diff options
| author |   Suzuki K Poulose <suzuki.poulose@arm.com> | 2018-03-26 15:12:40 +0100 |
|---|---|---|
| committer |   Will Deacon <will.deacon@arm.com> | 2018-03-26 18:01:40 +0100 |
| commit | d3aec8a28be3b88bf75442e7c24fd9da8d69a6df (patch) | |
| tree | 14768c5c5b61bf2d7d78140c46a30580547323ad /arch/arm64/include | |
| parent | arm64: capabilities: Introduce weak features based on local CPU (diff) | |
| download | linux-dev-d3aec8a28be3b88bf75442e7c24fd9da8d69a6df.tar.xz linux-dev-d3aec8a28be3b88bf75442e7c24fd9da8d69a6df.zip | |
arm64: capabilities: Restrict KPTI detection to boot-time CPUs
KPTI is treated as a system wide feature and is only detected if all
the CPUs in the sysetm needs the defense, unless it is forced via kernel
command line. This leaves a system with a mix of CPUs with and without
the defense vulnerable. Also, if a late CPU needs KPTI but KPTI was not
activated at boot time, the CPU is currently allowed to boot, which is a
potential security vulnerability.
This patch ensures that the KPTI is turned on if at least one CPU detects
the capability (i.e, change scope to SCOPE_LOCAL_CPU). Also rejetcs a late
CPU, if it requires the defense, when the system hasn't enabled it,
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/cpufeature.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index effb1c038221..4f050259dff3 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -248,6 +248,15 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \ ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) +/* + * CPU feature detected at boot time, on one or more CPUs. A late CPU + * is not allowed to have the capability when the system doesn't have it. + * It is Ok for a late CPU to miss the feature. + */ +#define ARM64_CPUCAP_BOOT_RESTRICTED_CPU_LOCAL_FEATURE \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU) + struct arm64_cpu_capabilities { const char *desc; u16 capability; |