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

Peter Zijlstra
2024-12-02T15:11:36Z

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 &&
+ strcmp(namespace+7, mod->name) == 0)
+ return 0;
+
for_each_modinfo_entry(imported_namespace, info, "import_ns") {
if (strcmp(namespace, imported_namespace) == 0)
return 0;
@@ -1613,15 +1620,30 @@ static void module_license_taint_check(s
}
}

-static void setup_modinfo(struct module *mod, struct load_info *info)
+static int setup_modinfo(struct module *mod, struct load_info *info)
{
struct module_attribute *attr;
+ char *imported_namespace;
int i;

for (i = 0; (attr = modinfo_attrs[i]); i++) {
if (attr->setup)
attr->setup(mod, get_modinfo(info, attr->attr.name));
}
+
+ for_each_modinfo_entry(imported_namespace, info, "import_ns") {
+ /*
+ * 'MODULE_' prefixed namespaces are implicit, disallow
+ * explicit imports.
+ */
+ if (strstarts(imported_namespace, "MODULE_")) {
+ pr_err("%s: module tries to import module namespace: %s\n",
+ mod->name, imported_namespace);
+ return -EPERM;
+ }
+ }
+
+ return 0;
}

static void free_modinfo(struct module *mod)
@@ -2935,7 +2957,9 @@ static int load_module(struct load_info
goto free_unload;

/* Set up MODINFO_ATTR fields */
- setup_modinfo(mod, info);
+ err = setup_modinfo(mod, info);
+ if (err)
+ goto free_modinfo;

/* Fix up syms, so that st_value is a pointer to location. */
err = simplify_symbols(mod, info);
--- 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);
}