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From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     x86@kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Vince Weaver <vincent.weaver@maine.edu>,
        Dave Jones <dsj@fb.com>, Jann Horn <jannh@google.com>,
        Miroslav Benes <mbenes@suse.cz>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH v2 09/11] x86/unwind/orc: Prevent unwinding before ORC initialization
Date:   Sat, 25 Apr 2020 05:03:08 -0500
Message-Id: <069d1499ad606d85532eb32ce39b2441679667d5.1587808742.git.jpoimboe@redhat.com>
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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")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
---
 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 e9f5a20c69c6..cb11567361cc 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;
=20
-	if (!orc_init)
-		return NULL;
-
 	if (ip =3D=3D 0)
 		return &null_orc_entry;
=20
@@ -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 =3D task;
=20
--=20
2.21.1