From: Will Deacon <will.dea...@arm.com>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit df057cc7b4fa59e9b55f07ffdb6c62bf02e99a00 ]
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.mari...@arm.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Sasha Levin <sasha.le...@oracle.com>
---
arch/arm64/Kconfig | 16 ++++++++++++++++
arch/arm64/Makefile | 4 ++++
arch/arm64/kernel/module.c | 2 ++
3 files changed, 22 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 88d6f7f..00b9c48 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -579,6 +579,22 @@ source "drivers/cpuidle/Kconfig"
source "drivers/cpufreq/Kconfig"
+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.
+
endmenu
source "net/Kconfig"
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 20901ff..e7391ae 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -32,6 +32,10 @@ endif
CHECKFLAGS += -D__aarch64__
+ifeq ($(CONFIG_ARM64_ERRATUM_843419), y)
+CFLAGS_MODULE += -mcmodel=large
+endif
+
# Default value
head-y := arch/arm64/kernel/head.o
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index 1eb1cc9..e366329 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -330,12 +330,14 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
AARCH64_INSN_IMM_ADR);
break;
+#ifndef CONFIG_ARM64_ERRATUM_843419
case R_AARCH64_ADR_PREL_PG_HI21_NC:
overflow_check = false;
case R_AARCH64_ADR_PREL_PG_HI21:
ovf = reloc_insn_imm(RELOC_OP_PAGE, loc, val, 12, 21,
AARCH64_INSN_IMM_ADR);
break;
+#endif
case R_AARCH64_ADD_ABS_LO12_NC:
case R_AARCH64_LDST8_ABS_LO12_NC:
overflow_check = false;
--
2.1.4
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