Commit 6497b66b authored by Mark Brown's avatar Mark Brown Committed by Catalin Marinas
Browse files

arm64/mm: Map pages for guarded control stack 



Map pages flagged as being part of a GCS as such rather than using the
full set of generic VM flags.

This is done using a conditional rather than extending the size of
protection_map since that would make for a very sparse array.

Reviewed-by: default avatarThiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-15-222b78d87eee@kernel.org


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent ae80e162

arch/arm64/include/asm/mman.h

+9 −0
Original line number Diff line number Diff line
@@ -71,6 +71,15 @@ static inline bool arch_validate_flags(unsigned long vm_flags) 
			return false;

	}



	if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) {

		/* An executable GCS isn't a good idea. */

		if (vm_flags & VM_EXEC)

			return false;



		/* The memory management core should prevent this */

		VM_WARN_ON(vm_flags & VM_SHARED);

	}



	return true;



}

arch/arm64/mm/mmap.c

+8 −1
Original line number Diff line number Diff line
@@ -83,8 +83,15 @@ arch_initcall(adjust_protection_map); 


pgprot_t vm_get_page_prot(unsigned long vm_flags)

{

	pteval_t prot = pgprot_val(protection_map[vm_flags &

	pteval_t prot;



	/* Short circuit GCS to avoid bloating the table. */

	if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) {

		prot = _PAGE_GCS_RO;

	} else {

		prot = pgprot_val(protection_map[vm_flags &

				   (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]);

	}



	if (vm_flags & VM_ARM64_BTI)

		prot |= PTE_GP;