linux-kernel - Re: [PATCH 06/14] tracing: add tracing support for compat syscalls

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Message-ID: <20100320061215.GN5085@nowhere>
Date:	Sat, 20 Mar 2010 07:12:17 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Jason Baron <jbaron@...hat.com>
Cc:	mingo@...e.hu, rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	laijs@...fujitsu.com, lizf@...fujitsu.com, hpa@...or.com,
	tglx@...utronix.de, mhiramat@...hat.com, heiko.carstens@...ibm.com,
	benh@...nel.crashing.org, davem@...emloft.net, lethal@...ux-sh.org,
	schwidefsky@...ibm.com, brueckner@...ux.vnet.ibm.com,
	tony.luck@...el.com
Subject: Re: [PATCH 06/14] tracing: add tracing support for compat syscalls

On Tue, Mar 16, 2010 at 01:46:36PM -0400, Jason Baron wrote:
>  #else /* CONFIG_COMPAT */
>  
> +#define NR_syscalls_compat 0
> +
>  static inline int is_compat_task(void)
>  {
>  	return 0;
> diff --git a/include/trace/syscall.h b/include/trace/syscall.h
> index 8f5ac38..1cc1d1e 100644
> --- a/include/trace/syscall.h
> +++ b/include/trace/syscall.h
> @@ -22,6 +22,7 @@
>  struct syscall_metadata {
>  	const char	*name;
>  	int		syscall_nr;
> +	int		compat_syscall_nr;



Why do you need both syscall_nr and compat_syscall_nr?
Compat and usual syscalls never share the same syscall
metadata.



> +#ifdef __HAVE_ARCH_FTRACE_COMPAT_SYSCALLS
> +	if (NR_syscalls_compat) {
> +		int match;
> +		struct ftrace_event_call *ftrace_event;
> +
> +		compat_syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
> +						NR_syscalls_compat, GFP_KERNEL);
> +		if (!compat_syscalls_metadata) {
> +			WARN_ON(1);
> +			kfree(syscalls_metadata);
> +			return -ENOMEM;
> +		}
> +		for (i = 0; i < NR_syscalls_compat; i++) {
> +			addr = arch_compat_syscall_addr(i);
> +			meta = find_syscall_meta(addr);
> +			if (!meta)
> +				continue;
> +
> +			meta->compat_syscall_nr = i;
> +			compat_syscalls_metadata[i] = meta;
> +		}
> +		/* now check if any compat_syscalls are not referenced */
> +		for (ftrace_event = __start_ftrace_events;
> +			(unsigned long)ftrace_event <
> +			(unsigned long)__stop_ftrace_events; ftrace_event++) {



You could reuse for_each_event()



> +			match = 0;
> +			if (!ftrace_event->name)
> +				continue;
> +			if (strcmp(ftrace_event->system, "compat_syscalls"))
> +				continue;
> +			for (i = 0; i < NR_syscalls_compat; i++) {
> +				if (ftrace_event->data ==
> +						compat_syscalls_metadata[i]) {
> +					match = 1;
> +					break;


Nano-neat: starting the whole block with if (NR_syscalls_compat)
or making the whole a separate init_ftrace_syscalls() would
have made it win one level of indentation.



> +				}
> +			}
> +			if (!match)
> +				ftrace_event->name = NULL;



Nice :)

Thanks.

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