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x86/dumpstack: Show registers dump with trace's log level

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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).

After all preparations are done, provide log_lvl parameter for
show_regs_if_on_stack() and wire up to actual log level used as
an argument for show_trace_log_lvl().

[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/20200629144847.492794-4-dima@arista.com
This commit is contained in:
Dmitry Safonov 2020-06-29 15:48:47 +01:00 committed by Thomas Gleixner
parent 44e215352c
commit ef2ff0f5d6
1 changed files with 5 additions and 5 deletions
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10
arch/x86/kernel/dumpstack.c
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@ -134,7 +134,7 @@ void show_iret_regs(struct pt_regs *regs, const char *log_lvl)
}
static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
bool partial)
bool partial, const char *log_lvl)
{
/*
* These on_stack() checks aren't strictly necessary: the unwind code
@ -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, KERN_DEFAULT);
__show_regs(regs, SHOW_REGS_SHORT, log_lvl);
} else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
IRET_FRAME_SIZE)) {
@ -155,7 +155,7 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
* full pt_regs might not have been saved yet. In that case
* just print the iret frame.
*/
show_iret_regs(regs, KERN_DEFAULT);
show_iret_regs(regs, log_lvl);
}
}
@ -210,7 +210,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
printk("%s <%s>\n", log_lvl, stack_name);
if (regs)
show_regs_if_on_stack(&stack_info, regs, partial);
show_regs_if_on_stack(&stack_info, regs, partial, log_lvl);
/*
* Scan the stack, printing any text addresses we find. At the
@ -271,7 +271,7 @@ next:
/* if the frame has entry regs, print them */
regs = unwind_get_entry_regs(&state, &partial);
if (regs)
show_regs_if_on_stack(&stack_info, regs, partial);
show_regs_if_on_stack(&stack_info, regs, partial, log_lvl);
}
if (stack_name)