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Clear whole XMM register file instead of only XMM0. Also clear x87

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registers.  This brings amd64 on par with i386, providing consistent
initial FPU state.

Note that we do not clear any extended state, at least because kernel
does not understand extended state structure and consequences of zero
overwrite after fninit()/fpusave().

Submitted by:	joss.upton@yahoo.com
PR:	206370
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2016-01-19 08:04:02 +00:00
parent c0b9f85bd6
commit b57e68141f
1 changed files with 8 additions and 6 deletions
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14
sys/amd64/amd64/fpu.c
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@ -318,13 +318,15 @@ fpuinitstate(void *arg __unused)
cpu_mxcsr_mask = 0xFFBF;
/*
* The fninit instruction does not modify XMM registers. The
* fpusave call dumped the garbage contained in the registers
* after reset to the initial state saved. Clear XMM
* registers file image to make the startup program state and
* signal handler XMM register content predictable.
* The fninit instruction does not modify XMM registers or x87
* registers (MM/ST). The fpusave call dumped the garbage
* contained in the registers after reset to the initial state
* saved. Clear XMM and x87 registers file image to make the
* startup program state and signal handler XMM/x87 register
* content predictable.
*/
bzero(&fpu_initialstate->sv_xmm[0], sizeof(struct xmmacc));
bzero(fpu_initialstate->sv_fp, sizeof(fpu_initialstate->sv_fp));
bzero(fpu_initialstate->sv_xmm, sizeof(fpu_initialstate->sv_xmm));
/*
* Create a table describing the layout of the CPU Extended