Backport 2.7: Fix the i386 MPI multiply helper assembly code #1849
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This fix adds the ebx register to the clobber list for the i386 inline assembly for the multiply helper function. ebx was used but not listed, so when the compiler chose to also use it, ebx was getting corrupted. I'm surprised this wasn't spotted sooner. Fixes Github issues Mbed-TLS#1550.
We don't compile in the assembly code if compiler optimisations are disabled as the number of registers used in the assembly code doesn't work with the -O0 option. Also anyone select -O0 probably doesn't want to compile in the assembly code anyway.
simonbutcher
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component-crypto
mpg
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Jul 11, 2018
Patater
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Jul 16, 2018
simonbutcher
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Description
This is a backport of #1778 to the
mbedtls-2.7branch, to fix GitHub issue #1550.The ebx register was used by the assembly code but not listed in the clobber list, so when the compiler chose to also use it, ebx was getting corrupted. I'm surprised this wasn't spotted sooner.
The fix is very simply to add the ebx register to the clobber list for the i386 inline assembly
for the multiply helper function.
This fixes both i386 and its SSE2 variant which was also broken.
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READY
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