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Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-perf-users@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jinchao Wang Subject: [PATCH v2 07/18] mm/ksw: add atomic watch on/off operations Date: Thu, 4 Sep 2025 08:21:04 +0800 Message-ID: <20250904002126.1514566-8-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250904002126.1514566-1-wangjinchao600@gmail.com> References: <20250904002126.1514566-1-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 support to atomically turn the hardware watch on and off without allocation overhead. The watch is pre-allocated and later retargeted using hw_breakpoint_modify_= local(). The current CPU is updated directly, while other CPUs are updated asynchronously via smp_call_function_single_async(). This allows KStackWatch to switch the watch in kprobe/fprobe handlers. Signed-off-by: Jinchao Wang --- mm/kstackwatch/kstackwatch.h | 2 + mm/kstackwatch/watch.c | 97 ++++++++++++++++++++++++++++++++++++ 2 files changed, 99 insertions(+) diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h index 2318779bde70..13ef8c79f855 100644 --- a/mm/kstackwatch/kstackwatch.h +++ b/mm/kstackwatch/kstackwatch.h @@ -41,5 +41,7 @@ extern bool panic_on_catch; /* watch management */ int ksw_watch_init(struct ksw_config *config); void ksw_watch_exit(void); +int ksw_watch_on(u64 watch_addr, u64 watch_len); +void ksw_watch_off(void); =20 #endif /* _KSTACKWATCH_H */ diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c index e7ed88700b49..c563f8d17829 100644 --- a/mm/kstackwatch/watch.c +++ b/mm/kstackwatch/watch.c @@ -16,9 +16,21 @@ =20 struct perf_event *__percpu *watch_events; struct ksw_config *watch_config; +static DEFINE_SPINLOCK(watch_lock); =20 static unsigned long long watch_holder; =20 +static struct watch_info { + u64 addr; + u64 len; +} watch_info; + +static void ksw_watch_on_local_cpu(void *info); + +static DEFINE_PER_CPU(call_single_data_t, + watch_csd) =3D CSD_INIT(ksw_watch_on_local_cpu, + &watch_info); + static void ksw_watch_handler(struct perf_event *bp, struct perf_sample_data *data, struct pt_regs *regs) @@ -32,6 +44,91 @@ static void ksw_watch_handler(struct perf_event *bp, panic("KSW: Stack corruption detected"); } =20 +/* + * set up watchon current CPU + * addr and len updated by ksw_watch_on() already + */ +static void ksw_watch_on_local_cpu(void *data) +{ + struct perf_event *bp; + struct perf_event_attr attr; + struct watch_info *watch_info =3D data; + + int cpu =3D smp_processor_id(); + int ret; + + bp =3D *per_cpu_ptr(watch_events, cpu); + if (!bp) + return; + attr.bp_addr =3D watch_info->addr; + attr.bp_len =3D watch_info->len; + attr.bp_type =3D bp->attr.bp_type; + + ret =3D hw_breakpoint_modify_local(bp, &attr); + if (ret) { + pr_err("KSW: failed to reinstall HWBP on CPU %d ret %d\n", cpu, + ret); + return; + } + + if (bp->attr.bp_addr =3D=3D (unsigned long)&watch_holder) { + pr_debug("KSW: watch off CPU %d\n", cpu); + } else { + pr_debug("KSW: watch on CPU %d at 0x%px (len %llu)\n", cpu, + (void *)bp->attr.bp_addr, bp->attr.bp_len); + } +} + +int ksw_watch_on(u64 watch_addr, u64 watch_len) +{ + unsigned long flags; + int cpu; + + if (!watch_addr) { + pr_err("KSW: watch with invalid address\n"); + return -EINVAL; + } + + spin_lock_irqsave(&watch_lock, flags); + + /* + * check if already watched + */ + if (watch_info.addr !=3D 0 && // not uninit + watch_info.addr !=3D (unsigned long)&watch_holder && // installed + watch_addr !=3D (unsigned long)&watch_holder) { //not restore + spin_unlock_irqrestore(&watch_lock, flags); + return -EBUSY; + } + + watch_info.addr =3D watch_addr; + watch_info.len =3D watch_len; + + spin_unlock_irqrestore(&watch_lock, flags); + + if (watch_addr =3D=3D (unsigned long)&watch_holder) + pr_debug("KSW: watch off starting\n"); + else + pr_debug("KSW: watch on starting\n"); + + for_each_online_cpu(cpu) { + if (cpu =3D=3D raw_smp_processor_id()) { + ksw_watch_on_local_cpu(&watch_info); + } else { + call_single_data_t *csd =3D &per_cpu(watch_csd, cpu); + + smp_call_function_single_async(cpu, csd); + } + } + + return 0; +} + +void ksw_watch_off(void) +{ + ksw_watch_on((unsigned long)&watch_holder, sizeof(watch_holder)); +} + int ksw_watch_init(struct ksw_config *config) { struct perf_event_attr attr; --=20 2.43.0