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

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

[Denis Efremov]

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

Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/mod/modpost.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..c51eef357721 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -169,6 +169,7 @@ struct symbol {
 	unsigned int kernel:1;     /* 1 if symbol is from kernel
 				    *  (only for external modules) **/
 	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
+	unsigned int is_static:1;  /* 1 if symbol is not global */
 	enum export  export;       /* Type of export */
 	char name[0];
 };
@@ -199,8 +200,9 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
 
 	memset(s, 0, sizeof(*s));
 	strcpy(s->name, name);
-	s->weak = weak;
-	s->next = next;
+	s->weak      = weak;
+	s->next      = next;
+	s->is_static = 1;
 	return s;
 }
 
@@ -1980,6 +1982,21 @@ static void read_symbols(const char *modname)
 		handle_modversions(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
 	}
+
+	// check for static EXPORT_SYMBOL_* functions && global vars
+	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+		unsigned char bind = ELF_ST_BIND(sym->st_info);
+		unsigned char type = ELF_ST_TYPE(sym->st_info);
+
+		if (type == STT_OBJECT || type == STT_FUNC) {
+			struct symbol *s =
+			    find_symbol(remove_dot(info.strtab + sym->st_name));
+
+			if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
+				s->is_static = 0;
+		}
+	}
+
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
@@ -2425,6 +2442,7 @@ int main(int argc, char **argv)
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
+	size_t n;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
@@ -2520,6 +2538,19 @@ int main(int argc, char **argv)
 	if (sec_mismatch_count && sec_mismatch_fatal)
 		fatal("modpost: Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
+	for (n = 0; n < SYMBOL_HASH_SIZE ; n++) {
+		struct symbol *s = symbolhash[n];
+
+		while (s) {
+			if (s->is_static)
+				warn("\"%s\" [%s] is a static %s symbol\n",
+					s->name, s->module->name,
+						export_str(s->export));
+
+			s = s->next;
+		}
+	}
+
 	free(buf.p);
 
 	return err;
-- 
2.21.0

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

[Emil Velikov]

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

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

[Masahiro Yamada]

Hi.

Thanks, this patch is very nice.


On Mon, Jul 15, 2019 at 12:28 AM Denis Efremov <efremov@linux.com> 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]

Could you drop the solved ones from the list?

I still see the following at least, but I will apply this patch anyway.

WARNING: "phys_base" [vmlinux] is a static EXPORT_SYMBOL symbol
WARNING: "drm_client_close" [vmlinux] is a static EXPORT_SYMBOL symbol
WARNING: "ahci_em_messages" [vmlinux] is a static EXPORT_SYMBOL_GPL symbol
WARNING: "ftrace_set_clr_event" [vmlinux] is a static EXPORT_SYMBOL_GPL symbol
WARNING: "empty_zero_page" [vmlinux] is a static EXPORT_SYMBOL symbol


The code looks good to me.
I commented on some minor style issues.


> 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
>
> Signed-off-by: Denis Efremov <efremov@linux.com>



> @@ -199,8 +200,9 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
>
>         memset(s, 0, sizeof(*s));
>         strcpy(s->name, name);
> -       s->weak = weak;
> -       s->next = next;
> +       s->weak      = weak;
> +       s->next      = next;

Could you drop this change?
I do not think we need to align the '=' operator.


> +       s->is_static = 1;
>         return s;
>  }
>
> @@ -1980,6 +1982,21 @@ static void read_symbols(const char *modname)
>                 handle_modversions(mod, &info, sym, symname);
>                 handle_moddevtable(mod, &info, sym, symname);
>         }
> +
> +       // check for static EXPORT_SYMBOL_* functions && global vars
> +       for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
> +               unsigned char bind = ELF_ST_BIND(sym->st_info);
> +               unsigned char type = ELF_ST_TYPE(sym->st_info);
> +
> +               if (type == STT_OBJECT || type == STT_FUNC) {
> +                       struct symbol *s =
> +                           find_symbol(remove_dot(info.strtab + sym->st_name));
> +
> +                       if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
> +                               s->is_static = 0;
> +               }
> +       }
> +
>         if (!is_vmlinux(modname) || vmlinux_section_warnings)
>                 check_sec_ref(mod, modname, &info);
>
> @@ -2425,6 +2442,7 @@ int main(int argc, char **argv)
>         char *dump_write = NULL, *files_source = NULL;
>         int opt;
>         int err;
> +       size_t n;
>         struct ext_sym_list *extsym_iter;
>         struct ext_sym_list *extsym_start = NULL;
>
> @@ -2520,6 +2538,19 @@ int main(int argc, char **argv)
>         if (sec_mismatch_count && sec_mismatch_fatal)
>                 fatal("modpost: Section mismatches detected.\n"
>                       "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
> +       for (n = 0; n < SYMBOL_HASH_SIZE ; n++) {
> +               struct symbol *s = symbolhash[n];
> +
> +               while (s) {
> +                       if (s->is_static)
> +                               warn("\"%s\" [%s] is a static %s symbol\n",
> +                                       s->name, s->module->name,
> +                                               export_str(s->export));

Could you follow the checkpatch.pl suggestion?

CHECK: Alignment should match open parenthesis
#2550: FILE: scripts/mod/modpost.c:2550:
    + warn("\"%s\" [%s] is a static %s symbol\n",
    + s->name, s->module->name,


(This file already has tons of checkpatch warnings,
but I want to try my best to not add new ones.)


Thanks.

-- 
Best Regards
Masahiro Yamada

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

[Denis Efremov]

Hi.

> Could you drop the solved ones from the list?

Yes, of course. Do you want me to remove all symbols fixed with patches 
or only those are in-tree now?

Should it be like this:
  1. "torture_onoff_cleanup" [kernel/torture]
     "torture_shuffle_cleanup" [kernel/torture]
     Patch: https://lkml.org/lkml/2019/7/4/411 (accepted)
  2. "LZ4HC_setExternalDict" [lib/lz4/lz4hc_compress]
     Patch: https://lkml.org/lkml/2019/7/8/842
  3. "drm_client_close" [drivers/gpu/drm/drm]
     Patch: https://lkml.org/lkml/2019/7/3/758 (accepted)
  4. "ahci_em_messages" [drivers/ata/libahci]
     Patch: https://lkml.org/lkml/2019/7/10/550 (reviewed)
  5. "ftrace_set_clr_event" [vmlinux]
     Patch: https://lkml.org/lkml/2019/7/4/609 (reviewed)
  6. "rmi_2d_sensor_set_input_params" [drivers/input/rmi4/rmi_core]
     Patch: https://lkml.org/lkml/2019/7/8/999 (accepted)
  10. "empty_zero_page" [vmlinux]
  11. "phys_base" [vmlinux]
  12. "hypercall_page" [vmlinux]

Or like this:
  1. "empty_zero_page" [vmlinux]
  2. "phys_base" [vmlinux]
  3. "hypercall_page" [vmlinux]

Well, I could remove this list at all. It seems like the following list 
with existing commits is enough to show the problem of static exported 
functions.

I will resend the patch shortly after.

Regards,
Denis

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

[Masahiro Yamada]

Hi.

On Sun, Jul 28, 2019 at 4:14 AM Denis Efremov <efremov@linux.com> wrote:
>
> Hi.
>
> > Could you drop the solved ones from the list?
>
> Yes, of course. Do you want me to remove all symbols fixed with patches
> or only those are in-tree now?
>
> Should it be like this:
>   1. "torture_onoff_cleanup" [kernel/torture]
>      "torture_shuffle_cleanup" [kernel/torture]
>      Patch: https://lkml.org/lkml/2019/7/4/411 (accepted)
>   2. "LZ4HC_setExternalDict" [lib/lz4/lz4hc_compress]
>      Patch: https://lkml.org/lkml/2019/7/8/842
>   3. "drm_client_close" [drivers/gpu/drm/drm]
>      Patch: https://lkml.org/lkml/2019/7/3/758 (accepted)
>   4. "ahci_em_messages" [drivers/ata/libahci]
>      Patch: https://lkml.org/lkml/2019/7/10/550 (reviewed)
>   5. "ftrace_set_clr_event" [vmlinux]
>      Patch: https://lkml.org/lkml/2019/7/4/609 (reviewed)
>   6. "rmi_2d_sensor_set_input_params" [drivers/input/rmi4/rmi_core]
>      Patch: https://lkml.org/lkml/2019/7/8/999 (accepted)
>   10. "empty_zero_page" [vmlinux]
>   11. "phys_base" [vmlinux]
>   12. "hypercall_page" [vmlinux]
>
> Or like this:
>   1. "empty_zero_page" [vmlinux]
>   2. "phys_base" [vmlinux]
>   3. "hypercall_page" [vmlinux]
>
> Well, I could remove this list at all. It seems like the following list
> with existing commits is enough to show the problem of static exported
> functions.

Yeah, I agree.
Showing some existing commits is enough.



> I will resend the patch shortly after.
>
> Regards,
> Denis



-- 
Best Regards
Masahiro Yamada

[PATCH] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

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.

This check could help to detect the following problems:
1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
2. 54638c6eaf44 ("net: phy: make exported variables non-static")
3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
9. ...

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.

Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/mod/modpost.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..85e885235c96 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -169,6 +169,7 @@ struct symbol {
 	unsigned int kernel:1;     /* 1 if symbol is from kernel
 				    *  (only for external modules) **/
 	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
+	unsigned int is_static:1;  /* 1 if symbol is not global */
 	enum export  export;       /* Type of export */
 	char name[0];
 };
@@ -201,6 +202,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
 	strcpy(s->name, name);
 	s->weak = weak;
 	s->next = next;
+	s->is_static = 1;
 	return s;
 }
 
@@ -1980,6 +1982,22 @@ static void read_symbols(const char *modname)
 		handle_modversions(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
 	}
+
+	// check for static EXPORT_SYMBOL_* functions && global vars
+	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+		unsigned char bind = ELF_ST_BIND(sym->st_info);
+		unsigned char type = ELF_ST_TYPE(sym->st_info);
+
+		if (type == STT_OBJECT || type == STT_FUNC) {
+			struct symbol *s =
+				find_symbol(remove_dot(info.strtab +
+						       sym->st_name));
+
+			if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
+				s->is_static = 0;
+		}
+	}
+
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
@@ -2425,6 +2443,7 @@ int main(int argc, char **argv)
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
+	size_t n;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
@@ -2520,6 +2539,19 @@ int main(int argc, char **argv)
 	if (sec_mismatch_count && sec_mismatch_fatal)
 		fatal("modpost: Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
+	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
+		struct symbol *s = symbolhash[n];
+
+		while (s) {
+			if (s->is_static)
+				warn("\"%s\" [%s] is the static %s\n",
+				     s->name, s->module->name,
+				     export_str(s->export));
+
+			s = s->next;
+		}
+	}
+
 	free(buf.p);
 
 	return err;
-- 
2.21.0

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

[Masahiro Yamada]

On Sun, Jul 28, 2019 at 7:09 PM Denis Efremov <efremov@linux.com> 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.
>
> This check could help to detect the following problems:
> 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> 9. ...
>
> 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.
>
> Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---
>  scripts/mod/modpost.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
>

>
> @@ -2425,6 +2443,7 @@ int main(int argc, char **argv)
>         char *dump_write = NULL, *files_source = NULL;
>         int opt;
>         int err;
> +       size_t n;

Sorry, I missed to ask this in the previous version.

If there is not a particular reason,
may I ask you to use 'int' instead of 'size_t' here?

SYMBOL_HASH_SIZE (= 1024) is small enough, and
it will keep consistency with
the write_dump() function in this file.

If it is tedious to send a new version,
may I fix-up 'size_t' -> 'int' ?

Thanks.


>         struct ext_sym_list *extsym_iter;
>         struct ext_sym_list *extsym_start = NULL;
>
> @@ -2520,6 +2539,19 @@ int main(int argc, char **argv)
>         if (sec_mismatch_count && sec_mismatch_fatal)
>                 fatal("modpost: Section mismatches detected.\n"
>                       "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
> +       for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
> +               struct symbol *s = symbolhash[n];
> +
> +               while (s) {
> +                       if (s->is_static)
> +                               warn("\"%s\" [%s] is the static %s\n",
> +                                    s->name, s->module->name,
> +                                    export_str(s->export));
> +
> +                       s = s->next;
> +               }
> +       }
> +
>         free(buf.p);
>
>         return err;
> --
> 2.21.0
>


-- 
Best Regards
Masahiro Yamada

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

[Stephen Rothwell]

[-- Attachment #1: Type: text/plain, Size: 340 bytes --]

Hi Denis,

On Sun, 28 Jul 2019 13:09:06 +0300 Denis Efremov <efremov@linux.com> wrote:
>
> Thus, the current implementation adds approx. 1 min for allmodconfig.

Just a reminder that some of us (just me?) do well over 100+ builds per
day ...  if this can be optimised some what that would be good.

-- 
Cheers,
Stephen Rothwell

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

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

[Denis Efremov]

> Just a reminder that some of us (just me?) do well over 100+ builds per
> day ...  if this can be optimised some what that would be good.

These measurements for the worst case (allmodconfig). Is it possible to 
measure the slowdown in your case? How it will perform on your typical 
workflow?

Looks like it is possible to optimize it, but I need some hints from 
Masahiro on how to do it properly. Because I don't know how to match 
__ksymtab_<symbol> with the <symbol> without an additional loop. 
Introduce another hash table?

The first loop from this patch could traverse only the exported symbols 
instead of all symbols. But in this case, I don't know how to break 
early from the loop because there can be many symbols with the same name 
but with the different scope (static/non-static).

For example, ring_buffer_size:
kernel/trace/ring_buffer.c
4334:unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4347:EXPORT_SYMBOL_GPL(ring_buffer_size);
And
drivers/usb/misc/ldusb.c
125:static int ring_buffer_size = 128;

Or for, nfs4_disable_idmapping:
fs/nfs/super.c
2920:bool nfs4_disable_idmapping = true;
2930:EXPORT_SYMBOL_GPL(nfs4_disable_idmapping);
fs/nfsd/nfs4idmap.c
48:static bool nfs4_disable_idmapping = true;

Regards,
Denis

[PATCH v2] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

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.

This check could help to detect the following problems:
1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
2. 54638c6eaf44 ("net: phy: make exported variables non-static")
3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
9. ...

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.

Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/mod/modpost.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..e138d763bcf2 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -169,6 +169,7 @@ struct symbol {
 	unsigned int kernel:1;     /* 1 if symbol is from kernel
 				    *  (only for external modules) **/
 	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
+	unsigned int is_static:1;  /* 1 if symbol is not global */
 	enum export  export;       /* Type of export */
 	char name[0];
 };
@@ -201,6 +202,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
 	strcpy(s->name, name);
 	s->weak = weak;
 	s->next = next;
+	s->is_static = 1;
 	return s;
 }
 
@@ -1980,6 +1982,22 @@ static void read_symbols(const char *modname)
 		handle_modversions(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
 	}
+
+	// check for static EXPORT_SYMBOL_* functions && global vars
+	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+		unsigned char bind = ELF_ST_BIND(sym->st_info);
+		unsigned char type = ELF_ST_TYPE(sym->st_info);
+
+		if (type == STT_OBJECT || type == STT_FUNC) {
+			struct symbol *s =
+				find_symbol(remove_dot(info.strtab +
+						       sym->st_name));
+
+			if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
+				s->is_static = 0;
+		}
+	}
+
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
@@ -2425,6 +2443,7 @@ int main(int argc, char **argv)
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
+	int n;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
@@ -2520,6 +2539,19 @@ int main(int argc, char **argv)
 	if (sec_mismatch_count && sec_mismatch_fatal)
 		fatal("modpost: Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
+	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
+		struct symbol *s = symbolhash[n];
+
+		while (s) {
+			if (s->is_static)
+				warn("\"%s\" [%s] is the static %s\n",
+				     s->name, s->module->name,
+				     export_str(s->export));
+
+			s = s->next;
+		}
+	}
+
 	free(buf.p);
 
 	return err;
-- 
2.21.0

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

[Masahiro Yamada]

On Mon, Jul 29, 2019 at 6:16 PM Denis Efremov <efremov@linux.com> wrote:
>
> > Just a reminder that some of us (just me?) do well over 100+ builds per
> > day ...  if this can be optimised some what that would be good.
>
> These measurements for the worst case (allmodconfig). Is it possible to
> measure the slowdown in your case? How it will perform on your typical
> workflow?
>
> Looks like it is possible to optimize it, but I need some hints from
> Masahiro on how to do it properly. Because I don't know how to match
> __ksymtab_<symbol> with the <symbol> without an additional loop.

Right.
This is not feasible without an additional loop
since we put only exported symbols into the hash table.


Perhaps, we could put every symbol into the hash table
so that we can quickly look-up <symbol> from __ksymtab_<symbol>,
but it would consume lots of memory.

So, I think the implementation is this patch is good enough.


> Introduce another hash table?
>
> The first loop from this patch could traverse only the exported symbols
> instead of all symbols. But in this case, I don't know how to break
> early from the loop because there can be many symbols with the same name
> but with the different scope (static/non-static).
>
> For example, ring_buffer_size:
> kernel/trace/ring_buffer.c
> 4334:unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
> 4347:EXPORT_SYMBOL_GPL(ring_buffer_size);
> And
> drivers/usb/misc/ldusb.c
> 125:static int ring_buffer_size = 128;
>
> Or for, nfs4_disable_idmapping:
> fs/nfs/super.c
> 2920:bool nfs4_disable_idmapping = true;
> 2930:EXPORT_SYMBOL_GPL(nfs4_disable_idmapping);
> fs/nfsd/nfs4idmap.c
> 48:static bool nfs4_disable_idmapping = true;





-- 
Best Regards
Masahiro Yamada

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

[Denis Efremov]

On 29.07.2019 06:29, Masahiro Yamada wrote:
> may I ask you to use 'int' instead of 'size_t' here?

Fixed in v2.

Regards,
Denis

Re: [PATCH v2] modpost: check for static EXPORT_SYMBOL* functions

[Stephen Rothwell]

[-- Attachment #1: Type: text/plain, Size: 288 bytes --]

Hi Denis,

Just a small note (nit? :-)):

On Mon, 29 Jul 2019 12:22:50 +0300 Denis Efremov <efremov@linux.com> wrote:
>
> +			if (s->is_static)
> +				warn("\"%s\" [%s] is the static %s\n",

This read a little wrong to me, maybe "is a static"?

-- 
Cheers,
Stephen Rothwell

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

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

[Stephen Rothwell]

[-- Attachment #1: Type: text/plain, Size: 1021 bytes --]

Hi Denis,

On Mon, 29 Jul 2019 12:16:29 +0300 Denis Efremov <efremov@linux.com> wrote:
>
> > Just a reminder that some of us (just me?) do well over 100+ builds per
> > day ...  if this can be optimised some what that would be good.  
> 
> These measurements for the worst case (allmodconfig). Is it possible to 
> measure the slowdown in your case? How it will perform on your typical 
> workflow?

I did 3 x86_64 allmodconfig builds without and with the patch (I do
-j 80 powerpc64 le hosted cross builds) and it doesn't look like the
patch has much impact at all.

Without the patch:

real	8m41.390s user	587m25.249s sys	22m0.411s
real	8m40.100s user	587m32.148s sys	21m58.419s
real	8m40.084s user	587m25.311s sys	22m2.794s

With the patch:

real	8m40.351s user	587m21.819s sys	21m57.389s
real	8m40.868s user	587m23.730s sys	21m58.737s
real	8m40.970s user	587m22.525s sys	22m2.467s

I do other builds as well, but that is the biggest, so actually looks
ok.
-- 
Cheers,
Stephen Rothwell

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH v2] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

On 7/29/19 3:20 PM, Stephen Rothwell wrote:
> Hi Denis,
> 
> Just a small note (nit? :-)):
> 
> On Mon, 29 Jul 2019 12:22:50 +0300 Denis Efremov <efremov@linux.com> wrote:
>>
>> +			if (s->is_static)
>> +				warn("\"%s\" [%s] is the static %s\n",
> 
> This read a little wrong to me, maybe "is a static"?
> 

Thank you! I will fix this in v3 in an hour.

Denis

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

[Denis Efremov]

On 7/29/19 3:40 PM, Stephen Rothwell wrote:
> Hi Denis,
> 
> On Mon, 29 Jul 2019 12:16:29 +0300 Denis Efremov <efremov@linux.com> wrote:
>>
>>> Just a reminder that some of us (just me?) do well over 100+ builds per
>>> day ...  if this can be optimised some what that would be good.  
>>
>> These measurements for the worst case (allmodconfig). Is it possible to 
>> measure the slowdown in your case? How it will perform on your typical 
>> workflow?
> 
> I did 3 x86_64 allmodconfig builds without and with the patch (I do
> -j 80 powerpc64 le hosted cross builds) and it doesn't look like the
> patch has much impact at all.
> 
> Without the patch:
> 
> real	8m41.390s user	587m25.249s sys	22m0.411s
> real	8m40.100s user	587m32.148s sys	21m58.419s
> real	8m40.084s user	587m25.311s sys	22m2.794s
> 
> With the patch:
> 
> real	8m40.351s user	587m21.819s sys	21m57.389s
> real	8m40.868s user	587m23.730s sys	21m58.737s
> real	8m40.970s user	587m22.525s sys	22m2.467s
> 
> I do other builds as well, but that is the biggest, so actually looks
> ok.
> 

Is it worth to include your measurements instead of mine in the commit
description? Maybe the note about performance downgrade could be omitted
at all in this case?

Denis

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

[Stephen Rothwell]

[-- Attachment #1: Type: text/plain, Size: 426 bytes --]

Hi Denis,

On Mon, 29 Jul 2019 15:52:15 +0300 Denis Efremov <efremov@linux.com> wrote:
>
> Is it worth to include your measurements instead of mine in the commit
> description? Maybe the note about performance downgrade could be omitted
> at all in this case?

Just leave your measurements (they are yours after all), but maybe say
"less than a minute" rather than "approx. 1 min".

-- 
Cheers,
Stephen Rothwell

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

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.

This check could help to detect the following problems:
1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
2. 54638c6eaf44 ("net: phy: make exported variables non-static")
3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
9. ...

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

The check adds less than a minute to a usual build.

Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/mod/modpost.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..332898d34e47 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -169,6 +169,7 @@ struct symbol {
 	unsigned int kernel:1;     /* 1 if symbol is from kernel
 				    *  (only for external modules) **/
 	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
+	unsigned int is_static:1;  /* 1 if symbol is not global */
 	enum export  export;       /* Type of export */
 	char name[0];
 };
@@ -201,6 +202,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
 	strcpy(s->name, name);
 	s->weak = weak;
 	s->next = next;
+	s->is_static = 1;
 	return s;
 }
 
@@ -1980,6 +1982,22 @@ static void read_symbols(const char *modname)
 		handle_modversions(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
 	}
+
+	// check for static EXPORT_SYMBOL_* functions && global vars
+	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+		unsigned char bind = ELF_ST_BIND(sym->st_info);
+		unsigned char type = ELF_ST_TYPE(sym->st_info);
+
+		if (type == STT_OBJECT || type == STT_FUNC) {
+			struct symbol *s =
+				find_symbol(remove_dot(info.strtab +
+						       sym->st_name));
+
+			if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
+				s->is_static = 0;
+		}
+	}
+
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
@@ -2425,6 +2443,7 @@ int main(int argc, char **argv)
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
+	int n;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
@@ -2520,6 +2539,19 @@ int main(int argc, char **argv)
 	if (sec_mismatch_count && sec_mismatch_fatal)
 		fatal("modpost: Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
+	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
+		struct symbol *s = symbolhash[n];
+
+		while (s) {
+			if (s->is_static)
+				warn("\"%s\" [%s] is a static %s\n",
+				     s->name, s->module->name,
+				     export_str(s->export));
+
+			s = s->next;
+		}
+	}
+
 	free(buf.p);
 
 	return err;
-- 
2.21.0

Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

[Stephen Rothwell]

[-- Attachment #1: Type: text/plain, Size: 1103 bytes --]

Hi Denis,

On Mon, 29 Jul 2019 17:18:01 +0300 Denis Efremov <efremov@linux.com> 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.

OK, this is now in linux-next and I am getting what look like false
positives :-(

My powerpc builds produce these:

WARNING: "ahci_em_messages" [vmlinux] is the static EXPORT_SYMBOL_GPL
WARNING: "ftrace_set_clr_event" [vmlinux] is the static EXPORT_SYMBOL_GPL
WARNING: "empty_zero_page" [vmlinux] is the static EXPORT_SYMBOL
WARNING: "jiffies" [vmlinux] is the static EXPORT_SYMBOL

empty_zero_page (at least) is not static.  It is defined in assembler ...

jiffies is defined in arch/powerpc/kernel/vmlinux.lds.S as an alias for
(part of) jiffies_64 which is not static (defined in kernel/time/timer.c).

The other 2 were OK.
-- 
Cheers,
Stephen Rothwell

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

On 30.07.2019 01:26, Stephen Rothwell wrote:
> Hi Denis,
> 
> On Mon, 29 Jul 2019 17:18:01 +0300 Denis Efremov <efremov@linux.com> 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.
> 
> OK, this is now in linux-next and I am getting what look like false
> positives :-(
> 
> My powerpc builds produce these:
> 
> WARNING: "ahci_em_messages" [vmlinux] is the static EXPORT_SYMBOL_GPL
> WARNING: "ftrace_set_clr_event" [vmlinux] is the static EXPORT_SYMBOL_GPL
> WARNING: "empty_zero_page" [vmlinux] is the static EXPORT_SYMBOL
> WARNING: "jiffies" [vmlinux] is the static EXPORT_SYMBOL
> 
> empty_zero_page (at least) is not static.  It is defined in assembler ...

This could be fixed either by adding the type, for example:
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -478,6 +478,7 @@ EXPORT_SYMBOL(phys_base)

         __PAGE_ALIGNED_BSS
  NEXT_PAGE(empty_zero_page)
+.type empty_zero_page, STT_OBJECT
         .skip PAGE_SIZE
  EXPORT_SYMBOL(empty_zero_page)

Or by updating the check in the patch:
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1988,7 +1988,9 @@ static void read_symbols(const char *modname)
                 unsigned char bind = ELF_ST_BIND(sym->st_info);
                 unsigned char type = ELF_ST_TYPE(sym->st_info);

-               if (type == STT_OBJECT || type == STT_FUNC) {
+               if (type == STT_OBJECT ||
+                   type == STT_FUNC ||
+                   type == STT_NOTYPE) {

Do I need to resend the whole patch or create new "patch-on-patch"?

Denis

Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

[Masahiro Yamada]

On Tue, Jul 30, 2019 at 4:00 PM Denis Efremov <efremov@linux.com> wrote:
>
> On 30.07.2019 01:26, Stephen Rothwell wrote:
> > Hi Denis,
> >
> > On Mon, 29 Jul 2019 17:18:01 +0300 Denis Efremov <efremov@linux.com> 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.
> >
> > OK, this is now in linux-next and I am getting what look like false
> > positives :-(
> >
> > My powerpc builds produce these:
> >
> > WARNING: "ahci_em_messages" [vmlinux] is the static EXPORT_SYMBOL_GPL
> > WARNING: "ftrace_set_clr_event" [vmlinux] is the static EXPORT_SYMBOL_GPL
> > WARNING: "empty_zero_page" [vmlinux] is the static EXPORT_SYMBOL
> > WARNING: "jiffies" [vmlinux] is the static EXPORT_SYMBOL
> >
> > empty_zero_page (at least) is not static.  It is defined in assembler ...
>
> This could be fixed either by adding the type, for example:
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -478,6 +478,7 @@ EXPORT_SYMBOL(phys_base)
>
>          __PAGE_ALIGNED_BSS
>   NEXT_PAGE(empty_zero_page)
> +.type empty_zero_page, STT_OBJECT
>          .skip PAGE_SIZE
>   EXPORT_SYMBOL(empty_zero_page)

This would require us to fix-up
all assembly files, wouldn't it?


> Or by updating the check in the patch:
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1988,7 +1988,9 @@ static void read_symbols(const char *modname)
>                  unsigned char bind = ELF_ST_BIND(sym->st_info);
>                  unsigned char type = ELF_ST_TYPE(sym->st_info);
>
> -               if (type == STT_OBJECT || type == STT_FUNC) {
> +               if (type == STT_OBJECT ||
> +                   type == STT_FUNC ||
> +                   type == STT_NOTYPE) {
>
> Do I need to resend the whole patch or create new "patch-on-patch"?

I prefer this, but why do you need to check type?

Doesn't this work?

for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
        unsigned char bind = ELF_ST_BIND(sym->st_info);

        struct symbol *s = find_symbol(remove_dot(info.strtab +
                                                  sym->st_name));

        if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
                s->is_static = 0;
}




-- 
Best Regards
Masahiro Yamada

Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

On 30.07.2019 19:29, Masahiro Yamada wrote:
> I prefer this, but why do you need to check type?
> 
> Doesn't this work?
> 
> for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
>          unsigned char bind = ELF_ST_BIND(sym->st_info);
> 
>          struct symbol *s = find_symbol(remove_dot(info.strtab +
>                                                    sym->st_name));
> 
>          if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
>                  s->is_static = 0;
> }

This works. However, I thought it will be too costly to call find_symbol 
on each symbol. Hence, 'type == STT_OBJECT || type == STT_FUNC || type 
== STT_NOTYPE' is a small performance optimization because we need to 
check only variables and functions. Is it worth to remove it in v4?

Denis

Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

[Masahiro Yamada]

On Wed, Jul 31, 2019 at 1:44 AM Denis Efremov <efremov@linux.com> wrote:
>
> On 30.07.2019 19:29, Masahiro Yamada wrote:
> > I prefer this, but why do you need to check type?
> >
> > Doesn't this work?
> >
> > for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
> >          unsigned char bind = ELF_ST_BIND(sym->st_info);
> >
> >          struct symbol *s = find_symbol(remove_dot(info.strtab +
> >                                                    sym->st_name));
> >
> >          if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
> >                  s->is_static = 0;
> > }
>
> This works. However, I thought it will be too costly to call find_symbol
> on each symbol. Hence, 'type == STT_OBJECT || type == STT_FUNC || type
> == STT_NOTYPE' is a small performance optimization because we need to
> check only variables and functions. Is it worth to remove it in v4?
>
> Denis


I checked the symbol table for ppc64_defconfig.

The following is the number of entries
for each combination of type and bind.

[1]  type: STT_NOTYPE,  bind: STB_LOCAL   -> 39502 entries
[2]  type: STT_NOTYPE,  bind: STB_GLOBAL  -> 30161 entries
[3]  type: STT_NOTYPE,  bind: STB_WEAK    -> 5 entries
[4]  type: STT_OBJECT,  bind: STB_LOCAL   -> 60326 entries
[5]  type: STT_OBJECT,  bind: STB_GLOBAL  -> 4126 entries
[6]  type: STT_OBJECT,  bind: STB_WEAK    -> 11 entries
[7]  type: STT_FUNC,    bind: STB_LOCAL   -> 38816 entries
[8]  type: STT_FUNC,    bind: STB_GLOBAL  -> 56196 entries
[9]  type: STT_FUNC,    bind: STB_WEAK    -> 350 entries
[10] type: STT_SECTION, bind: STB_LOCAL   -> 9027 entries
[11] type: STT_FILE,    bind: STB_LOCAL   -> 2918 entries

Checking 'type' beforehand
saves only 11945 look-ups ( [10] + [11]).

You can check 'bind' before the look-up, not after.
If bind == STB_LOCAL, you do not need to lookup the hash-table,
since you do not do anything.
This saves [1], [4], [7], [10], [11].


I think the following is simpler, and works more efficiently.

for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
        unsigned char bind = ELF_ST_BIND(sym->st_info);

        if (bind == STB_GLOBAL || bind == STB_WEAK) {
                  struct symbol *s =
                               find_symbol(remove_dot(info.strtab +
                                                      sym->st_name));

                  if (s)
                            s->is_static = 0;
         }
}



-- 
Best Regards
Masahiro Yamada

[PATCH v4] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

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.

This check could help to detect the following problems:
1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
2. 54638c6eaf44 ("net: phy: make exported variables non-static")
3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
9. ...

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

The check adds less than a minute to a usual build.

Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/mod/modpost.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..3e6d36ddfcdf 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -169,6 +169,7 @@ struct symbol {
 	unsigned int kernel:1;     /* 1 if symbol is from kernel
 				    *  (only for external modules) **/
 	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
+	unsigned int is_static:1;  /* 1 if symbol is not global */
 	enum export  export;       /* Type of export */
 	char name[0];
 };
@@ -201,6 +202,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
 	strcpy(s->name, name);
 	s->weak = weak;
 	s->next = next;
+	s->is_static = 1;
 	return s;
 }
 
@@ -1980,6 +1982,21 @@ static void read_symbols(const char *modname)
 		handle_modversions(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
 	}
+
+	// check for static EXPORT_SYMBOL_* functions && global vars
+	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+		unsigned char bind = ELF_ST_BIND(sym->st_info);
+
+		if (bind == STB_GLOBAL || bind == STB_WEAK) {
+			struct symbol *s =
+				find_symbol(remove_dot(info.strtab +
+						       sym->st_name));
+
+			if (s)
+				s->is_static = 0;
+		}
+	}
+
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
@@ -2425,6 +2442,7 @@ int main(int argc, char **argv)
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
+	int n;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
@@ -2520,6 +2538,19 @@ int main(int argc, char **argv)
 	if (sec_mismatch_count && sec_mismatch_fatal)
 		fatal("modpost: Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
+	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
+		struct symbol *s = symbolhash[n];
+
+		while (s) {
+			if (s->is_static)
+				warn("\"%s\" [%s] is a static %s\n",
+				     s->name, s->module->name,
+				     export_str(s->export));
+
+			s = s->next;
+		}
+	}
+
 	free(buf.p);
 
 	return err;
-- 
2.21.0

Re: [PATCH v4] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

Changes in v1:
1. Fixed indentations.
2. Removed lkml links from the description of the commit.
Changes in v2:
1. Changed the 'n' variable type in the main function from size_t to
    int.
Changes in v3:
1. Changed warning message from "%s is the static EXPORT_*" to
    "%s a static ..."
2. Improved the commit description from "approx. 1 min" to
    "less than a minute". Thanks Stephen Rothwell for additional
    measurements.
Changes in v4:
1. Dropped ELF_ST_TYPE check. This fixes false-positives detected by
    Stephen Rothwell.
2. Moved ELF_ST_BIND check before the call to find_symbol. Thanks
    Masahiro Yamada for suggesting it.

Denis

On 30.07.2019 21:11, 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.
> 
> This check could help to detect the following problems:
> 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> 9. ...
> 
> 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
> 
> The check adds less than a minute to a usual build.
> 
> Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---
>   scripts/mod/modpost.c | 31 +++++++++++++++++++++++++++++++
>   1 file changed, 31 insertions(+)
> 
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index f277e116e0eb..3e6d36ddfcdf 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -169,6 +169,7 @@ struct symbol {
>   	unsigned int kernel:1;     /* 1 if symbol is from kernel
>   				    *  (only for external modules) **/
>   	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
> +	unsigned int is_static:1;  /* 1 if symbol is not global */
>   	enum export  export;       /* Type of export */
>   	char name[0];
>   };
> @@ -201,6 +202,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
>   	strcpy(s->name, name);
>   	s->weak = weak;
>   	s->next = next;
> +	s->is_static = 1;
>   	return s;
>   }
>   
> @@ -1980,6 +1982,21 @@ static void read_symbols(const char *modname)
>   		handle_modversions(mod, &info, sym, symname);
>   		handle_moddevtable(mod, &info, sym, symname);
>   	}
> +
> +	// check for static EXPORT_SYMBOL_* functions && global vars
> +	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
> +		unsigned char bind = ELF_ST_BIND(sym->st_info);
> +
> +		if (bind == STB_GLOBAL || bind == STB_WEAK) {
> +			struct symbol *s =
> +				find_symbol(remove_dot(info.strtab +
> +						       sym->st_name));
> +
> +			if (s)
> +				s->is_static = 0;
> +		}
> +	}
> +
>   	if (!is_vmlinux(modname) || vmlinux_section_warnings)
>   		check_sec_ref(mod, modname, &info);
>   
> @@ -2425,6 +2442,7 @@ int main(int argc, char **argv)
>   	char *dump_write = NULL, *files_source = NULL;
>   	int opt;
>   	int err;
> +	int n;
>   	struct ext_sym_list *extsym_iter;
>   	struct ext_sym_list *extsym_start = NULL;
>   
> @@ -2520,6 +2538,19 @@ int main(int argc, char **argv)
>   	if (sec_mismatch_count && sec_mismatch_fatal)
>   		fatal("modpost: Section mismatches detected.\n"
>   		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
> +	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
> +		struct symbol *s = symbolhash[n];
> +
> +		while (s) {
> +			if (s->is_static)
> +				warn("\"%s\" [%s] is a static %s\n",
> +				     s->name, s->module->name,
> +				     export_str(s->export));
> +
> +			s = s->next;
> +		}
> +	}
> +
>   	free(buf.p);
>   
>   	return err;
> 

Re: [PATCH v4] modpost: check for static EXPORT_SYMBOL* functions

[Masahiro Yamada]

Hi.



On Wed, Jul 31, 2019 at 3:12 AM Denis Efremov <efremov@linux.com> 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.
>
> This check could help to detect the following problems:
> 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> 9. ...
>
> 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
>
> The check adds less than a minute to a usual build.


I am not convinced with this analysis.

Since commit  b7dca6dd1e591ad19,
scripts/mod/modpost is only invoked from scripts/Makefile.modpost.

So, it is much easier to to measure the elapsed time
of modpost directly.



I applied your patch on top next-20190731,
and the following:


diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 92ed02d7cd5e..e0db1a626e50 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -98,7 +98,7 @@ MODPOST += $(subst -i,-n,$(filter -i,$(MAKEFLAGS)))
-s -T - $(wildcard vmlinux)

 # We can go over command line length here, so be careful.
 quiet_cmd_modpost = MODPOST $(words $(modules)) modules
-      cmd_modpost = sed 's/ko$$/o/' $(modorder) | $(MODPOST)
+      cmd_modpost = sed 's/ko$$/o/' $(modorder) | time -o
modpost-time.txt $(MODPOST)

 PHONY += modules-modpost
 modules-modpost:





The difference is less than 1 sec (not 1 min!) even for allmodconfig.
So, the performance regression is almost unnoticeable level.


-- 
Best Regards
Masahiro Yamada

Re: [PATCH v4] modpost: check for static EXPORT_SYMBOL* functions

[Masahiro Yamada]

On Wed, Jul 31, 2019 at 5:54 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> Hi.
>
>
>
> On Wed, Jul 31, 2019 at 3:12 AM Denis Efremov <efremov@linux.com> 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.
> >
> > This check could help to detect the following problems:
> > 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> > 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> > 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> > 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> > 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> > 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> > 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> > 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> > 9. ...
> >
> > 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
> >
> > The check adds less than a minute to a usual build.

The build time impact is very limited.
I guess this measurement is unnecessary in the commit log.


-- 
Best Regards
Masahiro Yamada

[PATCH v5] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

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.

This check could help to detect the following problems:
1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
2. 54638c6eaf44 ("net: phy: make exported variables non-static")
3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
9. ...

The build time impact is very limited and is almost at the unnoticeable
level (< 1 sec).

Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/mod/modpost.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f277e116e0eb..3e6d36ddfcdf 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -169,6 +169,7 @@ struct symbol {
 	unsigned int kernel:1;     /* 1 if symbol is from kernel
 				    *  (only for external modules) **/
 	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers, or crc */
+	unsigned int is_static:1;  /* 1 if symbol is not global */
 	enum export  export;       /* Type of export */
 	char name[0];
 };
@@ -201,6 +202,7 @@ static struct symbol *alloc_symbol(const char *name, unsigned int weak,
 	strcpy(s->name, name);
 	s->weak = weak;
 	s->next = next;
+	s->is_static = 1;
 	return s;
 }
 
@@ -1980,6 +1982,21 @@ static void read_symbols(const char *modname)
 		handle_modversions(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
 	}
+
+	// check for static EXPORT_SYMBOL_* functions && global vars
+	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
+		unsigned char bind = ELF_ST_BIND(sym->st_info);
+
+		if (bind == STB_GLOBAL || bind == STB_WEAK) {
+			struct symbol *s =
+				find_symbol(remove_dot(info.strtab +
+						       sym->st_name));
+
+			if (s)
+				s->is_static = 0;
+		}
+	}
+
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
@@ -2425,6 +2442,7 @@ int main(int argc, char **argv)
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
+	int n;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
@@ -2520,6 +2538,19 @@ int main(int argc, char **argv)
 	if (sec_mismatch_count && sec_mismatch_fatal)
 		fatal("modpost: Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
+	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
+		struct symbol *s = symbolhash[n];
+
+		while (s) {
+			if (s->is_static)
+				warn("\"%s\" [%s] is a static %s\n",
+				     s->name, s->module->name,
+				     export_str(s->export));
+
+			s = s->next;
+		}
+	}
+
 	free(buf.p);
 
 	return err;
-- 
2.21.0

Re: [PATCH v4] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

On 01.08.2019 05:20, Masahiro Yamada wrote:
> 
> The build time impact is very limited.
> I guess this measurement is unnecessary in the commit log.
> 

Thank you for your observations! It was not easy for me to guess to do
it this way because of my limited knowledge about kbuild && modpost
work. In v5 I've only updated commit log: measurements removed, "The
build time impact is very limited and is almost at the unnoticeable
level (< 1 sec)" added instead. Fell free to edit it if you want.

Denis

Re: [PATCH v5] modpost: check for static EXPORT_SYMBOL* functions

[Masahiro Yamada]

On Thu, Aug 1, 2019 at 3:07 PM Denis Efremov <efremov@linux.com> 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.
>
> This check could help to detect the following problems:
> 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> 9. ...
>
> The build time impact is very limited and is almost at the unnoticeable
> level (< 1 sec).
>
> Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---

Applied to linux-kbuild. Thanks.




-- 
Best Regards
Masahiro Yamada

Re: [PATCH v5] modpost: check for static EXPORT_SYMBOL* functions

[Masahiro Yamada]

Hi Denis,


On Thu, Aug 8, 2019 at 12:12 AM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> On Thu, Aug 1, 2019 at 3:07 PM Denis Efremov <efremov@linux.com> 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.
> >
> > This check could help to detect the following problems:
> > 1. 550113d4e9f5 ("i2c: add newly exported functions to the header, too")
> > 2. 54638c6eaf44 ("net: phy: make exported variables non-static")
> > 3. 98ef2046f28b ("mm: remove the exporting of totalram_pages")
> > 4. 73df167c819e ("s390/zcrypt: remove the exporting of ap_query_configuration")
> > 5. a57caf8c527f ("sunrpc/cache: remove the exporting of cache_seq_next")
> > 6. e4e4730698c9 ("crypto: skcipher - remove the exporting of skcipher_walk_next")
> > 7. 14b4c48bb1ce ("gve: Remove the exporting of gve_probe")
> > 8. 9b79ee9773a8 ("scsi: libsas: remove the exporting of sas_wait_eh")
> > 9. ...
> >
> > The build time impact is very limited and is almost at the unnoticeable
> > level (< 1 sec).
> >
> > Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
> > Signed-off-by: Denis Efremov <efremov@linux.com>
> > ---
>
> Applied to linux-kbuild. Thanks.


I noticed this patch produces false-positive warnings
for external module build.


When I built my external module, it showed the following,
the last five are false positives.

make[1]: Entering directory '/home/masahiro/workspace/linux-kbuild'
  Building modules, stage 2.
  MODPOST 2 modules
WARNING: "drm_client_close" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "ahci_em_messages" [vmlinux] is a static EXPORT_SYMBOL_GPL
WARNING: "ftrace_set_clr_event" [vmlinux] is a static EXPORT_SYMBOL_GPL
WARNING: "nf_log_dump_packet_common" [net/netfilter/nf_log_common] is
a static EXPORT_SYMBOL_GPL
WARNING: "nf_log_l2packet" [net/netfilter/nf_log_common] is a static
EXPORT_SYMBOL_GPL
WARNING: "nf_log_dump_sk_uid_gid" [net/netfilter/nf_log_common] is a
static EXPORT_SYMBOL_GPL
WARNING: "nf_log_dump_udp_header" [net/netfilter/nf_log_common] is a
static EXPORT_SYMBOL_GPL
WARNING: "nf_log_dump_tcp_header" [net/netfilter/nf_log_common] is a
static EXPORT_SYMBOL_GPL
make[1]: Leaving directory '/home/masahiro/workspace/linux-kbuild'


I squashed the following fix-up.


diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3e6d36ddfcdf..2773f9f9bae2 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2386,6 +2386,7 @@ static void read_dump(const char *fname,
unsigned int kernel)
                s = sym_add_exported(symname, mod, export_no(export));
                s->kernel    = kernel;
                s->preloaded = 1;
+               s->is_static = 0;
                sym_update_crc(symname, mod, crc, export_no(export));
        }
        release_file(file, size);


-- 
Best Regards
Masahiro Yamada

Re: [PATCH v5] modpost: check for static EXPORT_SYMBOL* functions

[Denis Efremov]

On 13.08.2019 19:07, Masahiro Yamada wrote:
> Hi Denis,
>
> I squashed the following fix-up.
> 
> 
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 3e6d36ddfcdf..2773f9f9bae2 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -2386,6 +2386,7 @@ static void read_dump(const char *fname,
> unsigned int kernel)
>                 s = sym_add_exported(symname, mod, export_no(export));
>                 s->kernel    = kernel;
>                 s->preloaded = 1;
> +               s->is_static = 0;
>                 sym_update_crc(symname, mod, crc, export_no(export));
>         }
>         release_file(file, size);

Hi!

Thank you very much indeed.

Best regards,
Denis