linux-kernel - [PATCH v8 05/20] kasan, arm64: adjust shadow size for tag-based mode

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Message-Id: <a1cfb4f30807434d7bc57b6094f4cc6a134f8bcd.1537383101.git.andreyknvl@google.com>
Date:   Wed, 19 Sep 2018 20:54:44 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Dave Martin <dave.martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Ingo Molnar <mingo@...nel.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        kasan-dev@...glegroups.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sparse@...r.kernel.org, linux-mm@...ck.org,
        linux-kbuild@...r.kernel.org
Cc:     Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Jann Horn <jannh@...gle.com>,
        Mark Brand <markbrand@...gle.com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Vishwath Mohan <vishwath@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v8 05/20] kasan, arm64: adjust shadow size for tag-based mode

Tag-based KASAN uses 1 shadow byte for 16 bytes of kernel memory, so it
requires 1/16th of the kernel virtual address space for the shadow memory.

This commit sets KASAN_SHADOW_SCALE_SHIFT to 4 when the tag-based KASAN
mode is enabled.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 arch/arm64/Makefile             |  2 +-
 arch/arm64/include/asm/memory.h | 13 +++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 106039d25e2f..11f4750d8d41 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -94,7 +94,7 @@ endif
 # KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
 #				 - (1 << (64 - KASAN_SHADOW_SCALE_SHIFT))
 # in 32-bit arithmetic
-KASAN_SHADOW_SCALE_SHIFT := 3
+KASAN_SHADOW_SCALE_SHIFT := $(if $(CONFIG_KASAN_SW_TAGS), 4, 3)
 KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
 	(0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \
 	+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) \
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b96442960aea..0f1e024a951f 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -74,12 +74,17 @@
 #define KERNEL_END        _end
 
 /*
- * KASAN requires 1/8th of the kernel virtual address space for the shadow
- * region. KASAN can bloat the stack significantly, so double the (minimum)
- * stack size when KASAN is in use.
+ * Generic and tag-based KASAN require 1/8th and 1/16th of the kernel virtual
+ * address space for the shadow region respectively. They can bloat the stack
+ * significantly, so double the (minimum) stack size when they are in use.
  */
-#ifdef CONFIG_KASAN
+#ifdef CONFIG_KASAN_GENERIC
 #define KASAN_SHADOW_SCALE_SHIFT 3
+#endif
+#ifdef CONFIG_KASAN_SW_TAGS
+#define KASAN_SHADOW_SCALE_SHIFT 4
+#endif
+#ifdef CONFIG_KASAN
 #define KASAN_SHADOW_SIZE	(UL(1) << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
 #define KASAN_THREAD_SHIFT	1
 #else
-- 
2.19.0.397.gdd90340f6a-goog