Re: [PATCH 13/29] metag: Use get_signal() signal_setup_done()

[James Hogan]

Hi Richard,

(cc'd linux-metag)

On 08/10/13 12:33, Richard Weinberger wrote:
> Use the more generic functions get_signal() signal_setup_done()
> for signal delivery.
> 
> Signed-off-by: Richard Weinberger <richard@xxxxxx>
> ---
>  arch/metag/kernel/signal.c | 55 ++++++++++++++++++++--------------------------
>  1 file changed, 24 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/metag/kernel/signal.c b/arch/metag/kernel/signal.c
> index 3be61cf..9fa27c2 100644
> --- a/arch/metag/kernel/signal.c
> +++ b/arch/metag/kernel/signal.c
> @@ -152,18 +152,18 @@ static void __user *get_sigframe(struct k_sigaction *ka, unsigned long sp,
>  	return (void __user *)sp;
>  }
>  
> -static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
> -			  sigset_t *set, struct pt_regs *regs)
> +static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
> +			  struct pt_regs *regs)
>  {
>  	struct rt_sigframe __user *frame;
> -	int err = -EFAULT;
> +	int err;
>  	unsigned long code;
>  
> -	frame = get_sigframe(ka, regs->REG_SP, sizeof(*frame));
> +	frame = get_sigframe(&ksig->ka, regs->REG_SP, sizeof(*frame));
>  	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
> -		goto out;
> +		return -EFAULT;
>  
> -	err = copy_siginfo_to_user(&frame->info, info);
> +	err = copy_siginfo_to_user(&frame->info, &ksig->info);
>  
>  	/* Create the ucontext.  */
>  	err |= __put_user(0, &frame->uc.uc_flags);
> @@ -174,7 +174,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
>  	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
>  
>  	if (err)
> -		goto out;
> +		return -EFAULT;
>  
>  	/* Set up to return from userspace.  */
>  
> @@ -187,15 +187,15 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
>  	err |= __put_user(code, (unsigned long __user *)(&frame->retcode[1]));
>  
>  	if (err)
> -		goto out;
> +		return -EFAULT;
>  
>  	/* Set up registers for signal handler */
>  	regs->REG_RTP = (unsigned long) frame->retcode;
>  	regs->REG_SP = (unsigned long) frame + sizeof(*frame);
> -	regs->REG_ARG1 = sig;
> +	regs->REG_ARG1 = ksig->sig;
>  	regs->REG_ARG2 = (unsigned long) &frame->info;
>  	regs->REG_ARG3 = (unsigned long) &frame->uc;
> -	regs->REG_PC = (unsigned long) ka->sa.sa_handler;
> +	regs->REG_PC = (unsigned long) ksig->ka.sa.sa_handler;
>  
>  	pr_debug("SIG deliver (%s:%d): sp=%p pc=%08x pr=%08x\n",
>  		 current->comm, current->pid, frame, regs->REG_PC,
> @@ -205,24 +205,19 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
>  	 * effective cache flush - directed rather than 'full flush'.
>  	 */
>  	flush_cache_sigtramp(regs->REG_RTP, sizeof(frame->retcode));
> -out:
> -	if (err) {
> -		force_sigsegv(sig, current);
> -		return -EFAULT;
> -	}
> +
>  	return 0;
>  }
>  
> -static void handle_signal(unsigned long sig, siginfo_t *info,
> -			  struct k_sigaction *ka, struct pt_regs *regs)
> +static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
>  {
>  	sigset_t *oldset = sigmask_to_save();
> +	int ret;
>  
>  	/* Set up the stack frame */
> -	if (setup_rt_frame(sig, ka, info, oldset, regs))
> -		return;
> +	ret = setup_rt_frame(ksig, oldset, regs);
>  
> -	signal_delivered(sig, info, ka, regs, test_thread_flag(TIF_SINGLESTEP));
> +	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
>  }
>  
>   /*
> @@ -235,10 +230,8 @@ static void handle_signal(unsigned long sig, siginfo_t *info,
>  static int do_signal(struct pt_regs *regs, int syscall)
>  {
>  	unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
> -	struct k_sigaction ka;
> -	siginfo_t info;
> -	int signr;
>  	int restart = 0;
> +	struct ksignal ksig;
>  
>  	/*
>  	 * By the end of rt_sigreturn the context describes the point that the
> @@ -272,30 +265,30 @@ static int do_signal(struct pt_regs *regs, int syscall)
>  	}
>  
>  	/*
> -	 * Get the signal to deliver. When running under ptrace, at this point
> -	 * the debugger may change all our registers ...
> -	 */
> -	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
> -	/*
>  	 * Depending on the signal settings we may need to revert the decision
>  	 * to restart the system call. But skip this if a debugger has chosen to
>  	 * restart at a different PC.
>  	 */
>  	if (regs->REG_PC != restart_addr)
>  		restart = 0;

You've reordered the point where a ptrace debugger can change the registers
(get_signal_to_deliver) and the check of whether the PC has been changed by
the debugger (REG_PC != restart_addr).

I suggest this is changed to do something like 7e243643 (arm: switch to struct
ksignal * passing) does, moving the above REG_PC != restart_addr check into
the restart conditions below.

> -	if (signr > 0) {
> +
> +	/*
> +	 * Get the signal to deliver. When running under ptrace, at this point
> +	 * the debugger may change all our registers ...
> +	 */
> +	if (get_signal(&ksig)) {
>  		if (unlikely(restart)) {
>  			if (retval == -ERESTARTNOHAND
>  			    || retval == -ERESTART_RESTARTBLOCK
>  			    || (retval == -ERESTARTSYS
> -				&& !(ka.sa.sa_flags & SA_RESTART))) {
> +				&& !(ksig.ka.sa.sa_flags & SA_RESTART))) {
>  				regs->REG_RETVAL = -EINTR;
>  				regs->REG_PC = continue_addr;
>  			}
>  		}
>  
>  		/* Whee! Actually deliver the signal.  */
> -		handle_signal(signr, &info, &ka, regs);
> +		handle_signal(&ksig, regs);
>  		return 0;
>  	}
>  
> 

How does the fixup patch below look?

The rest looks good, so other than that problem:
Acked-by: James Hogan <james.hogan@xxxxxxxxxx>

Thanks
James

diff --git a/arch/metag/kernel/signal.c b/arch/metag/kernel/signal.c
index 9fa27c2..6f64ea2 100644
--- a/arch/metag/kernel/signal.c
+++ b/arch/metag/kernel/signal.c
@@ -265,19 +265,16 @@ static int do_signal(struct pt_regs *regs, int syscall)
 	}
 
 	/*
+	 * Get the signal to deliver. When running under ptrace, at this point
+	 * the debugger may change all our registers ...
+	 *
 	 * Depending on the signal settings we may need to revert the decision
 	 * to restart the system call. But skip this if a debugger has chosen to
 	 * restart at a different PC.
 	 */
-	if (regs->REG_PC != restart_addr)
-		restart = 0;
-
-	/*
-	 * Get the signal to deliver. When running under ptrace, at this point
-	 * the debugger may change all our registers ...
-	 */
 	if (get_signal(&ksig)) {
-		if (unlikely(restart)) {
+		/* Handler */
+		if (unlikely(restart) && regs->REG_PC == restart_addr) {
 			if (retval == -ERESTARTNOHAND
 			    || retval == -ERESTART_RESTARTBLOCK
 			    || (retval == -ERESTARTSYS
@@ -289,19 +286,24 @@ static int do_signal(struct pt_regs *regs, int syscall)
 
 		/* Whee! Actually deliver the signal.  */
 		handle_signal(&ksig, regs);
-		return 0;
-	}
-
-	/* Handlerless -ERESTART_RESTARTBLOCK re-enters via restart_syscall */
-	if (unlikely(restart < 0))
-		regs->REG_SYSCALL = __NR_restart_syscall;
-
-	/*
-	 * If there's no signal to deliver, we just put the saved sigmask back.
-	 */
-	restore_saved_sigmask();
+	} else {
+		/*
+		 * If there's no signal to deliver, we just put the saved
+		 * sigmask back.
+		 */
+		restore_saved_sigmask();
 
-	return restart;
+		/*
+		 * Handlerless -ERESTART_RESTARTBLOCK re-enters via
+		 * restart_syscall
+		 */
+		if (unlikely(restart) && regs->REG_PC == restart_addr) {
+			if (restart < 0)
+				regs->REG_SYSCALL = __NR_restart_syscall;
+			return restart;
+		}
+	}
+	return 0;
 }
 
 int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,

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