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x86/dumpstack: Add log_lvl to __show_regs()

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show_trace_log_lvl() provides x86 platform-specific way to unwind
backtrace with a given log level. Unfortunately, registers dump(s) are
not printed with the same log level - instead, KERN_DEFAULT is always
used.

Arista's switches uses quite common setup with rsyslog, where only
urgent messages goes to console (console_log_level=KERN_ERR), everything
else goes into /var/log/ as the console baud-rate often is indecently
slow (9600 bps).

Backtrace dumps without registers printed have proven to be as useful as
morning standups. Furthermore, in order to introduce KERN_UNSUPPRESSED
(which I believe is still the most elegant way to fix raciness of sysrq[1])
the log level should be passed down the stack to register dumping
functions. Besides, there is a potential use-case for printing traces
with KERN_DEBUG level [2] (where registers dump shouldn't appear with
higher log level).

Add log_lvl parameter to __show_regs().
Keep the used log level intact to separate visible change.

[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/
[2]: https://lore.kernel.org/linux-doc/20190724170249.9644-1-dima@arista.com/

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Petr Mladek <pmladek@suse.com>
Link: https://lkml.kernel.org/r/20200629144847.492794-3-dima@arista.com
This commit is contained in:
Dmitry Safonov
2020-06-29 15:48:46 +01:00
committed by Thomas Gleixner
parent fd07f802a7
commit 44e215352c
4 changed files with 49 additions and 43 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/x86/kernel/dumpstack.c
+6 -3
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@@ -146,7 +146,7 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
* they can be printed in the right context.
*/
if (!partial && on_stack(info, regs, sizeof(*regs))) {
__show_regs(regs, SHOW_REGS_SHORT);
__show_regs(regs, SHOW_REGS_SHORT, KERN_DEFAULT);
} else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
IRET_FRAME_SIZE)) {
@@ -345,7 +345,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
oops_exit();
/* Executive summary in case the oops scrolled away */
__show_regs(&exec_summary_regs, SHOW_REGS_ALL);
__show_regs(&exec_summary_regs, SHOW_REGS_ALL, KERN_DEFAULT);
if (!signr)
return;
@@ -437,9 +437,12 @@ void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr)
void show_regs(struct pt_regs *regs)
{
enum show_regs_mode print_kernel_regs;
show_regs_print_info(KERN_DEFAULT);
__show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
print_kernel_regs = user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL;
__show_regs(regs, print_kernel_regs, KERN_DEFAULT);
/*
* When in-kernel, we also print out the stack at the time of the fault..