[PATCH] arm64: errata: Add -mpc-relative-literal-loads to erratum #843419 build flags

GCC6 (and Linaro's 2015.12 snapshot of GCC5) has a new default that uses
adrp/ldr or adrp/add to address literal pools. When CONFIG_ARM64_ERRATUM_843419
is enabled, modules built with this toolchain fail to load:

  [ 2.156817] module libahci: unsupported RELA relocation: 275

Longterm, this will likely be superseded by -mfix-cortex-a53-843419, which
should disable this optimization in the future.

Cc: stable at vger.kernel.org
Fixes: df057cc7b4fa ("arm64: errata: add module build workaround for erratum #843419")
BugLink: http://bugs.launchpad.net/bugs/1533009
Suggested-by: Christophe Lyon <redacted>
Signed-off-by: dann frazier <redacted>
---
 arch/arm64/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index cd822d8..08e794d 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile

@@ -43,6 +43,7 @@ CHECKFLAGS	+= -D__aarch64__
 
 ifeq ($(CONFIG_ARM64_ERRATUM_843419), y)
 KBUILD_CFLAGS_MODULE	+= -mcmodel=large
+KBUILD_CFLAGS_MODULE	+= $(call cc-option, -mpc-relative-literal-loads)
 endif
 
 # Default value

-- 
2.7.0

On 23 January 2016 at 00:07, dann frazier [off-list ref] wrote:

GCC6 (and Linaro's 2015.12 snapshot of GCC5) has a new default that uses
adrp/ldr or adrp/add to address literal pools. When CONFIG_ARM64_ERRATUM_843419
is enabled, modules built with this toolchain fail to load:

(more context here https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63304)

Hi Dann,

I would prefer this new option to be set unconditionally (if
supported) both for the kernel and the modules, since we have no
requirement for supporting literals that are >1 MB away.

Thanks,
Ard.