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Wed, 03 Sep 2025 17:22:14 -0700 (PDT) From: Jinchao Wang To: Andrew Morton , Masami Hiramatsu , "Naveen N . 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 03/18] mm/ksw: add /proc/kstackwatch interface Date: Thu, 4 Sep 2025 08:21:00 +0800 Message-ID: <20250904002126.1514566-4-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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 29D97A0012 X-Stat-Signature: x4ie7bmhuysax7xz3f5ao9tism8pghs8 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1756945335-81075 X-HE-Meta: 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 fGbbgdRu XGPHr/bi4FGwg7Y8hHQQD1EYRvwXiiGQpIT6xaUDlOqqGv/z3AGmSCMIxu2yuaZYdu7yPb6d40tdD3+wuJHX36k1xHPIMaOKz0tq2+K14B5LKMuYO+nfihXAYr5J86bO4LhvsXRHoldS4Z5tDviLMUm52f5DzBBYpp0U/P3FjLcWF2Tf6EEd7J+BkUXxhHbb/N1mYdut8OUaRu7C2jZd871Jn4/RtVGpDP0UQ4YQAL1TQ4NrxgRQOqNJ70cdr8UOYZyWkSSDGWlq4qSMqBrGFvrgUN182HvXw7LSPVlZnoTaD1LkwpjVJ9ePJEvRI5phU/j4RIdGGJsb0R43lfHHvKtxmsuyKnPGeIMHzEs/UjhlkL/pe02D56xLzqVF43Vewv5cH9hi0F1KTh5SgpmHsIK+TMg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Provide the /proc/kstackwatch file to read or update the KSW configuration. Writing a valid config string starts watching; empty input stops watching. Invalid input stops watching and reports an error. Allocate a ksw_config struct on module init and free it on exit. Manage watching state with ksw_start_watching() and ksw_stop_watching(). Signed-off-by: Jinchao Wang --- mm/kstackwatch/kernel.c | 140 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) diff --git a/mm/kstackwatch/kernel.c b/mm/kstackwatch/kernel.c index 4a6dc49449fe..95ade95abde1 100644 --- a/mm/kstackwatch/kernel.c +++ b/mm/kstackwatch/kernel.c @@ -1,7 +1,10 @@ // SPDX-License-Identifier: GPL-2.0 #include #include +#include +#include #include +#include #include "kstackwatch.h" @@ -9,6 +12,29 @@ MODULE_AUTHOR("Jinchao Wang"); MODULE_DESCRIPTION("Kernel Stack Watch"); MODULE_LICENSE("GPL"); +struct ksw_config *ksw_config; +bool watching_active; + +bool panic_on_catch; +module_param(panic_on_catch, bool, 0644); +MODULE_PARM_DESC(panic_on_catch, + "Trigger a kernel panic immediately on corruption catch"); + +static int ksw_start_watching(void) +{ + watching_active = true; + + pr_info("KSW: start watching %s\n", ksw_config->config_str); + return 0; +} + +static void ksw_stop_watching(void) +{ + watching_active = false; + + pr_info("KSW: stop watching %s\n", ksw_config->config_str); +} + /* * Format of the configuration string: * function+ip_offset[+depth] [local_var_offset:local_var_len] @@ -74,8 +100,114 @@ static int ksw_parse_config(char *buf, struct ksw_config *config) return 0; } +/** + * kstackwatch_proc_write - Handle writes to the /proc/kstackwatch file + * @file: file struct for the proc entry + * @buffer: user-space buffer containing the command string + * @count: the number of bytes from the user-space buffer + * @pos: file offset + * + * This function processes user input to control the kernel stack watcher + * Before attempting to process any new configuration. It handles three + * cases based on the input string, In all three cases, the system will + * clear its state first, with subsequent actions determined by the input: + * + * 1. An empty or whitespace-only string + * Return a success code + * + * 2. An invalid configuration string + * Return a error code + * + * 3. A valid configuration string + * Start a new stack watch, return a success code + * + * Return: The number of bytes successfully processed on success, + * or a negative error code on failure. + */ +static ssize_t kstackwatch_proc_write(struct file *file, + const char __user *buffer, size_t count, + loff_t *pos) +{ + char input[MAX_CONFIG_STR_LEN]; + int ret; + + if (count == 0 || count >= sizeof(input)) + return -EINVAL; + + if (copy_from_user(input, buffer, count)) + return -EFAULT; + + if (watching_active) + ksw_stop_watching(); + memset(ksw_config, 0, sizeof(*ksw_config)); + + input[count] = '\0'; + strim(input); + + /* case 1 */ + if (!strlen(input)) { + pr_info("KSW: config cleared\n"); + return count; + } + + ret = ksw_parse_config(input, ksw_config); + if (ret) { + /* case 2 */ + pr_err("KSW: Failed to parse config %d\n", ret); + return ret; + } + + /* case 3 */ + ret = ksw_start_watching(); + if (ret) { + pr_err("KSW: Failed to start watching with %d\n", ret); + return ret; + } + + return count; +} + +static int kstackwatch_proc_show(struct seq_file *m, void *v) +{ + if (watching_active) { + seq_printf(m, "%s\n", ksw_config->config_str); + } else { + seq_puts(m, "not watching\n"); + seq_puts(m, "\nusage:\n"); + seq_puts( + m, + " echo 'function+ip_offset[+depth] [local_var_offset:local_var_len]' > /proc/kstackwatch\n"); + seq_puts(m, " Watch the canary without the local var part."); + } + + return 0; +} + +static int kstackwatch_proc_open(struct inode *inode, struct file *file) +{ + return single_open(file, kstackwatch_proc_show, NULL); +} + +static const struct proc_ops kstackwatch_proc_ops = { + .proc_open = kstackwatch_proc_open, + .proc_read = seq_read, + .proc_write = kstackwatch_proc_write, + .proc_lseek = seq_lseek, + .proc_release = single_release, +}; + static int __init kstackwatch_init(void) { + ksw_config = kmalloc(sizeof(*ksw_config), GFP_KERNEL); + if (!ksw_config) + return -ENOMEM; + + /* Create proc interface */ + if (!proc_create("kstackwatch", 0644, NULL, &kstackwatch_proc_ops)) { + pr_err("KSW: create proc kstackwatch fail"); + return -ENOMEM; + } + pr_info("KSW: module loaded\n"); pr_info("KSW: usage:\n"); pr_info("KSW: echo 'function+ip_offset[+depth] [local_var_offset:local_var_len]' > /proc/kstackwatch\n"); @@ -85,6 +217,14 @@ static int __init kstackwatch_init(void) static void __exit kstackwatch_exit(void) { + /* Cleanup active watching */ + if (watching_active) + ksw_stop_watching(); + + /* Remove proc interface */ + remove_proc_entry("kstackwatch", NULL); + kfree(ksw_config); + pr_info("KSW: Module unloaded\n"); } -- 2.43.0