On Wed, Apr 27, 2022 at 2:08 AM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
>
> On Sun, Apr 24, 2022 at 12:09 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
> >
> > Currently, modpost manages unresolved in a singly liked list; it adds
>
> s/liked/linked/
>
> > a new node to the head, and traverses the list from new to old.
> >
> > Use a doubly linked list to keep the order in the symbol table in the
> > ELF file.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> > ---
> >
> > scripts/mod/modpost.c | 20 ++++++++++++++------
> > scripts/mod/modpost.h | 2 +-
> > 2 files changed, 15 insertions(+), 7 deletions(-)
> >
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index 1c7d2831e89d..e1eb188d6282 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -185,6 +185,8 @@ static struct module *new_module(const char *modname)
> > mod = NOFAIL(malloc(sizeof(*mod) + strlen(modname) + 1));
> > memset(mod, 0, sizeof(*mod));
> >
> > + INIT_LIST_HEAD(&mod->unresolved_symbols);
> > +
> > strcpy(mod->name, modname);
> > mod->is_vmlinux = (strcmp(modname, "vmlinux") == 0);
> > mod->gpl_compatible = true;
> > @@ -201,6 +203,7 @@ static struct module *new_module(const char *modname)
> >
> > struct symbol {
> > struct symbol *next;
> > + struct list_head list;
>
> Isn't `list` meant to replace `next`?
No. 'next' is still used for the hash table.
modpost used it in various ways.
You need to read the code closely if you are interested in
how modpost works.
>
> > struct module *module;
> > unsigned int crc;
> > bool crc_valid;
> > @@ -255,8 +258,12 @@ static struct symbol *new_symbol(const char *name, struct module *module,
> >
> > static void sym_add_unresolved(const char *name, struct module *mod, bool weak)
> > {
> > - mod->unres = alloc_symbol(name, mod->unres);
> > - mod->unres->weak = weak;
> > + struct symbol *sym;
> > +
> > + sym = alloc_symbol(name, NULL);
> > + sym->weak = weak;
> > +
> > + list_add_tail(&sym->list, &mod->unresolved_symbols);
>
> Because I was curious here why NULL was passed, rather than remove the
> assignment to struct symbol's next member in alloc_symbol.
> I get why you replace the `unres` member of struct module. I guess I'm
> curious then why yet another list is added to struct symbol, rather
> than replace the next member.
'next' is used for ad-hoc hash table implementation.
I will be cleaned up by a later commit.
See this patch:
https://patchwork.kernel.org/project/linux-kbuild/patch/20220424190811.1678416-20-masahiroy@xxxxxxxxxx/
>
> Also, does adding a struct list_head member really not specify the
> _type_ of the next element? I guess when I look at the definition of
> struct module, at the member unresolved symbols, I don't know whether
> it's a list of struct module* or a list of struct symbol*.
This is how include/linux/list.h works.
struct list_head is really generic, does not specify a specific type definition.
>
> <snip>
>
> > diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
> > index c3b5d2f0e2bb..6a90bfc08458 100644
> > --- a/scripts/mod/modpost.h
> > +++ b/scripts/mod/modpost.h
> > @@ -117,7 +117,7 @@ struct namespace_list {
> > struct module {
> > struct list_head list;
> > int gpl_compatible;
> > - struct symbol *unres;
> > + struct list_head unresolved_symbols;
> > bool from_dump; /* true if module was loaded from *.symvers */
> > bool is_vmlinux;
> > bool seen;
> > --
> > 2.32.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
--
Best Regards
Masahiro Yamada
