AVX register corruption from signal delivery

Re:AVX register corruption from signal delivery by craz8 on Tuesday November 26, 2019 @11:32PM (#21645269)

There was code in IE 5 that used the original SSE instructions if the chip had them, and regular code as a fallback

We found a stepping of a 486 chip where this code crashed about 25% of the time

Since it was only that stepping, and we already had a fallback path, we just skipped the optimization for that chip version and didn’t investigate exactly what was broken though

Having a lot of customers with various CPU versions helped to track this down pretty quickly

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Re:AVX register corruption from signal delivery by mrb on Wednesday November 27, 2019 @01:47AM (#21645819)

Surely you meant x87 FP instructions? The 486 didn't have SSE instructions.

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Re:AVX register corruption from signal delivery by craz8 on Wednesday November 27, 2019 @02:05AM (#21645902)

Probably not 486 - this was 1999-2000 timeframe, so some sort of Pentium thing.

It was definitely the new instructions though, so whatever Intel chip had the new features had this 1 stepping that had this bug (and it wasn’t the first version of the chip either)

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Re:AVX register corruption from signal delivery by gpderetta on Wednesday November 27, 2019 @03:33AM (#21646243)

MMX then instead of SSE?

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Re:AVX register corruption from signal delivery by wahern on Thursday November 28, 2019 @12:34AM (#21654839)

486 didn't necessarily have FP, either. I started using Linux on a 486SX. FP instructions were trapped and emulated by the kernel.

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