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Subject: Re: [PATCH] tools/lib/traceevent, perf tools: Handle %pU format
 correctly
To:     Steven Rostedt <rostedt@goodmis.org>, Qu Wenruo <wqu@suse.com>
Cc:     linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-trace-devel@vger.kernel.org
References: <20191016063920.20791-1-wqu@suse.com>
 <20191016105456.0b8d2310@gandalf.local.home>
From:   Qu Wenruo <quwenruo.btrfs@gmx.com>
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Date:   Thu, 17 Oct 2019 07:46:03 +0800
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On 2019/10/16 =E4=B8=8B=E5=8D=8810:54, Steven Rostedt wrote:
> On Wed, 16 Oct 2019 14:39:20 +0800
> Qu Wenruo <wqu@suse.com> wrote:
>=20
>> +static void print_uuid_arg(struct trace_seq *s, void *data, int size,=

>> +			   struct tep_event *event, struct tep_print_arg *arg)
>> +{
>> +	const char *fmt;
>> +	unsigned char *buf;
>> +
>> +	fmt =3D "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02=
x%02x%02x";
>> +	if (arg->type !=3D TEP_PRINT_FIELD) {
>> +		trace_seq_printf(s, "ARG TYPE NOT FIELID but %d", arg->type);
>> +		return;
>> +	}
>> +
>> +	if (!arg->field.field) {
>> +		arg->field.field =3D tep_find_any_field(event, arg->field.name);
>> +		if (!arg->field.field) {
>> +			do_warning("%s: field %s not found",
>> +				   __func__, arg->field.name);
>> +			return;
>> +		}
>> +	}
>> +	buf =3D data + arg->field.field->offset;
>=20
> You also need to make sure the data field is not smaller than 16 bytes.=

>=20
> 	if (arg->field.field->size < 16) {
> 		trace_seq_puts(s, "INVALIDUUID");
> 		return;
> 	}
>=20

Oh, forgot that sanity check.

>> +
>> +	trace_seq_printf(s, fmt, buf[0], buf[1], buf[2], buf[3], buf[4], buf=
[5],
>> +		         buf[6], buf[7], buf[8], buf[9], buf[10], buf[11], buf[12],=

>> +			 buf[13], buf[14], buf[15]);
>> +}
>> +
>=20
> Hmm, I know print_mac_addr() does something similar as this, but this
> is getting a bit extreme (too many arguments!). What about doing:
>=20
> 	for (i =3D 0; i < 4; i++)
> 		trace_seq_printf(s, "%02x", buf++);
>=20
> 	for (i =3D 0; i < 3; i++)
> 		trace_seq_printf(s, "-%02x%02x", buf[i * 2], buf[i * 2 + 1]);
>=20
> 	buf +=3D 6;
>=20
> 	trace_seq_putc(s, '-');
>=20
> 	for (i =3D 0; i < 6; i++)
> 		trace_seq_printf(s, "%02x", buf++);
>=20
>=20
>=20
> Hmm, not sure the above is better, but having that many arguments just
> looks ugly to me.

Indeed, I'll update the patchset to make it more sane.

Thanks,
Qu
>=20
> -- Steve
>=20


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