mirror/freebsd
1
0
Fork 0
mirror of https://git.FreeBSD.org/src.git synced 2024-12-17 10:26:15 +00:00
Code Issues Releases Activity

Fixed a panic caused by over-optimizing npxdrop() in the non-FXSR case.

Browse Source 
frstor can trap despite it being a control instruction, since it bogusly
checks for pending exceptions in the state that it is overwriting.
This used to be a non-problem because frstor was always paired with a
previous fnsave, and fnsave does an implicit fninit so any pending
exceptions only remain live in the saved state.  Now frstor is sometimes
paired with npxdrop() and we must do a little more than just forget
that the npx was used in npxdrop() to avoid a trap later.  This is a
non-problem in the FXSR case because fxrstor doesn't do the bogus check.

FXSR is part of SSE, and npxdrop() is only in FreeBSD-5.x, so this bug
only affected old machines running FreeBSD-5.x.

PR:		68058
This commit is contained in:
Bruce Evans 2004-06-18 02:10:55 +00:00
parent 27de0135ce
commit bd1a3f1a7e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=130663
1 changed files with 9 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
sys/i386/isa/npx.c
View File

@ -872,6 +872,15 @@ npxdrop()
{
struct thread *td;
/*
* Discard pending exceptions in the !cpu_fxsr case so that unmasked
* ones don't cause a panic on the next frstor.
*/
#ifdef CPU_ENABLE_SSE
if (!cpu_fxsr)
#endif
fnclex();
td = PCPU_GET(fpcurthread);
PCPU_SET(fpcurthread, NULL);
td->td_pcb->pcb_flags &= ~PCB_NPXINITDONE;