Fix the i386 MPI multiply helper assembly code #1778
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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.
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This was referenced Jun 24, 2018
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RonEld
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This was referenced Jun 25, 2018
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mpg
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I've observed this PR doesn't work when |
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I'd like to suggest a resolution: skip the assembly when compiling with |
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.
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I've updated the PR, to disable the assembly code for |
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Description
This is a fix for GitHub issue #1550.
The
ebxregister was used by the assembly code but not listed in the clobber list, so when the compiler chose to also use it,ebxwas getting corrupted. I'm surprised this wasn't spotted sooner.The fix is very simply to add the
ebxregister to the clobber list for the i386 inline assemblyfor the multiply helper function.
This fixes both i386 and its SSE2 variant which was also broken.
Status
READY
Requires Backporting
Yes
Which branch?
mbedtls-2.1andmbedtls-2.7. I'll backport once this one's been approved.Additional comments
This should have been caught by the CI, so I suggest
all.shneeds to be extended. (I haven't checked where or how yet).Todos