event for this CPU + * @attr: the new attribute for @bp + * + * This does not release and reserve the slot of a HWBP; it just reuses the + * current slot on local CPU. So the users must update the other CPUs by + * themselves. + * Also, since this does not release/reserve the slot, this can not change the + * type to incompatible type of the HWBP. + * Return err if attr is invalid or the CPU fails to update debug register + * for new @attr. + */ +#ifdef CONFIG_HAVE_REINSTALL_HW_BREAKPOINT +int modify_wide_hw_breakpoint_local(struct perf_event *bp, + struct perf_event_attr *attr) +{ + struct arch_hw_breakpoint info; + int ret; + + if (find_slot_idx(bp->attr.bp_type) != find_slot_idx(attr->bp_type)) + return -EINVAL; + + ret = hw_breakpoint_arch_parse(bp, attr, &info); + if (ret) + return ret; + + *counter_arch_bp(bp) = info; + bp->attr.bp_addr = attr->bp_addr; + bp->attr.bp_type = attr->bp_type; + bp->attr.bp_len = attr->bp_len; + + return arch_reinstall_hw_breakpoint(bp); +} +#else +int modify_wide_hw_breakpoint_local(struct perf_event *bp, + struct perf_event_attr *attr) +{ + return -EOPNOTSUPP; +} +#endif +EXPORT_SYMBOL_GPL(modify_wide_hw_breakpoint_local); + /** * hw_breakpoint_is_used - check if breakpoints are currently used * -- 2.53.0