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DIR:OUT; SFP:1101; SCL:1; SRVR:BYAPR18MB2581; H:BYAPR18MB2424.namprd18.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; A:1; MX:1; received-spf: None (protection.outlook.com: marvell.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: w6GO52Ltu9aUvjJGHZDAYgu6okXFCkR7rHdgrCVm1ONuQ+IKqgxxzKeGXyjra0QmdV7gIaMkdtoB1ybO64SlYf9gGjmzRrNUDbuz2Lufsp/BPmUxjnMbFTUGzAUUf+9HbGa1bXs3/YPBUN/+dkwTVw5tdcBC7F/T7A7Duan/4/mBw24njtpw6NpSLdwzWy27LC9vfn+Os4WYF6/qefYmLjfOtz9oRaW2yp63LoY+xKVpA1MldrmInrkV0hMN/jO/UDAXNNS+7Mn9qkzYrVPXI7GYQ/XfjvYxZiL4gUprE6UOxwAHqxN5obbH3oQHjXOoAfF3Y+Qgt/FPUL1ZbTnkE+WzfB/xyjGH8d7WBz8QQ1oVyEXAJqiw//eLtE67tHJxCNXpMrWqHlAUKa1bhI4gTmG/ts0NzNXA6ZwcXdFDK4U= Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 0779ada5-298f-48eb-f0be-08d6ea878d7f X-MS-Exchange-CrossTenant-originalarrivaltime: 06 Jun 2019 14:02:03.2891 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 70e1fb47-1155-421d-87fc-2e58f638b6e0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: jerinj@marvell.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR18MB2581 X-OriginatorOrg: marvell.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-06-06_10:, , signatures=0 Subject: Re: [dpdk-dev] [EXT] [RFC PATCH 0/2] introduce __rte_internal tag X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > -----Original Message----- > From: Neil Horman > Sent: Thursday, June 6, 2019 7:05 PM > To: Jerin Jacob Kollanukkaran > Cc: Bruce Richardson ; dev@dpdk.org; > Thomas Monjalon > Subject: Re: [EXT] [RFC PATCH 0/2] introduce __rte_internal tag >=20 > On Thu, Jun 06, 2019 at 12:04:57PM +0000, Jerin Jacob Kollanukkaran wrote= : > > > -----Original Message----- > > > From: Neil Horman > > > Sent: Thursday, June 6, 2019 5:04 PM > > > To: Jerin Jacob Kollanukkaran > > > Cc: Bruce Richardson ; dev@dpdk.org; > > > Thomas Monjalon > > > Subject: Re: [EXT] [RFC PATCH 0/2] introduce __rte_internal tag > > > > > > On Thu, Jun 06, 2019 at 09:44:52AM +0000, Jerin Jacob Kollanukkaran > wrote: > > > > > -----Original Message----- > > > > > From: Neil Horman > > > > > Sent: Wednesday, June 5, 2019 11:41 PM > > > > > To: Bruce Richardson > > > > > Cc: Jerin Jacob Kollanukkaran ; > > > > > dev@dpdk.org; Thomas Monjalon > > > > > Subject: Re: [EXT] [RFC PATCH 0/2] introduce __rte_internal tag > > > > > > > > > > On Wed, Jun 05, 2019 at 05:45:41PM +0100, Bruce Richardson wrote: > > > > > > On Wed, Jun 05, 2019 at 04:24:09PM +0000, Jerin Jacob > > > > > > Kollanukkaran > > > > > wrote: > > > > > > > > -----Original Message----- > > > > > > > > From: Neil Horman > > > > > > > > Sent: Sunday, May 26, 2019 12:14 AM > > > > > > > > To: dev@dpdk.org > > > > > > > > Cc: Neil Horman ; Jerin Jacob > > > > > > > > Kollanukkaran ; Bruce Richardson > > > > > > > > ; Thomas Monjalon > > > > > > > > > > > > > > > > Subject: [EXT] [RFC PATCH 0/2] introduce __rte_internal > > > > > > > > tag > > > > > > > > > > > > > > > > Hey- > > > > > > > > Based on our recent conversations regarding the use of > > > > > > > > symbols only meant for internal dpdk consumption (between > > > > > > > > dpdk libraries), this is an idea that I've come up with > > > > > > > > that I'd like to get some feedback on > > > > > > > > > > > > > > > > Summary: > > > > > > > > 1) We have symbols in the DPDK that are meant to be used > > > > > > > > between DPDK libraries, but not by applications linking to > > > > > > > > them > > > > > > > > 2) We would like to document those symbols in the code, so > > > > > > > > as to note them clearly as for being meant for internal > > > > > > > > use only > > > > > > > > 3) Linker symbol visibility is a very coarse grained tool, > > > > > > > > and so there is no good way in a single library to mark > > > > > > > > items as being meant for use only by other DPDK libraries, > > > > > > > > at least not without some extensive runtime checking > > > > > > > > > > > > > > > > > > > > > > > > Proposal: > > > > > > > > I'm proposing that we introduce the __rte_internal tag. > > > > > > > > From a coding standpoint it works a great deal like the > > > > > > > > __rte_experimental tag in that it expempts the tagged > > > > > > > > symbol from ABI constraints (as the only users should be > > > > > > > > represented in the DPDK build environment). Additionally, > > > > > > > > the __rte_internal macro resolves differently based on the > > > > > > > > definition of the BUILDING_RTE_SDK flag (working under the > > > > > > > > assumption that said flag should only ever be set if we > > > > > > > > are actually building DPDK libraries which will make use > > > > > > > > of internal calls). If the BUILDING_RTE_SDK flag is set > > > > > > > > __rte_internal resolves to __attribute__((section > > > > > > > > "text.internal)), placing it in a special text section > > > > > > > > which is then used to validate that the the symbol appears > > > > > > > > in the INTERNAL section of the corresponding library versio= n > map). > > > > > > > > If BUILDING_RTE_SDK is not set, then __rte_internal > > > > > > > > resolves to > > > > > __attribute__((error("..."))), which causes any caller of the > > > > > tagged function to throw an error at compile time, indicating > > > > > that the symbol is not available for external use. > > > > > > > > > > > > > > > > This isn't a perfect solution, as applications can still > > > > > > > > hack around it of course, > > > > > > > > > > > > > > I think, one way to, avoid, hack around could be to, > > > > > > > > > > > > > > 1) at config stage, create a random number for the build > > > > > > > 2) introduce RTE_CALL_INTERNAL macro for calling internal > > > > > > > function, compare the generated random number for allowing > > > > > > > the calls to make within the library. i.e leverage the fact > > > > > > > that external library would never know the random number > > > > > > > generated for the DPDK build > > > > > and internal driver code does. > > > > > > > > > > > > > Do we really need to care about this. If have some determined > > > > > > enough to hack around our limitations, then they surely know > > > > > > that they have an unsupported configuration. We just need to > > > > > > protect against inadvertent use of internals, IMHO. > > > > > > > > > > > I agree, I too had thought about doing some sort of internal > > > > > runtime checking to match internal only symbols, such that they > > > > > were only accessable by internally approved users, but it > > > > > started to feel like a great > > > deal of overhead. > > > > > Its a good idea for a general mechanism I think, but I believe > > > > > the value here is more to internally document which apis we want > > > > > to mark as being for internal use only, and create a lightweight > > > > > roadblock at build time to catch users inadvertently using them. > > > > > Determined users will get around anything, and theres not much > > > > > we can do to stop > > > them. > > > > > > > > I agree too. IMHO, Simply having following items would be enough > > > > > > > > 1) Avoid exposing the internal function prototype through public > > > > header files > > > > 2) Add @internal to API documentation > > > > 3) Just decide the name space for internal API for tooling(i.e not > > > > start with rte_ or so) Using objdump scheme to detect internal > > > > functions > > > requires the the library to build prior to run the checkpatch. > > > > > > > > > > No, I'm not comfortable with that approach, and I've stated why: > > > 1) Not exposing the functions via header files is a fine start > > > > > > 2) Adding internal documentation is also fine, but does nothing to > > > correlate the code implementing those functions to the > > > documentation. Its valuable to have a tag on a function identifying = it as > internal only. > > > > > > 3) Using naming conventions to separate internal only from > > > non-internal functions is a vague approach, requiring future > > > developers to be cogniscent of the convention and make the > > > appropriate naming choices. It also implicitly restricts the > > > abliity for future developers to make naming changes in conflict > > > with that convention > > > > Enforcing the naming convention can be achieved through tooling as well= . > > > Sure, but why enforce any function naming at all, when you don't have to. May I ask, why to enforce __rte_internal, when you don't have to >=20 > > > > > > 4) Adding a tag like __rte_internal creates an interlock whereby, > > > not only are internal functions excused from ABI constraints, but > > > forces developers to intentionally mark their internal functions as > > > being internal in the code, which is beneficial to clarlity of unders= tanding > during the development process. > > > > No issues in adding __rte_internal. But, I am against current > > implementaion, Ie. adding objdump dependency > That dependency already exists for the __rte_external flag Sorry, I could not see the dependency. [master][dpdk.org] $ grep -ri "objdump" devtools/ [master][dpdk.org] $ grep -ri "objdump" usertools/ [master][dpdk.org] $ grep -ri "__rte_external" * >=20 > > to checkpatch i.e developer has to build the library first so that > > checkpatch can can know, Is it belongs to internal section or not? > > > What developer is running checkpatch/posting patches without first buildi= ng > their changes? # it is not developer, The CI/CD tools can quicky check the sanity of patch= es before the build itself. Why to add unnecessary dependency? # If some PMD is not building if the requirements are not meet(say AES NI P= MD for crypto) then how do take care of the dependency. >=20 >=20 > > > > > > 5) Adding a tag like __rte_internal is explicit, and allows > > > developers to use a single header file instead of multiple header > > > files if they so choose > > > > > > We went through this with experimental symbols as well[1], and it > > > just makes more sense to me to clearly document in the code what > > > constitutes an internal symbol rather than relying on naming > > > conventions and hoping that developers read the documentation before > > > exporting a symbol publically. > > > > > > > > > [1] https://mails.dpdk.org/archives/dev/2017-December/083828.html > > > > > > > > > > If we really wanted to go down that road, we could use a > > > > > mechainsm simmilar to the EXPORT_SYMBOL / EXPORT_SYMBOL_GPL > > > > > infrastructure that the kernel uses, but that would required > > > > > building our own custom linker script, which seems like overkill = here. > > > > > > > > > > Best > > > > > Neil > > > > > > > > > > > /Bruce > > > > > > > > > > > >