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Miller" , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org Cc: Jinchao Wang Subject: [PATCH v4 11/21] mm/ksw: add probe management helpers Date: Fri, 12 Sep 2025 18:11:21 +0800 Message-ID: <20250912101145.465708-12-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250912101145.465708-1-wangjinchao600@gmail.com> References: <20250912101145.465708-1-wangjinchao600@gmail.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Provide ksw_stack_init() and ksw_stack_exit() to manage entry and exit probes for the target function from ksw_get_config(). The entry/exit probe handlers use atomic ksw_stack_pid to ensure a singleton watch and current->kstackwatch_ctx.depth to track recursion depth. A watch is set up only when depth reaches the configured value. Signed-off-by: Jinchao Wang --- mm/kstackwatch/kstackwatch.h | 4 ++ mm/kstackwatch/stack.c | 113 +++++++++++++++++++++++++++++++++++ 2 files changed, 117 insertions(+) diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h index 0786fa961011..5ea2db76cdfb 100644 --- a/mm/kstackwatch/kstackwatch.h +++ b/mm/kstackwatch/kstackwatch.h @@ -38,6 +38,10 @@ struct ksw_config { // singleton, only modified in kernel.c const struct ksw_config *ksw_get_config(void); +/* stack management */ +int ksw_stack_init(void); +void ksw_stack_exit(void); + /* watch management */ int ksw_watch_init(void); void ksw_watch_exit(void); diff --git a/mm/kstackwatch/stack.c b/mm/kstackwatch/stack.c index cec594032515..ac52a9f81486 100644 --- a/mm/kstackwatch/stack.c +++ b/mm/kstackwatch/stack.c @@ -1 +1,114 @@ // SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include + +#include "kstackwatch.h" + +static struct kprobe entry_probe; +static struct fprobe exit_probe; +#define INVALID_PID -1 +static atomic_t ksw_stack_pid = ATOMIC_INIT(INVALID_PID); + +static int ksw_stack_prepare_watch(struct pt_regs *regs, + const struct ksw_config *config, + ulong *watch_addr, u16 *watch_len) +{ + /* implement logic will be added in following patches */ + *watch_addr = 0; + *watch_len = 0; + return 0; +} + +static void ksw_stack_entry_handler(struct kprobe *p, struct pt_regs *regs, + unsigned long flags) +{ + struct kstackwatch_ctx *ctx = ¤t->kstackwatch_ctx; + ulong watch_addr; + u16 watch_len; + int ret; + + if (ctx->depth++ != ksw_get_config()->depth) + return; + + if (atomic_cmpxchg(&ksw_stack_pid, INVALID_PID, current->pid) != + INVALID_PID) + return; + + ret = ksw_stack_prepare_watch(regs, ksw_get_config(), &watch_addr, + &watch_len); + if (ret) { + atomic_set(&ksw_stack_pid, INVALID_PID); + pr_err("failed to prepare watch target: %d\n", ret); + return; + } + + ret = ksw_watch_on(watch_addr, watch_len); + if (ret) { + atomic_set(&ksw_stack_pid, INVALID_PID); + pr_err("failed to watch on depth:%d addr:0x%lx len:%u %d\n", + ksw_get_config()->depth, watch_addr, watch_len, ret); + return; + } + + ctx->watch_addr = watch_addr; + ctx->watch_len = watch_len; + ctx->watch_on = true; +} + +static void ksw_stack_exit_handler(struct fprobe *fp, unsigned long ip, + unsigned long ret_ip, + struct ftrace_regs *regs, void *data) +{ + struct kstackwatch_ctx *ctx = ¤t->kstackwatch_ctx; + + if (--ctx->depth != ksw_get_config()->depth) + return; + + if (atomic_read(&ksw_stack_pid) != current->pid) + return; + WARN_ON_ONCE(!ctx->watch_on); + WARN_ON_ONCE(ksw_watch_off(ctx->watch_addr, ctx->watch_len)); + ctx->watch_on = false; + + atomic_set(&ksw_stack_pid, INVALID_PID); +} + +int ksw_stack_init(void) +{ + int ret; + char *symbuf = NULL; + + memset(&entry_probe, 0, sizeof(entry_probe)); + entry_probe.symbol_name = ksw_get_config()->function; + entry_probe.offset = ksw_get_config()->ip_offset; + entry_probe.post_handler = ksw_stack_entry_handler; + ret = register_kprobe(&entry_probe); + if (ret) { + pr_err("Failed to register kprobe ret %d\n", ret); + return ret; + } + + memset(&exit_probe, 0, sizeof(exit_probe)); + exit_probe.exit_handler = ksw_stack_exit_handler; + symbuf = (char *)ksw_get_config()->function; + + ret = register_fprobe_syms(&exit_probe, (const char **)&symbuf, 1); + if (ret < 0) { + pr_err("register_fprobe_syms fail %d\n", ret); + unregister_kprobe(&entry_probe); + return ret; + } + + return 0; +} + +void ksw_stack_exit(void) +{ + unregister_fprobe(&exit_probe); + unregister_kprobe(&entry_probe); +} -- 2.43.0