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[POWERPC] Fix incorrect enabling of VMX when building signal or user context 

When building a signal or a ucontext, we can incorrectly set the MSR_VEC
bit of the kernel pt_regs->msr before returning to userspace if the task
-ever- used VMX.

This can lead to funny result if that stack used it in the past, then
"lost" it (ie. it wasn't enabled after a context switch for example)
and then called get_context.  It can end up with VMX enabled and the
registers containing values from some other task.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Benjamin Herrenschmidt 2008-06-02 16:22:59 +10:00 committed by Paul Mackerras
parent efa58fbf19
commit 0be234a465
1 changed files with 3 additions and 1 deletions
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4
arch/powerpc/kernel/signal_64.c
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@ -87,6 +87,7 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
#ifdef CONFIG_ALTIVEC
elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
#endif
unsigned long msr = regs->msr;
long err = 0;
flush_fp_to_thread(current);
@ -102,7 +103,7 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
* contains valid data.
*/
regs->msr |= MSR_VEC;
msr |= MSR_VEC;
}
/* We always copy to/from vrsave, it's 0 if we don't have or don't
* use altivec.
@ -114,6 +115,7 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
err |= __put_user(&sc->gp_regs, &sc->regs);
WARN_ON(!FULL_REGS(regs));
err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
err |= __put_user(signr, &sc->signal);
err |= __put_user(handler, &sc->handler);