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Subject[PATCH v2 3/3] x86/dumpstack: Show registers dump with trace's log level
Date
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, I have 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/
Acked-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/x86/kernel/dumpstack.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 4954d6678cef..f9a3526af15d 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -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 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
/* 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)
--
2.27.0
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