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 <[email protected]> --- include/linux/kstackwatch.h | 4 ++ mm/kstackwatch/watch.c | 85 ++++++++++++++++++++++++++++++++++++- 2 files changed, 88 insertions(+), 1 deletion(-) diff --git a/include/linux/kstackwatch.h b/include/linux/kstackwatch.h index eb9f2b4f2109..d7ea89c8c6af 100644 --- a/include/linux/kstackwatch.h +++ b/include/linux/kstackwatch.h @@ -44,11 +44,15 @@ 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_len); +int ksw_watch_off(struct ksw_watchpoint *wp); #endif /* _KSTACKWATCH_H */ diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c index 4947eac32c61..3817a172dc25 100644 --- a/mm/kstackwatch/watch.c +++ b/mm/kstackwatch/watch.c @@ -27,11 +27,83 @@ static void ksw_watch_handler(struct perf_event *bp, panic("Stack corruption detected"); } +static void ksw_watch_on_local_cpu(void *info) +{ + struct ksw_watchpoint *wp = info; + struct perf_event *bp; + ulong flags; + int cpu; + int ret; + + local_irq_save(flags); + cpu = raw_smp_processor_id(); + bp = per_cpu(*wp->event, cpu); + if (!bp) { + local_irq_restore(flags); + return; + } + + ret = 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 len) +{ + call_single_data_t *csd; + int cur_cpu; + int cpu; + + wp->attr.bp_addr = addr; + wp->attr.bp_len = len; + + cur_cpu = raw_smp_processor_id(); + for_each_online_cpu(cpu) { + /* remote cpu first */ + if (cpu == cur_cpu) + continue; + csd = 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 = llist_del_first(&free_wp_list); + if (!node) + return -EBUSY; + + wp = llist_entry(node, struct ksw_watchpoint, node); + WARN_ON_ONCE(wp->attr.bp_addr != (u64)&holder); + + *out_wp = wp; + return 0; +} +int ksw_watch_on(struct ksw_watchpoint *wp, ulong watch_addr, u16 watch_len) +{ + 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 == (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 = ksw_get_config()->max_watch; struct ksw_watchpoint *wp; + call_single_data_t *csd; int success = 0; + int cpu; int ret; init_llist_head(&free_wp_list); @@ -41,6 +113,16 @@ static int ksw_watch_alloc(void) wp = kzalloc(sizeof(*wp), GFP_KERNEL); if (!wp) return success > 0 ? success : -EINVAL; + wp->csd = alloc_percpu(call_single_data_t); + if (!wp->csd) { + kfree(wp); + return success > 0 ? success : -EINVAL; + } + + for_each_possible_cpu(cpu) { + csd = per_cpu_ptr(wp->csd, cpu); + INIT_CSD(csd, ksw_watch_on_local_cpu, wp); + } hw_breakpoint_init(&wp->attr); wp->attr.bp_addr = (ulong)&holder; @@ -50,6 +132,7 @@ static int ksw_watch_alloc(void) ksw_watch_handler, wp); if (IS_ERR((void *)wp->event)) { ret = PTR_ERR((void *)wp->event); + free_percpu(wp->csd); kfree(wp); return success > 0 ? success : ret; } @@ -71,6 +154,7 @@ 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); @@ -84,7 +168,6 @@ int ksw_watch_init(void) if (ret <= 0) return -EBUSY; - return 0; } -- 2.43.0
