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Miller" , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org Cc: Jinchao Wang Subject: [PATCH v5 07/23] mm/ksw: add HWBP pre-allocation Date: Wed, 24 Sep 2025 20:24:40 +0800 Message-ID: <20250924122448.9101-1-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-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Pre-allocate per-CPU hardware breakpoints at init with a place holder address, which will be retargeted dynamically in kprobe handler. This avoids allocation in atomic context. At most max_watch breakpoints are allocated (0 means no limit). Signed-off-by: Jinchao Wang --- mm/kstackwatch/kstackwatch.h | 13 +++++ mm/kstackwatch/watch.c | 97 ++++++++++++++++++++++++++++++++++++ 2 files changed, 110 insertions(+) diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h index 983125d5cf18..4eac1be3b325 100644 --- a/mm/kstackwatch/kstackwatch.h +++ b/mm/kstackwatch/kstackwatch.h @@ -2,6 +2,9 @@ #ifndef _KSTACKWATCH_H #define _KSTACKWATCH_H +#include +#include +#include #include #define MAX_CONFIG_STR_LEN 128 @@ -32,4 +35,14 @@ struct ksw_config { // singleton, only modified in kernel.c const struct ksw_config *ksw_get_config(void); +/* watch management */ +struct ksw_watchpoint { + struct perf_event *__percpu *event; + 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); + #endif /* _KSTACKWATCH_H */ diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c index cec594032515..1d8e24fede54 100644 --- a/mm/kstackwatch/watch.c +++ b/mm/kstackwatch/watch.c @@ -1 +1,98 @@ // SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include + +#include "kstackwatch.h" + +static LLIST_HEAD(free_wp_list); +static LIST_HEAD(all_wp_list); +static DEFINE_MUTEX(all_wp_mutex); + +static ulong holder; +bool panic_on_catch; +module_param(panic_on_catch, bool, 0644); +MODULE_PARM_DESC(panic_on_catch, "panic immediately on corruption catch"); + +static void ksw_watch_handler(struct perf_event *bp, + struct perf_sample_data *data, + struct pt_regs *regs) +{ + pr_err("========== KStackWatch: Caught stack corruption =======\n"); + pr_err("config %s\n", ksw_get_config()->user_input); + dump_stack(); + pr_err("=================== KStackWatch End ===================\n"); + + if (panic_on_catch) + panic("Stack corruption detected"); +} + +static int ksw_watch_alloc(void) +{ + int max_watch = ksw_get_config()->max_watch; + struct ksw_watchpoint *wp; + int success = 0; + int ret; + + init_llist_head(&free_wp_list); + + //max_watch=0 means at most + while (!max_watch || success < max_watch) { + wp = kzalloc(sizeof(*wp), GFP_KERNEL); + if (!wp) + return success > 0 ? success : -EINVAL; + + hw_breakpoint_init(&wp->attr); + wp->attr.bp_addr = (ulong)&holder; + wp->attr.bp_len = sizeof(ulong); + wp->attr.bp_type = HW_BREAKPOINT_W; + wp->event = register_wide_hw_breakpoint(&wp->attr, + ksw_watch_handler, wp); + if (IS_ERR((void *)wp->event)) { + ret = PTR_ERR((void *)wp->event); + kfree(wp); + return success > 0 ? success : ret; + } + llist_add(&wp->node, &free_wp_list); + mutex_lock(&all_wp_mutex); + list_add(&wp->list, &all_wp_list); + mutex_unlock(&all_wp_mutex); + success++; + } + + return success; +} + +static void ksw_watch_free(void) +{ + struct ksw_watchpoint *wp, *tmp; + + mutex_lock(&all_wp_mutex); + list_for_each_entry_safe(wp, tmp, &all_wp_list, list) { + list_del(&wp->list); + unregister_wide_hw_breakpoint(wp->event); + kfree(wp); + } + mutex_unlock(&all_wp_mutex); +} + +int ksw_watch_init(void) +{ + int ret; + + ret = ksw_watch_alloc(); + if (ret <= 0) + return -EBUSY; + + + return 0; +} + +void ksw_watch_exit(void) +{ + ksw_watch_free(); +} -- 2.43.0