From: Will Deacon <[email protected]> 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 <[email protected]> Tested-by: Mark Rutland <[email protected]> Signed-off-by: Will Deacon <[email protected]> Cc: <[email protected]> # v3.18.y (cherry picked from commit 905e8c5dcaa147163672b06fe9dcb5abaacbc711) Signed-off-by: Kevin Hilman <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- arch/arm64/Kconfig | 21 +++++++++++++++++++++ arch/arm64/include/asm/cpufeature.h | 3 ++- arch/arm64/kernel/cpu_errata.c | 8 ++++++++ arch/arm64/kernel/entry.S | 20 ++++++++++++++++++++ 4 files changed, 51 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index db4465b..dc2d66c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -298,6 +298,27 @@ config ARM64_ERRATUM_832075 If unsure, say Y. +config ARM64_ERRATUM_845719 + bool "Cortex-A53: 845719: a load might read incorrect data" + depends on COMPAT + default y + help + This option adds an alternative code sequence to work around ARM + erratum 845719 on Cortex-A53 parts up to r0p4. + + When running a compat (AArch32) userspace on an affected Cortex-A53 + part, 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. + + The workaround is to write the contextidr_el1 register on exception + return to a 32-bit task. + Please note that this does not necessarily enable the workaround, + as it depends on the alternative framework, which will only patch + the kernel if an affected CPU is detected. + + If unsure, say Y. + endmenu diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 0362f80..c008bae 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -23,8 +23,9 @@ #define ARM64_WORKAROUND_CLEAN_CACHE 0 #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE 1 +#define ARM64_WORKAROUND_845719 2 -#define NCAPS 2 +#define NCAPS 3 #ifndef __ASSEMBLY__ diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 5a5226f..8b32340 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -91,6 +91,14 @@ struct arm64_cpu_capabilities arm64_errata[] = { MIDR_RANGE(MIDR_CORTEX_A57, 0x00, 0x12), }, #endif +#ifdef CONFIG_ARM64_ERRATUM_845719 + { + /* Cortex-A53 r0p[01234] */ + .desc = "ARM erratum 845719", + .capability = ARM64_WORKAROUND_845719, + MIDR_RANGE(MIDR_CORTEX_A53, 0x00, 0x04), + }, +#endif { } }; diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 726b910..2b0f3d5 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> @@ -118,6 +120,24 @@ .if \el == 0 ct_user_enter ldr x23, [sp, #S_SP] // load return stack pointer + +#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 .if \ret ldr x1, [sp, #S_X1] // preserve x0 (syscall return) -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
