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Miller" , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org Cc: Jinchao Wang Subject: [PATCH v5 08/23] mm/ksw: Add atomic watchpoint management api Date: Wed, 24 Sep 2025 19:50:51 +0800 Message-ID: <20250924115124.194940-9-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250924115124.194940-1-wangjinchao600@gmail.com> References: <20250924115124.194940-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" Add three functions for atomic lifecycle management of watchpoints: - ksw_watch_get(): Acquires a watchpoint from a llist. - ksw_watch_on(): Enables the watchpoint on all online CPUs. - ksw_watch_off(): Disables the watchpoint and returns it to the llist. For cross-CPU synchronization, updates are propagated using direct modification on the local CPU and asynchronous IPIs for remote CPUs. Signed-off-by: Jinchao Wang --- mm/kstackwatch/kstackwatch.h | 4 ++ mm/kstackwatch/watch.c | 85 +++++++++++++++++++++++++++++++++++- 2 files changed, 88 insertions(+), 1 deletion(-) diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h index 4eac1be3b325..850fc2b18a9c 100644 --- a/mm/kstackwatch/kstackwatch.h +++ b/mm/kstackwatch/kstackwatch.h @@ -38,11 +38,15 @@ const struct ksw_config *ksw_get_config(void); /* watch management */ struct ksw_watchpoint { struct perf_event *__percpu *event; + call_single_data_t __percpu *csd; struct perf_event_attr attr; struct llist_node node; // for atomic watch_on and off struct list_head list; // for cpu online and offline }; int ksw_watch_init(void); void ksw_watch_exit(void); +int ksw_watch_get(struct ksw_watchpoint **out_wp); +int ksw_watch_on(struct ksw_watchpoint *wp, ulong watch_addr, u16 watch_le= n); +int ksw_watch_off(struct ksw_watchpoint *wp); =20 #endif /* _KSTACKWATCH_H */ diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c index 1d8e24fede54..887cc13292dc 100644 --- a/mm/kstackwatch/watch.c +++ b/mm/kstackwatch/watch.c @@ -31,11 +31,83 @@ static void ksw_watch_handler(struct perf_event *bp, panic("Stack corruption detected"); } =20 +static void ksw_watch_on_local_cpu(void *info) +{ + struct ksw_watchpoint *wp =3D info; + struct perf_event *bp; + ulong flags; + int cpu; + int ret; + + local_irq_save(flags); + cpu =3D raw_smp_processor_id(); + bp =3D per_cpu(*wp->event, cpu); + if (!bp) { + local_irq_restore(flags); + return; + } + + ret =3D modify_wide_hw_breakpoint_local(bp, &wp->attr); + local_irq_restore(flags); + WARN(ret, "fail to reinstall HWBP on CPU%d ret %d", cpu, ret); +} + +static void ksw_watch_update(struct ksw_watchpoint *wp, ulong addr, u16 le= n) +{ + call_single_data_t *csd; + int cur_cpu; + int cpu; + + wp->attr.bp_addr =3D addr; + wp->attr.bp_len =3D len; + + cur_cpu =3D raw_smp_processor_id(); + for_each_online_cpu(cpu) { + /* remote cpu first */ + if (cpu =3D=3D cur_cpu) + continue; + csd =3D per_cpu_ptr(wp->csd, cpu); + smp_call_function_single_async(cpu, csd); + } + ksw_watch_on_local_cpu(wp); +} + +int ksw_watch_get(struct ksw_watchpoint **out_wp) +{ + struct ksw_watchpoint *wp; + struct llist_node *node; + + node =3D llist_del_first(&free_wp_list); + if (!node) + return -EBUSY; + + wp =3D llist_entry(node, struct ksw_watchpoint, node); + WARN_ON_ONCE(wp->attr.bp_addr !=3D (u64)&holder); + + *out_wp =3D wp; + return 0; +} +int ksw_watch_on(struct ksw_watchpoint *wp, ulong watch_addr, u16 watch_le= n) +{ + ksw_watch_update(wp, watch_addr, watch_len); + return 0; +} + +int ksw_watch_off(struct ksw_watchpoint *wp) +{ + WARN_ON_ONCE(wp->attr.bp_addr =3D=3D (u64)&holder); + ksw_watch_update(wp, (ulong)&holder, sizeof(ulong)); + llist_add(&wp->node, &free_wp_list); + return 0; +} + static int ksw_watch_alloc(void) { int max_watch =3D ksw_get_config()->max_watch; struct ksw_watchpoint *wp; + call_single_data_t *csd; int success =3D 0; + int cpu; int ret; =20 init_llist_head(&free_wp_list); @@ -45,6 +117,16 @@ static int ksw_watch_alloc(void) wp =3D kzalloc(sizeof(*wp), GFP_KERNEL); if (!wp) return success > 0 ? success : -EINVAL; + wp->csd =3D alloc_percpu(call_single_data_t); + if (!wp->csd) { + kfree(wp); + return success > 0 ? success : -EINVAL; + } + + for_each_possible_cpu(cpu) { + csd =3D per_cpu_ptr(wp->csd, cpu); + INIT_CSD(csd, ksw_watch_on_local_cpu, wp); + } =20 hw_breakpoint_init(&wp->attr); wp->attr.bp_addr =3D (ulong)&holder; @@ -54,6 +136,7 @@ static int ksw_watch_alloc(void) ksw_watch_handler, wp); if (IS_ERR((void *)wp->event)) { ret =3D PTR_ERR((void *)wp->event); + free_percpu(wp->csd); kfree(wp); return success > 0 ? success : ret; } @@ -75,6 +158,7 @@ static void ksw_watch_free(void) list_for_each_entry_safe(wp, tmp, &all_wp_list, list) { list_del(&wp->list); unregister_wide_hw_breakpoint(wp->event); + free_percpu(wp->csd); kfree(wp); } mutex_unlock(&all_wp_mutex); @@ -88,7 +172,6 @@ int ksw_watch_init(void) if (ret <=3D 0) return -EBUSY; =20 - return 0; } =20 --=20 2.43.0