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Message-ID: <CANpmjNOuA3q3BweB9kTUpAX4CX1U25Pqa0Hiyt__=7zio81=Uw@mail.gmail.com>
Date: Wed, 24 Sep 2025 22:49:35 +0200
From: Marco Elver <elver@...gle.com>
To: Jinchao Wang <wangjinchao600@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Masami Hiramatsu <mhiramat@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, Mike Rapoport <rppt@...nel.org>,
Alexander Potapenko <glider@...gle.com>, Randy Dunlap <rdunlap@...radead.org>,
Jonathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Valentin Schneider <vschneid@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
"Liang, Kan" <kan.liang@...ux.intel.com>, David Hildenbrand <david@...hat.com>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>, Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Sami Tolvanen <samitolvanen@...gle.com>,
Miguel Ojeda <ojeda@...nel.org>, Masahiro Yamada <masahiroy@...nel.org>, Rong Xu <xur@...gle.com>,
Naveen N Rao <naveen@...nel.org>, David Kaplan <david.kaplan@....com>,
Andrii Nakryiko <andrii@...nel.org>, Jinjie Ruan <ruanjinjie@...wei.com>,
Nam Cao <namcao@...utronix.de>, workflows@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
linux-mm@...ck.org, llvm@...ts.linux.dev,
Andrey Ryabinin <ryabinin.a.a@...il.com>, Andrey Konovalov <andreyknvl@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>,
kasan-dev@...glegroups.com, "David S. Miller" <davem@...emloft.net>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v5 06/23] mm/ksw: add singleton /proc/kstackwatch interface
On Wed, 24 Sept 2025 at 13:51, Jinchao Wang <wangjinchao600@...il.com> wrote:
>
> Provide the /proc/kstackwatch file to read or update the configuration.
> Only a single process can open this file at a time, enforced using atomic
> config_file_busy, to prevent concurrent access.
Why is this in /proc and not debugfs?
> ksw_get_config() exposes the configuration pointer as const.
>
> Signed-off-by: Jinchao Wang <wangjinchao600@...il.com>
> ---
> mm/kstackwatch/kernel.c | 77 +++++++++++++++++++++++++++++++++++-
> mm/kstackwatch/kstackwatch.h | 3 ++
> 2 files changed, 79 insertions(+), 1 deletion(-)
>
> diff --git a/mm/kstackwatch/kernel.c b/mm/kstackwatch/kernel.c
> index 3b7009033dd4..4a06ddadd9c7 100644
> --- a/mm/kstackwatch/kernel.c
> +++ b/mm/kstackwatch/kernel.c
> @@ -3,11 +3,15 @@
>
> #include <linux/kstrtox.h>
> #include <linux/module.h>
> +#include <linux/proc_fs.h>
> +#include <linux/seq_file.h>
> #include <linux/string.h>
> +#include <linux/uaccess.h>
>
> #include "kstackwatch.h"
>
> static struct ksw_config *ksw_config;
> +static atomic_t config_file_busy = ATOMIC_INIT(0);
>
> struct param_map {
> const char *name; /* long name */
> @@ -74,7 +78,7 @@ static int ksw_parse_param(struct ksw_config *config, const char *key,
> * - sp_offset |so (u16) : offset from stack pointer at func_offset
> * - watch_len |wl (u16) : watch length (1,2,4,8)
> */
> -static int __maybe_unused ksw_parse_config(char *buf, struct ksw_config *config)
> +static int ksw_parse_config(char *buf, struct ksw_config *config)
> {
> char *part, *key, *val;
> int ret;
> @@ -109,18 +113,89 @@ static int __maybe_unused ksw_parse_config(char *buf, struct ksw_config *config)
> return 0;
> }
>
> +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;
> +
> + input[count] = '\0';
> + strim(input);
> +
> + if (!strlen(input)) {
> + pr_info("config cleared\n");
> + return count;
> + }
> +
> + ret = ksw_parse_config(input, ksw_config);
> + if (ret) {
> + pr_err("Failed to parse config %d\n", ret);
> + return ret;
> + }
> +
> + return count;
> +}
> +
> +static int kstackwatch_proc_show(struct seq_file *m, void *v)
> +{
> + seq_printf(m, "%s\n", ksw_config->user_input);
> + return 0;
> +}
> +
> +static int kstackwatch_proc_open(struct inode *inode, struct file *file)
> +{
> + if (atomic_cmpxchg(&config_file_busy, 0, 1))
> + return -EBUSY;
> +
> + return single_open(file, kstackwatch_proc_show, NULL);
> +}
> +
> +static int kstackwatch_proc_release(struct inode *inode, struct file *file)
> +{
> + atomic_set(&config_file_busy, 0);
> + return single_release(inode, file);
> +}
> +
> +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 = kstackwatch_proc_release,
> +};
> +
> +const struct ksw_config *ksw_get_config(void)
> +{
> + return ksw_config;
> +}
> static int __init kstackwatch_init(void)
> {
> ksw_config = kzalloc(sizeof(*ksw_config), GFP_KERNEL);
> if (!ksw_config)
> return -ENOMEM;
>
> + if (!proc_create("kstackwatch", 0600, NULL, &kstackwatch_proc_ops)) {
> + pr_err("create proc kstackwatch fail");
> + kfree(ksw_config);
> + return -ENOMEM;
> + }
> +
> pr_info("module loaded\n");
> return 0;
> }
>
> static void __exit kstackwatch_exit(void)
> {
> + remove_proc_entry("kstackwatch", NULL);
> + kfree(ksw_config->func_name);
> + kfree(ksw_config->user_input);
> kfree(ksw_config);
>
> pr_info("module unloaded\n");
> diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
> index a7bad207f863..983125d5cf18 100644
> --- a/mm/kstackwatch/kstackwatch.h
> +++ b/mm/kstackwatch/kstackwatch.h
> @@ -29,4 +29,7 @@ struct ksw_config {
> char *user_input;
> };
>
> +// singleton, only modified in kernel.c
> +const struct ksw_config *ksw_get_config(void);
> +
> #endif /* _KSTACKWATCH_H */
> --
> 2.43.0
>
> --
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