linux-kernel - Re: [PATCH 1/2] Blackfin: initial tracehook support

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Date:	Thu, 11 Feb 2010 12:46:53 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Mike Frysinger <vapier@...too.org>
Cc:	Christoph Hellwig <hch@....de>, oleg@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH 1/2] Blackfin: initial tracehook support

>  config BLACKFIN
>  	def_bool y
>  	select HAVE_ARCH_KGDB
> +	select HAVE_ARCH_TRACEHOOK

Don't define this until you have all its constituents as listed in the
arch/Kconfig comment.  I don't see user_regset support.

> +static inline void
> +syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
> +                      unsigned int i, unsigned int n, unsigned long *args)
> +{
> +	/* wtf is "i" ? */
> +	BUG_ON(i);

i is the starting number.  args[0] gets the i'th argument,
args[n - 1] gets the i+n-1'th argument.

> +asmlinkage void syscall_trace_leave(struct pt_regs *regs)
> +{
> +	if (test_thread_flag(TIF_SYSCALL_TRACE))
> +		tracehook_report_syscall_exit(regs, 0);
>  }

Is it in fact true that single-step reports still come normally after a
syscall instruction?

> @@ -213,7 +213,7 @@ setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t * info,
>  	 */
>  	if (regs->syscfg & TRACE_BITS) {
>  		regs->syscfg &= ~TRACE_BITS;
> -		ptrace_notify(SIGTRAP);
> +		tracehook_signal_handler(sig, info, ka, regs, 1);
>  	}

This call should be made unconditionally, and it should be made after the
signal mask changes have been made (i.e. at the end of handle_signal).  I
think it's wrong to clear the single-step flag here.  Instead, pass
(regs->syscfg & TRACE_BITS) as the last argument.

With ptrace, it makes no difference one way or the other because it will
always either explicitly clear or explicitly set single-step before it
resumes.  But in future, it will matter.

Thanks,
Roland
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