linux-kernel - Re: [PATCH -v2 4/7] module: Add module specific symbol namespace support

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Message-ID: <CAK7LNAR=ggfxVoQ=06PE4wkpyRCTvhpkkOSiRKx9eR2UezZK4Q@mail.gmail.com>
Date: Sat, 8 Feb 2025 01:22:15 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mcgrof@...nel.org, x86@...nel.org, hpa@...or.com, petr.pavlu@...e.com, 
	samitolvanen@...gle.com, da.gomez@...sung.com, nathan@...nel.org, 
	nicolas@...sle.eu, linux-kernel@...r.kernel.org, 
	linux-modules@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	hch@...radead.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH -v2 4/7] module: Add module specific symbol namespace support

On Tue, Dec 3, 2024 at 12:11 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Designate the "MODULE_${modname}" symbol namespace to mean: 'only
> export to the named module'.
>
> Notably, explicit imports of anything in the "MODULE_" space is
> forbidden. Modules implicitly get the "MODULE_${modname}" namespace
> added.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/module/main.c  |   28 ++++++++++++++++++++++++++--
>  scripts/mod/modpost.c |    5 +++++
>  2 files changed, 31 insertions(+), 2 deletions(-)
>
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -1070,6 +1070,13 @@ static int verify_namespace_is_imported(
>
>         namespace = kernel_symbol_namespace(sym);
>         if (namespace && namespace[0]) {
> +               /*
> +                * Implicitly import MODULE_${mod->name} namespace.
> +                */
> +               if (strncmp(namespace, "MODULE_", 7) == 0 &&

strncmp() -> strstarts()

> +                   strcmp(namespace+7, mod->name) == 0)
> +                       return 0;
> +


You can add verify_module_namespace() in this commit
with a simple implementation.

static bool verify_module_namespace(const char *namespace, const char *modname)
{
        const char *prefix = "module:";

        return strstarts(namespace, prefix) &&
                  !strcmp(namespace + strlen(prefix), modname);
}


Then, you can extend it in the next commit,
to support the glob pattern in verify_module_namespace()






> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1565,6 +1565,7 @@ static const char *mod_basename(const ch
>
>  static void read_symbols(const char *modname)
>  {
> +       char module_namespace[MODULE_NAME_LEN + 8];
>         const char *symname;
>         char *version;
>         char *license;
> @@ -1600,6 +1601,10 @@ static void read_symbols(const char *mod
>                      namespace = get_next_modinfo(&info, "import_ns", namespace))
>                         add_namespace(&mod->imported_namespaces, namespace);
>
> +               snprintf(module_namespace, sizeof(module_namespace), "MODULE_%s",
> +                        mod_basename(mod->name));
> +               add_namespace(&mod->imported_namespaces, module_namespace);
> +
>                 if (extra_warn && !get_modinfo(&info, "description"))
>                         warn("missing MODULE_DESCRIPTION() in %s\n", modname);
>         }


This is a noise change, as you immediately remove this code in the next commit.

So, I recommend adding verify_module_namespace() in this commit.
Then, you can extend it in the next commit for glob pattern support.







index d4abcd8ee2ed..58fbcb6bb718 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1674,6 +1674,14 @@ void buf_write(struct buffer *buf, const char
*s, int len)
        buf->pos += len;
 }

+static bool verify_module_namespace(const char *namespace, const char *modname)
+{
+       const char *prefix = "module:";
+
+       return strstarts(namespace, prefix) &&
+               !strcmp(namespace + strlen(prefix), modname);
+}
+
 static void check_exports(struct module *mod)
 {
        struct symbol *s, *exp;
@@ -1701,7 +1709,8 @@ static void check_exports(struct module *mod)

                basename = mod_basename(mod->name);

-               if (!contains_namespace(&mod->imported_namespaces,
exp->namespace)) {
+               if (!verify_module_namespace(exp->namespace, mod->name) &&
+                   !contains_namespace(&mod->imported_namespaces,
exp->namespace)) {
                        modpost_log(!allow_missing_ns_imports,
                                    "module %s uses symbol %s from
namespace %s, but does not import it.\n",
                                    basename, exp->name, exp->namespace);








--
Best Regards
Masahiro Yamada