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authorWill Deacon <will.deacon@arm.com>2015-03-23 19:07:02 +0000
committerWill Deacon <will.deacon@arm.com>2015-04-01 10:24:31 +0100
commit905e8c5dcaa147163672b06fe9dcb5abaacbc711 (patch)
tree4284f6e2ecac493b6e4938e4b60e57fb521c3790 /arch/arm64/kernel/entry.S
parentcc3979b54d5f1d5b5059b404892888c304d28080 (diff)
downloadlinux-905e8c5dcaa147163672b06fe9dcb5abaacbc711.tar.bz2
arm64: errata: add workaround for cortex-a53 erratum #845719
When running a compat (AArch32) userspace on Cortex-A53, a load at EL0 from a virtual address that matches the bottom 32 bits of the virtual address used by a recent load at (AArch64) EL1 might return incorrect data. This patch works around the issue by writing to the contextidr_el1 register on the exception return path when returning to a 32-bit task. This workaround is patched in at runtime based on the MIDR value of the processor. Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
-rw-r--r--arch/arm64/kernel/entry.S20
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index cf21bb3bf752..959fe8733560 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -21,8 +21,10 @@
#include <linux/init.h>
#include <linux/linkage.h>
+#include <asm/alternative-asm.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
+#include <asm/cpufeature.h>
#include <asm/errno.h>
#include <asm/esr.h>
#include <asm/thread_info.h>
@@ -120,6 +122,24 @@
ct_user_enter
ldr x23, [sp, #S_SP] // load return stack pointer
msr sp_el0, x23
+
+#ifdef CONFIG_ARM64_ERRATUM_845719
+ alternative_insn \
+ "nop", \
+ "tbz x22, #4, 1f", \
+ ARM64_WORKAROUND_845719
+#ifdef CONFIG_PID_IN_CONTEXTIDR
+ alternative_insn \
+ "nop; nop", \
+ "mrs x29, contextidr_el1; msr contextidr_el1, x29; 1:", \
+ ARM64_WORKAROUND_845719
+#else
+ alternative_insn \
+ "nop", \
+ "msr contextidr_el1, xzr; 1:", \
+ ARM64_WORKAROUND_845719
+#endif
+#endif
.endif
msr elr_el1, x21 // set up the return data
msr spsr_el1, x22