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panic: add 'panic_sys_info' sysctl to take human readable string parameter
Bitmap definition for 'panic_print' is hard to remember and decode. Add 'panic_sys_info='sysctl to take human readable string like "tasks,mem,timers,locks,ftrace,..." and translate it into bitmap. The detailed mapping is: SYS_INFO_TASKS "tasks" SYS_INFO_MEM "mem" SYS_INFO_TIMERS "timers" SYS_INFO_LOCKS "locks" SYS_INFO_FTRACE "ftrace" SYS_INFO_ALL_CPU_BT "all_bt" SYS_INFO_BLOCKED_TASKS "blocked_tasks" [nathan@kernel.org: add __maybe_unused to sys_info_avail] Link: https://lkml.kernel.org/r/20250708-fix-clang-sys_info_avail-warning-v1-1-60d239eacd64@kernel.org Link: https://lkml.kernel.org/r/20250703021004.42328-4-feng.tang@linux.alibaba.com Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com> Suggested-by: Petr Mladek <pmladek@suse.com> Cc: John Ogness <john.ogness@linutronix.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Lance Yang <lance.yang@linux.dev> Cc: "Paul E . McKenney" <paulmck@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -899,6 +899,24 @@ So for example to print tasks and memory info on panic, user can::
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echo 3 > /proc/sys/kernel/panic_print
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panic_sys_info
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==============
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A comma separated list of extra information to be dumped on panic,
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for example, "tasks,mem,timers,...". It is a human readable alternative
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to 'panic_print'. Possible values are:
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============= ===================================================
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tasks print all tasks info
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mem print system memory info
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timer print timers info
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lock print locks info if CONFIG_LOCKDEP is on
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ftrace print ftrace buffer
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all_bt print all CPUs backtrace (if available in the arch)
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blocked_tasks print only tasks in uninterruptible (blocked) state
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============= ===================================================
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panic_on_rcu_stall
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==================
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@ -2,6 +2,8 @@
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#ifndef _LINUX_SYS_INFO_H
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#define _LINUX_SYS_INFO_H
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#include <linux/sysctl.h>
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/*
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* SYS_INFO_PANIC_CONSOLE_REPLAY is for panic case only, as it needs special
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* handling which only fits panic case.
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@ -16,5 +18,11 @@
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#define SYS_INFO_BLOCKED_TASKS 0x00000080
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void sys_info(unsigned long si_mask);
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unsigned long sys_info_parse_param(char *str);
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#ifdef CONFIG_SYSCTL
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int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
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void *buffer, size_t *lenp,
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loff_t *ppos);
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#endif
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#endif /* _LINUX_SYS_INFO_H */
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@ -126,6 +126,13 @@ static const struct ctl_table kern_panic_table[] = {
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.mode = 0644,
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.proc_handler = proc_douintvec,
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},
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{
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.procname = "panic_sys_info",
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.data = &panic_print,
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.maxlen = sizeof(panic_print),
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.mode = 0644,
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.proc_handler = sysctl_sys_info_handler,
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},
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};
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static __init int kernel_panic_sysctls_init(void)
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@ -3,10 +3,100 @@
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#include <linux/console.h>
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#include <linux/kernel.h>
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#include <linux/ftrace.h>
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#include <linux/sysctl.h>
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#include <linux/nmi.h>
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#include <linux/sys_info.h>
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struct sys_info_name {
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unsigned long bit;
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const char *name;
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};
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/*
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* When 'si_names' gets updated, please make sure the 'sys_info_avail'
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* below is updated accordingly.
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*/
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static const struct sys_info_name si_names[] = {
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{ SYS_INFO_TASKS, "tasks" },
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{ SYS_INFO_MEM, "mem" },
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{ SYS_INFO_TIMERS, "timers" },
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{ SYS_INFO_LOCKS, "locks" },
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{ SYS_INFO_FTRACE, "ftrace" },
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{ SYS_INFO_ALL_CPU_BT, "all_bt" },
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{ SYS_INFO_BLOCKED_TASKS, "blocked_tasks" },
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};
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/* Expecting string like "xxx_sys_info=tasks,mem,timers,locks,ftrace,..." */
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unsigned long sys_info_parse_param(char *str)
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{
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unsigned long si_bits = 0;
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char *s, *name;
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int i;
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s = str;
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while ((name = strsep(&s, ",")) && *name) {
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for (i = 0; i < ARRAY_SIZE(si_names); i++) {
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if (!strcmp(name, si_names[i].name)) {
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si_bits |= si_names[i].bit;
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break;
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}
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}
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}
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return si_bits;
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}
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#ifdef CONFIG_SYSCTL
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static const char sys_info_avail[] __maybe_unused = "tasks,mem,timers,locks,ftrace,all_bt,blocked_tasks";
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int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
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void *buffer, size_t *lenp,
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loff_t *ppos)
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{
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char names[sizeof(sys_info_avail) + 1];
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struct ctl_table table;
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unsigned long *si_bits_global;
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si_bits_global = ro_table->data;
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if (write) {
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unsigned long si_bits;
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int ret;
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table = *ro_table;
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table.data = names;
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table.maxlen = sizeof(names);
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ret = proc_dostring(&table, write, buffer, lenp, ppos);
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if (ret)
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return ret;
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si_bits = sys_info_parse_param(names);
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/* The access to the global value is not synchronized. */
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WRITE_ONCE(*si_bits_global, si_bits);
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return 0;
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} else {
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/* for 'read' operation */
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char *delim = "";
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int i, len = 0;
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for (i = 0; i < ARRAY_SIZE(si_names); i++) {
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if (*si_bits_global & si_names[i].bit) {
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len += scnprintf(names + len, sizeof(names) - len,
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"%s%s", delim, si_names[i].name);
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delim = ",";
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}
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}
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table = *ro_table;
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table.data = names;
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table.maxlen = sizeof(names);
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return proc_dostring(&table, write, buffer, lenp, ppos);
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}
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}
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#endif
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void sys_info(unsigned long si_mask)
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{
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if (si_mask & SYS_INFO_TASKS)
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