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x86/dumpstack: Add log_lvl to show_iret_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_iret_regs() as a preparation to add it
to __show_regs() and show_regs_if_on_stack().

[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/20200629144847.492794-2-dima@arista.com
This commit is contained in:
Dmitry Safonov 2020-06-29 15:48:45 +01:00 • committed by Thomas Gleixner
parent ba47d845d7
commit fd07f802a7
3 changed files with 6 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

8
arch/x86/kernel/dumpstack.c
View file

@ -126,10 +126,10 @@ void show_ip(struct pt_regs *regs, const char *loglvl)
show_opcodes(regs, loglvl);
}
void show_iret_regs(struct pt_regs *regs)
void show_iret_regs(struct pt_regs *regs, const char *log_lvl)
{
show_ip(regs, KERN_DEFAULT);
printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,
show_ip(regs, log_lvl);
printk("%sRSP: %04x:%016lx EFLAGS: %08lx", log_lvl, (int)regs->ss,
regs->sp, regs->flags);
}
@ -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);
show_iret_regs(regs, KERN_DEFAULT);
}
}