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pc kernel: simulate FXSAVE/FXRSTOR tag-byte from x87 tag-word, copy fp state across fork

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the tag-word is not compatible between x87 and sse, have to convert
properly for emulation to work.

we now copy fp state across fork (again!) to preserve FCW and MXCSR
registers. this might not be neccesary as we could probably just
get the current value for the curren process and avoid the fpsave()
call, but become conservative again.
This commit is contained in:
cinap_lenrek 2013-05-30 23:16:22 +02:00
parent 6a0d21acca
commit 9652f5bec5
1 changed files with 59 additions and 3 deletions
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62
sys/src/9/pc/main.c
View file

@ -480,11 +480,23 @@ confinit(void)
void
fpx87save(FPsave *fps)
{
ushort tag;
fpx87save0(fps);
/*
* convert x87 tag word to fxsave tag byte:
* 00, 01, 10 -> 1, 11 -> 0
*/
tag = ~fps->tag;
tag = (tag | (tag >> 1)) & 0x5555;
tag = (tag | (tag >> 1)) & 0x3333;
tag = (tag | (tag >> 2)) & 0x0F0F;
tag = (tag | (tag >> 4)) & 0x00FF;
/* NOP fps->fcw = fps->control; */
fps->fsw = fps->status;
fps->ftw = fps->tag;
fps->ftw = tag;
fps->fop = fps->opcode;
fps->fpuip = fps->pc;
fps->cs = fps->selector;
@ -528,6 +540,36 @@ fpx87save(FPsave *fps)
void
fpx87restore(FPsave *fps)
{
ushort msk, tos, tag, *reg;
/* convert fxsave tag byte to x87 tag word */
tag = 0;
tos = 7 - ((fps->fsw >> 11) & 7);
for(msk = 0x80; msk != 0; tos--, msk >>= 1){
tag <<= 2;
if((fps->ftw & msk) != 0){
reg = (ushort*)&fps->xregs[(tos & 7) << 4];
switch(reg[4] & 0x7fff){
case 0x0000:
if((reg[0] | reg[1] | reg[2] | reg[3]) == 0){
tag |= 1; /* 01 zero */
break;
}
/* no break */
case 0x7fff:
tag |= 2; /* 10 special */
break;
default:
if((reg[3] & 0x8000) == 0)
break; /* 00 valid */
tag |= 2; /* 10 special */
break;
}
}else{
tag |= 3; /* 11 empty */
}
}
#define MOVA(d,s) \
*((ulong*)(d)) = *((ulong*)(s)), \
*((ulong*)(d+4)) = *((ulong*)(s+4)), \
@ -546,10 +588,10 @@ fpx87restore(FPsave *fps)
fps->oselector = fps->ds;
fps->operand = fps->fpudp;
fps->opcode = (fps->fop & 0x7ff);
fps->opcode = fps->fop & 0x7ff;
fps->selector = fps->cs;
fps->pc = fps->fpuip;
fps->tag = fps->ftw;
fps->tag = tag;
fps->status = fps->fsw;
/* NOP fps->control = fps->fcw; */
@ -726,6 +768,8 @@ procsetup(Proc *p)
void
procfork(Proc *p)
{
int s;
p->kentry = up->kentry;
p->pcycles = -p->kentry;
@ -738,6 +782,18 @@ procfork(Proc *p)
memmove(p->ldt, up->ldt, sizeof(Segdesc) * up->nldt);
p->nldt = up->nldt;
}
/* save floating point state */
s = splhi();
switch(up->fpstate & ~FPillegal){
case FPactive:
fpsave(&up->fpsave);
up->fpstate = FPinactive;
case FPinactive:
p->fpsave = up->fpsave;
p->fpstate = FPinactive;
}
splx(s);
}
void