[tip: x86/urgent] x86/unwind/orc: Prevent unwinding before ORC initialization - tip-bot2 for Josh Poimboeuf

From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Miroslav Benes <mbenes@suse.cz>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>,
	Dave Jones <dsj@fb.com>, Jann Horn <jannh@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vince Weaver <vincent.weaver@maine.edu>, x86 <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: [tip: x86/urgent] x86/unwind/orc: Prevent unwinding before ORC initialization
Date: Sun, 26 Apr 2020 06:47:40 -0000	[thread overview]
Message-ID: <158788366000.28353.11850032447179748567.tip-bot2@tip-bot2> (raw)
In-Reply-To: <069d1499ad606d85532eb32ce39b2441679667d5.1587808742.git.jpoimboe@redhat.com>

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     98d0c8ebf77e0ba7c54a9ae05ea588f0e9e3f46e
Gitweb:        https://git.kernel.org/tip/98d0c8ebf77e0ba7c54a9ae05ea588f0e9e3f46e
Author:        Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate:    Sat, 25 Apr 2020 05:03:08 -05:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 25 Apr 2020 12:22:29 +02:00

x86/unwind/orc: Prevent unwinding before ORC initialization

If the unwinder is called before the ORC data has been initialized,
orc_find() returns NULL, and it tries to fall back to using frame
pointers.  This can cause some unexpected warnings during boot.

Move the 'orc_init' check from orc_find() to __unwind_init(), so that it
doesn't even try to unwind from an uninitialized state.

Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Jones <dsj@fb.com>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lore.kernel.org/r/069d1499ad606d85532eb32ce39b2441679667d5.1587808742.git.jpoimboe@redhat.com
---
 arch/x86/kernel/unwind_orc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index e9f5a20..cb11567 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -148,9 +148,6 @@ static struct orc_entry *orc_find(unsigned long ip)
 {
 	static struct orc_entry *orc;
 
-	if (!orc_init)
-		return NULL;
-
 	if (ip == 0)
 		return &null_orc_entry;
 
@@ -591,6 +588,9 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
 void __unwind_start(struct unwind_state *state, struct task_struct *task,
 		    struct pt_regs *regs, unsigned long *first_frame)
 {
+	if (!orc_init)
+		goto done;
+
 	memset(state, 0, sizeof(*state));
 	state->task = task;
 
