[PATCH 1/2] module: expose imported namespaces via sysfs

[Nicholas Sielicki <linux@opensource.nslick.com>]

Currently, the only way for userspace to determine which symbol
namespaces a module imports is to locate the .ko file on disk (which may
not match the loaded module), then either parsing the binary manually
and handling any potential compression, or shelling-out to modinfo.

This is painful in cases where userspace wants to distinguish between
module variants that share the same name but import different
namespaces. For example, the nvidia-uvm module exists in both open and
closed source variants; the open source version imports the DMA_BUF
namespace while the closed source version does not, and networking
middleware may want to initialize itself differently depending on that.

Add /sys/module/*/import_ns to expose imported namespaces for loaded
modules. The file contains one namespace per line and only exists for
modules that import at least one namespace.

Signed-off-by: Nicholas Sielicki <linux@opensource.nslick.com>
---
 Documentation/ABI/testing/sysfs-module |  9 ++++
 include/linux/module.h                 |  1 +
 kernel/module/main.c                   | 62 +++++++++++++++++++++++++-
 3 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module
index 6bc9af6229f0..d8e2a33fd514 100644
--- a/Documentation/ABI/testing/sysfs-module
+++ b/Documentation/ABI/testing/sysfs-module
@@ -48,6 +48,15 @@ Contact:	Kay Sievers <kay.sievers@vrfy.org>
 Description:	Show the initialization state(live, coming, going) of
 		the module.
 
+What:		/sys/module/*/import_ns
+Date:		January 2026
+KernelVersion:	6.20
+Contact:	linux-modules@vger.kernel.org
+Description:	List of symbol namespaces imported by this module via
+		MODULE_IMPORT_NS(). Each namespace appears on a separate line.
+		This file only exists for modules that import at least one
+		namespace.
+
 What:		/sys/module/*/taint
 Date:		Jan 2012
 KernelVersion:	3.3
diff --git a/include/linux/module.h b/include/linux/module.h
index d80c3ea57472..f1bcca03f90b 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -419,6 +419,7 @@ struct module {
 	struct module_attribute *modinfo_attrs;
 	const char *version;
 	const char *srcversion;
+	const char *imported_namespaces;
 	struct kobject *holders_dir;
 
 	/* Exported symbols */
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 710ee30b3bea..6c41934f1135 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -607,6 +607,23 @@ static const struct module_attribute modinfo_##field = {              \
 MODINFO_ATTR(version);
 MODINFO_ATTR(srcversion);
 
+static ssize_t show_modinfo_import_ns(const struct module_attribute *mattr,
+				      struct module_kobject *mk, char *buffer)
+{
+	return sysfs_emit(buffer, "%s\n", mk->mod->imported_namespaces);
+}
+
+static int modinfo_import_ns_exists(struct module *mod)
+{
+	return mod->imported_namespaces != NULL;
+}
+
+static const struct module_attribute modinfo_import_ns = {
+	.attr = { .name = "import_ns", .mode = 0444 },
+	.show = show_modinfo_import_ns,
+	.test = modinfo_import_ns_exists,
+};
+
 static struct {
 	char name[MODULE_NAME_LEN];
 	char taints[MODULE_FLAGS_BUF_SIZE];
@@ -1058,6 +1075,7 @@ const struct module_attribute *const modinfo_attrs[] = {
 	&module_uevent,
 	&modinfo_version,
 	&modinfo_srcversion,
+	&modinfo_import_ns,
 	&modinfo_initstate,
 	&modinfo_coresize,
 #ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
@@ -1753,11 +1771,48 @@ static void module_license_taint_check(struct module *mod, const char *license)
 	}
 }
 
+static int copy_modinfo_import_ns(struct module *mod, struct load_info *info)
+{
+	char *ns;
+	size_t len, total_len = 0;
+	char *buf, *p;
+
+	for_each_modinfo_entry(ns, info, "import_ns")
+		total_len += strlen(ns) + 1;
+
+	if (!total_len) {
+		mod->imported_namespaces = NULL;
+		return 0;
+	}
+
+	buf = kmalloc(total_len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	p = buf;
+	for_each_modinfo_entry(ns, info, "import_ns") {
+		len = strlen(ns);
+		memcpy(p, ns, len);
+		p += len;
+		*p++ = '\n';
+	}
+	/* Replace trailing newline with null terminator. */
+	*(p - 1) = '\0';
+
+	mod->imported_namespaces = buf;
+	return 0;
+}
+
+static void free_modinfo_import_ns(struct module *mod)
+{
+	kfree(mod->imported_namespaces);
+}
+
 static int setup_modinfo(struct module *mod, struct load_info *info)
 {
 	const struct module_attribute *attr;
 	char *imported_namespace;
-	int i;
+	int i, err;
 
 	for (i = 0; (attr = modinfo_attrs[i]); i++) {
 		if (attr->setup)
@@ -1776,6 +1831,10 @@ static int setup_modinfo(struct module *mod, struct load_info *info)
 		}
 	}
 
+	err = copy_modinfo_import_ns(mod, info);
+	if (err)
+		return err;
+
 	return 0;
 }
 
@@ -1788,6 +1847,7 @@ static void free_modinfo(struct module *mod)
 		if (attr->free)
 			attr->free(mod);
 	}
+	free_modinfo_import_ns(mod);
 }
 
 bool __weak module_init_section(const char *name)
-- 
2.52.0