linux-kernel - [tip:efi/core] efi/libstub/arm64: Force 'hidden' visibility for section markers

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Date:   Mon, 21 Aug 2017 02:16:21 -0700
From:   tip-bot for Ard Biesheuvel <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, peterz@...radead.org, linux-kernel@...r.kernel.org,
        mka@...omium.org, tglx@...utronix.de,
        torvalds@...ux-foundation.org, ard.biesheuvel@...aro.org,
        matt@...eblueprint.co.uk, mingo@...nel.org
Subject: [tip:efi/core] efi/libstub/arm64: Force 'hidden' visibility for
 section markers

Commit-ID:  0426a4e68f18d75515414361de9e3e1445d2644e
Gitweb:     http://git.kernel.org/tip/0426a4e68f18d75515414361de9e3e1445d2644e
Author:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
AuthorDate: Fri, 18 Aug 2017 20:49:36 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 21 Aug 2017 09:43:49 +0200

efi/libstub/arm64: Force 'hidden' visibility for section markers

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>
---
 drivers/firmware/efi/libstub/arm64-stub.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index b4c2589..f7a6970 100644
--- 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"