From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: Mark Brown <broonie@kernel.org>, linux-arm-kernel@lists.infradead.org
Subject: [PATCH v7 2/4] arm64: Factor out checks for KASLR in KPTI code into separate function
Date: Wed, 6 Nov 2019 13:00:50 +0000 [thread overview]
Message-ID: <20191106130052.10642-3-broonie@kernel.org> (raw)
In-Reply-To: <20191106130052.10642-1-broonie@kernel.org>
In preparation for integrating E0PD support with KASLR factor out the
checks for interaction between KASLR and KPTI done in boot context into
a new function kaslr_requires_kpti(), in the process clarifying the
distinction between what we do in boot context and what we do at
runtime.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/mmu.h | 53 +++++++++++++++++++++++-----------
arch/arm64/kernel/cpufeature.c | 2 +-
2 files changed, 37 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index f217e3292919..55e285fff262 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -35,10 +35,37 @@ static inline bool arm64_kernel_unmapped_at_el0(void)
cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0);
}
-static inline bool arm64_kernel_use_ng_mappings(void)
+static inline bool kaslr_requires_kpti(void)
{
bool tx1_bug;
+ if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
+ return false;
+
+ /*
+ * Systems affected by Cavium erratum 24756 are incompatible
+ * with KPTI.
+ */
+ if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
+ tx1_bug = false;
+#ifndef MODULE
+ } else if (!static_branch_likely(&arm64_const_caps_ready)) {
+ extern const struct midr_range cavium_erratum_27456_cpus[];
+
+ tx1_bug = is_midr_in_range_list(read_cpuid_id(),
+ cavium_erratum_27456_cpus);
+#endif
+ } else {
+ tx1_bug = __cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456);
+ }
+ if (tx1_bug)
+ return false;
+
+ return kaslr_offset() > 0;
+}
+
+static inline bool arm64_kernel_use_ng_mappings(void)
+{
/* What's a kpti? Use global mappings if we don't know. */
if (!IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
return false;
@@ -52,29 +79,21 @@ static inline bool arm64_kernel_use_ng_mappings(void)
if (arm64_kernel_unmapped_at_el0())
return true;
- if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
+ /*
+ * Once we are far enough into boot for capabilities to be
+ * ready we will have confirmed if we are using non-global
+ * mappings so don't need to consider anything else here.
+ */
+ if (static_branch_likely(&arm64_const_caps_ready))
return false;
/*
* KASLR is enabled so we're going to be enabling kpti on non-broken
* CPUs regardless of their susceptibility to Meltdown. Rather
* than force everybody to go through the G -> nG dance later on,
- * just put down non-global mappings from the beginning.
+ * just put down non-global mappings from the beginning
*/
- if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
- tx1_bug = false;
-#ifndef MODULE
- } else if (!static_branch_likely(&arm64_const_caps_ready)) {
- extern const struct midr_range cavium_erratum_27456_cpus[];
-
- tx1_bug = is_midr_in_range_list(read_cpuid_id(),
- cavium_erratum_27456_cpus);
-#endif
- } else {
- tx1_bug = __cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456);
- }
-
- return !tx1_bug && kaslr_offset() > 0;
+ return kaslr_requires_kpti();
}
typedef void (*bp_hardening_cb_t)(void);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 2cf2b129ebb4..0d551af06421 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1003,7 +1003,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
}
/* Useful for KASLR robustness */
- if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0) {
+ if (kaslr_requires_kpti()) {
if (!__kpti_forced) {
str = "KASLR";
__kpti_forced = 1;
--
2.20.1
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next prev parent reply other threads:[~2019-11-06 13:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 13:00 [PATCH v7 0/4] E0PD support Mark Brown
2019-11-06 13:00 ` [PATCH v7 1/4] arm64: Add initial support for E0PD Mark Brown
2019-11-07 10:12 ` Suzuki K Poulose
2019-11-07 11:55 ` Mark Brown
2019-11-06 13:00 ` Mark Brown [this message]
2019-11-06 13:00 ` [PATCH v7 3/4] arm64: Don't use KPTI where we have E0PD Mark Brown
2019-11-07 12:01 ` Suzuki K Poulose
2019-11-07 14:37 ` Mark Brown
2019-11-07 15:03 ` Suzuki K Poulose
2019-11-08 14:10 ` Mark Brown
2019-11-07 14:48 ` Mark Brown
2019-11-06 13:00 ` [PATCH v7 4/4] arm64: Use a variable to store non-global mappings decision Mark Brown
2019-11-07 11:11 ` Suzuki K Poulose
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