[PATCH v2 02/18] mm/ksw: add ksw_config struct and parser

Jinchao Wang
2025-09-04T00:22:09Z

Add struct ksw_config and ksw_parse_config() to parse user string.

Update `Makefile` to pass compilation.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
mm/kstackwatch/Makefile | 2 ++
mm/kstackwatch/kernel.c | 70 +++++++++++++++++++++++++++++++++++-
mm/kstackwatch/kstackwatch.h | 34 ++++++++++++++++++
3 files changed, 105 insertions(+), 1 deletion(-)

diff --git a/mm/kstackwatch/Makefile b/mm/kstackwatch/Makefile
index 84a46cb9a766..d422f0e114dd 100644
--- a/mm/kstackwatch/Makefile
+++ b/mm/kstackwatch/Makefile
@@ -1,2 +1,4 @@
obj-$(CONFIG_KSTACK_WATCH) += kstackwatch.o
kstackwatch-y := kernel.o stack.o watch.o
+
+CFLAGS_kernel.o := -Wno-error=unused-function
diff --git a/mm/kstackwatch/kernel.c b/mm/kstackwatch/kernel.c
index 93379a0a0f7e..4a6dc49449fe 100644
--- a/mm/kstackwatch/kernel.c
+++ b/mm/kstackwatch/kernel.c
@@ -1,11 +1,79 @@
// SPDX-License-Identifier: GPL-2.0
-
+#include <linux/kstrtox.h>
#include <linux/module.h>
+#include <linux/string.h>
+
+#include "kstackwatch.h"

MODULE_AUTHOR("Jinchao Wang");
MODULE_DESCRIPTION("Kernel Stack Watch");
MODULE_LICENSE("GPL");

+/*
+ * Format of the configuration string:
+ * function+ip_offset[+depth] [local_var_offset:local_var_len]
+ *
+ * - function : name of the target function
+ * - ip_offset : instruction pointer offset within the function
+ * - depth : recursion depth to watch
+ * - local_var_offset : offset from the stack pointer at function+ip_offset
+ * - local_var_len : length of the local variable
+ */
+static int ksw_parse_config(char *buf, struct ksw_config *config)
+{
+ char *func_part, *local_var_part = NULL;
+ char *token;
+
+ /* Set the watch type to the default canary-based monitoring */
+ config->type = WATCH_CANARY;
+
+ func_part = strim(buf);
+ strscpy(config->config_str, func_part, MAX_CONFIG_STR_LEN);
+
+ local_var_part = strchr(func_part, ' ');
+ if (local_var_part) {
+ *local_var_part = '\0'; // Terminate the function part
+ local_var_part = strim(local_var_part + 1);
+ }
+
+ /* 1. Parse the function part: function+ip_offset[+depth] */
+ token = strsep(&func_part, "+");
+ if (!token)
+ return -EINVAL;
+
+ strscpy(config->function, token, MAX_FUNC_NAME_LEN - 1);
+
+ token = strsep(&func_part, "+");
+ if (!token || kstrtou16(token, 0, &config->ip_offset)) {
+ pr_err("KSW: failed to parse instruction offset\n");
+ return -EINVAL;
+ }
+
+ token = strsep(&func_part, "+");
+ if (token && kstrtou16(token, 0, &config->depth)) {
+ pr_err("KSW: failed to parse depth\n");
+ return -EINVAL;
+ }
+ if (!local_var_part || !(*local_var_part))
+ return 0;
+
+ /* 2. Parse the optional local var: offset:len */
+ config->type = WATCH_LOCAL_VAR;
+ token = strsep(&local_var_part, ":");
+ if (!token || kstrtou16(token, 0, &config->local_var_offset)) {
+ pr_err("KSW: failed to parse stack variable offset\n");
+ return -EINVAL;
+ }
+
+ if (!local_var_part ||
+ kstrtou16(local_var_part, 0, &config->local_var_len)) {
+ pr_err("KSW: failed to parse stack variable length\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int __init kstackwatch_init(void)
{
pr_info("KSW: module loaded\n");
diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index 0273ef478a26..b5f1835586c1 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -2,4 +2,38 @@
#ifndef _KSTACKWATCH_H
#define _KSTACKWATCH_H

+#include <linux/types.h>
+
+#define MAX_FUNC_NAME_LEN 64
+#define MAX_CONFIG_STR_LEN 128
+#define MAX_FRAME_SEARCH 128
+
+enum watch_type {
+ WATCH_CANARY = 0,
+ WATCH_LOCAL_VAR,
+};
+
+struct ksw_config {
+ /* function part */
+ char function[MAX_FUNC_NAME_LEN];
+ u16 ip_offset;
+ u16 depth;
+
+ /* local var, useless for canary watch */
+ /* offset from rsp at function+ip_offset */
+ u16 local_var_offset;
+
+ /*
+ * local var size (1,2,4,8 bytes)
+ * it will be the watching len
+ */
+ u16 local_var_len;
+
+ /* easy for understand*/
+ enum watch_type type;
+
+ /* save to show */
+ char config_str[MAX_CONFIG_STR_LEN];
+};
+
#endif /* _KSTACKWATCH_H */
--
2.43.0