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This commit is contained in:
Jeffrey Walton 2018-08-13 01:51:01 -04:00
parent de7f4a0894
commit 78939cb685
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1 changed files with 6 additions and 5 deletions
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11
adv-simd.h
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@ -1843,11 +1843,12 @@ inline size_t AdvancedProcessBlocks128_6x1_ALTIVEC(F1 func1, F6 func6,
// Hack due to big-endian loads used by POWER8 (and maybe ARM-BE).
// CTR_ModePolicy::OperateKeystream is wired such that after
// returning from this function if the last counter byte is 0 then
// CTR_ModePolicy increments the next to last byte. The problem is,
// with a big-endian load, inBlocks[15] is located at index 15. The
// vector addition using a 32-bit element generates a carry into
// inBlocks[14] and then CTR_ModePolicy increments inBlocks[14] too.
// returning from this function CTR_ModePolicy will detect wrap on
// on the last counter byte and increment the next to last byte.
// The problem is, with a big-endian load, inBlocks[15] is really
// located at index 15. The vector addition using a 32-bit element
// generates a carry into inBlocks[14] and then CTR_ModePolicy
// increments inBlocks[14] too.
//
// To find this bug we needed a test case with a ctr of 0xNN...FA.
// The last octet is 0xFA and adding 6 creates the wrap to trigger