Thread (38 messages) 38 messages, 7 authors, 2019-08-20

Re: [PATCH] arm64: fix CONFIG_KASAN_SW_TAGS && CONFIG_KASAN_INLINE (was: Re: [PATCH V5 03/12] arm64: kasan: Switch to using) KASAN_SHADOW_OFFSET

From: Steve Capper <hidden>
Date: 2019-08-14 17:53:58

On Wed, Aug 14, 2019 at 05:03:24PM +0100, Mark Rutland wrote:
On Wed, Aug 14, 2019 at 04:57:11PM +0100, Will Deacon wrote:
quoted
On Wed, Aug 14, 2019 at 04:20:18PM +0100, Mark Rutland wrote:
quoted
On Wed, Aug 07, 2019 at 04:55:15PM +0100, Steve Capper wrote:
quoted
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b2400f9c1213..2b7db0d41498 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -126,14 +126,6 @@ KBUILD_CFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
 KBUILD_CPPFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
 KBUILD_AFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
 
-# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
-#				 - (1 << (64 - KASAN_SHADOW_SCALE_SHIFT))
-# in 32-bit arithmetic
-KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
-	(0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 1 - 32))) \
-	+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) \
-	- (1 << (64 - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) )) )
-
 export	TEXT_OFFSET GZFLAGS
 
 core-y		+= arch/arm64/kernel/ arch/arm64/mm/
I've just spotted this breaks build using CONFIG_KASAN_SW_TAGS &&
CONFIG_KASAN_INLINE, as scripts/Makefile.kasan only propagates
CONFIG_KASAN_SHADOW_OFFSET into KASAN_SHADOW_OFFSET when
CONFIG_KASAN_GENERIC is selected, but consumes KASAN_SHADOW_OFFSET
regardless.

I think that's by accident rather than by design, but to
minimize/localize the fixup, how about the below? I can send a cleanup
patch for scripts/Makefile.kasan later.
How much work is that? I've dropped this stuff from -next for now, so we
have time to fix it properly as long as it's not going to take weeks.
I wrote it first, so no effort; patch below.

Andrey, would you be happy with this?

Thanks,
Mark.
FWIW, this one worked well for me too (52-bit VA runtime, SW TAGS +
GENERIC both inlined).

Tested-by: Steve Capper <redacted>

Cheers,
-- 
Steve

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