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[v4,11/36] arm64/mm: Map pages for guarded control stack

Message ID 20230807-arm64-gcs-v4-11-68cfa37f9069@kernel.org
State New
Headers show
Series arm64/gcs: Provide support for GCS in userspace | expand

Commit Message

Mark Brown Aug. 7, 2023, 10 p.m. UTC 
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.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/mm/mmap.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
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Patch

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 8f5b7ce857ed..8f40198cd44e 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -79,8 +79,18 @@  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;
+
+	/* If this is a GCS then only interpret VM_WRITE. */
+	if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) {
+		if (vm_flags & VM_WRITE)
+			prot = _PAGE_GCS;
+		else
+			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;