linux-kernel - [PATCH 4.19 252/280] x86/unwind/orc: Fix ORC unwind table alignment

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Date:   Fri, 22 Mar 2019 12:16:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nick Desaulniers <ndesaulniers@...gle.com>,
        Dmitry Golovin <dima@...ovin.in>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 4.19 252/280] x86/unwind/orc: Fix ORC unwind table alignment

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josh Poimboeuf <jpoimboe@...hat.com>

commit f76a16adc485699f95bb71fce114f97c832fe664 upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -727,7 +727,7 @@
 		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))					\