Re: [RFC PATCH] modpost: check for static EXPORT_SYMBOL* functions

From: Emil Velikov <emil.l.velikov@gmail.com>
To: Denis Efremov <efremov@linux.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] modpost: check for static EXPORT_SYMBOL* functions
Date: Mon, 15 Jul 2019 15:43:06 +0100	[thread overview]
Message-ID: <20190715144306.GA24120@arch-x1c3> (raw)
In-Reply-To: <20190714152817.24693-1-efremov@linux.com>

Hi Denis,

On 2019/07/14, Denis Efremov wrote:
> This patch adds a check to warn about static EXPORT_SYMBOL* functions
> during the modpost. In most of the cases, a static symbol marked for
> exporting is an odd combination that should be fixed either by deleting
> the exporting mark or by removing the static attribute and adding the
> appropriate declaration to headers.
> 
> If this check will be considered useful, I will resend the patch with
> review fixes.
> 
> Currently, this check emits the warnings on the following symbols, most
> of which are accepted to be fixed:
> 1. "sas_wait_eh" [drivers/scsi/libsas/libsas]
>    Patch: https://lkml.org/lkml/2019/7/8/970 (accepted)
> 2. "torture_onoff_cleanup" [kernel/torture]
>    "torture_shuffle_cleanup" [kernel/torture]
>    Patch: https://lkml.org/lkml/2019/7/4/411 (accepted)
> 3. "LZ4HC_setExternalDict" [lib/lz4/lz4hc_compress]
>    Patch: https://lkml.org/lkml/2019/7/8/842
> 4. "drm_client_close" [drivers/gpu/drm/drm]
>    Patch: https://lkml.org/lkml/2019/7/3/758 (accepted)
> 5. "gve_probe" [drivers/net/ethernet/google/gve/gve]
>    Patch: https://lkml.org/lkml/2019/7/14/65
> 6. "i2c_new_client_device" [vmlinux]
>    "i2c_new_dummy_device" [vmlinux]
>    Patch: https://lkml.org/lkml/2019/7/7/226 (fixed in a different patch)
> 7. "ahci_em_messages" [drivers/ata/libahci]
>    Patch: https://lkml.org/lkml/2019/7/10/550 (reviwed)
> 8. "ftrace_set_clr_event" [vmlinux]
>    Patch: https://lkml.org/lkml/2019/7/4/609 (reviwed)
> 9. "rmi_2d_sensor_set_input_params" [drivers/input/rmi4/rmi_core]
>    Patch: https://lkml.org/lkml/2019/7/8/999
> 10. "empty_zero_page" [vmlinux]
> 11. "phys_base" [vmlinux]
> 12. "hypercall_page" [vmlinux]
> 
> Similar commits:
> 1. 54638c6eaf44 ("net: phy: make exported variables non-static")
> 2. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> 3. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> 4. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> 5. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> 
> Build time impact, allmodconfig, Dell XPS 15 9570 (measurements 3x):
> $ make mrproper; make allmodconfig; time make -j12; \
>   git checkout HEAD~1; \
>   make mrproper; make allmodconfig; time make -j12
> 1.
>    (with patch) 17635,94s user 1895,54s system 1085% cpu 29:59,22 total
>    (w/o  patch) 17275,42s user 1803,87s system 1112% cpu 28:35,66 total
> 2.
>    (with patch) 17369,51s user 1763,28s system 1111% cpu 28:41,47 total
>    (w/o  patch) 16880,50s user 1670,93s system 1113% cpu 27:46,56 total
> 3.
>    (with patch) 17937,88s user 1842,53s system 1109% cpu 29:42,26 total
>    (w/o  patch) 17267,55s user 1725,09s system 1111% cpu 28:28,17 total
> 
> Thus, the current implementation adds approx. 1 min for allmodconfig.
> However, it's possible to do the check in a more optimal way if it will
> be considered useful.
> 
> Also, this kind of check could be implemented as a separate script instead.
> Here is the implementation:
> https://gist.github.com/evdenis/bf2322d094f0c02c0f60fe0a225848b2
> 

Personally I think this is a pretty good feature.

If I did my numbers correctly, the above numbers show ~2% increase.
Although one should be able to reduce that if people feel too strongly.

That said, the patch is:
Acked-by: Emil Velikov <emil.l.velikov@gmail.com>

Can we make sure that patches for all issues are out (on the respective
mailing lists, or merged) before this lands.

HTH
Emil