提交 7e875e9d 编写于 作者: M Michael Neuling 提交者: Paul Mackerras

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: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>
上级 4c6cf428
......@@ -145,6 +145,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX)
beq 1f
PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
li r3,MSR_FP|MSR_FE0|MSR_FE1
#ifdef CONFIG_VSX
BEGIN_FTR_SECTION
oris r3,r3,MSR_VSX@h
END_FTR_SECTION_IFSET(CPU_FTR_VSX)
#endif
andc r4,r4,r3 /* disable FP for previous task */
PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1:
......
......@@ -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:
......
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