Commit e4e9f6df authored May 12, 2020 by Mark Brown Committed by Will Deacon May 12, 2020

arm64: bti: Fix support for userspace only BTI

When setting PTE_MAYBE_GP we check system_supports_bti() but this is
true for systems where only CONFIG_BTI is set causing us to enable BTI
on some kernel text. Add an extra check for the kernel mode option,
using an ifdef due to line length.

Fixes: c8027285 ("arm64: Set GP bit in kernel page tables to enable BTI for the kernel")
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200512113950.29996-1-broonie@kernel.org

Signed-off-by: Will Deacon <will@kernel.org>

parent 3a88d7c5

arch/arm64/include/asm/pgtable-prot.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -32,7 +32,15 @@ extern bool arm64_use_ng_mappings;
		#define PTE_MAYBE_NG (arm64_use_ng_mappings ? PTE_NG : 0)
		#define PMD_MAYBE_NG (arm64_use_ng_mappings ? PMD_SECT_NG : 0)

		/*
		* If we have userspace only BTI we don't want to mark kernel pages
		* guarded even if the system does support BTI.
		*/
		#ifdef CONFIG_ARM64_BTI_KERNEL
		#define PTE_MAYBE_GP (system_supports_bti() ? PTE_GP : 0)
		#else
		#define PTE_MAYBE_GP 0
		#endif

		#define PROT_DEFAULT (_PROT_DEFAULT \| PTE_MAYBE_NG)
		#define PROT_SECT_DEFAULT (_PROT_SECT_DEFAULT \| PMD_MAYBE_NG)