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arm64: errata: add module build workaround for erratum #843419

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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>
This commit is contained in:
Will Deacon 2015-03-17 12:15:02 +00:00
parent bdec97a855
commit df057cc7b4
3 changed files with 22 additions and 0 deletions
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16
arch/arm64/Kconfig
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@ -332,6 +332,22 @@ config ARM64_ERRATUM_845719
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.
endmenu

4
arch/arm64/Makefile
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@ -41,6 +41,10 @@ endif
CHECKFLAGS += -D__aarch64__
ifeq ($(CONFIG_ARM64_ERRATUM_843419), y)
CFLAGS_MODULE += -mcmodel=large
endif
# Default value
head-y := arch/arm64/kernel/head.o

2
arch/arm64/kernel/module.c
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@ -332,12 +332,14 @@ 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;