1. 03 11月, 2017 1 次提交
  2. 23 1月, 2017 1 次提交
    • D
      crypto: x86 - make constants readonly, allow linker to merge them · e183914a
      Denys Vlasenko 提交于
      A lot of asm-optimized routines in arch/x86/crypto/ keep its
      constants in .data. This is wrong, they should be on .rodata.
      
      Mnay of these constants are the same in different modules.
      For example, 128-bit shuffle mask 0x000102030405060708090A0B0C0D0E0F
      exists in at least half a dozen places.
      
      There is a way to let linker merge them and use just one copy.
      The rules are as follows: mergeable objects of different sizes
      should not share sections. You can't put them all in one .rodata
      section, they will lose "mergeability".
      
      GCC puts its mergeable constants in ".rodata.cstSIZE" sections,
      or ".rodata.cstSIZE.<object_name>" if -fdata-sections is used.
      This patch does the same:
      
      	.section .rodata.cst16.SHUF_MASK, "aM", @progbits, 16
      
      It is important that all data in such section consists of
      16-byte elements, not larger ones, and there are no implicit
      use of one element from another.
      
      When this is not the case, use non-mergeable section:
      
      	.section .rodata[.VAR_NAME], "a", @progbits
      
      This reduces .data by ~15 kbytes:
      
          text    data     bss     dec      hex filename
      11097415 2705840 2630712 16433967  fac32f vmlinux-prev.o
      11112095 2690672 2630712 16433479  fac147 vmlinux.o
      
      Merged objects are visible in System.map:
      
      ffffffff81a28810 r POLY
      ffffffff81a28810 r POLY
      ffffffff81a28820 r TWOONE
      ffffffff81a28820 r TWOONE
      ffffffff81a28830 r PSHUFFLE_BYTE_FLIP_MASK <- merged regardless of
      ffffffff81a28830 r SHUF_MASK   <------------- the name difference
      ffffffff81a28830 r SHUF_MASK
      ffffffff81a28830 r SHUF_MASK
      ..
      ffffffff81a28d00 r K512 <- merged three identical 640-byte tables
      ffffffff81a28d00 r K512
      ffffffff81a28d00 r K512
      
      Use of object names in section name suffixes is not strictly necessary,
      but might help if someday link stage will use garbage collection
      to eliminate unused sections (ld --gc-sections).
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      CC: Herbert Xu <herbert@gondor.apana.org.au>
      CC: Josh Poimboeuf <jpoimboe@redhat.com>
      CC: Xiaodong Liu <xiaodong.liu@intel.com>
      CC: Megha Dey <megha.dey@intel.com>
      CC: linux-crypto@vger.kernel.org
      CC: x86@kernel.org
      CC: linux-kernel@vger.kernel.org
      Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
      e183914a
  3. 16 8月, 2016 1 次提交
  4. 27 6月, 2016 1 次提交