On Mon, Jun 02, 2025 at 04:45:36PM +0900, Masahiro Yamada wrote:
> On Tue, May 27, 2025 at 6:08 PM Alexey Gladkov <leg...@kernel.org> wrote:
> >
> > In order to avoid symbol conflicts if they appear in the same binary, a
> > more unique alias identifier can be generated.
>
> Why must this be unique?
>
> What problem would happen if the same symbol names
> appear in MODULE_DEVICE_TABLE()?
Before these patches this was not a problem as non-unique characters are
in separate object files when the module is compiled separately.
But when the modules are compiled into the kernel, there is a symbol
conflict when linking vmlinuz. We have modules that export multiple device
tables from different object files.
>
> >
> > Signed-off-by: Alexey Gladkov <leg...@kernel.org>
> > Reviewed-by: Petr Pavlu <petr.pa...@suse.com>
> > ---
> > include/linux/module.h | 14 ++++++++++++--
> > scripts/mod/file2alias.c | 18 ++++++++++++++----
> > 2 files changed, 26 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/module.h b/include/linux/module.h
> > index 88048561360f..e7506684069d 100644
> > --- a/include/linux/module.h
> > +++ b/include/linux/module.h
> > @@ -249,10 +249,20 @@ struct module_kobject
> > *lookup_or_create_module_kobject(const char *name);
> > /* What your module does. */
> > #define MODULE_DESCRIPTION(_description) MODULE_INFO(description,
> > _description)
> >
> > +/* Format: __mod_device_table__<counter>__kmod_<modname>__<type>__<name> */
> > +#define __mod_device_table(type, name) \
> > + __PASTE(__mod_device_table__, \
> > + __PASTE(__COUNTER__, \
> > + __PASTE(__, \
> > + __PASTE(__KBUILD_MODNAME, \
> > + __PASTE(__, \
> > + __PASTE(type, \
> > + __PASTE(__, name)))))))
> > +
> > #ifdef MODULE
> > /* Creates an alias so file2alias.c can find device table. */
> > -#define MODULE_DEVICE_TABLE(type, name)
> > \
> > -extern typeof(name) __mod_device_table__##type##__##name \
> > +#define MODULE_DEVICE_TABLE(type, name) \
> > +extern typeof(name) __mod_device_table(type, name) \
> > __attribute__ ((unused, alias(__stringify(name))))
> > #else /* !MODULE */
> > #define MODULE_DEVICE_TABLE(type, name)
> > diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> > index 00586119a25b..dff1799a4c79 100644
> > --- a/scripts/mod/file2alias.c
> > +++ b/scripts/mod/file2alias.c
> > @@ -1476,8 +1476,8 @@ void handle_moddevtable(struct module *mod, struct
> > elf_info *info,
> > {
> > void *symval;
> > char *zeros = NULL;
> > - const char *type, *name;
> > - size_t typelen;
> > + const char *type, *name, *modname;
> > + size_t typelen, modnamelen;
> > static const char *prefix = "__mod_device_table__";
> >
> > /* We're looking for a section relative symbol */
> > @@ -1488,10 +1488,20 @@ void handle_moddevtable(struct module *mod, struct
> > elf_info *info,
> > if (ELF_ST_TYPE(sym->st_info) != STT_OBJECT)
> > return;
> >
> > - /* All our symbols are of form __mod_device_table__<type>__<name>.
> > */
> > + /* All our symbols are of form
> > __mod_device_table__<counter>__kmod_<modname>__<type>__<name>. */
> > if (!strstarts(symname, prefix))
> > return;
> > - type = symname + strlen(prefix);
> > +
> > + modname = strstr(symname, "__kmod_");
> > + if (!modname)
> > + return;
> > + modname += strlen("__kmod_");
> > +
> > + type = strstr(modname, "__");
> > + if (!type)
> > + return;
> > + modnamelen = type - modname;
> > + type += strlen("__");
> >
> > name = strstr(type, "__");
> > if (!name)
> > --
> > 2.49.0
> >
>
>
> --
> Best Regards
> Masahiro Yamada
>
--
Rgrds, legion
