[GSOC 2014][PATCH 3/4] JSON: Add basic support for syscalls in io.c

[Dmitry V. Levin]

Hi YangMin,

On Thu, Jun 19, 2014 at 12:29:49AM +0800, Zhu YangMin wrote:
> The basic means that all the arguments are simply wrapped in
> a string value even for those complicated arguments printed by
> specific functions such as printflags(). We need to do more work
> to change those functions to be more like JSON-style.
> 
> * io.c(sys_read, sys_write, sys_readv, sys_writev,
> sys_pread, sys_pwrite, sys_preadv, sys_pwritev,
> sys_sendfile, sys_sendfile64, sys_tee, sys_splice,
> sys_vmsplice, sys_ioctl): Modified to use the hook
> framework to support printing in JSON format. Note: The
> support of ioctl() is very limited and need to be improved.

Thanks for these examples.  Let's have a look at the first one:

> int
> sys_read(struct tcb *tcp)
> {
> 	JSON_BEGIN_META_MODE;
> 
> 	if (entering(tcp)) {
> 		JSON_META( printfd(tcp, tcp->u_arg[0]); );
> 		tprints(", ");
> 
> 		json_event(1, EVENT_ARG | SEPARATOR);
> 	} else {
> 		json_type_event first;
> 
> 		if (syserror(tcp)) {
> 			tprintf("%#lx", tcp->u_arg[1]);
> 			first = EVENT_ERROR;
> 		}
> 		else {
> 			JSON_META( printstr(tcp, tcp->u_arg[1], tcp->u_rval) );
> 			first = EVENT_ARG;
> 		}
> 		tprintf(", %lu", tcp->u_arg[2]);
> 
> 		json_event(2, first | SEPARATOR, EVENT_ARG);
> 	}
> 	return 0;
> }

Well, compared to the original code, it looks rather complicated.
I thought it could be something easier to read, for example,

int
sys_read(struct tcb *tcp)
{
	if (entering(tcp)) {
		print_args_open();
		print_arg_fd(tcp->u_arg[0]);
	} else {
		if (syserror(tcp))
			print_arg_fmt("%#lx", tcp->u_arg[1]);
		else
			print_arg_str_at(tcp->u_arg[1], tcp->u_rval);
		print_arg_fmt("%lu", tcp->u_arg[2]);
		print_args_close();
	}
	return 0;
}

That is, with all JSON related details hidden from syscall parsers.
What do you think?


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