From: "Xueming(Steven) Li" <xuemingl@mellanox.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: Adrien Mazarguil <adrien.mazarguil@6wind.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2] lib/cmdline: init CLI parsing memory
Date: Fri, 19 Jan 2018 18:18:37 +0000 [thread overview]
Message-ID: <VI1PR05MB1678F81EA27C10CA02EBEC1FACEF0@VI1PR05MB1678.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20180119090702.fpko3aiz27b3heau@platinum>
> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> Sent: Friday, January 19, 2018 5:07 PM
> To: Xueming(Steven) Li <xuemingl@mellanox.com>
> Cc: Adrien Mazarguil <adrien.mazarguil@6wind.com>; dev@dpdk.org
> Subject: Re: [PATCH v2] lib/cmdline: init CLI parsing memory
>
> On Thu, Jan 18, 2018 at 04:29:59AM +0000, Xueming(Steven) Li wrote:
> >
> >
> > > -----Original Message-----
> > > From: Olivier Matz [mailto:olivier.matz@6wind.com]
> > > Sent: Tuesday, January 16, 2018 8:46 PM
> > > To: Xueming(Steven) Li <xuemingl@mellanox.com>
> > > Cc: Adrien Mazarguil <adrien.mazarguil@6wind.com>; dev@dpdk.org
> > > Subject: Re: [PATCH v2] lib/cmdline: init CLI parsing memory
> > >
> > > Hi Xueming,
> > >
> > > Sorry for the late response.
> > >
> > > On Tue, Dec 26, 2017 at 12:57:41PM +0000, Xueming(Steven) Li wrote:
> > > > HI Olivier,
> > > >
> > > > By reading p1 comments carefully, looks like the pointer to result
> > > > buffer issue not resolved by result copy. How about this:
> > > >
> > > > @@ -263,6 +263,7 @@
> > > > #ifdef RTE_LIBRTE_CMDLINE_DEBUG
> > > > char debug_buf[BUFSIZ];
> > > > #endif
> > > > + char *result_buf = result.buf;
> > > >
> > > > if (!cl || !buf)
> > > > return CMDLINE_PARSE_BAD_ARGS;
> > > > @@ -312,16 +313,13 @@
> > > > debug_printf("INST %d\n", inst_num);
> > > >
> > > > /* fully parsed */
> > > > - tok = match_inst(inst, buf, 0, tmp_result.buf,
> > > > - sizeof(tmp_result.buf));
> > > > + tok = match_inst(inst, buf, 0, result_buf,
> sizeof(result.buf));
> > >
> > > If we don't use tmp_result, it is maybe better to also replace
> > > sizeof(result.buf) by CMDLINE_PARSE_RESULT_BUFSIZE
> >
> > Thanks, would like to send out new version soon
> >
> > >
> > > >
> > > > if (tok > 0) /* we matched at least one token */
> > > > err = CMDLINE_PARSE_BAD_ARGS;
> > > >
> > > > else if (!tok) {
> > > > debug_printf("INST fully parsed\n");
> > > > - memcpy(&result, &tmp_result,
> > > > - sizeof(result));
> > > > /* skip spaces */
> > > > while (isblank2(*curbuf)) {
> > > > curbuf++;
> > > > @@ -332,6 +330,7 @@
> > > > if (!f) {
> > > > memcpy(&f, &inst->f, sizeof(f));
> > > > memcpy(&data, &inst->data,
> sizeof(data));
> > > > + result_buf = tmp_result.buf;
> > > > }
> > > > else {
> > > > /* more than 1 inst matches */
> > > >
> > >
> > >
> > > I guess the issue you are talking about is the one described in
> > > "cmdline: fix dynamic tokens parsing" in my previous description?
> > >
> > > I think this patch is ok, and is probably better than the initial
> > > suggestion, because it avoids to copy the buffer. However, I don't
> > > understand why the previous patch was wrong, can you detail?
> >
> > Let me quote your last email:
> > " When using dynamic tokens, the result buffer contains pointers
> > to some location inside the result buffer. When the content of
> > the temporary buffer is copied in the final one, these pointers
> > still point to the temporary buffer."
> > If pointer exist in buffer, the new copy still pint to the old copy
> > which very probably being changed.
>
> In patch v2, I still think it was correct because there were 2 copies:
>
> 1/ tok = match_inst(inst, buf, 0, result.buf, sizeof(result.buf));
>
> result is set, it may contain pointers to itself
>
> 2/ result_ok = result;
>
> result is copied in result_ok
> result_ok may contain pointer to result
>
> 3/ other calls to match_inst(inst, buf, 0, result...)
>
> this can clobber the result buffer
>
> 4/ result = result_ok; // before calling f()
>
> restores the content of result as it was in 1/
> it may contain pointers to itself, which is valid
You are correct, I ignored this step, blind hit.
>
> Was there another problem I missed?
>
>
> Anyway, I think your v3 is better because it avoids buffer copies.
> If it's ok for you, please send a v4 with the small updated regarding
> sizeof(result.buf) -> CMDLINE_PARSE_RESULT_BUFSIZE.
>
> Thanks,
> Olivier
next prev parent reply other threads:[~2018-01-19 18:18 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-15 15:54 [dpdk-dev] [PATCH] lib/cmdline: init parse result memeory Xueming Li
2017-12-07 14:48 ` Olivier MATZ
2017-12-07 15:05 ` Xueming(Steven) Li
2017-12-07 15:35 ` Xueming(Steven) Li
2017-12-07 17:13 ` Adrien Mazarguil
2017-12-08 7:02 ` [dpdk-dev] [PATCH v1] lib/cmdline: init parse result memory Xueming Li
2017-12-08 12:27 ` Adrien Mazarguil
2017-12-08 13:51 ` Olivier MATZ
2017-12-08 14:50 ` Xueming(Steven) Li
2017-12-08 15:04 ` Adrien Mazarguil
2017-12-08 15:26 ` Olivier MATZ
2017-12-09 15:39 ` [dpdk-dev] [PATCH v2] lib/cmdline: init CLI parsing memory Xueming Li
2017-12-14 15:35 ` Olivier MATZ
2017-12-18 10:51 ` Adrien Mazarguil
2017-12-18 13:44 ` Xueming(Steven) Li
2017-12-26 12:57 ` Xueming(Steven) Li
2018-01-16 12:45 ` Olivier Matz
2018-01-18 4:29 ` Xueming(Steven) Li
2018-01-19 9:07 ` Olivier Matz
2018-01-19 18:18 ` Xueming(Steven) Li [this message]
2018-01-19 18:16 ` [dpdk-dev] [PATCH v3] cmdline: fix dynamic tokens parsing Xueming Li
2018-01-22 13:13 ` Olivier Matz
2018-01-25 22:14 ` [dpdk-dev] [dpdk-stable] " Thomas Monjalon
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