On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > 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 Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > --- > 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 >
