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authorArd Biesheuvel <ardb@kernel.org>2024-02-14 13:29:02 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2024-02-16 12:42:32 +0000
commit293d865f0af58e6ff2ff0ba0e890674e00d036b1 (patch)
tree5581033bbf73a940bc92e58c47e10458effa4f65
parentaa6a52b2470c375ecd71b1d81c89d93b11134b56 (diff)
arm64: mm: Make kaslr_requires_kpti() a static inline
In preparation for moving the first assignment of arm64_use_ng_mappings to an earlier stage in the boot, ensure that kaslr_requires_kpti() is accessible without relying on the core kernel's view on whether or not KASLR is enabled. So make it a static inline, and move the kaslr_enabled() check out of it and into the callers, one of which will disappear in a subsequent patch. Once/when support for the obsolete ThunderX 1 platform is dropped, this check reduces to a E0PD feature check on the local CPU. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20240214122845.2033971-61-ardb+git@google.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/include/asm/mmu.h38
-rw-r--r--arch/arm64/kernel/cpufeature.c42
-rw-r--r--arch/arm64/kernel/setup.c2
3 files changed, 39 insertions, 43 deletions
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 2fcf51231d6e..d0b8b4b413b6 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -71,7 +71,43 @@ extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
pgprot_t prot, bool page_mappings_only);
extern void *fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot);
extern void mark_linear_text_alias_ro(void);
-extern bool kaslr_requires_kpti(void);
+
+/*
+ * This check is triggered during the early boot before the cpufeature
+ * is initialised. Checking the status on the local CPU allows the boot
+ * CPU to detect the need for non-global mappings and thus avoiding a
+ * pagetable re-write after all the CPUs are booted. This check will be
+ * anyway run on individual CPUs, allowing us to get the consistent
+ * state once the SMP CPUs are up and thus make the switch to non-global
+ * mappings if required.
+ */
+static inline bool kaslr_requires_kpti(void)
+{
+ /*
+ * E0PD does a similar job to KPTI so can be used instead
+ * where available.
+ */
+ if (IS_ENABLED(CONFIG_ARM64_E0PD)) {
+ u64 mmfr2 = read_sysreg_s(SYS_ID_AA64MMFR2_EL1);
+ if (cpuid_feature_extract_unsigned_field(mmfr2,
+ ID_AA64MMFR2_EL1_E0PD_SHIFT))
+ return false;
+ }
+
+ /*
+ * Systems affected by Cavium erratum 24756 are incompatible
+ * with KPTI.
+ */
+ if (IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
+ extern const struct midr_range cavium_erratum_27456_cpus[];
+
+ if (is_midr_in_range_list(read_cpuid_id(),
+ cavium_erratum_27456_cpus))
+ return false;
+ }
+
+ return true;
+}
#define INIT_MM_CONTEXT(name) \
.pgd = init_pg_dir,
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index d0ffb872a31a..7064cf13f226 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1620,46 +1620,6 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope)
return has_cpuid_feature(entry, scope);
}
-/*
- * This check is triggered during the early boot before the cpufeature
- * is initialised. Checking the status on the local CPU allows the boot
- * CPU to detect the need for non-global mappings and thus avoiding a
- * pagetable re-write after all the CPUs are booted. This check will be
- * anyway run on individual CPUs, allowing us to get the consistent
- * state once the SMP CPUs are up and thus make the switch to non-global
- * mappings if required.
- */
-bool kaslr_requires_kpti(void)
-{
- if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
- return false;
-
- /*
- * E0PD does a similar job to KPTI so can be used instead
- * where available.
- */
- if (IS_ENABLED(CONFIG_ARM64_E0PD)) {
- u64 mmfr2 = read_sysreg_s(SYS_ID_AA64MMFR2_EL1);
- if (cpuid_feature_extract_unsigned_field(mmfr2,
- ID_AA64MMFR2_EL1_E0PD_SHIFT))
- return false;
- }
-
- /*
- * Systems affected by Cavium erratum 24756 are incompatible
- * with KPTI.
- */
- if (IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
- extern const struct midr_range cavium_erratum_27456_cpus[];
-
- if (is_midr_in_range_list(read_cpuid_id(),
- cavium_erratum_27456_cpus))
- return false;
- }
-
- return kaslr_enabled();
-}
-
static bool __meltdown_safe = true;
static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
@@ -1712,7 +1672,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
}
/* Useful for KASLR robustness */
- if (kaslr_requires_kpti()) {
+ if (kaslr_enabled() && kaslr_requires_kpti()) {
if (!__kpti_forced) {
str = "KASLR";
__kpti_forced = 1;
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 97d2143669cf..0ef45d1927b3 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -288,7 +288,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
* mappings from the start, avoiding the cost of rewriting
* everything later.
*/
- arm64_use_ng_mappings = kaslr_requires_kpti();
+ arm64_use_ng_mappings = kaslr_enabled() && kaslr_requires_kpti();
early_fixmap_init();
early_ioremap_init();