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Remove special case for FixedSizeAllocatorWithCleanup x86_64 (GH #988)

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Jeffrey Walton 2020-12-27 00:14:41 -05:00
parent 0e117ee65b
commit b434e4cfbd
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1 changed files with 16 additions and 24 deletions
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40
secblock.h
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@ -486,43 +486,35 @@ public:
private:
#if CRYPTOPP_BOOL_ALIGN16 && (defined(_M_X64) || defined(__x86_64__))
// Before we can add additional platforms we need to check the
// linker documentation for alignment behavior for stack variables.
// CRYPTOPP_ALIGN_DATA(16) is known OK on Linux, OS X, Solaris.
// Also see http://stackoverflow.com/a/1468656/608639.
T* GetAlignedArray() {
CRYPTOPP_ASSERT(IsAlignedOn(m_array, 16));
return m_array;
}
CRYPTOPP_ALIGN_DATA(16) T m_array[S];
#elif CRYPTOPP_BOOL_ALIGN16
#if CRYPTOPP_BOOL_ALIGN16
// There be demons here... We cannot use CRYPTOPP_ALIGN_DATA(16)
// because linkers on 32-bit machines (and some 64-bit machines)
// align the stack to 8-bytes or less by default, not 16-bytes as
// requested. Additionally, the AIX linker seems to use 4-bytes
// by default. However, all linkers tested appear to honor
// CRYPTOPP_ALIGN_DATA(8). Also see
// http://stackoverflow.com/a/1468656/608639.
// because linkers on 32-bit machines and some 64-bit machines
// align the stack to 8-bytes or less, and not 16-bytes as
// requested. We can only count on a smaller alignment. All
// toolchains tested appear to honor CRYPTOPP_ALIGN_DATA(8). Also
// see http://stackoverflow.com/a/1468656/608639.
//
// The 16-byte alignment is achieved by padding the requested
// size with extra elements so we have at least 16-bytes of slack
// size with extra elements so we have at least 8-bytes of slack
// to work with. Then the array pointer is moved to achieve a
// 16-byte alignment.
//
// The additional 16-bytes introduces a small secondary issue.
// The additional 8-bytes introduces a small secondary issue.
// The secondary issue is, a large T results in 0 = 8/sizeof(T).
// The library is OK but users may hit it. So we need to guard
// for a large T, and that is what the enum and PAD achieves.
T* GetAlignedArray() {
// m_array is aligned on 8 byte boundaries due to
// CRYPTOPP_ALIGN_DATA(8). If m_array%16 is 0, then
// the buffer is 16-byte aligned and nothing needs
// to be done. if m_array%16 is 8, then the buffer
// is not 16-byte aligned and we need to add 8.
// CRYPTOPP_ALIGN_DATA(8). If m_array%16 is 0, then the buffer
// is 16-byte aligned and nothing needs to be done. if
// m_array%16 is 8, then the buffer is not 16-byte aligned and
// we need to add 8. 8 has that nice symmetric property.
//
// If we needed to use CRYPTOPP_ALIGN_DATA(4) due to toolchain
// limitations, then the calculation would be slightly more
// costly: ptr = m_array + (16 - (m_array % 16)) % 16;
CRYPTOPP_ASSERT(IsAlignedOn(m_array, 8));
int off = reinterpret_cast<uintptr_t>(m_array) % 16;
byte* ptr = reinterpret_cast<byte*>(m_array) + off;