powerpc/tm: Fix 32bit non-rt signal return

[Michael Neuling]

benh,

Hold off on taking this for now... I'm seeing a crash with it on power7.

Mikey

Michael Neuling <mikey at neuling.org> wrote:
> Currently sys_sigreturn() is transactional memory unaware, hence if we take a
> 32 bit signal without SIGINFO (non RT) inside a transaction, we don't restore
> the signal frame correctly on return.
> 
> This checks if the signal frame being restoring is an active transaction, and
> if so, it copies the additional state to the ptregs so it can be restored.
> 
> Signed-off-by: Michael Neuling <mikey at neuling.org>
> cc: <stable at vger.kernel.org> # 3.9 only
> 
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index 201385c..0bc961b 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -1481,16 +1481,22 @@ badframe:
>  long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
>  		       struct pt_regs *regs)
>  {
> +	struct sigframe __user *sf;
>  	struct sigcontext __user *sc;
>  	struct sigcontext sigctx;
>  	struct mcontext __user *sr;
>  	void __user *addr;
>  	sigset_t set;
> +#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> +	struct mcontext __user *mcp, *tm_mcp;
> +	unsigned long msr_hi;
> +#endif
>  
>  	/* Always make any pending restarted system calls return -EINTR */
>  	current_thread_info()->restart_block.fn = do_no_restart_syscall;
>  
> -	sc = (struct sigcontext __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
> +	sf = (struct sigframe __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
> +	sc = &sf->sctx;
>  	addr = sc;
>  	if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
>  		goto badframe;
> @@ -1507,12 +1513,23 @@ long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
>  #endif
>  	set_current_blocked(&set);
>  
> -	sr = (struct mcontext __user *)from_user_ptr(sigctx.regs);
> -	addr = sr;
> -	if (!access_ok(VERIFY_READ, sr, sizeof(*sr))
> -	    || restore_user_regs(regs, sr, 1))
> +#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> +	mcp = (struct mcontext __user *)&sf->mctx;
> +	tm_mcp = (struct mcontext __user *)&sf->mctx_transact;
> +	if (__get_user(msr_hi, &mcp->mc_gregs[PT_MSR]))
>  		goto badframe;
> -
> +	if MSR_TM_ACTIVE(msr_hi<<32) {
> +		if (restore_tm_user_regs(regs, mcp, tm_mcp))
> +			goto badframe;
> +	} else
> +#endif
> +	{
> +		sr = (struct mcontext __user *)from_user_ptr(sigctx.regs);
> +		addr = sr;
> +		if (!access_ok(VERIFY_READ, sr, sizeof(*sr))
> +		    || restore_user_regs(regs, sr, 1))
> +			goto badframe;
> +	}
>  	set_thread_flag(TIF_RESTOREALL);
>  	return 0;
>  
>