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arm64/mm: Map pages for guarded control stack

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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: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-15-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Brown 2024-10-01 23:58:54 +01:00 committed by Catalin Marinas
parent ae80e1629a
commit 6497b66ba6
2 changed files with 17 additions and 1 deletions
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9
arch/arm64/include/asm/mman.h
View File

@ -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;
}

9
arch/arm64/mm/mmap.c
View File

@ -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;