From b0343ab330ae4d6c8d4210de5c16da704c2d4743 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Thu, 13 May 2021 10:59:23 +0100
Subject: [PATCH] ARM: reduce the information printed in call traces
A while back, Linus complained about the numeric values printed by the
ARM backtracing code. Printing these values does not make sense if one
does not have access to the kernel ELF image (as is normally the case
when helping a third party on a mailing list), but if one does, they
can be very useful to find the code, rather than searching for the
function name, and then doing hex math to work out where the backtrace
entry is referring to.
Provide an option to control whether this information is included,
which will only be visible if EXPERT is enabled.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
arch/arm/Kconfig.debug | 11 +++++++++++
arch/arm/kernel/traps.c | 8 +++++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 98436702e0c7e..07055a5030225 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -81,6 +81,17 @@ endchoice
config ARM_UNWIND
bool
+config BACKTRACE_VERBOSE
+ bool "Verbose backtrace"
+ depends on EXPERT
+ help
+ When the kernel produces a warning or oops, the kernel prints a
+ trace of the call chain. This option controls whether we include
+ the numeric addresses or only include the symbolic information.
+
+ In most cases, say N here, unless you are intending to debug the
+ kernel and have access to the kernel binary image.
+
config FRAME_POINTER
bool
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 195dff58bafc7..c5e25cf7219b6 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -67,12 +67,14 @@ void dump_backtrace_entry(unsigned long where, unsigned long from,
{
unsigned long end = frame + 4 + sizeof(struct pt_regs);
-#ifdef CONFIG_KALLSYMS
+#ifndef CONFIG_KALLSYMS
+ printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
+ loglvl, where, from);
+#elif defined CONFIG_BACKTRACE_VERBOSE
printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
loglvl, where, (void *)where, from, (void *)from);
#else
- printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
- loglvl, where, from);
+ printk("%s %ps from %pS\n", loglvl, (void *)where, (void *)from);
#endif
if (in_entry_text(from) && end <= ALIGN(frame, THREAD_SIZE))
--
2.30.2