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authorMatthias Maennich <maennich@google.com>2019-09-06 11:32:27 +0100
committerJessica Yu <jeyu@kernel.org>2019-09-10 10:30:17 +0200
commit8651ec01daedad26290f76beeb4736f9d2da4b87 (patch)
treeaddd8a0c1a51b5000c96218a1b349fde30ff4f29 /kernel/module.c
parented13fc33f763035a7c290f11c7111877c3a5daab (diff)
downloadlinux-8651ec01daedad26290f76beeb4736f9d2da4b87.tar.bz2
module: add support for symbol namespaces.
The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to export a symbol to a specific namespace. There are no _GPL_FUTURE and _UNUSED variants because these are currently unused, and I'm not sure they are necessary. I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the namespace of ASM exports to NULL by default. In case of relative references, it will be relocatable to NULL. If there's a need, this should be pretty easy to add. A module that wants to use a symbol exported to a namespace must add a MODULE_IMPORT_NS() statement to their module code; otherwise, modpost will complain when building the module, and the kernel module loader will emit an error and fail when loading the module. MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That tag can be observed by the modinfo command, modpost and kernel/module.c at the time of loading the module. The ELF symbols are renamed to include the namespace with an asm label; for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes 'usb_stor_suspend.USB_STORAGE'. This allows modpost to do namespace checking, without having to go through all the effort of parsing ELF and relocation records just to get to the struct kernel_symbols. On x86_64 I saw no difference in binary size (compression), but at runtime this will require a word of memory per export to hold the namespace. An alternative could be to store namespaced symbols in their own section and use a separate 'struct namespaced_kernel_symbol' for that section, at the cost of making the module loader more complex. Co-developed-by: Martijn Coenen <maco@android.com> Signed-off-by: Martijn Coenen <maco@android.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Matthias Maennich <maennich@google.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
Diffstat (limited to 'kernel/module.c')
-rw-r--r--kernel/module.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/kernel/module.c b/kernel/module.c
index 3ee507c0a92f..6bb9b938f9c7 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -544,6 +544,15 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
#endif
}
+static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
+{
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+ return offset_to_ptr(&sym->namespace_offset);
+#else
+ return sym->namespace;
+#endif
+}
+
static int cmp_name(const void *va, const void *vb)
{
const char *a;
@@ -1379,6 +1388,34 @@ static inline int same_magic(const char *amagic, const char *bmagic,
}
#endif /* CONFIG_MODVERSIONS */
+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_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 +1444,12 @@ 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);