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From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 6/9] x86/fault: Dump user opcode bytes on fatal faults
Date: Tue, 17 Apr 2018 18:11:21 +0200	[thread overview]
Message-ID: <20180417161124.5294-7-bp@alien8.de> (raw)
In-Reply-To: <20180417161124.5294-1-bp@alien8.de>

From: Borislav Petkov <bp@suse.de>

Sometimes it is useful to see which user opcode bytes RIP points to
when a fault happens: be it to rule out RIP corruption, to dump info
early during boot, when doing core dumps is impossible due to not having
writable fs yet.

Sometimes it is useful if debugging an issue and one doesn't have access
to the executable which caused the fault in order to disassemble it.

That last aspect might have some security implications so
show_unhandled_signals could be revisited for that or a new config
option added.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/mm/fault.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 73bd8c95ac71..a3fd94eff04d 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -828,6 +828,8 @@ static inline void
 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 		unsigned long address, struct task_struct *tsk)
 {
+	const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
+
 	if (!unhandled_signal(tsk, SIGSEGV))
 		return;
 
@@ -835,13 +837,14 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 		return;
 
 	printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
-		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
-		tsk->comm, task_pid_nr(tsk), address,
+		loglvl, tsk->comm, task_pid_nr(tsk), address,
 		(void *)regs->ip, (void *)regs->sp, error_code);
 
 	print_vma_addr(KERN_CONT " in ", regs->ip);
 
 	printk(KERN_CONT "\n");
+
+	show_opcodes((u8 *)regs->ip, loglvl);
 }
 
 static void
-- 
2.13.0

  parent reply	other threads:[~2018-04-17 16:13 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17 16:11 [PATCH 0/9] x86/dumpstack: Cleanups and user opcode bytes Code: section, v3 Borislav Petkov
2018-04-17 16:11 ` [PATCH 1/9] x86/dumpstack: Remove code_bytes Borislav Petkov
2018-04-26 14:18   ` [tip:x86/cleanups] " tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 2/9] x86/dumpstack: Unexport oops_begin() Borislav Petkov
2018-04-26 14:19   ` [tip:x86/cleanups] " tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 3/9] x86/dumpstack: Carve out Code: dumping into a function Borislav Petkov
2018-04-26 14:19   ` [tip:x86/cleanups] x86/dumpstack: Carve out code-dumping " tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 4/9] x86/dumpstack: Improve opcodes dumping in the Code: section Borislav Petkov
2018-04-26 14:20   ` [tip:x86/cleanups] x86/dumpstack: Improve opcodes dumping in the code section tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 5/9] x86/dumpstack: Add loglevel argument to show_opcodes() Borislav Petkov
2018-04-26 14:20   ` [tip:x86/cleanups] " tip-bot for Borislav Petkov
2018-04-17 16:11 ` Borislav Petkov [this message]
2018-04-26 14:21   ` [tip:x86/cleanups] x86/fault: Dump user opcode bytes on fatal faults tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 7/9] x86/dumpstack: Add a show_ip() function Borislav Petkov
2018-04-26 14:21   ` [tip:x86/cleanups] " tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 8/9] x86/dumpstack: Save first regs set for the executive summary Borislav Petkov
2018-04-26 14:22   ` [tip:x86/cleanups] " tip-bot for Borislav Petkov
2018-04-17 16:11 ` [PATCH 9/9] x86/dumpstack: Explain the reasoning for the prologue and buffer size Borislav Petkov
2018-04-26 14:22   ` [tip:x86/cleanups] " tip-bot for Borislav Petkov
  -- strict thread matches above, loose matches on Subject: below --
2018-03-15 15:44 [PATCH 0/9] x86/dumpstack: Cleanups and user opcode bytes Code: section, v2 Borislav Petkov
2018-03-15 15:44 ` [PATCH 6/9] x86/fault: Dump user opcode bytes on fatal faults Borislav Petkov

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