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

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Date:   Fri, 16 Oct 2020 10:31:41 +0800
From:   Xiaoming Ni <nixiaoming@...wei.com>
To:     <linux@...linux.org.uk>, <dima@...sta.com>, <will@...nel.org>,
        <jpoimboe@...hat.com>, <akpm@...ux-foundation.org>,
        <christian.brauner@...ntu.com>, <viro@...iv.linux.org.uk>,
        <ldufour@...ux.ibm.com>, <amanieu@...il.com>, <walken@...gle.com>,
        <ben.dooks@...ethink.co.uk>, <tglx@...utronix.de>,
        <bigeasy@...utronix.de>, <mingo@...nel.org>,
        <vincent.whitchurch@...s.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <nixiaoming@...wei.com>,
        <wangle6@...wei.com>, <luohaizheng@...wei.com>
Subject: [PATCH v2] arm:traps: Don't print stack or raw PC/LR hex values in backtraces

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@...wei.com>

-------
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@huawei.com/
  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