linux-kernel - [PATCH 4.9 29/59] efi/libstub/arm64: Force hidden visibility for section markers

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Date:   Wed, 21 Nov 2018 20:06:44 +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, Matthias Kaehlcke <mka@...omium.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 4.9 29/59] efi/libstub/arm64: Force hidden visibility for section markers

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

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

From: Ard Biesheuvel <ard.biesheuvel@...aro.org>

commit 0426a4e68f18d75515414361de9e3e1445d2644e upstream.

To prevent the compiler from emitting absolute references to the section
markers when running in PIC mode, override the visibility to 'hidden' for
all contents of asm/sections.h

Tested-by: Matthias Kaehlcke <mka@...omium.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Link: http://lkml.kernel.org/r/20170818194947.19347-4-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/firmware/efi/libstub/arm64-stub.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -9,9 +9,17 @@
  * published by the Free Software Foundation.
  *
  */
+
+/*
+ * To prevent the compiler from emitting GOT-indirected (and thus absolute)
+ * references to the section markers, override their visibility as 'hidden'
+ */
+#pragma GCC visibility push(hidden)
+#include <asm/sections.h>
+#pragma GCC visibility pop
+
 #include <linux/efi.h>
 #include <asm/efi.h>
-#include <asm/sections.h>
 #include <asm/sysreg.h>
 
 #include "efistub.h"