The patch titled
Subject: panic: add an option to replay all the printk messages in buffer
has been added to the -mm tree. Its filename is
panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Feng Tang <feng.tang@xxxxxxxxx>
Subject: panic: add an option to replay all the printk messages in buffer
Currently on panic, kernel will lower the loglevel and print out
new printk msg only with console_flush_on_panic().
Add an option for users to configure the "panic_print" to see
all dmesg in buffer, some of which they may have never seen due
to the loglevel setting, which will help debugging too.
Thanks to Petr Mladek as somes codes come directly from the sample
code in his review comments.
Link: http://lkml.kernel.org/r/20190410153718.22905-1-feng.tang@xxxxxxxxx
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Cc: Aaro Koskinen <aaro.koskinen@xxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 1
include/linux/console.h | 1
kernel/panic.c | 5 +
kernel/printk/printk.c | 46 +++++++++++---
4 files changed, 44 insertions(+), 9 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -3145,6 +3145,7 @@
bit 2: print timer info
bit 3: print locks info if CONFIG_LOCKDEP is on
bit 4: print ftrace buffer
+ bit 5: print all printk messages in buffer
panic_on_warn panic() instead of WARN(). Useful to cause kdump
on a WARN().
--- a/include/linux/console.h~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/include/linux/console.h
@@ -176,6 +176,7 @@ extern void console_unlock(void);
extern void console_conditional_schedule(void);
extern void console_unblank(void);
extern void console_flush_on_panic(void);
+extern void console_replay_on_panic(void);
extern struct tty_driver *console_device(int *);
extern void console_stop(struct console *);
extern void console_start(struct console *);
--- a/kernel/panic.c~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/kernel/panic.c
@@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(panic_timeout);
#define PANIC_PRINT_TIMER_INFO 0x00000004
#define PANIC_PRINT_LOCK_INFO 0x00000008
#define PANIC_PRINT_FTRACE_INFO 0x00000010
+#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020
unsigned long panic_print;
ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
@@ -134,6 +135,10 @@ EXPORT_SYMBOL(nmi_panic);
static void panic_print_sys_info(void)
{
+ /* Replay existing messages before adding other sys info. */
+ if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
+ console_replay_on_panic();
+
if (panic_print & PANIC_PRINT_TASK_INFO)
show_state();
--- a/kernel/printk/printk.c~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/kernel/printk/printk.c
@@ -275,6 +275,9 @@ EXPORT_SYMBOL(console_set_on_cmdline);
/* Flag: console code may call schedule() */
static int console_may_schedule;
+/* Whether to print all messages in buffer */
+static int console_replay;
+
enum con_msg_format_flags {
MSG_FORMAT_DEFAULT = 0,
MSG_FORMAT_SYSLOG = (1 << 0),
@@ -2396,21 +2399,32 @@ again:
for (;;) {
struct printk_log *msg;
+ int reset_idx = 0;
size_t ext_len = 0;
- size_t len;
+ size_t len = 0;
printk_safe_enter_irqsave(flags);
raw_spin_lock(&logbuf_lock);
+
if (console_seq < log_first_seq) {
len = sprintf(text,
"** %llu printk messages dropped **\n",
log_first_seq - console_seq);
/* messages are gone, move to first one */
+ reset_idx = 1;
+ }
+
+ if (console_replay) {
+ len += sprintf(text + len,
+ "Replaying the entire log:\n");
+ reset_idx = 1;
+ console_replay = 0;
+ }
+
+ if (reset_idx) {
console_seq = log_first_seq;
console_idx = log_first_idx;
- } else {
- len = 0;
}
skip:
if (console_seq == log_next_seq)
@@ -2533,12 +2547,7 @@ void console_unblank(void)
console_unlock();
}
-/**
- * console_flush_on_panic - flush console content on panic
- *
- * Immediately output all pending messages no matter what.
- */
-void console_flush_on_panic(void)
+static void __flush_on_panic(int replay)
{
/*
* If someone else is holding the console lock, trylock will fail
@@ -2549,9 +2558,28 @@ void console_flush_on_panic(void)
*/
console_trylock();
console_may_schedule = 0;
+ console_replay = replay ? 1 : 0;
console_unlock();
}
+/**
+ * console_flush_on_panic - flush console content on panic
+ *
+ * Immediately output all pending messages no matter what.
+ */
+void console_flush_on_panic(void)
+{
+ __flush_on_panic(0);
+}
+
+/**
+ * console_replay_on_panic - replay all messages in buffer on panic
+ */
+void console_replay_on_panic(void)
+{
+ __flush_on_panic(1);
+}
+
/*
* Return the console tty driver structure and its associated index
*/
_
Patches currently in -mm which might be from feng.tang@xxxxxxxxx are
panic-avoid-the-extra-noise-dmesg.patch
panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
