From b57e68141f21d305ce46dd61baa51a9d773d6205 Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Tue, 19 Jan 2016 08:04:02 +0000 Subject: [PATCH] Clear whole XMM register file instead of only XMM0. Also clear x87 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 --- sys/amd64/amd64/fpu.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/sys/amd64/amd64/fpu.c b/sys/amd64/amd64/fpu.c index 562951e2d7e..91ceab232dd 100644 --- a/sys/amd64/amd64/fpu.c +++ b/sys/amd64/amd64/fpu.c @@ -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