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From: Martijn Coenen <maco@android.com>
To: Jessica Yu <jeyu@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Oliver Neukum <oneukum@suse.com>, Arnd Bergmann <arnd@arndb.de>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Sam Ravnborg <sam@ravnborg.org>,
	linux-kbuild@vger.kernel.org,
	linux-m68k <linux-m68k@lists.linux-m68k.org>,
	USB list <linux-usb@vger.kernel.org>,
	USB Storage list <usb-storage@lists.one-eyed-alien.net>,
	linux-scsi@vger.kernel.org,
	Linux-Arch <linux-arch@vger.kernel.org>,
	Martijn Coenen <maco@google.com>,
	Sandeep Patil <sspatil@google.com>,
	Iliyan Malchev <malchev@google.com>,
	Joel Fernandes <joelaf@google.com>
Subject: Re: [PATCH 2/6] module: add support for symbol namespaces.
Date: Fri, 20 Jul 2018 17:42:07 +0200
Message-ID: <CAB0TPYFQvkTsMvfJCTSFSJAoCbmOUJz7mCQGoORs6nRcC3Fhdg@mail.gmail.com> (raw)
In-Reply-To: <20180720144916.fyqpmrtgt23sax6n@linux-8ccs>

On Fri, Jul 20, 2018 at 4:49 PM, Jessica Yu <jeyu@kernel.org> wrote:
> Thanks. Also, it looks like we're currently just warning (in both
> modpost and on module load) if a module uses symbols from a namespace
> it doesn't import. Are you also planning to eventually introduce
> namespace enforcement?

This is something I've definitely been thinking about, and was curious
what others would think. My main concern with enforcement is that it
will start failing to load out-of-tree modules that use newly
namespaced symbols. On the other hand, I think those modules will need
to be rebuilt anyway to be able to load, because the changes to struct
kernel_symbol make them incompatible with the current kernel. That
could be another reason for having these symbols in a special section
(with its own struct namespaced_kernel_symbol); but on the other hand,
it would make the module loader more complex just to facilitate
out-of-tree drivers, and I'm not sure where the trade-off between
those two falls.

> It'd be trivial to fail the module build in
> modpost as well as reject the module on load if it uses an exported
> symbol belonging to a namespace it doesn't import. Although, I'd go
> with the warnings for a development cycle or two, to gently introduce
> the change in API and let other subsystems as well as out-of-tree
> module developers catch up.

An approach like that makes sense to me. Another alternative would be
to make it a CONFIG_ option, and let distros/etc. decide what they are
comfortable with.

Thanks,
Martijn

>
>
> Jessica
>
>
>>> Also, this would get rid of the extra __knsimport section, the extra
>>> ns_dependencies field in struct module, and all those helper functions
>>> that
>>> manage it. In addition, having the modinfo tag may potentially help with
>>> debugging as we have the namespace imports clearly listed if we don't
>>> have
>>> the source code for a module. We'd probably need to modify get_modinfo()
>>> to
>>> handle multiple import: tags though. Luis [1] had written some code a
>>> while
>>> ago to handle multiple (of the same) modinfo tags.
>>>
>>> Thoughts on this?
>>>
>>> Thanks,
>>>
>>> Jessica
>>>
>>> [1] https://lkml.kernel.org/r/20171130023605.29568-3-mcgrof@kernel.org
>>>
>>>
>>>> getname:
>>>>         /* We must make copy under the lock if we failed to get ref. */
>>>>         strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
>>>> @@ -3061,6 +3118,11 @@ static int find_module_sections(struct module
>>>> *mod,
>>>> struct load_info *info)
>>>>                                      sizeof(*mod->gpl_syms),
>>>>                                      &mod->num_gpl_syms);
>>>>         mod->gpl_crcs = section_addr(info, "__kcrctab_gpl");
>>>> +
>>>> +       mod->ns_imports = section_objs(info, "__knsimport",
>>>> +                                      sizeof(*mod->ns_imports),
>>>> +                                      &mod->num_ns_imports);
>>>> +
>>>>         mod->gpl_future_syms = section_objs(info,
>>>>                                             "__ksymtab_gpl_future",
>>>>
>>>> sizeof(*mod->gpl_future_syms),
>>>> @@ -3381,6 +3443,19 @@ static int post_relocation(struct module *mod,
>>>> const struct load_info *info)
>>>>         return module_finalize(info->hdr, info->sechdrs, mod);
>>>> }
>>>>
>>>> +static void verify_namespace_dependencies(struct module *mod)
>>>> +{
>>>> +       struct module_ns_dep *ns_dep;
>>>> +
>>>> +       list_for_each_entry(ns_dep, &mod->ns_dependencies, ns_dep) {
>>>> +               if (!module_imports_ns(mod, ns_dep->namespace)) {
>>>> +                       pr_warn("%s: module uses symbols from namespace
>>>> %s,"
>>>> +                               " but does not import it.\n",
>>>> +                               mod->name, ns_dep->namespace);
>>>> +               }
>>>> +       }
>>>> +}
>>>> +
>>>> /* Is this module of this name done loading?  No locks held. */
>>>> static bool finished_loading(const char *name)
>>>> {
>>>> @@ -3682,6 +3757,8 @@ static int load_module(struct load_info *info,
>>>> const
>>>> char __user *uargs,
>>>>         if (err)
>>>>                 goto free_module;
>>>>
>>>> +       INIT_LIST_HEAD(&mod->ns_dependencies);
>>>> +
>>>> #ifdef CONFIG_MODULE_SIG
>>>>         mod->sig_ok = info->sig_ok;
>>>>         if (!mod->sig_ok) {
>>>> @@ -3730,6 +3807,8 @@ static int load_module(struct load_info *info,
>>>> const
>>>> char __user *uargs,
>>>>         if (err < 0)
>>>>                 goto free_modinfo;
>>>>
>>>> +       verify_namespace_dependencies(mod);
>>>> +
>>>>         flush_module_icache(mod);
>>>>
>>>>         /* Now copy in args */
>>>> --
>>>> 2.18.0.203.gfac676dfb9-goog
>>>>
>>>
>

  reply index

Thread overview: 134+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-16 12:21 [PATCH 0/6] Symbol namespaces Martijn Coenen
2018-07-16 12:21 ` [PATCH 1/6] export: explicitly align struct kernel_symbol Martijn Coenen
2018-07-16 12:21 ` [PATCH 2/6] module: add support for symbol namespaces Martijn Coenen
2018-07-19 16:32   ` Jessica Yu
2018-07-20  7:54     ` Martijn Coenen
2018-07-20 14:49       ` Jessica Yu
2018-07-20 15:42         ` Martijn Coenen [this message]
2018-07-23 11:12           ` Jessica Yu
2018-07-24  7:44             ` Martijn Coenen
2018-07-24  7:56   ` Martijn Coenen
2018-07-25 15:55     ` Jessica Yu
2018-07-25 16:48       ` Lucas De Marchi
2018-07-26  7:44         ` Martijn Coenen
2018-07-16 12:21 ` [PATCH 3/6] modpost: add support for checking " Martijn Coenen
2018-07-16 12:21 ` [PATCH 4/6] modpost: add support for generating namespace dependencies Martijn Coenen
2018-07-23  6:49   ` Jessica Yu
2018-07-16 12:21 ` [PATCH 5/6] scripts: Coccinelle script for " Martijn Coenen
2018-07-16 12:21 ` [PATCH 6/6] RFC: USB: storage: move symbols into USB_STORAGE namespace Martijn Coenen
2018-07-17 15:04   ` Alan Stern
2018-07-18 13:28     ` Martijn Coenen
2018-07-16 15:33 ` [PATCH 0/6] Symbol namespaces Greg Kroah-Hartman
2018-07-23 14:28 ` Arnd Bergmann
2018-07-24  8:09   ` Martijn Coenen
2018-07-24  9:08     ` Arnd Bergmann
2019-08-13 12:16 ` [PATCH v2 0/10] Symbol namespaces - RFC Matthias Maennich
2019-08-13 12:16   ` [PATCH v2 01/10] module: support reading multiple values per modinfo tag Matthias Maennich
2019-08-13 12:40     ` Greg KH
2019-08-13 12:16   ` [PATCH v2 02/10] export: explicitly align struct kernel_symbol Matthias Maennich
2019-08-13 12:41     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 03/10] module: add support for symbol namespaces Matthias Maennich
2019-08-13 15:26     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 04/10] modpost: " Matthias Maennich
2019-08-13 15:27     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 05/10] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-08-13 18:17     ` Greg KH
2019-08-13 20:15     ` Saravana Kannan
2019-08-14 12:54       ` Matthias Maennich
2019-08-14 17:34         ` Saravana Kannan
2019-08-13 12:17   ` [PATCH v2 06/10] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-08-13 18:16     ` Greg KH
2019-08-13 18:16     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 07/10] modpost: add support for generating namespace dependencies Matthias Maennich
2019-08-13 18:21     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 08/10] scripts: Coccinelle script for " Matthias Maennich
2019-08-13 12:31     ` Julia Lawall
2019-08-13 12:44     ` Greg KH
2019-08-14  6:36     ` [Cocci] " Himanshu Jha
2019-08-14  8:03       ` Matthias Maennich
2019-08-15 13:50     ` [v2 " Markus Elfring
2019-08-22  9:18       ` Matthias Maennich
2019-08-22 11:00         ` Markus Elfring
2019-08-13 12:17   ` [PATCH v2 09/10] usb-storage: remove single-use define for debugging Matthias Maennich
2019-08-13 12:42     ` Greg KH
2019-08-13 13:12       ` Greg KH
2019-08-13 12:17   ` [PATCH v2 10/10] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-08-13 12:45     ` Greg KH
2019-08-13 12:47     ` Greg KH
2019-08-13 15:02       ` Matthias Maennich
     [not found]   ` <20190821114955.12788-1-maennich@google.com>
2019-08-21 11:49     ` [PATCH v3 01/11] module: support reading multiple values per modinfo tag Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 02/11] export: explicitly align struct kernel_symbol Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 03/11] module: add support for symbol namespaces Matthias Maennich
2019-08-27 15:37       ` Jessica Yu
2019-08-27 16:04         ` Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 04/11] modpost: " Matthias Maennich
2019-08-26 16:21       ` Jessica Yu
2019-08-27 14:41         ` Matthias Maennich
2019-08-28  9:43           ` Jessica Yu
2019-08-28  9:55             ` Matthias Maennich
2019-08-28 10:16               ` Jessica Yu
2019-08-21 11:49     ` [PATCH v3 05/11] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 06/11] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-08-28 10:49       ` Jessica Yu
2019-08-28 10:56         ` Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 07/11] modpost: add support for generating namespace dependencies Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 08/11] scripts: Coccinelle script for " Matthias Maennich
2019-08-22  6:09       ` [v3 " Markus Elfring
2019-08-29 12:13       ` [PATCH v3 " Jessica Yu
2019-08-21 11:49     ` [PATCH v3 09/11] usb-storage: remove single-use define for debugging Matthias Maennich
2019-08-21 12:37       ` Greg KH
2019-08-21 13:21       ` Thomas Gleixner
2019-08-21 13:32         ` Greg KH
2019-08-21 11:49     ` [PATCH v3 10/11] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-08-21 12:38       ` Greg KH
2019-08-21 14:36         ` Jessica Yu
2019-08-21 23:13       ` Christoph Hellwig
2019-08-22  8:32         ` Matthias Maennich
2019-09-03 15:06 ` [PATCH v4 00/12] Symbol Namespaces Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 01/12] module: support reading multiple values per modinfo tag Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 02/12] export: explicitly align struct kernel_symbol Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 03/12] module: add support for symbol namespaces Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 04/12] modpost: " Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 05/12] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 06/12] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 07/12] modpost: add support for generating namespace dependencies Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 08/12] scripts: Coccinelle script for " Matthias Maennich
2019-09-04  9:53     ` Masahiro Yamada
2019-09-05 14:46       ` Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 09/12] docs: Add documentation for Symbol Namespaces Matthias Maennich
2019-09-04  7:16     ` Greg KH
2019-09-03 15:06   ` [PATCH v4 10/12] usb-storage: remove single-use define for debugging Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 11/12] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 12/12] RFC: watchdog: export core symbols in WATCHDOG_CORE namespace Matthias Maennich
2019-09-03 16:10     ` Guenter Roeck
2019-09-04  8:45       ` Masahiro Yamada
2019-09-04 12:12         ` Guenter Roeck
2019-09-04 16:16           ` [usb-storage] " Matthew Dharm
2019-09-05 10:41             ` Jessica Yu
2019-09-05 10:52               ` Arnd Bergmann
2019-09-05 11:16                 ` Jessica Yu
2019-09-05 11:25                   ` Masahiro Yamada
2019-09-05 12:00                     ` Greg Kroah-Hartman
2019-09-05 11:25               ` Matthias Maennich
2019-09-04  9:37   ` [PATCH v4 00/12] Symbol Namespaces Masahiro Yamada
2019-09-06 10:32 ` [PATCH v5 00/11] " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 01/11] module: support reading multiple values per modinfo tag Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 02/11] export: explicitly align struct kernel_symbol Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 03/11] module: add support for symbol namespaces Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 04/11] modpost: " Matthias Maennich
2019-09-26 22:24     ` [PATCH] modpost: Copy namespace string into 'struct symbol' Shaun Ruffell
2019-09-27  5:31       ` Greg Kroah-Hartman
2019-09-27  8:03       ` Matthias Maennich
2019-09-30 21:20         ` Shaun Ruffell
2019-10-01 16:19           ` Matthias Maennich
2019-10-01 19:37             ` Shaun Ruffell
2019-09-06 10:32   ` [PATCH v5 05/11] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 06/11] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 07/11] modpost: add support for generating namespace dependencies Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 08/11] scripts: Coccinelle script for " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 09/11] docs: Add documentation for Symbol Namespaces Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 10/11] usb-storage: remove single-use define for debugging Matthias Maennich
2019-09-06 12:59     ` Jessica Yu
2019-09-06 13:22       ` Greg KH
2019-09-06 10:32   ` [PATCH v5 11/11] usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-09-09  8:35   ` [PATCH v5 00/11] Symbol Namespaces Jessica Yu

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