Add an arm64 helper called cpu_supports_mte() that exposes information about whether the CPU supports memory tagging and that can be called during early boot (unlike system_supports_mte()). Use that helper to implement a generic cpu_supports_tags() helper, that will be used by hardware tag-based KASAN. Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Link: https://linux-review.googlesource.com/id/Ib4b56a42c57c6293df29a0cdfee334c3ca7bdab4 --- arch/arm64/include/asm/memory.h | 1 + arch/arm64/include/asm/mte-kasan.h | 6 ++++++ arch/arm64/kernel/mte.c | 20 ++++++++++++++++++++ mm/kasan/kasan.h | 4 ++++ 4 files changed, 31 insertions(+) diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index b5d6b824c21c..f496abfcf7f5 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -232,6 +232,7 @@ static inline const void *__tag_set(const void *addr, u8 tag) } #ifdef CONFIG_KASAN_HW_TAGS +#define arch_cpu_supports_tags() cpu_supports_mte() #define arch_init_tags(max_tag) mte_init_tags(max_tag) #define arch_get_random_tag() mte_get_random_tag() #define arch_get_mem_tag(addr) mte_get_mem_tag(addr) diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h index a4c61b926d4a..4c3f2c6b4fe6 100644 --- a/arch/arm64/include/asm/mte-kasan.h +++ b/arch/arm64/include/asm/mte-kasan.h @@ -9,6 +9,7 @@ #ifndef __ASSEMBLY__ +#include <linux/init.h> #include <linux/types.h> /* @@ -30,6 +31,7 @@ u8 mte_get_random_tag(void); void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag); void mte_init_tags(u64 max_tag); +bool __init cpu_supports_mte(void); #else /* CONFIG_ARM64_MTE */ @@ -54,6 +56,10 @@ static inline void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag) static inline void mte_init_tags(u64 max_tag) { } +static inline bool cpu_supports_mte(void) +{ + return false; +} #endif /* CONFIG_ARM64_MTE */ diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index ca8206b7f9a6..8fcd17408515 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -134,6 +134,26 @@ void mte_init_tags(u64 max_tag) gcr_kernel_excl = ~incl & SYS_GCR_EL1_EXCL_MASK; } +/* + * This function can be used during early boot to determine whether the CPU + * supports MTE. The alternative that must be used after boot is completed is + * system_supports_mte(), but it only works after the cpufeature framework + * learns about MTE. + */ +bool __init cpu_supports_mte(void) +{ + u64 pfr1; + u32 val; + + if (!IS_ENABLED(CONFIG_ARM64_MTE)) + return false; + + pfr1 = read_cpuid(ID_AA64PFR1_EL1); + val = cpuid_feature_extract_unsigned_field(pfr1, ID_AA64PFR1_MTE_SHIFT); + + return val >= ID_AA64PFR1_MTE; +} + static void update_sctlr_el1_tcf0(u64 tcf0) { /* ISB required for the kernel uaccess routines */ diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index da08b2533d73..f7ae0c23f023 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -240,6 +240,9 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag) #define set_tag(addr, tag) ((void *)arch_kasan_set_tag((addr), (tag))) #define get_tag(addr) arch_kasan_get_tag(addr) +#ifndef arch_cpu_supports_tags +#define arch_cpu_supports_tags() (false) +#endif #ifndef arch_init_tags #define arch_init_tags(max_tag) #endif @@ -253,6 +256,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag) #define arch_set_mem_tag_range(addr, size, tag) ((void *)(addr)) #endif +#define cpu_supports_tags() arch_cpu_supports_tags() #define init_tags(max_tag) arch_init_tags(max_tag) #define get_random_tag() arch_get_random_tag() #define get_mem_tag(addr) arch_get_mem_tag(addr) -- 2.29.0.rc1.297.gfa9743e501-goog
