linux-kernel - [PATCH v2 17/44] proc: fix return address printk conversion specifer in /proc/<pid>/stack

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Message-Id: <df5679be5e83e60588b44efa92ff045bd0307616.1470345772.git.jpoimboe@redhat.com>
Date:	Thu,  4 Aug 2016 17:22:13 -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>
Subject: [PATCH v2 17/44] proc: fix return address printk conversion specifer in /proc/<pid>/stack

When printing call return addresses found on a stack, /proc/<pid>/stack
can sometimes give a confusing result.  If the call instruction was the
last instruction in the function (which can happen when calling a
noreturn function), '%pS' will incorrectly display the name of the
function which happens to be next in the object code, rather than the
name of the actual calling function.

Use '%pB' instead, which was created for this exact purpose.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 fs/proc/base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 31370da..cc4d81c 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -483,7 +483,7 @@ static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
 		save_stack_trace_tsk(task, &trace);
 
 		for (i = 0; i < trace.nr_entries; i++) {
-			seq_printf(m, "[<%pK>] %pS\n",
+			seq_printf(m, "[<%pK>] %pB\n",
 				   (void *)entries[i], (void *)entries[i]);
 		}
 		unlock_trace(task);
-- 
2.7.4