linux-kernel - [tip:x86/urgent] x86/unwind/orc: Fix ORC unwind table alignment

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Message-ID: <tip-f76a16adc485699f95bb71fce114f97c832fe664@git.kernel.org>
Date:   Wed, 6 Mar 2019 11:40:09 -0800
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, ndesaulniers@...gle.com,
        mingo@...nel.org, jpoimboe@...hat.com, sedat.dilek@...il.com,
        dima@...ovin.in, tglx@...utronix.de, hpa@...or.com,
        peterz@...radead.org
Subject: [tip:x86/urgent] x86/unwind/orc: Fix ORC unwind table alignment

Commit-ID:  f76a16adc485699f95bb71fce114f97c832fe664
Gitweb:     https://git.kernel.org/tip/f76a16adc485699f95bb71fce114f97c832fe664
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Wed, 6 Mar 2019 11:07:24 -0600
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Wed, 6 Mar 2019 20:36:32 +0100

x86/unwind/orc: Fix ORC unwind table alignment

The .orc_unwind section is a packed array of 6-byte structs.  It's
currently aligned to 6 bytes, which is causing warnings in the LLD
linker.

Six isn't a power of two, so it's not a valid alignment value.  The
actual alignment doesn't matter much because it's an array of packed
structs.  An alignment of two is sufficient.  In reality it always gets
aligned to four bytes because it comes immediately after the
4-byte-aligned .orc_unwind_ip section.

Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reported-by: Dmitry Golovin <dima@...ovin.in>
Reported-by: Sedat Dilek <sedat.dilek@...il.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Sedat Dilek <sedat.dilek@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: stable@...r.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/218
Link: https://lkml.kernel.org/r/d55027ee95fe73e952dcd8be90aebd31b0095c45.1551892041.git.jpoimboe@redhat.com

---
 include/asm-generic/vmlinux.lds.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 3d7a6a9c2370..f8f6f04c4453 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -733,7 +733,7 @@
 		KEEP(*(.orc_unwind_ip))					\
 		__stop_orc_unwind_ip = .;				\
 	}								\
-	. = ALIGN(6);							\
+	. = ALIGN(2);							\
 	.orc_unwind : AT(ADDR(.orc_unwind) - LOAD_OFFSET) {		\
 		__start_orc_unwind = .;					\
 		KEEP(*(.orc_unwind))					\