[tip:x86/asm] x86/dumpstack/ftrace: Don't print unreliable addresses in print_context_stack_bp()

[tip-bot for Josh Poimboeuf <tipbot@zytor.com>]

Commit-ID:  13e25bab7e51bdd4ba7df1ef2388961294bb565e
Gitweb:     http://git.kernel.org/tip/13e25bab7e51bdd4ba7df1ef2388961294bb565e
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:53:02 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:15 +0200

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@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c51aef578d8027791b38d2ad9bac0c7f499fde91.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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;