CVS commit: src/sys/arch/amd64/amd64

["Jared D. McNeill" <jmcneill%netbsd.org@localhost>]

Module Name:    src
Committed By:   jmcneill
Date:           Tue Dec 20 13:17:05 UTC 2011

Modified Files:
        src/sys/arch/amd64/amd64: process_machdep.c

Log Message:
from 
http://www.freshbsd.org/commit/openbsd/ae7f934ae5bdf57dcf3431ba55fd1da93b8f1963

Initialize abridged tag word properly. x87 spec says FNINIT says tag word
contains FFFFh (all stack locations empty) which would make abridged tag
word 00h. From the Intel 64 and IA-32 Architectures Software Developer's
Manual:

"The FXSAVE instruction saves an abridged version of the x87 FPU tag word
in the FTW field (unlike the FSAVE instruction, which saves the complete
tag word). The tag information is saved in physical register order (R0
through R7), rather than in top-of- stack (TOS) order. With the FXSAVE
instruction, however, only a single bit (1 for valid or 0 for empty) is
saved for each tag."

ok rmind@


To generate a diff of this commit:
cvs rdiff -u -r1.18 -r1.19 src/sys/arch/amd64/amd64/process_machdep.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.