Modules updates for v5.6

Summary of modules changes for the 5.6 merge window:
 
 - Add "MS" (SHF_MERGE|SHF_STRINGS) section flags to __ksymtab_strings to
   indicate to the linker that it can perform string deduplication (i.e.,
   duplicate strings are reduced to a single copy in the string table).
   This means any repeated namespace string would be merged to just one
   entry in __ksymtab_strings.
 
 - Various code cleanups and small fixes (fix small memleak in error path,
   improve moduleparam docs, silence rcu warnings, improve error logging)
 
 Signed-off-by: Jessica Yu <jeyu@kernel.org>
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Merge tag 'modules-for-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux

Pull module updates from Jessica Yu:
 "Summary of modules changes for the 5.6 merge window:

   - Add "MS" (SHF_MERGE|SHF_STRINGS) section flags to __ksymtab_strings
     to indicate to the linker that it can perform string deduplication
     (i.e., duplicate strings are reduced to a single copy in the string
     table). This means any repeated namespace string would be merged to
     just one entry in __ksymtab_strings.

   - Various code cleanups and small fixes (fix small memleak in error
     path, improve moduleparam docs, silence rcu warnings, improve error
     logging)"

* tag 'modules-for-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
  module.h: Annotate mod_kallsyms with __rcu
  module: avoid setting info->name early in case we can fall back to info->mod->name
  modsign: print module name along with error message
  kernel/module: Fix memleak in module_add_modinfo_attrs()
  export.h: reduce __ksymtab_strings string duplication by using "MS" section flags
  moduleparam: fix kerneldoc
  modules: lockdep: Suppress suspicious RCU usage warning

include/asm-generic/export.h

@@ -27,9 +27,11 @@
 .endm
 
 /*
- * note on .section use: @progbits vs %progbits nastiness doesn't matter,
- * since we immediately emit into those sections anyway.
+ * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
+ * section flag requires it. Use '%progbits' instead of '@progbits' since the
+ * former apparently works on all arches according to the binutils source.
  */
+
 .macro ___EXPORT_SYMBOL name,val,sec
 #ifdef CONFIG_MODULES
 	.section ___ksymtab\sec+\name,"a"
@@ -37,7 +39,7 @@
 __ksymtab_\name:
 	__put \val, __kstrtab_\name
 	.previous
-	.section __ksymtab_strings,"a"
+	.section __ksymtab_strings,"aMS",%progbits,1
 __kstrtab_\name:
 	.asciz "\name"
 	.previous

include/linux/export.h

@@ -82,16 +82,29 @@ struct kernel_symbol {
 
 #else
 
-/* For every exported symbol, place a struct in the __ksymtab section */
-#define ___EXPORT_SYMBOL(sym, sec, ns)					\
-	extern typeof(sym) sym;						\
-	__CRC_SYMBOL(sym, sec);						\
-	static const char __kstrtab_##sym[]				\
-	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= #sym;								\
-	static const char __kstrtabns_##sym[]				\
-	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= ns;								\
+/*
+ * For every exported symbol, do the following:
+ *
+ * - If applicable, place a CRC entry in the __kcrctab section.
+ * - Put the name of the symbol and namespace (empty string "" for none) in
+ *   __ksymtab_strings.
+ * - Place a struct kernel_symbol entry in the __ksymtab section.
+ *
+ * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
+ * section flag requires it. Use '%progbits' instead of '@progbits' since the
+ * former apparently works on all arches according to the binutils source.
+ */
+#define ___EXPORT_SYMBOL(sym, sec, ns)						\
+	extern typeof(sym) sym;							\
+	extern const char __kstrtab_##sym[];					\
+	extern const char __kstrtabns_##sym[];					\
+	__CRC_SYMBOL(sym, sec);							\
+	asm("	.section \"__ksymtab_strings\",\"aMS\",%progbits,1	\n"	\
+	    "__kstrtab_" #sym ":					\n"	\
+	    "	.asciz 	\"" #sym "\"					\n"	\
+	    "__kstrtabns_" #sym ":					\n"	\
+	    "	.asciz 	\"" ns "\"					\n"	\
+	    "	.previous						\n");	\
 	__KSYMTAB_ENTRY(sym, sec)
 
 #endif

include/linux/module.h

@@ -429,7 +429,7 @@ struct module {
 
 #ifdef CONFIG_KALLSYMS
 	/* Protected by RCU and/or module_mutex: use rcu_dereference() */
-	struct mod_kallsyms *kallsyms;
+	struct mod_kallsyms __rcu *kallsyms;
 	struct mod_kallsyms core_kallsyms;
 
 	/* Section attributes */

include/linux/moduleparam.h

@@ -128,6 +128,9 @@ struct kparam_array
 
 /**
  * module_param_unsafe - same as module_param but taints kernel
+ * @name: the variable to alter, and exposed parameter name.
+ * @type: the type of the parameter
+ * @perm: visibility in sysfs.
  */
 #define module_param_unsafe(name, type, perm)			\
 	module_param_named_unsafe(name, name, type, perm)
@@ -150,6 +153,10 @@ struct kparam_array
 
 /**
  * module_param_named_unsafe - same as module_param_named but taints kernel
+ * @name: a valid C identifier which is the parameter name.
+ * @value: the actual lvalue to alter.
+ * @type: the type of the parameter
+ * @perm: visibility in sysfs.
  */
 #define module_param_named_unsafe(name, value, type, perm)		\
 	param_check_##type(name, &(value));				\
@@ -160,6 +167,7 @@ struct kparam_array
  * module_param_cb - general callback for a module/cmdline parameter
  * @name: a valid C identifier which is the parameter name.
  * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
  * @perm: visibility in sysfs.
  *
  * The ops can have NULL set or get functions.
@@ -171,36 +179,96 @@ struct kparam_array
 	__module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, -1,    \
 			    KERNEL_PARAM_FL_UNSAFE)
 
+#define __level_param_cb(name, ops, arg, perm, level)			\
+	__module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, level, 0)
 /**
- * <level>_param_cb - general callback for a module/cmdline parameter
- *                    to be evaluated before certain initcall level
+ * core_param_cb - general callback for a module/cmdline parameter
+ *                 to be evaluated before core initcall level
  * @name: a valid C identifier which is the parameter name.
  * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
  * @perm: visibility in sysfs.
  *
  * The ops can have NULL set or get functions.
  */
-#define __level_param_cb(name, ops, arg, perm, level)			\
-	__module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, level, 0)
-
 #define core_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 1)
 
+/**
+ * postcore_param_cb - general callback for a module/cmdline parameter
+ *                     to be evaluated before postcore initcall level
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
 #define postcore_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 2)
 
+/**
+ * arch_param_cb - general callback for a module/cmdline parameter
+ *                 to be evaluated before arch initcall level
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
 #define arch_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 3)
 
+/**
+ * subsys_param_cb - general callback for a module/cmdline parameter
+ *                   to be evaluated before subsys initcall level
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
 #define subsys_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 4)
 
+/**
+ * fs_param_cb - general callback for a module/cmdline parameter
+ *               to be evaluated before fs initcall level
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
 #define fs_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 5)
 
+/**
+ * device_param_cb - general callback for a module/cmdline parameter
+ *                   to be evaluated before device initcall level
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
 #define device_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 6)
 
+/**
+ * late_param_cb - general callback for a module/cmdline parameter
+ *                 to be evaluated before late initcall level
+ * @name: a valid C identifier which is the parameter name.
+ * @ops: the set & get operations for this parameter.
+ * @arg: args for @ops
+ * @perm: visibility in sysfs.
+ *
+ * The ops can have NULL set or get functions.
+ */
 #define late_param_cb(name, ops, arg, perm)		\
 	__level_param_cb(name, ops, arg, perm, 7)
 
@@ -263,6 +331,10 @@ static inline void kernel_param_unlock(struct module *mod)
 
 /**
  * core_param_unsafe - same as core_param but taints kernel
+ * @name: the name of the cmdline and sysfs parameter (often the same as var)
+ * @var: the variable
+ * @type: the type of the parameter
+ * @perm: visibility in sysfs
  */
 #define core_param_unsafe(name, var, type, perm)		\
 	param_check_##type(name, &(var));				\

kernel/module.c

@@ -214,7 +214,8 @@ static struct module *mod_find(unsigned long addr)
 {
 	struct module *mod;
 
-	list_for_each_entry_rcu(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list,
+				lockdep_is_held(&module_mutex)) {
 		if (within_module(addr, mod))
 			return mod;
 	}
@@ -448,7 +449,8 @@ bool each_symbol_section(bool (*fn)(const struct symsearch *arr,
 	if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data))
 		return true;
 
-	list_for_each_entry_rcu(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list,
+				lockdep_is_held(&module_mutex)) {
 		struct symsearch arr[] = {
 			{ mod->syms, mod->syms + mod->num_syms, mod->crcs,
 			  NOT_GPL_ONLY, false },
@@ -616,7 +618,8 @@ static struct module *find_module_all(const char *name, size_t len,
 
 	module_assert_mutex_or_preempt();
 
-	list_for_each_entry_rcu(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list,
+				lockdep_is_held(&module_mutex)) {
 		if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)
 			continue;
 		if (strlen(mod->name) == len && !memcmp(mod->name, name, len))
@@ -1781,6 +1784,8 @@ static int module_add_modinfo_attrs(struct module *mod)
 error_out:
 	if (i > 0)
 		module_remove_modinfo_attrs(mod, --i);
+	else
+		kfree(mod->modinfo_attrs);
 	return error;
 }
 
@@ -2834,7 +2839,7 @@ static int module_sig_check(struct load_info *info, int flags)
 		reason = "Loading of module with unavailable key";
 	decide:
 		if (is_module_sig_enforced()) {
-			pr_notice("%s is rejected\n", reason);
+			pr_notice("%s: %s is rejected\n", info->name, reason);
 			return -EKEYREJECTED;
 		}
 
@@ -3011,9 +3016,7 @@ static int setup_load_info(struct load_info *info, int flags)
 
 	/* Try to find a name early so we can log errors with a module name */
 	info->index.info = find_sec(info, ".modinfo");
-	if (!info->index.info)
-		info->name = "(missing .modinfo section)";
-	else
+	if (info->index.info)
 		info->name = get_modinfo(info, "name");
 
 	/* Find internal symbols and strings. */
@@ -3028,14 +3031,15 @@ static int setup_load_info(struct load_info *info, int flags)
 	}
 
 	if (info->index.sym == 0) {
-		pr_warn("%s: module has no symbols (stripped?)\n", info->name);
+		pr_warn("%s: module has no symbols (stripped?)\n",
+			info->name ?: "(missing .modinfo section or name field)");
 		return -ENOEXEC;
 	}
 
 	info->index.mod = find_sec(info, ".gnu.linkonce.this_module");
 	if (!info->index.mod) {
 		pr_warn("%s: No module found in object\n",
-			info->name ?: "(missing .modinfo name field)");
+			info->name ?: "(missing .modinfo section or name field)");
 		return -ENOEXEC;
 	}
 	/* This is temporary: point mod into copy of data. */