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Message-Id: <20240203-arm64-gcs-v8-12-c9fec77673ef@kernel.org>
Date: Sat, 03 Feb 2024 12:25:38 +0000
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>, Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>, James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>, Arnd Bergmann <arnd@...db.de>,
Oleg Nesterov <oleg@...hat.com>, Eric Biederman <ebiederm@...ssion.com>,
Kees Cook <keescook@...omium.org>, Shuah Khan <shuah@...nel.org>,
"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
Deepak Gupta <debug@...osinc.com>, Ard Biesheuvel <ardb@...nel.org>,
Szabolcs Nagy <Szabolcs.Nagy@....com>
Cc: "H.J. Lu" <hjl.tools@...il.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Florian Weimer <fweimer@...hat.com>, Christian Brauner <brauner@...nel.org>,
Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
linux-arch@...r.kernel.org, linux-mm@...ck.org,
linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH v8 12/38] 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.
Signed-off-by: Mark Brown <broonie@...nel.org>
---
arch/arm64/include/asm/mman.h | 9 +++++++++
arch/arm64/mm/mmap.c | 13 ++++++++++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index c21849ffdd88..6d3fe6433a62 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -61,6 +61,15 @@ 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, and the mm
+ * core can't cope with a shared GCS.
+ */
+ if (vm_flags & (VM_EXEC | VM_ARM64_BTI | VM_SHARED))
+ return false;
+ }
+
return true;
}
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 645fe60d000f..e44ce6fcfad9 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -79,9 +79,20 @@ 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)]);
+ }
+ /* VM_ARM64_BTI on a GCS is rejected in arch_validate_flags() */
if (vm_flags & VM_ARM64_BTI)
prot |= PTE_GP;
--
2.30.2
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