[PATCH v2 08/18] mm/ksw: add stack probe support

Jinchao Wang
2025-09-04T00:23:05Z

Introduce stack management for KStackWatch using kprobes and fprobes to
enable dynamic watch switching:

- Entry: prepare target address/length and enable watch
- Exit: disable watch

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
mm/kstackwatch/kstackwatch.h | 4 ++
mm/kstackwatch/stack.c | 91 ++++++++++++++++++++++++++++++++++++
2 files changed, 95 insertions(+)

diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index 13ef8c79f855..bc8664af4fa6 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -38,6 +38,10 @@ struct ksw_config {

extern bool panic_on_catch;

+/* stack management */
+int ksw_stack_init(struct ksw_config *config);
+void ksw_stack_exit(void);
+
/* watch management */
int ksw_watch_init(struct ksw_config *config);
void ksw_watch_exit(void);
diff --git a/mm/kstackwatch/stack.c b/mm/kstackwatch/stack.c
index cec594032515..3b72177315cc 100644
--- a/mm/kstackwatch/stack.c
+++ b/mm/kstackwatch/stack.c
@@ -1 +1,92 @@
// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/fprobe.h>
+#include <linux/kprobes.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+
+#include "kstackwatch.h"
+
+struct ksw_config *probe_config;
+
+/* prepare watch_addr and watch_len for watch */
+static int ksw_stack_prepare_watch(struct pt_regs *regs,
+ struct ksw_config *config, u64 *watch_addr,
+ u64 *watch_len)
+{
+ /* TODO: implement logic */
+ *watch_addr = 0;
+ *watch_len = 0;
+ return 0;
+}
+
+static struct kprobe entry_probe;
+static struct fprobe exit_probe_fprobe;
+
+static void ksw_stack_entry_handler(struct kprobe *p, struct pt_regs *regs,
+ unsigned long flags)
+{
+ int ret;
+ u64 watch_addr;
+ u64 watch_len;
+
+ ret = ksw_stack_prepare_watch(regs, probe_config, &watch_addr,
+ &watch_len);
+ if (ret) {
+ pr_err("KSW: failed to prepare watch target: %d\n", ret);
+ return;
+ }
+
+ ret = ksw_watch_on(watch_addr, watch_len);
+ if (ret) {
+ pr_err("KSW: failed to watch on addr:0x%llx len:%llx %d\n",
+ watch_addr, watch_len, ret);
+ return;
+ }
+}
+
+static void ksw_stack_exit_handler(struct fprobe *fp, unsigned long ip,
+ unsigned long ret_ip,
+ struct ftrace_regs *regs, void *data)
+{
+ ksw_watch_off();
+}
+
+int ksw_stack_init(struct ksw_config *config)
+{
+ int ret;
+ char *symbuf = NULL;
+
+ /* Setup entry probe */
+ memset(&entry_probe, 0, sizeof(entry_probe));
+ entry_probe.symbol_name = config->function;
+ entry_probe.offset = config->ip_offset;
+ entry_probe.post_handler = ksw_stack_entry_handler;
+ probe_config = config;
+ ret = register_kprobe(&entry_probe);
+ if (ret < 0) {
+ pr_err("KSW: Failed to register kprobe ret %d\n", ret);
+ return ret;
+ }
+
+ /* Setup exit probe */
+ memset(&exit_probe_fprobe, 0, sizeof(exit_probe_fprobe));
+ exit_probe_fprobe.exit_handler = ksw_stack_exit_handler;
+ symbuf = probe_config->function;
+
+ ret = register_fprobe_syms(&exit_probe_fprobe, (const char **)&symbuf,
+ 1);
+ if (ret < 0) {
+ pr_err("KSW: register_fprobe_syms fail %d\n", ret);
+ unregister_kprobe(&entry_probe);
+ return ret;
+ }
+
+ return 0;
+}
+
+void ksw_stack_exit(void)
+{
+ unregister_fprobe(&exit_probe_fprobe);
+ unregister_kprobe(&entry_probe);
+}
--
2.43.0