[PATCH v4 05/21] mm/ksw: add ksw_config struct and parser

[Jinchao Wang <wangjinchao600@gmail.com>]

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

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/kernel.c      | 91 ++++++++++++++++++++++++++++++++++++
 mm/kstackwatch/kstackwatch.h | 33 +++++++++++++
 2 files changed, 124 insertions(+)

diff --git a/mm/kstackwatch/kernel.c b/mm/kstackwatch/kernel.c
index 40aa7e9ff513..1502795e02af 100644
--- a/mm/kstackwatch/kernel.c
+++ b/mm/kstackwatch/kernel.c
@@ -1,20 +1,111 @@
 // SPDX-License-Identifier: GPL-2.0
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#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");
 
+static struct ksw_config *ksw_config;
+
+/*
+ * 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(1,2,4,8)
+ */
+static int __maybe_unused ksw_parse_config(char *buf, struct ksw_config *config)
+{
+	char *func_part, *local_var_part = NULL;
+	char *token;
+	u16 local_var_len;
+
+	memset(ksw_config, 0, sizeof(*ksw_config));
+
+	/* set the watch type to the default canary-based watching */
+	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);
+	}
+
+	/* parse the function part: function+ip_offset[+depth] */
+	token = strsep(&func_part, "+");
+	if (!token)
+		goto fail;
+
+	strscpy(config->function, token, MAX_FUNC_NAME_LEN - 1);
+
+	token = strsep(&func_part, "+");
+	if (!token || kstrtou16(token, 0, &config->ip_offset)) {
+		pr_err("failed to parse instruction offset\n");
+		goto fail;
+	}
+
+	token = strsep(&func_part, "+");
+	if (token && kstrtou16(token, 0, &config->depth)) {
+		pr_err("failed to parse depth\n");
+		goto fail;
+	}
+	if (!local_var_part || !(*local_var_part))
+		return 0;
+
+	/* 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("failed to parse local var offset\n");
+		goto fail;
+	}
+
+	if (!local_var_part || kstrtou16(local_var_part, 0, &local_var_len)) {
+		pr_err("failed to parse local var len\n");
+		goto fail;
+	}
+
+	if (local_var_len != 1 && local_var_len != 2 &&
+	    local_var_len != 4 && local_var_len != 8) {
+		pr_err("invalid local var len %u (must be 1,2,4,8)\n",
+		       local_var_len);
+		goto fail;
+	}
+	config->local_var_len = local_var_len;
+
+	return 0;
+fail:
+	pr_err("invalid input: %s\n", config->config_str);
+	config->config_str[0] = '\0';
+	return -EINVAL;
+}
+
 static int __init kstackwatch_init(void)
 {
+	ksw_config = kzalloc(sizeof(*ksw_config), GFP_KERNEL);
+	if (!ksw_config)
+		return -ENOMEM;
+
 	pr_info("module loaded\n");
 	return 0;
 }
 
 static void __exit kstackwatch_exit(void)
 {
+	kfree(ksw_config);
+
 	pr_info("module unloaded\n");
 }
 
diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index 0273ef478a26..7c595c5c24d1 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -2,4 +2,37 @@
 #ifndef _KSTACKWATCH_H
 #define _KSTACKWATCH_H
 
+#include <linux/types.h>
+
+#define MAX_FUNC_NAME_LEN 64
+#define MAX_CONFIG_STR_LEN 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