arm64: avoid overflow in VA_START and PAGE_OFFSET
authorNick Desaulniers <ndesaulniers@google.com>
Thu, 3 Aug 2017 18:03:58 +0000 (11:03 -0700)
committerWill Deacon <will.deacon@arm.com>
Fri, 4 Aug 2017 14:06:35 +0000 (15:06 +0100)
commit82cd588052815eb4146f9f7c5347ca5e32c56360
tree074b02c750f56f8d41f0f48eba80c031c6adf8bd
parent6d332747fa5f0a6843b56b5b129168ba909336d1
arm64: avoid overflow in VA_START and PAGE_OFFSET

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: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Suggested-by: Yury Norov <ynorov@caviumnetworks.com>
Suggested-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
arch/arm64/include/asm/memory.h