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Mon, 23 Jun 2025 07:04:58 -0700 (PDT) Date: Mon, 23 Jun 2025 16:04:56 +0200 From: Petr Mladek To: Feng Tang Cc: Andrew Morton , Steven Rostedt , Lance Yang , Jonathan Corbet , linux-kernel@vger.kernel.org, paulmck@kernel.org, john.ogness@linutronix.de Subject: Re: [PATCH V2 3/5] sys_info: add help to translate sys_info string to bitmap Message-ID: References: <20250616010840.38258-1-feng.tang@linux.alibaba.com> <20250616010840.38258-4-feng.tang@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250616010840.38258-4-feng.tang@linux.alibaba.com> 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 > Signed-off-by: Feng Tang > --- > 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 > #include > > +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