arm64: errata: add module build workaround for erratum #843419
Cortex-A53 processors <= r0p4 are affected by erratum #843419 which can
lead to a memory access using an incorrect address in certain sequences
headed by an ADRP instruction.
There is a linker fix to generate veneers for ADRP instructions, but
this doesn't work for kernel modules which are built as unlinked ELF
objects.
This patch adds a new config option for the erratum which, when enabled,
builds kernel modules with the mcmodel=large flag. This uses absolute
addressing for all kernel symbols, thereby removing the use of ADRP as
a PC-relative form of addressing. The ADRP relocs are removed from the
module loader so that we fail to load any potentially affected modules.
Cc: <stable@vger.kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 8b6e378..07d1811 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -332,6 +332,22 @@
If unsure, say Y.
+config ARM64_ERRATUM_843419
+ bool "Cortex-A53: 843419: A load or store might access an incorrect address"
+ depends on MODULES
+ default y
+ help
+ This option builds kernel modules using the large memory model in
+ order to avoid the use of the ADRP instruction, which can cause
+ a subsequent memory access to use an incorrect address on Cortex-A53
+ parts up to r0p4.
+
+ Note that the kernel itself must be linked with a version of ld
+ which fixes potentially affected ADRP instructions through the
+ use of veneers.
+
+ If unsure, say Y.
+
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