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Message-ID: <aFlfCCFZQJ9IJm-8@pathway.suse.cz>
Date: Mon, 23 Jun 2025 16:04:56 +0200
From: Petr Mladek <pmladek@...e.com>
To: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Steven Rostedt <rostedt@...dmis.org>,
Lance Yang <lance.yang@...ux.dev>, Jonathan Corbet <corbet@....net>,
linux-kernel@...r.kernel.org, paulmck@...nel.org,
john.ogness@...utronix.de
Subject: Re: [PATCH V2 3/5] sys_info: add help to translate sys_info string
to bitmap
On Mon 2025-06-16 09:08:38, Feng Tang wrote:
> Bitmap definition is hard to remember and decode. Add sysctl interface
> to translate human readable string like "tasks,mem,timer,lock,ftrace,..."
> to bitmap.
>
> Suggested-by: Petr Mladek <pmladek@...e.com>
> Signed-off-by: Feng Tang <feng.tang@...ux.alibaba.com>
> ---
> include/linux/sys_info.h | 7 +++
> lib/sys_info.c | 97 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 104 insertions(+)
>
> diff --git a/include/linux/sys_info.h b/include/linux/sys_info.h
> index 79bf4a942e5f..0b49863cd414 100644
> --- a/include/linux/sys_info.h
> +++ b/include/linux/sys_info.h
> @@ -16,5 +16,12 @@
> #define SYS_SHOW_BLOCKED_TASKS 0x00000080
>
> extern void sys_show_info(unsigned long info_mask);
> +extern unsigned long sys_info_parse_param(char *str);
>
> +#ifdef CONFIG_SYSCTL
> +struct ctl_table;
> +extern int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
> + void *buffer, size_t *lenp,
> + loff_t *ppos);
> +#endif
> #endif /* _LINUX_SYS_INFO_H */
> diff --git a/lib/sys_info.c b/lib/sys_info.c
> index 90a79b5164c9..9693542435ba 100644
> --- a/lib/sys_info.c
> +++ b/lib/sys_info.c
> @@ -5,6 +5,103 @@
> #include <linux/console.h>
> #include <linux/nmi.h>
>
> +struct sys_info_name {
> + unsigned long bit;
> + const char *name;
> +};
> +
> +static const char sys_info_avail[] = "tasks,mem,timer,lock,ftrace,all_bt,blocked_tasks";
> +
> +static const struct sys_info_name si_names[] = {
> + { SYS_SHOW_TASK_INFO, "tasks" },
> + { SYS_SHOW_MEM_INFO, "mem" },
> + { SYS_SHOW_TIMER_INFO, "timer" },
I see that the naming is a bit inconsistent in using singulars
vs. plurals. I suggest to use plulars when it makes sense.
It means here:
{ SYS_SHOW_TIMERS_INFO, "timers" },
> + { SYS_SHOW_LOCK_INFO, "lock" },
and here
{ SYS_SHOW_LOCKS_INFO, "locks" },
> + { SYS_SHOW_FTRACE_INFO, "ftrace" },
> + { SYS_SHOW_ALL_CPU_BT, "all_bt" },
> + { SYS_SHOW_BLOCKED_TASKS, "blocked_tasks" },
> +};
[...]
> +#ifdef CONFIG_SYSCTL
> +int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
> + void *buffer, size_t *lenp,
> + loff_t *ppos)
> +{
> + char names[sizeof(sys_info_avail) + 1];
> + struct ctl_table table;
> + unsigned long *si_bits_global;
> + int i, ret, len;
> +
> + si_bits_global = ro_table->data;
> +
> + if (write) {
> + unsigned long si_bits;
> +
> + table = *ro_table;
> + table.data = names;
> + table.maxlen = sizeof(names);
> + ret = proc_dostring(&table, write, buffer, lenp, ppos);
> + if (ret)
> + return ret;
> +
> + si_bits = sys_info_parse_param(names);
> + /*
> + * The access to the global value is not synchronized.
> + */
Nit, the comment fits on a single line. I would use:
/* The access to the global value is not synchronized. */
> + WRITE_ONCE(*si_bits_global, si_bits);
> + return 0;
> + } else {
> + /* for 'read' operation */
> + bool first = true;
> + char *buf;
> +
> + buf = names;
> + for (i = 0; i < ARRAY_SIZE(si_names); i++) {
> + if (*si_bits_global & si_names[i].bit) {
> +
> + if (first) {
> + first = false;
> + } else {
> + *buf = ',';
> + buf++;
> + }
> +
> + len = strlen(si_names[i].name);
> + strncpy(buf, si_names[i].name, len);
I am afraid of a buffer overflow when people add new entry into
si_names[] table but they forget to update sys_info_avail[] string.
I would prefer to limit the write to the buffer by the size of the buffer.
Something like (on top of this patch):
--- a/lib/sys_info.c
+++ b/lib/sys_info.c
@@ -50,7 +50,7 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
char names[sizeof(sys_info_avail) + 1];
struct ctl_table table;
unsigned long *si_bits_global;
- int i, ret, len;
+ int i, ret;
si_bits_global = ro_table->data;
@@ -72,27 +72,18 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
return 0;
} else {
/* for 'read' operation */
- bool first = true;
- char *buf;
+ char *delim = "";
+ int len = 0;
- buf = names;
+ names[0] = '\0';
for (i = 0; i < ARRAY_SIZE(si_names); i++) {
if (*si_bits_global & si_names[i].bit) {
-
- if (first) {
- first = false;
- } else {
- *buf = ',';
- buf++;
- }
-
- len = strlen(si_names[i].name);
- strncpy(buf, si_names[i].name, len);
- buf += len;
+ len += scnprintf(names + len, sizeof(names) - len,
+ "%s%s", delim, si_names[i].name);
+ delim = ",";
}
}
- *buf = '\0';
table = *ro_table;
table.data = names;
Best Regards,
Petr
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