[coreboot] [PATCH] xmmstack fixes
r.marek at assembler.cz
Fri Oct 9 22:24:57 CEST 2009
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> It looks like either the xmm or mxx space is used. However, my read
> of the docs says both xmm and mxx can be used at the same time - this
> could increase the space from 128 bytes to 192 bytes.
Yes I think one must have SSE2 and not SSE for this.
> The code only fixes pointers relative to %esp, but I don't think
> anything stops gcc from using non-esp pointers when referring to the
Well I believe if -fomit-frame pointer is used all is addressed relatively to esp.
> I think the code could be extended to fixup all memory
> accesses. Unfortunately, this would break those places where the code
> needs to access real-memory (eg, pci space or constants in flash). To
> get around this, the wrapper functions could check the absolute
> address of the access and only use xmm/mmx for those accesses between
> say 0x0040-0x00c0 (where the stack could be located). In order to test
> the address, instructions that set flags would be needed, but backing
> up and restoring the flags doesn't sound too hard (with lahf/"seto
Yes looks feasible.
> Finally, it appears much of xmmstack is static code inserted at the
> top of the file. I think moving the static code into it's own
> assembler file that is included might make what's going on a little
> more clear.
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