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

Masahiro Yamada
2025-02-07T16:22:54Z

On Tue, Dec 3, 2024 at 12:11 AM Peter Zijlstra <peterz@infradead.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@infradead.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