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pc64: fix fpu bug

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fpurestore() unconditionally changed fpstate to FPinactive when
the kernel used the FPU. but in the FPinit case, the registers are
not saved by mathemu(), resulting in all zero initialized registers
being loaded once userspace uses the FPU so the process would have
wrong MXCR value.

the index overflow check was wrong with using shifted value.
This commit is contained in:
cinap_lenrek 2018-05-21 19:23:54 +02:00
parent 930efe67e8
commit 66eac7d687
1 changed files with 4 additions and 3 deletions
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7
sys/src/9/pc64/main.c
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@ -535,7 +535,7 @@ mathemu(Ureg *ureg, void*)
case FPinit: case FPinit:
fpinit(); fpinit();
index = up->fpstate >> FPindexs; index = up->fpstate >> FPindexs;
if(index < 0 || index > FPindexm) if(index < 0 || index > (FPindexm>>FPindexs))
panic("fpslot index overflow: %d", index); panic("fpslot index overflow: %d", index);
if(userureg(ureg)){ if(userureg(ureg)){
if(index != 0) if(index != 0)
@ -684,7 +684,7 @@ procsave(Proc *p)
* emulation fault to activate the FPU. * emulation fault to activate the FPU.
*/ */
fpsave(p->fpsave); fpsave(p->fpsave);
p->fpstate = FPinactive | (p->fpstate & (FPpush|FPnouser|FPkernel|FPindexm)); p->fpstate = FPinactive | (p->fpstate & ~FPactive);
break; break;
} }
@ -729,7 +729,8 @@ fpurestore(int ostate)
if((astate & ~(FPnouser|FPkernel|FPindexm)) == FPactive) if((astate & ~(FPnouser|FPkernel|FPindexm)) == FPactive)
_stts(); _stts();
up->fpsave = up->fpslot[ostate>>FPindexs]; up->fpsave = up->fpslot[ostate>>FPindexs];
ostate = FPinactive | (ostate & (FPillegal|FPpush|FPnouser|FPkernel|FPindexm)); if(ostate & FPactive)
ostate = FPinactive | (ostate & ~FPactive);
} }
up->fpstate = ostate; up->fpstate = ostate;
} }