Messages in this thread | | | From | Ard Biesheuvel <> | Date | Thu, 3 Aug 2017 18:20:32 +0100 | Subject | Re: [PATCH] arm64: avoid overflow in VA_START and PAGE_OFFSET |
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On 3 August 2017 at 18:11, Nick Desaulniers <ndesaulniers@google.com> wrote: > The bitmask used to define these values produces overflow, as seen by > this compiler warning: > > arch/arm64/kernel/head.S:47:8: warning: > integer overflow in preprocessor expression > #elif (PAGE_OFFSET & 0x1fffff) != 0 > ^~~~~~~~~~~ > arch/arm64/include/asm/memory.h:52:46: note: > expanded from macro 'PAGE_OFFSET' > #define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - > 1)) > ~~~~~~~~~~~~~~~~~~ ^ > > It would be preferrable to use GENMASK_ULL() instead, but it's not set > up to be used from assembly (the UL() macro token pastes UL suffixes > when not included in assembly sources). > > Suggested-by: Yury Norov <ynorov@caviumnetworks.com> > Suggested-by: Matthias Kaehlcke <mka@chromium.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > --- > arch/arm64/include/asm/memory.h | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > index 32f82723338a..dde717a31dee 100644 > --- a/arch/arm64/include/asm/memory.h > +++ b/arch/arm64/include/asm/memory.h > @@ -64,8 +64,9 @@ > * TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area. > */ > #define VA_BITS (CONFIG_ARM64_VA_BITS) > -#define VA_START (UL(0xffffffffffffffff) << VA_BITS) > -#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1)) > +#define VA_START ((UL(0xffffffffffffffff) >> VA_BITS) << VA_BITS) > +#define PAGE_OFFSET ((UL(0xffffffffffffffff) >> (VA_BITS - 1)) \ > + << (VA_BITS - 1)) > #define KIMAGE_VADDR (MODULES_END) > #define MODULES_END (MODULES_VADDR + MODULES_VSIZE) > #define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE) > -- > 2.14.0.rc1.383.gd1ce394fe2-goog >
Would
#define VA_START (UL(0xffffffffffffffff) - (1 << VA_BITS) + 1)
also work?
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