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Message-Id: <20220819013526.2682765-1-pcc@google.com>
Date: Thu, 18 Aug 2022 18:35:26 -0700
From: Peter Collingbourne <pcc@...gle.com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Peter Collingbourne <pcc@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Andrey Konovalov <andreyknvl@...il.com>,
Mark Brown <broonie@...nel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] arm64: mte: move register initialization to C
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@...gle.com>
Suggested-by: Catalin Marinas <catalin.marinas@....com>
Link: https://linux-review.googlesource.com/id/I2c7df6bd4ea2dfc59376a8b9b5d3562b015c7198
---
arch/arm64/kernel/cpufeature.c | 39 +++++++++++++++++++++++++++++++
arch/arm64/mm/proc.S | 42 ++--------------------------------
2 files changed, 41 insertions(+), 40 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 907401e4fffb..3554ff869f4b 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2030,8 +2030,47 @@ 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_SHIFT) &
+ SYS_RGSR_EL1_SEED_MASK;
+ 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 7837a69524c5..6f01f5a54cc2 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -58,7 +58,7 @@
/*
* 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 +426,8 @@ 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
+ TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS | TCR_MTE_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
-
- 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
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