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authorMichael Neuling <mikey@neuling.org>2009-04-01 18:02:42 (GMT)
committerPaul Mackerras <paulus@samba.org>2009-04-07 05:18:59 (GMT)
commit7e875e9dc8af70d126fa632446e967327ac3fdda (patch)
tree22757e6faff097d01931194c4af051017cb1c359 /arch/powerpc/kernel/misc_64.S
parent4c6cf42843e924fd2f71439d87e85b739b2aa973 (diff)
downloadlinux-7e875e9dc8af70d126fa632446e967327ac3fdda.tar.xz
powerpc: Disable VSX or current process in giveup_fpu/altivec
When we call giveup_fpu, we need to need to turn off VSX for the current process. If we don't, on return to userspace it may execute a VSX instruction before the next FP instruction, and not have its register state refreshed correctly from the thread_struct. Ditto for altivec. This caused a bug where an unaligned lfs or stfs results in fix_alignment calling giveup_fpu so it can use the FPRs (in order to do a single <-> double conversion), and then returning to userspace with FP off but VSX on. Then if a VSX instruction is executed, before another FP instruction, it will proceed without another exception and hence have the incorrect register state for VSX registers 0-31. lfs unaligned <- alignment exception turns FP off but leaves VSX on VSX instruction <- no exception since VSX on, hence we get the wrong VSX register values for VSX registers 0-31, which overlap the FPRs. Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel/misc_64.S')
-rw-r--r--arch/powerpc/kernel/misc_64.S8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 3053fe5..b9530b2 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -495,7 +495,15 @@ _GLOBAL(giveup_altivec)
stvx vr0,r4,r3
beq 1f
ld r4,_MSR-STACK_FRAME_OVERHEAD(r5)
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+ lis r3,(MSR_VEC|MSR_VSX)@h
+FTR_SECTION_ELSE
+ lis r3,MSR_VEC@h
+ALT_FTR_SECTION_END_IFSET(CPU_FTR_VSX)
+#else
lis r3,MSR_VEC@h
+#endif
andc r4,r4,r3 /* disable FP for previous task */
std r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1: