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Message-ID: <aNSj3j1P9O-XWbRE@mdev>
Date: Thu, 25 Sep 2025 10:07:26 +0800
From: Jinchao Wang <wangjinchao600@...il.com>
To: Marco Elver <elver@...gle.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, Sep 24, 2025 at 10:49:35PM +0200, Marco Elver wrote:
> 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?
Thanks, will fix in next version.
>
> > 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
> >
> > --
> > You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@...glegroups.com.
> > To view this discussion visit https://groups.google.com/d/msgid/kasan-dev/20250924115124.194940-7-wangjinchao600%40gmail.com.
--
Jinchao
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