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| author |   Daniel Axtens <dja@axtens.net> | 2017-03-15 23:37:35 +1100 |
|---|---|---|
| committer |   Herbert Xu <herbert@gondor.apana.org.au> | 2017-03-24 22:02:53 +0800 |
| commit | 08c7dd1bd4b3a59c0d57b3ce4fe5ba1a90123685 (patch) | |
| tree | eb6b8a7c7cd0324f212b1e3c33e54da3b50def92 /arch/powerpc/crypto/crc32-vpmsum_core.S | |
| parent | crypto: powerpc - Factor out the core CRC vpmsum algorithm (diff) | |
| download | linux-dev-08c7dd1bd4b3a59c0d57b3ce4fe5ba1a90123685.tar.xz linux-dev-08c7dd1bd4b3a59c0d57b3ce4fe5ba1a90123685.zip | |
crypto: powerpc - Re-enable non-REFLECTed CRCs
When CRC32c was included in the kernel, Anton ripped out
the #ifdefs around reflected polynomials, because CRC32c
is always reflected. However, not all CRCs use reflection
so we'd like to make it optional.
Restore the REFLECT parts from Anton's original CRC32
implementation (https://github.com/antonblanchard/crc32-vpmsum)
That implementation is available under GPLv2+, so we're OK
from a licensing point of view:
https://github.com/antonblanchard/crc32-vpmsum/blob/master/LICENSE.TXT
As CRC32c requires REFLECT, add that #define.
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'arch/powerpc/crypto/crc32-vpmsum_core.S')
| -rw-r--r-- | arch/powerpc/crypto/crc32-vpmsum_core.S | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/arch/powerpc/crypto/crc32-vpmsum_core.S b/arch/powerpc/crypto/crc32-vpmsum_core.S index 7c6be6a5c977..aadb59c96a27 100644 --- a/arch/powerpc/crypto/crc32-vpmsum_core.S +++ b/arch/powerpc/crypto/crc32-vpmsum_core.S @@ -35,7 +35,9 @@ .text -#if defined(__BIG_ENDIAN__) +#if defined(__BIG_ENDIAN__) && defined(REFLECT) +#define BYTESWAP_DATA +#elif defined(__LITTLE_ENDIAN__) && !defined(REFLECT) #define BYTESWAP_DATA #else #undef BYTESWAP_DATA @@ -108,7 +110,11 @@ FUNC_START(CRC_FUNCTION_NAME) /* Get the initial value into v8 */ vxor v8,v8,v8 MTVRD(v8, R3) +#ifdef REFLECT vsldoi v8,zeroes,v8,8 /* shift into bottom 32 bits */ +#else + vsldoi v8,v8,zeroes,4 /* shift into top 32 bits */ +#endif #ifdef BYTESWAP_DATA addis r3,r2,.byteswap_constant@toc@ha @@ -354,6 +360,7 @@ FUNC_START(CRC_FUNCTION_NAME) vxor v6,v6,v14 vxor v7,v7,v15 +#ifdef REFLECT /* * vpmsumd produces a 96 bit result in the least significant bits * of the register. Since we are bit reflected we have to shift it @@ -368,6 +375,7 @@ FUNC_START(CRC_FUNCTION_NAME) vsldoi v5,v5,zeroes,4 vsldoi v6,v6,zeroes,4 vsldoi v7,v7,zeroes,4 +#endif /* xor with last 1024 bits */ lvx v8,0,r4 @@ -511,13 +519,33 @@ FUNC_START(CRC_FUNCTION_NAME) vsldoi v1,v0,v0,8 vxor v0,v0,v1 /* xor two 64 bit results together */ +#ifdef REFLECT /* shift left one bit */ vspltisb v1,1 vsl v0,v0,v1 +#endif vand v0,v0,mask_64bit +#ifndef REFLECT + /* + * Now for the Barrett reduction algorithm. The idea is to calculate q, + * the multiple of our polynomial that we need to subtract. By + * doing the computation 2x bits higher (ie 64 bits) and shifting the + * result back down 2x bits, we round down to the nearest multiple. + */ + VPMSUMD(v1,v0,const1) /* ma */ + vsldoi v1,zeroes,v1,8 /* q = floor(ma/(2^64)) */ + VPMSUMD(v1,v1,const2) /* qn */ + vxor v0,v0,v1 /* a - qn, subtraction is xor in GF(2) */ /* + * Get the result into r3. We need to shift it left 8 bytes: + * V0 [ 0 1 2 X ] + * V0 [ 0 X 2 3 ] + */ + vsldoi v0,v0,zeroes,8 /* shift result into top 64 bits */ +#else + /* * The reflected version of Barrett reduction. Instead of bit * reflecting our data (which is expensive to do), we bit reflect our * constants and our algorithm, which means the intermediate data in @@ -537,6 +565,7 @@ FUNC_START(CRC_FUNCTION_NAME) * V0 [ 0 X 2 3 ] */ vsldoi v0,v0,zeroes,4 /* shift result into top 64 bits of */ +#endif /* Get it into r3 */ MFVRD(R3, v0) |