From: Peter Collingbourne pcc@google.com

If FEAT_MTE2 is disabled via the arm64.nomte command line argument on a CPU that claims to support FEAT_MTE2, the kernel will use Tagged Normal in the MAIR. If we interpret arm64.nomte to mean that the CPU does not in fact implement FEAT_MTE2, setting the system register like this may lead to UNSPECIFIED behavior. Fix it by arranging for MAIR to be set in the C function cpu_enable_mte which is called based on the sanitized version of the system register.

There is no need for the rest of the MTE-related system register initialization to happen from assembly, with the exception of TCR_EL1, which must be set to include at least TBI1 because the secondary CPUs access KASan-allocated data structures early. Therefore, make the TCR_EL1 initialization unconditional and move the rest of the initialization to cpu_enable_mte so that we no longer have a dependency on the unsanitized ID register value.

Co-developed-by: Evgenii Stepanov eugenis@google.com Signed-off-by: Peter Collingbourne pcc@google.com Signed-off-by: Evgenii Stepanov eugenis@google.com Suggested-by: Catalin Marinas catalin.marinas@arm.com Reported-by: kernel test robot lkp@intel.com Fixes: 3b714d24ef17 ("arm64: mte: CPU feature detection and initial sysreg configuration") Cc: stable@vger.kernel.org # 5.10.x --- Changelong since v3: - Removed extra isb barrier. - Fixed build without CONFIG_ARM64_MTE.

Changelog since v2: - Fixed register initialization on cpu_resume code path.

Changelog since v1: - Keep TBI1 off unless CONFIG_ARM64_MTE - Fixed mask application in the RGSR_EL1 computation (bug found by Kenny Root). - Changed code formatting

arch/arm64/include/asm/mte.h | 5 ++++ arch/arm64/kernel/cpufeature.c | 3 +- arch/arm64/kernel/mte.c | 51 ++++++++++++++++++++++++++++++++++ arch/arm64/kernel/suspend.c | 2 ++ arch/arm64/mm/proc.S | 46 ++++-------------------------- 5 files changed, 65 insertions(+), 42 deletions(-)

diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index aa523591a44e5..760c62f8e22f8 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -42,7 +42,9 @@ void mte_sync_tags(pte_t old_pte, pte_t pte); void mte_copy_page_tags(void *kto, const void *kfrom); void mte_thread_init_user(void); void mte_thread_switch(struct task_struct *next); +void mte_cpu_setup(void); void mte_suspend_enter(void); +void mte_suspend_exit(void); long set_mte_ctrl(struct task_struct *task, unsigned long arg); long get_mte_ctrl(struct task_struct *task); int mte_ptrace_copy_tags(struct task_struct *child, long request, @@ -72,6 +74,9 @@ static inline void mte_thread_switch(struct task_struct *next) static inline void mte_suspend_enter(void) { } +static inline void mte_suspend_exit(void) +{ +} static inline long set_mte_ctrl(struct task_struct *task, unsigned long arg) { return 0; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index af4de817d7123..d7a077b5ccd1c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2034,7 +2034,8 @@ static void bti_enable(const struct arm64_cpu_capabilities *__unused) static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) { sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ATA | SCTLR_EL1_ATA0); - isb(); + + mte_cpu_setup();

/* * Clear the tags in the zero page. This needs to be done via the diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index b2b730233274b..aca88470fb69d 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -285,6 +285,49 @@ void mte_thread_switch(struct task_struct *next) mte_check_tfsr_el1(); }

+void mte_cpu_setup(void) +{ + u64 rgsr; + + /* + * CnP must be enabled only after the MAIR_EL1 register has been set + * up. Inconsistent MAIR_EL1 between CPUs sharing the same TLB may + * lead to the wrong memory type being used for a brief window during + * CPU power-up. + * + * CnP is not a boot feature so MTE gets enabled before CnP, but let's + * make sure that is the case. + */ + BUG_ON(read_sysreg(ttbr0_el1) & TTBR_CNP_BIT); + BUG_ON(read_sysreg(ttbr1_el1) & TTBR_CNP_BIT); + + /* Normal Tagged memory type at the corresponding MAIR index */ + sysreg_clear_set(mair_el1, + MAIR_ATTRIDX(MAIR_ATTR_MASK, MT_NORMAL_TAGGED), + MAIR_ATTRIDX(MAIR_ATTR_NORMAL_TAGGED, + MT_NORMAL_TAGGED)); + + write_sysreg_s(KERNEL_GCR_EL1, SYS_GCR_EL1); + + /* + * If GCR_EL1.RRND=1 is implemented the same way as RRND=0, then + * RGSR_EL1.SEED must be non-zero for IRG to produce + * pseudorandom numbers. As RGSR_EL1 is UNKNOWN out of reset, we + * must initialize it. + */ + rgsr = (read_sysreg(CNTVCT_EL0) & SYS_RGSR_EL1_SEED_MASK) << + SYS_RGSR_EL1_SEED_SHIFT; + if (rgsr == 0) + rgsr = 1 << SYS_RGSR_EL1_SEED_SHIFT; + write_sysreg_s(rgsr, SYS_RGSR_EL1); + + /* clear any pending tag check faults in TFSR*_EL1 */ + write_sysreg_s(0, SYS_TFSR_EL1); + write_sysreg_s(0, SYS_TFSRE0_EL1); + + local_flush_tlb_all(); +} + void mte_suspend_enter(void) { if (!system_supports_mte()) @@ -301,6 +344,14 @@ void mte_suspend_enter(void) mte_check_tfsr_el1(); }

+void mte_suspend_exit(void) +{ + if (!system_supports_mte()) + return; + + mte_cpu_setup(); +} + long set_mte_ctrl(struct task_struct *task, unsigned long arg) { u64 mte_ctrl = (~((arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT) & diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c index 9135fe0f3df53..8b02d310838f9 100644 --- a/arch/arm64/kernel/suspend.c +++ b/arch/arm64/kernel/suspend.c @@ -43,6 +43,8 @@ void notrace __cpu_suspend_exit(void) { unsigned int cpu = smp_processor_id();

+ mte_suspend_exit(); + /* * We are resuming from reset with the idmap active in TTBR0_EL1. * We must uninstall the idmap and restore the expected MMU diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 7837a69524c53..f38bccdd374a5 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -48,17 +48,19 @@

#ifdef CONFIG_KASAN_HW_TAGS #define TCR_MTE_FLAGS TCR_TCMA1 | TCR_TBI1 | TCR_TBID1 -#else +#elif defined(CONFIG_ARM64_MTE) /* * The mte_zero_clear_page_tags() implementation uses DC GZVA, which relies on * TBI being enabled at EL1. */ #define TCR_MTE_FLAGS TCR_TBI1 | TCR_TBID1 +#else +#define TCR_MTE_FLAGS 0 #endif

/* * Default MAIR_EL1. MT_NORMAL_TAGGED is initially mapped as Normal memory and - * changed during __cpu_setup to Normal Tagged if the system supports MTE. + * changed during mte_cpu_setup to Normal Tagged if the system supports MTE. */ #define MAIR_EL1_SET \ (MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRnE, MT_DEVICE_nGnRnE) | \ @@ -426,46 +428,8 @@ SYM_FUNC_START(__cpu_setup) mov_q mair, MAIR_EL1_SET mov_q tcr, TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \ TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \ - TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS - -#ifdef CONFIG_ARM64_MTE - /* - * Update MAIR_EL1, GCR_EL1 and TFSR*_EL1 if MTE is supported - * (ID_AA64PFR1_EL1[11:8] > 1). - */ - mrs x10, ID_AA64PFR1_EL1 - ubfx x10, x10, #ID_AA64PFR1_MTE_SHIFT, #4 - cmp x10, #ID_AA64PFR1_MTE - b.lt 1f - - /* Normal Tagged memory type at the corresponding MAIR index */ - mov x10, #MAIR_ATTR_NORMAL_TAGGED - bfi mair, x10, #(8 * MT_NORMAL_TAGGED), #8 + TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS | TCR_MTE_FLAGS

- mov x10, #KERNEL_GCR_EL1 - msr_s SYS_GCR_EL1, x10 - - /* - * If GCR_EL1.RRND=1 is implemented the same way as RRND=0, then - * RGSR_EL1.SEED must be non-zero for IRG to produce - * pseudorandom numbers. As RGSR_EL1 is UNKNOWN out of reset, we - * must initialize it. - */ - mrs x10, CNTVCT_EL0 - ands x10, x10, #SYS_RGSR_EL1_SEED_MASK - csinc x10, x10, xzr, ne - lsl x10, x10, #SYS_RGSR_EL1_SEED_SHIFT - msr_s SYS_RGSR_EL1, x10 - - /* clear any pending tag check faults in TFSR*_EL1 */ - msr_s SYS_TFSR_EL1, xzr - msr_s SYS_TFSRE0_EL1, xzr - - /* set the TCR_EL1 bits */ - mov_q x10, TCR_MTE_FLAGS - orr tcr, tcr, x10 -1: -#endif tcr_clear_errata_bits tcr, x9, x5

#ifdef CONFIG_ARM64_VA_BITS_52