linux-kernel - [PATCH 5/7] unwinder: show_stack, check also ret_addr

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Date:   Fri,  5 May 2017 14:21:58 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     akpm@...ux-foundation.org
Cc:     torvalds@...ux-foundation.org, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH 5/7] unwinder: show_stack, check also ret_addr_p's contents

The DWARF unwinder stores the return address in an internal structure.
This is returned to the generic unwinder. So do not check only
ret_addr_p against the current stack pointer, but also if the address is
the return address.

This makes the unwinder to really think the addresses are reliable.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/kernel/dumpstack.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index dbce3cca94cb..963c6b60887f 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -123,7 +123,8 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 				continue;
 			}
 
-			if (stack == ret_addr_p)
+			if (stack == ret_addr_p ||
+					(ret_addr_p && addr == *ret_addr_p))
 				reliable = 1;
 
 			/*
-- 
2.12.2