diff options
| author | Paul Mackerras <paulus@samba.org> | 2013-10-23 09:40:02 +0100 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-10-23 22:34:19 +1100 |
| commit | 955c1cab809edfb5429603c68493363074ac20cf (patch) | |
| tree | 366056342adca338a8efc6b7e8caf52279765647 /arch/powerpc/kernel/vector.S | |
| parent | 18461960cbf50bf345ef0667d45d5f64de8fb893 (diff) | |
powerpc: Don't corrupt user registers on 32-bit
Commit de79f7b9f6 ("powerpc: Put FP/VSX and VR state into structures")
modified load_up_fpu() and load_up_altivec() in such a way that they
now use r7 and r8. Unfortunately, the callers of these functions on
32-bit machines then return to userspace via fast_exception_return,
which doesn't restore all of the volatile GPRs, but only r1, r3 -- r6
and r9 -- r12. This was causing userspace segfaults and other
userspace misbehaviour on 32-bit machines.
This fixes the problem by changing the register usage of load_up_fpu()
and load_up_altivec() to avoid using r7 and r8 and instead use r6 and
r10. This also adds comments to those functions saying which registers
may be used.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Tested-by: Scott Wood <scottwood@freescale.com> (on e500mc, so no altivec)
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/vector.S')
| -rw-r--r-- | arch/powerpc/kernel/vector.S | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/arch/powerpc/kernel/vector.S b/arch/powerpc/kernel/vector.S index eacda4eea2d..0458a9aaba9 100644 --- a/arch/powerpc/kernel/vector.S +++ b/arch/powerpc/kernel/vector.S @@ -64,6 +64,9 @@ _GLOBAL(store_vr_state) * Enables the VMX for use in the kernel on return. * On SMP we know the VMX is free, since we give it up every * switch (ie, no lazy save of the vector registers). + * + * Note that on 32-bit this can only use registers that will be + * restored by fast_exception_return, i.e. r3 - r6, r10 and r11. */ _GLOBAL(load_up_altivec) mfmsr r5 /* grab the current MSR */ @@ -89,11 +92,11 @@ _GLOBAL(load_up_altivec) /* Save VMX state to last_task_used_altivec's THREAD struct */ toreal(r4) addi r4,r4,THREAD - addi r7,r4,THREAD_VRSTATE - SAVE_32VRS(0,r5,r7) + addi r6,r4,THREAD_VRSTATE + SAVE_32VRS(0,r5,r6) mfvscr vr0 li r10,VRSTATE_VSCR - stvx vr0,r10,r7 + stvx vr0,r10,r6 /* Disable VMX for last_task_used_altivec */ PPC_LL r5,PT_REGS(r4) toreal(r5) @@ -125,13 +128,13 @@ _GLOBAL(load_up_altivec) oris r12,r12,MSR_VEC@h std r12,_MSR(r1) #endif - addi r7,r5,THREAD_VRSTATE + addi r6,r5,THREAD_VRSTATE li r4,1 li r10,VRSTATE_VSCR stw r4,THREAD_USED_VR(r5) - lvx vr0,r10,r7 + lvx vr0,r10,r6 mtvscr vr0 - REST_32VRS(0,r4,r7) + REST_32VRS(0,r4,r6) #ifndef CONFIG_SMP /* Update last_task_used_altivec to 'current' */ subi r4,r5,THREAD /* Back to 'current' */ |