Commit 293d865f authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
Browse files

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: default avatarArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240214122845.2033971-61-ardb+git@google.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent aa6a52b2

arch/arm64/include/asm/mmu.h

+37 −1
Original line number Diff line number Diff line
@@ -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,

arch/arm64/kernel/cpufeature.c

+1 −41
Original line number Diff line number Diff line
@@ -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;

arch/arm64/kernel/setup.c

+1 −1
Original line number Diff line number Diff line
@@ -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();