[PATCH v2] arm:traps: Don't print stack or raw PC/LR hex values in backtraces

[Xiaoming Ni]

Printing raw pointer values in backtraces has potential security
implications and are of questionable value anyway.

This patch follows x86 and arm64's lead and removes the "Exception stack:"
dump from kernel backtraces:
	commit a25ffd3a6302a6 ("arm64: traps: Don't print stack or raw
	 PC/LR values in backtraces")
	commit bb5e5ce545f203 ("x86/dumpstack: Remove kernel text
	 addresses from stack dump")

Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>

-------
v2:
 Delete [<hex numbers>] from the stack according to the email discussion
 in patch V1, Other information processing will be discussed in subsequent
 patches.

v1: https://lore.kernel.org/lkml/20201009075957.110017-1-nixiaoming@xxxxxxxxxx/
  1. Don't print stack or raw PC/LR hex values in backtraces
  2. Don't print stack mem in backtraces
  3. if (!panic_on_oops), Don't print stack mem in __die()
---
 arch/arm/kernel/process.c | 3 +--
 arch/arm/kernel/traps.c   | 4 ++--
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 8e6ace03e960..71c9e5597d39 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -121,8 +121,7 @@ void __show_regs(struct pt_regs *regs)
 
 	printk("PC is at %pS\n", (void *)instruction_pointer(regs));
 	printk("LR is at %pS\n", (void *)regs->ARM_lr);
-	printk("pc : [<%08lx>]    lr : [<%08lx>]    psr: %08lx\n",
-	       regs->ARM_pc, regs->ARM_lr, regs->ARM_cpsr);
+	printk("psr: %08lx\n", regs->ARM_cpsr);
 	printk("sp : %08lx  ip : %08lx  fp : %08lx\n",
 	       regs->ARM_sp, regs->ARM_ip, regs->ARM_fp);
 	printk("r10: %08lx  r9 : %08lx  r8 : %08lx\n",
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 17d5a785df28..911bbf164875 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -68,8 +68,8 @@ void dump_backtrace_entry(unsigned long where, unsigned long from,
 	unsigned long end = frame + 4 + sizeof(struct pt_regs);
 
 #ifdef CONFIG_KALLSYMS
-	printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
-		loglvl, where, (void *)where, from, (void *)from);
+	printk("%s (%ps) from (%pS)\n",
+		loglvl, (void *)where, (void *)from);
 #else
 	printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
 		loglvl, where, from);
-- 
2.27.0