linux-kernel - [PATCH] ARM: fix kmemleak for XIP

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Date:   Tue, 22 Nov 2016 15:28:11 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Russell King <linux@...linux.org.uk>
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-s390@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Chris Brandt <chris.brandt@...esas.com>,
        Kees Cook <keescook@...omium.org>,
        Nicolas Pitre <nico@...aro.org>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ARM: fix kmemleak for XIP_KERNEL

The newly added check for RO_AFTER_INIT_DATA in kmemleak breaks ARM whenever
XIP_KERNEL is enabled:

mm/kmemleak.o: In function `kmemleak_scan':
kmemleak.c:(.text.kmemleak_scan+0x2e4): undefined reference to `__end_data_ro_after_init'
kmemleak.c:(.text.kmemleak_scan+0x2e8): undefined reference to `__start_data_ro_after_init'

This adds the start/end symbols for the section even in the case of having
no data in the section, to make the check work while keeping the architecture
specific override in one place.

Fixes: d7c19b066dcf ("mm: kmemleak: scan .data.ro_after_init")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
The patch causing this was merged late into v4.9-rc, this one should
probably go there as well.

I assume the same problem exists on s390, but I have not checked that.
---
 arch/arm/kernel/vmlinux-xip.lds.S | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
index 06c178214629..bf900f5421a1 100644
--- a/arch/arm/kernel/vmlinux-xip.lds.S
+++ b/arch/arm/kernel/vmlinux-xip.lds.S
@@ -3,8 +3,11 @@
  * Written by Martin Mares <mj@...ey.karlin.mff.cuni.cz>
  */
 
-/* No __ro_after_init data in the .rodata section - which will always be ro */
-#define RO_AFTER_INIT_DATA
+/* empty __ro_after_init data in the .rodata section - it will always be ro */
+#define RO_AFTER_INIT_DATA						\
+	__start_data_ro_after_init = .;                                 \
+	__end_data_ro_after_init = .;
+
 
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/cache.h>
-- 
2.9.0