linux-kernel - [PATCH 8/8] x86/dumpstack/ftrace: don't print unreliable addresses in print_context_stack

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Message-Id: <c51aef578d8027791b38d2ad9bac0c7f499fde91.1471607358.git.jpoimboe@redhat.com>
Date:   Fri, 19 Aug 2016 06:53:02 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Nilay Vaish <nilayvaish@...il.com>
Subject: [PATCH 8/8] x86/dumpstack/ftrace: don't print unreliable addresses in print_context_stack_bp()

When function graph tracing is enabled, print_context_stack_bp() can
report return_to_handler() as an unreliable address, which is confusing
and misleading: return_to_handler() is really only useful as a hint for
debugging, whereas print_context_stack_bp() users only care about the
actual 'reliable' call path.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/kernel/dumpstack.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 6aad8d4..01072e9 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -126,8 +126,6 @@ print_context_stack_bp(struct task_struct *task,
 			break;
 
 		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
-		if (real_addr != addr && ops->address(data, addr, 0))
-			break;
 		if (ops->address(data, real_addr, 1))
 			break;
 
-- 
2.7.4