path: root/kernel
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authorLinus Torvalds <>2019-09-22 10:34:46 -0700
committerLinus Torvalds <>2019-09-22 10:34:46 -0700
commite0703556644a531e50b5dc61b9f6ea83af5f6604 (patch)
treea0aa73809630d716f25b124cd2aa99a1f4743a55 /kernel
parent8808cf8cbc4da1ceef9307fba7e499563908c211 (diff)
parent2e6fcfeb9df6048a63fe0d5f7dfa39274bacbb71 (diff)
Merge tag 'modules-for-v5.4' of git://
Pull modules updates from Jessica Yu: "The main bulk of this pull request introduces a new exported symbol namespaces feature. The number of exported symbols is increasingly growing with each release (we're at about 31k exports as of 5.3-rc7) and we currently have no way of visualizing how these symbols are "clustered" or making sense of this huge export surface. Namespacing exported symbols allows kernel developers to more explicitly partition and categorize exported symbols, as well as more easily limiting the availability of namespaced symbols to other parts of the kernel. For starters, we have introduced the USB_STORAGE namespace to demonstrate the API's usage. I have briefly summarized the feature and its main motivations in the tag below. Summary: - Introduce exported symbol namespaces. This new feature allows subsystem maintainers to partition and categorize their exported symbols into explicit namespaces. Module authors are now required to import the namespaces they need. Some of the main motivations of this feature include: allowing kernel developers to better manage the export surface, allow subsystem maintainers to explicitly state that usage of some exported symbols should only be limited to certain users (think: inter-module or inter-driver symbols, debugging symbols, etc), as well as more easily limiting the availability of namespaced symbols to other parts of the kernel. With the module import requirement, it is also easier to spot the misuse of exported symbols during patch review. Two new macros are introduced: EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL(). The API is thoroughly documented in Documentation/kbuild/namespaces.rst. - Some small code and kbuild cleanups here and there" * tag 'modules-for-v5.4' of git:// module: Remove leftover '#undef' from export header module: remove unneeded casts in cmp_name() module: move CONFIG_UNUSED_SYMBOLS to the sub-menu of MODULES module: remove redundant 'depends on MODULES' module: Fix link failure due to invalid relocation on namespace offset usb-storage: export symbols in USB_STORAGE namespace usb-storage: remove single-use define for debugging docs: Add documentation for Symbol Namespaces scripts: Coccinelle script for namespace dependencies. modpost: add support for generating namespace dependencies export: allow definition default namespaces in Makefiles or sources module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS modpost: add support for symbol namespaces module: add support for symbol namespaces. export: explicitly align struct kernel_symbol module: support reading multiple values per modinfo tag
Diffstat (limited to 'kernel')
1 files changed, 69 insertions, 7 deletions
diff --git a/kernel/module.c b/kernel/module.c
index 9ee93421269c..32873bcce738 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -544,12 +544,20 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
-static int cmp_name(const void *va, const void *vb)
+static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
- const char *a;
- const struct kernel_symbol *b;
- a = va; b = vb;
- return strcmp(a, kernel_symbol_name(b));
+ if (!sym->namespace_offset)
+ return NULL;
+ return offset_to_ptr(&sym->namespace_offset);
+ return sym->namespace;
+static int cmp_name(const void *name, const void *sym)
+ return strcmp(name, kernel_symbol_name(sym));
static bool find_exported_symbol_in_section(const struct symsearch *syms,
@@ -1379,6 +1387,41 @@ static inline int same_magic(const char *amagic, const char *bmagic,
+static char *get_modinfo(const struct load_info *info, const char *tag);
+static char *get_next_modinfo(const struct load_info *info, const char *tag,
+ char *prev);
+static int verify_namespace_is_imported(const struct load_info *info,
+ const struct kernel_symbol *sym,
+ struct module *mod)
+ const char *namespace;
+ char *imported_namespace;
+ namespace = kernel_symbol_namespace(sym);
+ if (namespace) {
+ imported_namespace = get_modinfo(info, "import_ns");
+ while (imported_namespace) {
+ if (strcmp(namespace, imported_namespace) == 0)
+ return 0;
+ imported_namespace = get_next_modinfo(
+ info, "import_ns", imported_namespace);
+ }
+ pr_warn(
+ pr_err(
+ "%s: module uses symbol (%s) from namespace %s, but does not import it.\n",
+ mod->name, kernel_symbol_name(sym), namespace);
+ return -EINVAL;
+ }
+ return 0;
/* Resolve a symbol for this module. I.e. if we find one, record usage. */
static const struct kernel_symbol *resolve_symbol(struct module *mod,
const struct load_info *info,
@@ -1407,6 +1450,12 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
goto getname;
+ err = verify_namespace_is_imported(info, sym, mod);
+ if (err) {
+ sym = ERR_PTR(err);
+ goto getname;
+ }
err = ref_module(mod, owner);
if (err) {
sym = ERR_PTR(err);
@@ -2481,7 +2530,8 @@ static char *next_string(char *string, unsigned long *secsize)
return string;
-static char *get_modinfo(struct load_info *info, const char *tag)
+static char *get_next_modinfo(const struct load_info *info, const char *tag,
+ char *prev)
char *p;
unsigned int taglen = strlen(tag);
@@ -2492,13 +2542,25 @@ static char *get_modinfo(struct load_info *info, const char *tag)
* get_modinfo() calls made before rewrite_section_headers()
* must use sh_offset, as sh_addr isn't set!
- for (p = (char *)info->hdr + infosec->sh_offset; p; p = next_string(p, &size)) {
+ char *modinfo = (char *)info->hdr + infosec->sh_offset;
+ if (prev) {
+ size -= prev - modinfo;
+ modinfo = next_string(prev, &size);
+ }
+ for (p = modinfo; p; p = next_string(p, &size)) {
if (strncmp(p, tag, taglen) == 0 && p[taglen] == '=')
return p + taglen + 1;
return NULL;
+static char *get_modinfo(const struct load_info *info, const char *tag)
+ return get_next_modinfo(info, tag, NULL);
static void setup_modinfo(struct module *mod, struct load_info *info)
struct module_attribute *attr;