Messages in this thread Patch in this message | | | Date | Wed, 24 Aug 2022 19:15:32 -0700 | Subject | [PATCH v2] arm64: mte: move register initialization to C | From | Evgenii Stepanov <> |
| |
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.
Signed-off-by: Peter Collingbourne <pcc@google.com> Signed-off-by: Evgenii Stepanov <eugenis@google.com> Suggested-by: Catalin Marinas <catalin.marinas@arm.com> Link: https://lore.kernel.org/linux-arm-kernel/YwCsIm2nCXCEEgAd@arm.com/T/ Link: https://linux-review.googlesource.com/id/I2c7df6bd4ea2dfc59376a8b9b5d3562b015c7198 X-PCC-To: Catalin Marinas <catalin.marinas@arm.com> X-PCC-Cc: Evgenii Stepanov <eugenis@google.com>, Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Andrey Konovalov <andreyknvl@gmail.com>, Mark Brown <broonie@kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, LKML <linux-kernel@vger.kernel.org> --- 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/kernel/cpufeature.c | 40 +++++++++++++++++++++++++++++ arch/arm64/mm/proc.S | 46 ++++------------------------------ 2 files changed, 45 insertions(+), 41 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 907401e4fffb1..9692e75e2ee44 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2030,8 +2030,48 @@ static void bti_enable(const struct arm64_cpu_capabilities *__unused) #ifdef CONFIG_ARM64_MTE static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) { + u64 rgsr; + sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ATA | SCTLR_EL1_ATA0); + + /* + * 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); + isb(); + local_flush_tlb_all(); /* * Clear the tags in the zero page. This needs to be done via the diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 7837a69524c53..870e1b259ef7b 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 cpu_enable_mte 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 -- 2.37.1.595.g718a3a8f04-goog
| |