Kbuild updates for v6.16

- Add support for the EXPORT_SYMBOL_GPL_FOR_MODULES() macro, which exports a symbol only to specified modules - Improve ABI handling in gendwarfksyms - Forcibly link lib-y objects to vmlinux even if CONFIG_MODULES=n - Add checkers for redundant or missing <linux/export.h> inclusion - Deprecate the extra-y syntax - Fix a genksyms bug when including enum constants from *.symref files -----BEGIN PGP SIGNATURE----- iQJJBAABCgAzFiEEbmPs18K1szRHjPqEPYsBB53g2wYFAmhEZc4VHG1hc2FoaXJv eUBrZXJuZWwub3JnAAoJED2LAQed4NsGVAgQAKLRdBGga1kBJJFIkUOHWC5+g/je U/dO5rGnuOLviWDexC6QT8AQV2N+dQXhB11x+KacSu1bwowsEvwuegtA6VqwbETs tyWmB0PftEzVyPfc+Rjfy0LDfKkiKkm4RhXiMwcem/rlw45gvJXrVU7jJin9fI3A So8glpOAX+mEizUHkjZkS51nkYCZFDsn7hVo0X43vqjeFrrFGLEQ5xas4Ci+dkY3 9g8Q5bFL8CC5PHjSO8wFftCcAWwTukAht6CSSb522MKGnCVZ9RxTmRwEPXrBmXtS 5eWa8yg6y0tFVmot8iwZGBYleAWDNsj0a2j2oVjUN+EF91sk3WQApJVNBok/nQFb 4MgO3N3UXZdy4tYkBX8tMgOcGkfjZAFoNxSUm5oVouh9NyT0dpqYHhJHBNVbVJoF igQWeVOYcioDjeU1iXnP2cw64q44ROfxmOpDxOSRz9PTM6CCya1R0m/zzBLV6Lwk rzlXk1LLf+jIfgmS5RLlkCgrXS1U0vNGXxQH9Ui9dZSEtzdU7qt5WQ/Rz44bEBhS OeIlJfMMx6QYJztJc/BaUjkKsutTkII52QctRbRCj/nKswHd8SnHV+xk1c2WPxrg yKq10rPpdg1BcvmODY6cmcndt7ogDRfkogm2gvGQIBZEglRimpmpg51sZQRD0ueE 0rt12TmktsLbglB4 =Dy49 -----END PGP SIGNATURE----- Merge tag 'kbuild-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Add support for the EXPORT_SYMBOL_GPL_FOR_MODULES() macro, which exports a symbol only to specified modules - Improve ABI handling in gendwarfksyms - Forcibly link lib-y objects to vmlinux even if CONFIG_MODULES=n - Add checkers for redundant or missing <linux/export.h> inclusion - Deprecate the extra-y syntax - Fix a genksyms bug when including enum constants from *.symref files * tag 'kbuild-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (28 commits) genksyms: Fix enum consts from a reference affecting new values arch: use always-$(KBUILD_BUILTIN) for vmlinux.lds kbuild: set y instead of 1 to KBUILD_{BUILTIN,MODULES} efi/libstub: use 'targets' instead of extra-y in Makefile module: make __mod_device_table__* symbols static scripts/misc-check: check unnecessary #include <linux/export.h> when W=1 scripts/misc-check: check missing #include <linux/export.h> when W=1 scripts/misc-check: add double-quotes to satisfy shellcheck kbuild: move W=1 check for scripts/misc-check to top-level Makefile scripts/tags.sh: allow to use alternative ctags implementation kconfig: introduce menu type enum docs: symbol-namespaces: fix reST warning with literal block kbuild: link lib-y objects to vmlinux forcibly even when CONFIG_MODULES=n tinyconfig: enable CONFIG_LD_DEAD_CODE_DATA_ELIMINATION docs/core-api/symbol-namespaces: drop table of contents and section numbering modpost: check forbidden MODULE_IMPORT_NS("module:") at compile time kbuild: move kbuild syntax processing to scripts/Makefile.build Makefile: remove dependency on archscripts for header installation Documentation/kbuild: Add new gendwarfksyms kABI rules Documentation/kbuild: Drop section numbers ...
2025-10-22 15:03:53 +02:00 · 2025-06-07 10:05:35 -07:00 · 2025-06-07 10:05:35 -07:00 · 8630c59e99
commit 8630c59e99
parent b3154a6ff1 c50a04f8f4
49 changed files with 919 additions and 335 deletions
--- a/Documentation/core-api/symbol-namespaces.rst
+++ b/Documentation/core-api/symbol-namespaces.rst
@ -6,18 +6,8 @@ The following document describes how to use Symbol Namespaces to structure the
 export surface of in-kernel symbols exported through the family of
 EXPORT_SYMBOL() macros.

-.. Table of Contents
-
-	=== 1 Introduction
-	=== 2 How to define Symbol Namespaces
-	   --- 2.1 Using the EXPORT_SYMBOL macros
-	   --- 2.2 Using the DEFAULT_SYMBOL_NAMESPACE define
-	=== 3 How to use Symbols exported in Namespaces
-	=== 4 Loading Modules that use namespaced Symbols
-	=== 5 Automatically creating MODULE_IMPORT_NS statements
-
-1. Introduction
-===============
+Introduction
+============

 Symbol Namespaces have been introduced as a means to structure the export
 surface of the in-kernel API. It allows subsystem maintainers to partition
@ -28,15 +18,18 @@ kernel. As of today, modules that make use of symbols exported into namespaces,
 are required to import the namespace. Otherwise the kernel will, depending on
 its configuration, reject loading the module or warn about a missing import.

-2. How to define Symbol Namespaces
-==================================
+Additionally, it is possible to put symbols into a module namespace, strictly
+limiting which modules are allowed to use these symbols.
+
+How to define Symbol Namespaces
+===============================

 Symbols can be exported into namespace using different methods. All of them are
 changing the way EXPORT_SYMBOL and friends are instrumented to create ksymtab
 entries.

-2.1 Using the EXPORT_SYMBOL macros
-==================================
+Using the EXPORT_SYMBOL macros
+------------------------------

 In addition to the macros EXPORT_SYMBOL() and EXPORT_SYMBOL_GPL(), that allow
 exporting of kernel symbols to the kernel symbol table, variants of these are
@ -54,8 +47,8 @@ refer to ``NULL``. There is no default namespace if none is defined. ``modpost``
 and kernel/module/main.c make use the namespace at build time or module load
 time, respectively.

-2.2 Using the DEFAULT_SYMBOL_NAMESPACE define
-=============================================
+Using the DEFAULT_SYMBOL_NAMESPACE define
+-----------------------------------------

 Defining namespaces for all symbols of a subsystem can be very verbose and may
 become hard to maintain. Therefore a default define (DEFAULT_SYMBOL_NAMESPACE)
@ -83,8 +76,24 @@ unit as preprocessor statement. The above example would then read::
 within the corresponding compilation unit before the #include for
 <linux/export.h>. Typically it's placed before the first #include statement.

-3. How to use Symbols exported in Namespaces
-============================================
+Using the EXPORT_SYMBOL_GPL_FOR_MODULES() macro
+-----------------------------------------------
+
+Symbols exported using this macro are put into a module namespace. This
+namespace cannot be imported.
+
+The macro takes a comma separated list of module names, allowing only those
+modules to access this symbol. Simple tail-globs are supported.
+
+For example::
+
+  EXPORT_SYMBOL_GPL_FOR_MODULES(preempt_notifier_inc, "kvm,kvm-*")
+
+will limit usage of this symbol to modules whoes name matches the given
+patterns.
+
+How to use Symbols exported in Namespaces
+=========================================

 In order to use symbols that are exported into namespaces, kernel modules need
 to explicitly import these namespaces. Otherwise the kernel might reject to
@ -106,11 +115,10 @@ inspected with modinfo::


 It is advisable to add the MODULE_IMPORT_NS() statement close to other module
-metadata definitions like MODULE_AUTHOR() or MODULE_LICENSE(). Refer to section
-5. for a way to create missing import statements automatically.
+metadata definitions like MODULE_AUTHOR() or MODULE_LICENSE().

-4. Loading Modules that use namespaced Symbols
-==============================================
+Loading Modules that use namespaced Symbols
+===========================================

 At module loading time (e.g. ``insmod``), the kernel will check each symbol
 referenced from the module for its availability and whether the namespace it
@ -121,8 +129,8 @@ allow loading of modules that don't satisfy this precondition, a configuration
 option is available: Setting MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=y will
 enable loading regardless, but will emit a warning.

-5. Automatically creating MODULE_IMPORT_NS statements
-=====================================================
+Automatically creating MODULE_IMPORT_NS statements
+==================================================

 Missing namespaces imports can easily be detected at build time. In fact,
 modpost will emit a warning if a module uses a symbol from a namespace
@ -154,3 +162,6 @@ in-tree modules::
 You can also run nsdeps for external module builds. A typical usage is::

 	$ make -C <path_to_kernel_src> M=$PWD nsdeps
+
+Note: it will happily generate an import statement for the module namespace;
+which will not work and generates build and runtime failures.
--- a/Documentation/kbuild/gendwarfksyms.rst
+++ b/Documentation/kbuild/gendwarfksyms.rst
@ -2,8 +2,8 @@
 DWARF module versioning
 =======================

-1. Introduction
-===============
+Introduction
+============

 When CONFIG_MODVERSIONS is enabled, symbol versions for modules
 are typically calculated from preprocessed source code using the
@ -14,8 +14,8 @@ selected, **gendwarfksyms** is used instead to calculate symbol versions
 from the DWARF debugging information, which contains the necessary
 details about the final module ABI.

-1.1. Usage
-==========
+Usage
+-----

 gendwarfksyms accepts a list of object files on the command line, and a
 list of symbol names (one per line) in standard input::
@ -33,8 +33,8 @@ list of symbol names (one per line) in standard input::
          -h, --help           Print this message


-2. Type information availability
-================================
+Type information availability
+=============================

 While symbols are typically exported in the same translation unit (TU)
 where they're defined, it's also perfectly fine for a TU to export
@ -56,8 +56,8 @@ type for calculating symbol versions even if the symbol is defined
 elsewhere. The name of the symbol pointer is expected to start with
 `__gendwarfksyms_ptr_`, followed by the name of the exported symbol.

-3. Symtypes output format
-=========================
+Symtypes output format
+======================

 Similarly to genksyms, gendwarfksyms supports writing a symtypes
 file for each processed object that contain types for exported
@ -85,8 +85,8 @@ produces C-style type strings, gendwarfksyms uses the same simple parsed
 DWARF format produced by **--dump-dies**, but with type references
 instead of fully expanded strings.

-4. Maintaining a stable kABI
-============================
+Maintaining a stable kABI
+=========================

 Distribution maintainers often need the ability to make ABI compatible
 changes to kernel data structures due to LTS updates or backports. Using
@ -104,8 +104,8 @@ for source code annotation. Note that as these features are only used to
 transform the inputs for symbol versioning, the user is responsible for
 ensuring that their changes actually won't break the ABI.

-4.1. kABI rules
-===============
+kABI rules
+----------

 kABI rules allow distributions to fine-tune certain parts
 of gendwarfksyms output and thus control how symbol
@ -125,22 +125,25 @@ the rules. The fields are as follows:
  qualified name of the DWARF Debugging Information Entry (DIE).
 - `value`: Provides rule-specific data.

-The following helper macro, for example, can be used to specify rules
+The following helper macros, for example, can be used to specify rules
 in the source code::

-	#define __KABI_RULE(hint, target, value)                             \
-		static const char __PASTE(__gendwarfksyms_rule_,             \
+	#define ___KABI_RULE(hint, target, value)			    \
+		static const char __PASTE(__gendwarfksyms_rule_,	     \
 					  __COUNTER__)[] __used __aligned(1) \
 			__section(".discard.gendwarfksyms.kabi_rules") =     \
-				"1\0" #hint "\0" #target "\0" #value
+				"1\0" #hint "\0" target "\0" value
+
+	#define __KABI_RULE(hint, target, value) \
+		___KABI_RULE(hint, #target, #value)


 Currently, only the rules discussed in this section are supported, but
 the format is extensible enough to allow further rules to be added as
 need arises.

-4.1.1. Managing definition visibility
-=====================================
+Managing definition visibility
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 A declaration can change into a full definition when additional includes
 are pulled into the translation unit. This changes the versions of any
@ -168,8 +171,8 @@ Example usage::

 	KABI_DECLONLY(s);

-4.1.2. Adding enumerators
-=========================
+Adding enumerators
+~~~~~~~~~~~~~~~~~~

 For enums, all enumerators and their values are included in calculating
 symbol versions, which becomes a problem if we later need to add more
@ -223,8 +226,89 @@ Example usage::
 	KABI_ENUMERATOR_IGNORE(e, C);
 	KABI_ENUMERATOR_VALUE(e, LAST, 2);

-4.3. Adding structure members
-=============================
+Managing structure size changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A data structure can be partially opaque to modules if its allocation is
+handled by the core kernel, and modules only need to access some of its
+members. In this situation, it's possible to append new members to the
+structure without breaking the ABI, as long as the layout for the original
+members remains unchanged.
+
+To append new members, we can hide them from symbol versioning as
+described in section :ref:`Hiding members <hiding_members>`, but we can't
+hide the increase in structure size. The `byte_size` rule allows us to
+override the structure size used for symbol versioning.
+
+The rule fields are expected to be as follows:
+
+- `type`: "byte_size"
+- `target`: The fully qualified name of the target data structure
+  (as shown in **--dump-dies** output).
+- `value`: A positive decimal number indicating the structure size
+  in bytes.
+
+Using the `__KABI_RULE` macro, this rule can be defined as::
+
+        #define KABI_BYTE_SIZE(fqn, value) \
+                __KABI_RULE(byte_size, fqn, value)
+
+Example usage::
+
+	struct s {
+                /* Unchanged original members */
+		unsigned long a;
+                void *p;
+
+                /* Appended new members */
+                KABI_IGNORE(0, unsigned long n);
+	};
+
+	KABI_BYTE_SIZE(s, 16);
+
+Overriding type strings
+~~~~~~~~~~~~~~~~~~~~~~~
+
+In rare situations where distributions must make significant changes to
+otherwise opaque data structures that have inadvertently been included
+in the published ABI, keeping symbol versions stable using the more
+targeted kABI rules can become tedious. The `type_string` rule allows us
+to override the full type string for a type or a symbol, and even add
+types for versioning that no longer exist in the kernel.
+
+The rule fields are expected to be as follows:
+
+- `type`: "type_string"
+- `target`: The fully qualified name of the target data structure
+  (as shown in **--dump-dies** output) or symbol.
+- `value`: A valid type string (as shown in **--symtypes**) output)
+  to use instead of the real type.
+
+Using the `__KABI_RULE` macro, this rule can be defined as::
+
+	#define KABI_TYPE_STRING(type, str) \
+		___KABI_RULE("type_string", type, str)
+
+Example usage::
+
+	/* Override type for a structure */
+	KABI_TYPE_STRING("s#s",
+		"structure_type s { "
+			"member base_type int byte_size(4) "
+				"encoding(5) n "
+			"data_member_location(0) "
+		"} byte_size(8)");
+
+	/* Override type for a symbol */
+	KABI_TYPE_STRING("my_symbol", "variable s#s");
+
+The `type_string` rule should be used only as a last resort if maintaining
+a stable symbol versions cannot be reasonably achieved using other
+means. Overriding a type string increases the risk of actual ABI breakages
+going unnoticed as it hides all changes to the type.
+
+Adding structure members
+------------------------

 Perhaps the most common ABI compatible change is adding a member to a
 kernel data structure. When changes to a structure are anticipated,
@ -237,8 +321,8 @@ natural method. This section describes gendwarfksyms support for using
 reserved space in data structures and hiding members that don't change
 the ABI when calculating symbol versions.

-4.3.1. Reserving space and replacing members
-============================================
+Reserving space and replacing members
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 Space is typically reserved for later use by appending integer types, or
 arrays, to the end of the data structure, but any type can be used. Each
@ -276,8 +360,10 @@ The examples include `KABI_(RESERVE|USE|REPLACE)*` macros that help
 simplify the process and also ensure the replacement member is correctly
 aligned and its size won't exceed the reserved space.

-4.3.2. Hiding members
-=====================
+.. _hiding_members:
+
+Hiding members
+~~~~~~~~~~~~~~

 Predicting which structures will require changes during the support
 timeframe isn't always possible, in which case one might have to resort
@ -305,4 +391,5 @@ member to a union where one of the fields has a name starting with
                unsigned long b;
        };

-With **--stable**, both versions produce the same symbol version.
+With **--stable**, both versions produce the same symbol version. The
+examples include a `KABI_IGNORE` macro to simplify the code.
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@ -291,6 +291,10 @@ Example::
  # arch/x86/kernel/Makefile
  extra-y	+= vmlinux.lds

+extra-y is now deprecated because this is equivalent to:
+
+  always-$(KBUILD_BUILTIN) += vmlinux.lds
+
 $(extra-y) should only contain targets needed for vmlinux.

 Kbuild skips extra-y when vmlinux is apparently not a final goal.
--- a/Documentation/translations/it_IT/core-api/symbol-namespaces.rst
+++ b/Documentation/translations/it_IT/core-api/symbol-namespaces.rst
@ -10,8 +10,8 @@ Questo documento descrive come usare lo spazio dei nomi dei simboli
 per strutturare quello che viene esportato internamente al kernel
 grazie alle macro della famiglia EXPORT_SYMBOL().

-1. Introduzione
-===============
+Introduzione
+============

 Lo spazio dei nomi dei simboli è stato introdotto come mezzo per strutturare
 l'API esposta internamente al kernel. Permette ai manutentori di un
@ -24,15 +24,15 @@ devono prima importare detto spazio. Altrimenti il kernel, a seconda
 della configurazione, potrebbe rifiutare di caricare il modulo o
 avvisare l'utente di un'importazione mancante.

-2. Come definire uno spazio dei nomi dei simboli
-================================================
+Come definire uno spazio dei nomi dei simboli
+=============================================

 I simboli possono essere esportati in spazi dei nomi usando diversi
 meccanismi.  Tutti questi meccanismi cambiano il modo in cui
 EXPORT_SYMBOL e simili vengono guidati verso la creazione di voci in ksymtab.

-2.1 Usare le macro EXPORT_SYMBOL
-================================
+Usare le macro EXPORT_SYMBOL
+----------------------------

 In aggiunta alle macro EXPORT_SYMBOL() e EXPORT_SYMBOL_GPL(), che permettono
 di esportare simboli del kernel nella rispettiva tabella, ci sono
@ -53,8 +53,8 @@ di base. Il programma ``modpost`` e il codice in kernel/module/main.c usano lo
 spazio dei nomi, rispettivamente, durante la compilazione e durante il
 caricamento di un modulo.

-2.2 Usare il simbolo di preprocessore DEFAULT_SYMBOL_NAMESPACE
-==============================================================
+Usare il simbolo di preprocessore DEFAULT_SYMBOL_NAMESPACE
+----------------------------------------------------------

 Definire lo spazio dei nomi per tutti i simboli di un sottosistema può essere
 logorante e di difficile manutenzione. Perciò è stato fornito un simbolo
@ -83,8 +83,8 @@ direttamente nei file da compilare. L'esempio precedente diventerebbe::

 Questo va messo prima di un qualsiasi uso di EXPORT_SYMBOL.

-3. Come usare i simboli esportati attraverso uno spazio dei nomi
-================================================================
+Come usare i simboli esportati attraverso uno spazio dei nomi
+=============================================================

 Per usare i simboli esportati da uno spazio dei nomi, i moduli del
 kernel devono esplicitamente importare il relativo spazio dei nomi; altrimenti
@ -108,12 +108,10 @@ modinfo::


 Si consiglia di posizionare la dichiarazione MODULE_IMPORT_NS() vicino
-ai metadati del modulo come MODULE_AUTHOR() o MODULE_LICENSE(). Fate
-riferimento alla sezione 5. per creare automaticamente le importazioni
-mancanti.
+ai metadati del modulo come MODULE_AUTHOR() o MODULE_LICENSE().

-4. Caricare moduli che usano simboli provenienti da spazi dei nomi
-==================================================================
+Caricare moduli che usano simboli provenienti da spazi dei nomi
+===============================================================

 Quando un modulo viene caricato (per esempio usando ``insmod``), il kernel
 verificherà la disponibilità di ogni simbolo usato e se lo spazio dei nomi
@ -125,8 +123,8 @@ un'opzione di configurazione: impostare
 MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=y caricherà i moduli comunque ma
 emetterà un avviso.

-5. Creare automaticamente la dichiarazione MODULE_IMPORT_NS
-===========================================================
+Creare automaticamente la dichiarazione MODULE_IMPORT_NS
+========================================================

 La mancanza di un'importazione può essere individuata facilmente al momento
 della compilazione. Infatti, modpost emetterà un avviso se il modulo usa
--- a/Documentation/translations/zh_CN/core-api/symbol-namespaces.rst
+++ b/Documentation/translations/zh_CN/core-api/symbol-namespaces.rst
@ -14,18 +14,8 @@

 本文档描述了如何使用符号命名空间来构造通过EXPORT_SYMBOL()系列宏导出的内核内符号的导出面。

-.. 目录
-
-       === 1 简介
-       === 2 如何定义符号命名空间
-          --- 2.1 使用EXPORT_SYMBOL宏
-          --- 2.2 使用DEFAULT_SYMBOL_NAMESPACE定义
-       === 3 如何使用命名空间中导出的符号
-       === 4 加载使用命名空间符号的模块
-       === 5 自动创建MODULE_IMPORT_NS声明
-
-1. 简介
-=======
+简介
+====

 符号命名空间已经被引入，作为构造内核内API的导出面的一种手段。它允许子系统维护者将
 他们导出的符号划分进独立的命名空间。这对于文档的编写非常有用（想想SUBSYSTEM_DEBUG
@ -33,14 +23,14 @@
 的模块必须导入命名空间。否则，内核将根据其配置，拒绝加载该模块或警告说缺少
 导入。

-2. 如何定义符号命名空间
-=======================
+如何定义符号命名空间
+====================

 符号可以用不同的方法导出到命名空间。所有这些都在改变 EXPORT_SYMBOL 和与之类似的那些宏
 被检测到的方式，以创建 ksymtab 条目。

-2.1 使用EXPORT_SYMBOL宏
-=======================
+使用EXPORT_SYMBOL宏
+-------------------

 除了允许将内核符号导出到内核符号表的宏EXPORT_SYMBOL()和EXPORT_SYMBOL_GPL()之外，
 这些宏的变体还可以将符号导出到某个命名空间：EXPORT_SYMBOL_NS() 和 EXPORT_SYMBOL_NS_GPL()。
@ -54,8 +44,8 @@
 导出时未指明命名空间的符号将指向 ``NULL`` 。如果没有定义命名空间，则默认没有。
 ``modpost`` 和kernel/module/main.c分别在构建时或模块加载时使用名称空间。

-2.2 使用DEFAULT_SYMBOL_NAMESPACE定义
-====================================
+使用DEFAULT_SYMBOL_NAMESPACE定义
+--------------------------------

 为一个子系统的所有符号定义命名空间可能会非常冗长，并可能变得难以维护。因此，我
 们提供了一个默认定义（DEFAULT_SYMBOL_NAMESPACE），如果设置了这个定义， 它将成
@ -80,8 +70,8 @@

 应置于相关编译单元中任何 EXPORT_SYMBOL 宏之前

-3. 如何使用命名空间中导出的符号
-===============================
+如何使用命名空间中导出的符号
+============================

 为了使用被导出到命名空间的符号，内核模块需要明确地导入这些命名空间。
 否则内核可能会拒绝加载该模块。模块代码需要使用宏MODULE_IMPORT_NS来
@ -100,11 +90,10 @@


 建议将 MODULE_IMPORT_NS() 语句添加到靠近其他模块元数据定义的地方，
-如 MODULE_AUTHOR() 或 MODULE_LICENSE() 。关于自动创建缺失的导入
-语句的方法，请参考第5节。
+如 MODULE_AUTHOR() 或 MODULE_LICENSE() 。

-4. 加载使用命名空间符号的模块
-=============================
+加载使用命名空间符号的模块
+==========================

 在模块加载时（比如 ``insmod`` ），内核将检查每个从模块中引用的符号是否可
 用，以及它可能被导出到的名字空间是否被模块导入。内核的默认行为是拒绝
@ -113,8 +102,8 @@ EINVAL方式失败。要允许加载不满足这个前提条件的模块，可
 设置 MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=y 将使加载不受影响，但会
 发出警告。

-5. 自动创建MODULE_IMPORT_NS声明
-===============================
+自动创建MODULE_IMPORT_NS声明
+============================

 缺少命名空间的导入可以在构建时很容易被检测到。事实上，如果一个模块
 使用了一个命名空间的符号而没有导入它，modpost会发出警告。
--- a/28
+++ b/28
@ -754,7 +754,7 @@ targets :=
 # Normally, just do built-in.

 KBUILD_MODULES :=
-KBUILD_BUILTIN := 1
+KBUILD_BUILTIN := y

 # If we have only "make modules", don't compile built-in objects.
 ifeq ($(MAKECMDGOALS),modules)
@ -766,11 +766,11 @@ endif
 # Just "make" or "make all" shall build modules as well

 ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
-  KBUILD_MODULES := 1
+  KBUILD_MODULES := y
 endif

 ifeq ($(MAKECMDGOALS),)
-  KBUILD_MODULES := 1
+  KBUILD_MODULES := y
 endif

 export KBUILD_MODULES KBUILD_BUILTIN
@ -1189,13 +1189,8 @@ export ARCH_LIB		:= $(filter %/, $(libs-y))
 export ARCH_DRIVERS	:= $(drivers-y) $(drivers-m)
 # Externally visible symbols (used by link-vmlinux.sh)

-KBUILD_VMLINUX_OBJS := ./built-in.a
-ifdef CONFIG_MODULES
-KBUILD_VMLINUX_OBJS += $(patsubst %/, %/lib.a, $(filter %/, $(libs-y)))
+KBUILD_VMLINUX_OBJS := built-in.a $(patsubst %/, %/lib.a, $(filter %/, $(libs-y)))
 KBUILD_VMLINUX_LIBS := $(filter-out %/, $(libs-y))
-else
-KBUILD_VMLINUX_LIBS := $(patsubst %/,%/lib.a, $(libs-y))
-endif

 export KBUILD_VMLINUX_LIBS
 export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds
@ -1203,7 +1198,7 @@ export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds
 ifdef CONFIG_TRIM_UNUSED_KSYMS
 # For the kernel to actually contain only the needed exported symbols,
 # we have to build modules as well to determine what those symbols are.
-KBUILD_MODULES := 1
+KBUILD_MODULES := y
 endif

 # '$(AR) mPi' needs 'T' to workaround the bug of llvm-ar <= 14
@ -1370,7 +1365,7 @@ PHONY += archheaders archscripts
 hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj

 PHONY += headers
-headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
+headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders
 ifdef HEADER_ARCH
 	$(Q)$(MAKE) -f $(srctree)/Makefile HEADER_ARCH= SRCARCH=$(HEADER_ARCH) headers
 else
@ -1543,7 +1538,7 @@ all: modules
 # the built-in objects during the descend as well, in order to
 # make sure the checksums are up to date before we record them.
 ifdef CONFIG_MODVERSIONS
-  KBUILD_BUILTIN := 1
+  KBUILD_BUILTIN := y
 endif

 # Build modules
@ -1552,7 +1547,7 @@ endif
 # *.ko are usually independent of vmlinux, but CONFIG_DEBUG_INFO_BTF_MODULES
 # is an exception.
 ifdef CONFIG_DEBUG_INFO_BTF_MODULES
-KBUILD_BUILTIN := 1
+KBUILD_BUILTIN := y
 modules: vmlinux
 endif

@ -1837,9 +1832,12 @@ rustfmtcheck: rustfmt
 # Misc
 # ---------------------------------------------------------------------------

+# Run misc checks when ${KBUILD_EXTRA_WARN} contains 1
 PHONY += misc-check
+ifneq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
 misc-check:
 	$(Q)$(srctree)/scripts/misc-check
+endif

 all: misc-check

@ -1865,7 +1863,7 @@ filechk_kernel.release = echo $(KERNELRELEASE)

 # We are always building only modules.
 KBUILD_BUILTIN :=
-KBUILD_MODULES := 1
+KBUILD_MODULES := y

 build-dir := .

@ -1993,7 +1991,7 @@ endif

 single-goals := $(addprefix $(build-dir)/, $(single-no-ko))

-KBUILD_MODULES := 1
+KBUILD_MODULES := y

 endif

--- a/arch/alpha/kernel/Makefile
+++ b/arch/alpha/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the linux kernel.
 #

-extra-y		:= vmlinux.lds
+always-$(KBUILD_BUILTIN)	:= vmlinux.lds
 asflags-y	:= $(KBUILD_CFLAGS)
 ccflags-y	:= -Wno-sign-compare

--- a/arch/arc/kernel/Makefile
+++ b/arch/arc/kernel/Makefile
@ -26,4 +26,4 @@ ifdef CONFIG_ISA_ARCOMPACT
 CFLAGS_fpu.o   += -mdpfp
 endif

-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@ -104,4 +104,4 @@ obj-$(CONFIG_HAVE_ARM_SMCCC)	+= smccc-call.o

 obj-$(CONFIG_GENERIC_CPU_VULNERABILITIES) += spectre.o

-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@ -78,7 +78,7 @@ $(obj)/vdso32-wrap.o: $(obj)/vdso32/vdso.so

 obj-y					+= probes/
 obj-y					+= head.o
-extra-y					+= vmlinux.lds
+always-$(KBUILD_BUILTIN)		+= vmlinux.lds

 ifeq ($(CONFIG_DEBUG_EFI),y)
 AFLAGS_head.o += -DVMLINUX_PATH="\"$(realpath $(objtree)/vmlinux)\""
--- a/arch/csky/kernel/Makefile
+++ b/arch/csky/kernel/Makefile
@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds

 obj-y += head.o entry.o atomic.o signal.o traps.o irq.o time.o vdso.o vdso/
 obj-y += power.o syscall.o syscall_table.o setup.o
--- a/arch/hexagon/kernel/Makefile
+++ b/arch/hexagon/kernel/Makefile
@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds

 obj-y += head.o
 obj-$(CONFIG_SMP) += smp.o
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@ -5,7 +5,7 @@

 OBJECT_FILES_NON_STANDARD_head.o := y

-extra-y		:= vmlinux.lds
+always-$(KBUILD_BUILTIN)	:= vmlinux.lds

 obj-y		+= head.o cpu-probe.o cacheinfo.o env.o setup.o entry.o genex.o \
 		   traps.o irq.o idle.o process.o dma.o mem.o reset.o switch.o \
--- a/arch/m68k/kernel/Makefile
+++ b/arch/m68k/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the linux kernel.
 #

-extra-y			+= vmlinux.lds
+always-$(KBUILD_BUILTIN)	+= vmlinux.lds

 obj-$(CONFIG_MMU_MOTOROLA)	:= head.o
 obj-$(CONFIG_SUN3)		:= sun3-head.o
--- a/arch/microblaze/kernel/Makefile
+++ b/arch/microblaze/kernel/Makefile
@ -11,7 +11,7 @@ CFLAGS_REMOVE_ftrace.o = -pg
 CFLAGS_REMOVE_process.o = -pg
 endif

-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds

 obj-y += head.o dma.o exceptions.o \
 	hw_exception_handler.o irq.o \
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the Linux/MIPS kernel.
 #

-extra-y		:= vmlinux.lds
+always-$(KBUILD_BUILTIN)	:= vmlinux.lds

 obj-y		+= head.o branch.o cmpxchg.o elf.o entry.o genex.o idle.o irq.o \
 		   process.o prom.o ptrace.o reset.o setup.o signal.o \
--- a/arch/nios2/kernel/Makefile
+++ b/arch/nios2/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the nios2 linux kernel.
 #

-extra-y	+= vmlinux.lds
+always-$(KBUILD_BUILTIN)	+= vmlinux.lds

 obj-y	+= head.o
 obj-y	+= cpuinfo.o
--- a/arch/openrisc/kernel/Makefile
+++ b/arch/openrisc/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the linux kernel.
 #

-extra-y	:= vmlinux.lds
+always-$(KBUILD_BUILTIN)	:= vmlinux.lds

 obj-y	:= head.o setup.o or32_ksyms.o process.o dma.o \
 	   traps.o time.o irq.o entry.o ptrace.o signal.o \
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for arch/parisc/kernel
 #

-extra-y		:= vmlinux.lds
+always-$(KBUILD_BUILTIN)		:= vmlinux.lds

 obj-y		:= head.o cache.o pacache.o setup.o pdt.o traps.o time.o irq.o \
 		   syscall.o entry.o sys_parisc.o firmware.o \
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@ -126,7 +126,7 @@ obj-$(CONFIG_PPC_BOOK3S_32)	+= head_book3s_32.o
 obj-$(CONFIG_44x)		+= head_44x.o
 obj-$(CONFIG_PPC_8xx)		+= head_8xx.o
 obj-$(CONFIG_PPC_85xx)		+= head_85xx.o
-extra-y				+= vmlinux.lds
+always-$(KBUILD_BUILTIN)	+= vmlinux.lds

 obj-$(CONFIG_RELOCATABLE)	+= reloc_$(BITS).o

--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@ -43,7 +43,7 @@ CFLAGS_sbi_ecall.o += -D__NO_FORTIFY
 endif
 endif

-extra-y += vmlinux.lds
+always-$(KBUILD_BUILTIN) += vmlinux.lds

 obj-y	+= head.o
 obj-y	+= soc.o
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@ -46,7 +46,7 @@ obj-y	+= nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o unwind_bc.o
 obj-y	+= smp.o text_amode31.o stacktrace.o abs_lowcore.o facility.o uv.o wti.o
 obj-y	+= diag/

-extra-y				+= vmlinux.lds
+always-$(KBUILD_BUILTIN)	+= vmlinux.lds

 obj-$(CONFIG_SYSFS)		+= nospec-sysfs.o
 CFLAGS_REMOVE_nospec-branch.o	+= $(CC_FLAGS_EXPOLINE)
--- a/arch/sh/kernel/Makefile
+++ b/arch/sh/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the Linux/SuperH kernel.
 #

-extra-y	:= vmlinux.lds
+always-$(KBUILD_BUILTIN)	:= vmlinux.lds

 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
--- a/arch/sparc/kernel/Makefile
+++ b/arch/sparc/kernel/Makefile
@ -9,7 +9,7 @@ asflags-y := -ansi
 # Undefine sparc when processing vmlinux.lds - it is used
 # And teach CPP we are doing $(BITS) builds (for this case)
 CPPFLAGS_vmlinux.lds := -Usparc -m$(BITS)
-extra-y              += vmlinux.lds
+always-$(KBUILD_BUILTIN) += vmlinux.lds

 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
--- a/arch/um/kernel/Makefile
+++ b/arch/um/kernel/Makefile
@ -12,7 +12,7 @@ CPPFLAGS_vmlinux.lds := -DSTART=$(LDS_START)		\
                        -DELF_ARCH=$(LDS_ELF_ARCH)	\
                        -DELF_FORMAT=$(LDS_ELF_FORMAT)	\
 			$(LDS_EXTRA)
-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds

 obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \
 	physmem.o process.o ptrace.o reboot.o sigio.o \
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the linux kernel.
 #

-extra-y	+= vmlinux.lds
+always-$(KBUILD_BUILTIN)	+= vmlinux.lds

 CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)

--- a/arch/xtensa/kernel/Makefile
+++ b/arch/xtensa/kernel/Makefile
@ -3,7 +3,7 @@
 # Makefile for the Linux/Xtensa kernel.
 #

-extra-y := vmlinux.lds
+always-$(KBUILD_BUILTIN) := vmlinux.lds

 obj-y := head.o align.o coprocessor.o entry.o irq.o platform.o process.o \
 	 ptrace.o setup.o signal.o stacktrace.o syscall.o time.o traps.o \
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@ -101,7 +101,7 @@ lib-$(CONFIG_EFI_ZBOOT)		+= zboot.o $(zboot-obj-y)

 lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o

-extra-y				:= $(lib-y)
+targets				:= $(lib-y)
 lib-y				:= $(patsubst %.o,%.stub.o,$(lib-y))

 # Even when -mbranch-protection=none is set, Clang will generate a
--- a/include/linux/export.h
+++ b/include/linux/export.h
@ -24,11 +24,17 @@
 	.long sym
 #endif

-#define ___EXPORT_SYMBOL(sym, license, ns)		\
+/*
+ * LLVM integrated assembler cam merge adjacent string literals (like
+ * C and GNU-as) passed to '.ascii', but not to '.asciz' and chokes on:
+ *
+ *   .asciz "MODULE_" "kvm" ;
+ */
+#define ___EXPORT_SYMBOL(sym, license, ns...)		\
 	.section ".export_symbol","a"		ASM_NL	\
 	__export_symbol_##sym:			ASM_NL	\
 		.asciz license			ASM_NL	\
-		.asciz ns			ASM_NL	\
+		.ascii ns "\0"			ASM_NL	\
 		__EXPORT_SYMBOL_REF(sym)	ASM_NL	\
 	.previous

@ -85,4 +91,6 @@
 #define EXPORT_SYMBOL_NS(sym, ns)	__EXPORT_SYMBOL(sym, "", ns)
 #define EXPORT_SYMBOL_NS_GPL(sym, ns)	__EXPORT_SYMBOL(sym, "GPL", ns)

+#define EXPORT_SYMBOL_GPL_FOR_MODULES(sym, mods) __EXPORT_SYMBOL(sym, "GPL", "module:" mods)
+
 #endif /* _LINUX_EXPORT_H */
--- a/include/linux/module.h
+++ b/include/linux/module.h
@ -249,8 +249,8 @@ struct module_kobject *lookup_or_create_module_kobject(const char *name);
 #ifdef MODULE
 /* Creates an alias so file2alias.c can find device table. */
 #define MODULE_DEVICE_TABLE(type, name)					\
-extern typeof(name) __mod_device_table__##type##__##name		\
-  __attribute__ ((unused, alias(__stringify(name))))
+static typeof(name) __mod_device_table__##type##__##name		\
+  __attribute__ ((used, alias(__stringify(name))))
 #else  /* !MODULE */
 #define MODULE_DEVICE_TABLE(type, name)
 #endif
--- a/kernel/configs/tiny.config
+++ b/kernel/configs/tiny.config
@ -2,3 +2,4 @@ CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_KERNEL_XZ=y
 CONFIG_SLUB=y
 CONFIG_SLUB_TINY=y
+CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@ -169,6 +169,30 @@ static inline void add_taint_module(struct module *mod, unsigned flag,
 	set_bit(flag, &mod->taints);
 }

+/*
+ * Like strncmp(), except s/-/_/g as per scripts/Makefile.lib:name-fix-token rule.
+ */
+static int mod_strncmp(const char *str_a, const char *str_b, size_t n)
+{
+	for (int i = 0; i < n; i++) {
+		char a = str_a[i];
+		char b = str_b[i];
+		int d;
+
+		if (a == '-') a = '_';
+		if (b == '-') b = '_';
+
+		d = a - b;
+		if (d)
+			return d;
+
+		if (!a)
+			break;
+	}
+
+	return 0;
+}
+
 /*
 * A thread that wants to hold a reference to a module only while it
 * is running can call this to safely exit.
@ -1083,6 +1107,46 @@ static char *get_modinfo(const struct load_info *info, const char *tag)
 	return get_next_modinfo(info, tag, NULL);
 }

+/**
+ * verify_module_namespace() - does @modname have access to this symbol's @namespace
+ * @namespace: export symbol namespace
+ * @modname: module name
+ *
+ * If @namespace is prefixed with "module:" to indicate it is a module namespace
+ * then test if @modname matches any of the comma separated patterns.
+ *
+ * The patterns only support tail-glob.
+ */
+static bool verify_module_namespace(const char *namespace, const char *modname)
+{
+	size_t len, modlen = strlen(modname);
+	const char *prefix = "module:";
+	const char *sep;
+	bool glob;
+
+	if (!strstarts(namespace, prefix))
+		return false;
+
+	for (namespace += strlen(prefix); *namespace; namespace = sep) {
+		sep = strchrnul(namespace, ',');
+		len = sep - namespace;
+
+		glob = false;
+		if (sep[-1] == '*') {
+			len--;
+			glob = true;
+		}
+
+		if (*sep)
+			sep++;
+
+		if (mod_strncmp(namespace, modname, len) == 0 && (glob || len == modlen))
+			return true;
+	}
+
+	return false;
+}
+
 static int verify_namespace_is_imported(const struct load_info *info,
 					const struct kernel_symbol *sym,
 					struct module *mod)
@ -1092,6 +1156,10 @@ static int verify_namespace_is_imported(const struct load_info *info,

 	namespace = kernel_symbol_namespace(sym);
 	if (namespace && namespace[0]) {
+
+		if (verify_module_namespace(namespace, mod->name))
+			return 0;
+
 		for_each_modinfo_entry(imported_namespace, info, "import_ns") {
 			if (strcmp(namespace, imported_namespace) == 0)
 				return 0;
@ -1658,15 +1726,30 @@ static void module_license_taint_check(struct module *mod, const char *license)
 	}
 }

-static void setup_modinfo(struct module *mod, struct load_info *info)
+static int setup_modinfo(struct module *mod, struct load_info *info)
 {
 	const 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)
@ -3323,7 +3406,9 @@ static int load_module(struct load_info *info, const char __user *uargs,
 		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/Makefile.build
+++ b/scripts/Makefile.build
@ -37,6 +37,90 @@ include $(srctree)/scripts/Makefile.compiler
 include $(kbuild-file)
 include $(srctree)/scripts/Makefile.lib

+# flags that take effect in current and sub directories
+KBUILD_AFLAGS += $(subdir-asflags-y)
+KBUILD_CFLAGS += $(subdir-ccflags-y)
+KBUILD_RUSTFLAGS += $(subdir-rustflags-y)
+
+# Figure out what we need to build from the various variables
+# ===========================================================================
+
+# When an object is listed to be built compiled-in and modular,
+# only build the compiled-in version
+obj-m := $(filter-out $(obj-y),$(obj-m))
+
+# Libraries are always collected in one lib file.
+# Filter out objects already built-in
+lib-y := $(filter-out $(obj-y), $(sort $(lib-y) $(lib-m)))
+
+# Subdirectories we need to descend into
+subdir-ym := $(sort $(subdir-y) $(subdir-m) \
+			$(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m))))
+
+# Handle objects in subdirs:
+# - If we encounter foo/ in $(obj-y), replace it by foo/built-in.a and
+#   foo/modules.order
+# - If we encounter foo/ in $(obj-m), replace it by foo/modules.order
+#
+# Generate modules.order to determine modorder. Unfortunately, we don't have
+# information about ordering between -y and -m subdirs. Just put -y's first.
+
+ifdef need-modorder
+obj-m := $(patsubst %/,%/modules.order, $(filter %/, $(obj-y)) $(obj-m))
+else
+obj-m := $(filter-out %/, $(obj-m))
+endif
+
+ifdef need-builtin
+obj-y		:= $(patsubst %/, %/built-in.a, $(obj-y))
+else
+obj-y		:= $(filter-out %/, $(obj-y))
+endif
+
+# Expand $(foo-objs) $(foo-y) etc. by replacing their individuals
+suffix-search = $(strip $(foreach s, $3, $($(1:%$(strip $2)=%$s))))
+# List composite targets that are constructed by combining other targets
+multi-search = $(sort $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $m)))
+# List primitive targets that are compiled from source files
+real-search = $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $(call suffix-search, $m, $2, $3), $m))
+
+# If $(foo-objs), $(foo-y), $(foo-m), or $(foo-) exists, foo.o is a composite object
+multi-obj-y := $(call multi-search, $(obj-y), .o, -objs -y)
+multi-obj-m := $(call multi-search, $(obj-m), .o, -objs -y -m)
+multi-obj-ym := $(multi-obj-y) $(multi-obj-m)
+
+# Replace multi-part objects by their individual parts,
+# including built-in.a from subdirectories
+real-obj-y := $(call real-search, $(obj-y), .o, -objs -y)
+real-obj-m := $(call real-search, $(obj-m), .o, -objs -y -m)
+
+always-y += $(always-m)
+
+# hostprogs-always-y += foo
+# ... is a shorthand for
+# hostprogs += foo
+# always-y  += foo
+hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)
+always-y += $(hostprogs-always-y) $(hostprogs-always-m)
+
+# userprogs-always-y is likewise.
+userprogs += $(userprogs-always-y) $(userprogs-always-m)
+always-y += $(userprogs-always-y) $(userprogs-always-m)
+
+# Add subdir path
+
+ifneq ($(obj),.)
+extra-y		:= $(addprefix $(obj)/, $(extra-y))
+always-y	:= $(addprefix $(obj)/, $(always-y))
+targets		:= $(addprefix $(obj)/, $(targets))
+obj-m		:= $(addprefix $(obj)/, $(obj-m))
+lib-y		:= $(addprefix $(obj)/, $(lib-y))
+real-obj-y	:= $(addprefix $(obj)/, $(real-obj-y))
+real-obj-m	:= $(addprefix $(obj)/, $(real-obj-m))
+multi-obj-m	:= $(addprefix $(obj)/, $(multi-obj-m))
+subdir-ym	:= $(addprefix $(obj)/, $(subdir-ym))
+endif
+
 ifndef obj
 $(warning kbuild: Makefile.build is included improperly)
 endif
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@ -1,89 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0

-# flags that take effect in current and sub directories
-KBUILD_AFLAGS += $(subdir-asflags-y)
-KBUILD_CFLAGS += $(subdir-ccflags-y)
-KBUILD_RUSTFLAGS += $(subdir-rustflags-y)
-
-# Figure out what we need to build from the various variables
-# ===========================================================================
-
-# When an object is listed to be built compiled-in and modular,
-# only build the compiled-in version
-obj-m := $(filter-out $(obj-y),$(obj-m))
-
-# Libraries are always collected in one lib file.
-# Filter out objects already built-in
-lib-y := $(filter-out $(obj-y), $(sort $(lib-y) $(lib-m)))
-
-# Subdirectories we need to descend into
-subdir-ym := $(sort $(subdir-y) $(subdir-m) \
-			$(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m))))
-
-# Handle objects in subdirs:
-# - If we encounter foo/ in $(obj-y), replace it by foo/built-in.a and
-#   foo/modules.order
-# - If we encounter foo/ in $(obj-m), replace it by foo/modules.order
-#
-# Generate modules.order to determine modorder. Unfortunately, we don't have
-# information about ordering between -y and -m subdirs. Just put -y's first.
-
-ifdef need-modorder
-obj-m := $(patsubst %/,%/modules.order, $(filter %/, $(obj-y)) $(obj-m))
-else
-obj-m := $(filter-out %/, $(obj-m))
-endif
-
-ifdef need-builtin
-obj-y		:= $(patsubst %/, %/built-in.a, $(obj-y))
-else
-obj-y		:= $(filter-out %/, $(obj-y))
-endif
-
-# Expand $(foo-objs) $(foo-y) etc. by replacing their individuals
-suffix-search = $(strip $(foreach s, $3, $($(1:%$(strip $2)=%$s))))
-# List composite targets that are constructed by combining other targets
-multi-search = $(sort $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $m)))
-# List primitive targets that are compiled from source files
-real-search = $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $(call suffix-search, $m, $2, $3), $m))
-
-# If $(foo-objs), $(foo-y), $(foo-m), or $(foo-) exists, foo.o is a composite object
-multi-obj-y := $(call multi-search, $(obj-y), .o, -objs -y)
-multi-obj-m := $(call multi-search, $(obj-m), .o, -objs -y -m)
-multi-obj-ym := $(multi-obj-y) $(multi-obj-m)
-
-# Replace multi-part objects by their individual parts,
-# including built-in.a from subdirectories
-real-obj-y := $(call real-search, $(obj-y), .o, -objs -y)
-real-obj-m := $(call real-search, $(obj-m), .o, -objs -y -m)
-
-always-y += $(always-m)
-
-# hostprogs-always-y += foo
-# ... is a shorthand for
-# hostprogs += foo
-# always-y  += foo
-hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)
-always-y += $(hostprogs-always-y) $(hostprogs-always-m)
-
-# userprogs-always-y is likewise.
-userprogs += $(userprogs-always-y) $(userprogs-always-m)
-always-y += $(userprogs-always-y) $(userprogs-always-m)
-
-# Add subdir path
-
-ifneq ($(obj),.)
-extra-y		:= $(addprefix $(obj)/,$(extra-y))
-always-y	:= $(addprefix $(obj)/,$(always-y))
-targets		:= $(addprefix $(obj)/,$(targets))
-obj-m		:= $(addprefix $(obj)/,$(obj-m))
-lib-y		:= $(addprefix $(obj)/,$(lib-y))
-real-obj-y	:= $(addprefix $(obj)/,$(real-obj-y))
-real-obj-m	:= $(addprefix $(obj)/,$(real-obj-m))
-multi-obj-m	:= $(addprefix $(obj)/, $(multi-obj-m))
-subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
-endif
-
 # Finds the multi-part object the current object will be linked into.
 # If the object belongs to two or more multi-part objects, list them all.
 modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@ -228,12 +228,24 @@ static void process_fqn(struct die *cache, Dwarf_Die *die)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(accessibility)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(bit_size)
-DEFINE_PROCESS_UDATA_ATTRIBUTE(byte_size)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(data_bit_offset)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(data_member_location)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(discr_value)

+static void process_byte_size_attr(struct die *cache, Dwarf_Die *die)
+{
+	Dwarf_Word value;
+	unsigned long override;
+
+	if (get_udata_attr(die, DW_AT_byte_size, &value)) {
+		if (stable && kabi_get_byte_size(cache->fqn, &override))
+			value = override;
+
+		process_fmt(cache, " byte_size(%" PRIu64 ")", value);
+	}
+}
+
 /* Match functions -- die_match_callback_t */
 #define DEFINE_MATCH(type)                                     \
 	static bool match_##type##_type(Dwarf_Die *die)        \
--- a/scripts/gendwarfksyms/examples/kabi.h
+++ b/scripts/gendwarfksyms/examples/kabi.h
@ -37,11 +37,14 @@
 #define __stringify(x...) __stringify_1(x)
 #endif

-#define __KABI_RULE(hint, target, value)                             \
+#define ___KABI_RULE(hint, target, value)                            \
 	static const char __PASTE(__gendwarfksyms_rule_,             \
 				  __COUNTER__)[] __used __aligned(1) \
 		__section(".discard.gendwarfksyms.kabi_rules") =     \
-			"1\0" #hint "\0" #target "\0" #value
+			"1\0" #hint "\0" target "\0" value
+
+#define __KABI_RULE(hint, target, value) \
+	___KABI_RULE(hint, #target, #value)

 #define __KABI_NORMAL_SIZE_ALIGN(_orig, _new)                                             \
 	union {                                                                           \
@ -89,6 +92,20 @@
 #define KABI_ENUMERATOR_VALUE(fqn, field, value) \
 	__KABI_RULE(enumerator_value, fqn field, value)

+/*
+ * KABI_BYTE_SIZE(fqn, value)
+ *   Set the byte_size attribute for the struct/union/enum fqn to
+ *   value bytes.
+ */
+#define KABI_BYTE_SIZE(fqn, value) __KABI_RULE(byte_size, fqn, value)
+
+/*
+ * KABI_TYPE_STRING(type, str)
+ *   For the given type, override the type string used in symtypes
+ *   output and version calculation with str.
+ */
+#define KABI_TYPE_STRING(type, str) ___KABI_RULE(type_string, type, str)
+
 /*
 * KABI_RESERVE
 *   Reserve some "padding" in a structure for use by LTS backports.
--- a/scripts/gendwarfksyms/examples/kabi_ex.c
+++ b/scripts/gendwarfksyms/examples/kabi_ex.c
@ -28,3 +28,10 @@ struct ex2c ex2c;
 struct ex3a ex3a;
 struct ex3b ex3b;
 struct ex3c ex3c;
+
+struct ex4a ex4a;
+
+struct ex5a ex5a;
+struct ex5b ex5b;
+
+int ex6a;
--- a/scripts/gendwarfksyms/examples/kabi_ex.h
+++ b/scripts/gendwarfksyms/examples/kabi_ex.h
@ -21,6 +21,12 @@
 * 	./gendwarfksyms --stable --dump-dies \
 * 		examples/kabi_ex.o 2>&1 >/dev/null | \
 * 	FileCheck examples/kabi_ex.h --check-prefix=STABLE
+
+ * $ nm examples/kabi_ex.o | awk '{ print $NF }' | \
+ * 	./gendwarfksyms --stable --dump-versions \
+ * 		examples/kabi_ex.o 2>&1 >/dev/null | \
+ * 	sort | \
+ * 	FileCheck examples/kabi_ex.h --check-prefix=VERSIONS
 */

 #ifndef __KABI_EX_H__
@ -170,7 +176,7 @@ struct ex2a {
 /*
 * STABLE:      variable structure_type ex2a {
 * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
- * STABLE-NEXT:   member base_type [[ULONG:long unsigned int|unsigned long]] byte_size(8) encoding(7) b data_member_location(8)
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) b data_member_location(8)
 * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) c data_member_location(16) ,
 * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) d data_member_location(24)
 * STABLE-NEXT: } byte_size(32)
@ -227,7 +233,7 @@ struct ex3a {

 /*
 * STABLE:      variable structure_type ex3a {
- * STABLE-NEXT:   member base_type [[ULONG:long unsigned int|unsigned long]] byte_size(8) encoding(7) a data_member_location(0)
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) a data_member_location(0)
 * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) unused data_member_location(8)
 * STABLE-NEXT: } byte_size(16)
 */
@ -260,4 +266,95 @@ _Static_assert(sizeof(struct ex3a) == sizeof(struct ex3c), "ex3a size doesn't ma
 * STABLE-NEXT: } byte_size(16)
 */

+/*
+ * Example: An ignored field added to an end of a partially opaque struct,
+ * while keeping the byte_size attribute unchanged.
+ */
+
+struct ex4a {
+	unsigned long a;
+	KABI_IGNORE(0, unsigned long b);
+};
+
+/*
+ * This may be safe if the structure allocation is managed by the core kernel
+ * and the layout remains unchanged except for appended new members.
+ */
+KABI_BYTE_SIZE(ex4a, 8);
+
+/*
+ * STABLE:      variable structure_type ex4a {
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) a data_member_location(0)
+ * STABLE-NEXT: } byte_size(8)
+ */
+
+/*
+ * Example: A type string override.
+ */
+
+struct ex5a {
+	unsigned long a;
+};
+
+/*
+ * This may be safe if the structure is fully opaque to modules, even though
+ * its definition has inadvertently become part of the ABI.
+ */
+KABI_TYPE_STRING(
+	"s#ex5a",
+	"structure_type ex5a { member pointer_type { s#ex4a } byte_size(8) p data_member_location(0) } byte_size(8)");
+
+/*
+ * Make sure the fully expanded type string includes ex4a.
+ *
+ * VERSIONS:      ex5a variable structure_type ex5a {
+ * VERSIONS-SAME:   member pointer_type {
+ * VERSIONS-SAME:     structure_type ex4a {
+ * VERSIONS-SAME:       member base_type [[ULONG:long unsigned int|unsigned long]] byte_size(8) encoding(7) a data_member_location(0)
+ * VERSIONS-SAME:     } byte_size(8)
+ * VERSIONS-SAME:   } byte_size(8) p data_member_location(0)
+ * VERSIONS-SAME: } byte_size(8)
+ */
+
+/*
+ * Example: A type string definition for a non-existent type.
+ */
+
+struct ex5b {
+	unsigned long a;
+};
+
+/* Replace the type string for struct ex5b */
+KABI_TYPE_STRING(
+	"s#ex5b",
+	"structure_type ex5b { member pointer_type { s#ex5c } byte_size(8) p data_member_location(0) } byte_size(8)");
+
+/* Define a type string for a non-existent struct ex5c */
+KABI_TYPE_STRING(
+	"s#ex5c",
+	"structure_type ex5c { member base_type int byte_size(4) encoding(5) n data_member_location(0) } byte_size(8)");
+
+/*
+ * Make sure the fully expanded type string includes the definition for ex5c.
+ *
+ * VERSIONS:      ex5b variable structure_type ex5b {
+ * VERSIONS-SAME:   member pointer_type {
+ * VERSIONS-SAME:     structure_type ex5c {
+ * VERSIONS-SAME:       member base_type int byte_size(4) encoding(5) n data_member_location(0)
+ * VERSIONS-SAME:     } byte_size(8)
+ * VERSIONS-SAME:   } byte_size(8) p data_member_location(0)
+ * VERSIONS-SAME: } byte_size(8)
+ */
+
+/*
+ * Example: A type string override for a symbol.
+ */
+
+KABI_TYPE_STRING("ex6a", "variable s#ex5c");
+
+/*
+ * VERSIONS:      ex6a variable structure_type ex5c {
+ * VERSIONS-SAME:   member base_type int byte_size(4) encoding(5) n data_member_location(0)
+ * VERSIONS-SAME: } byte_size(8)
+ */
 #endif /* __KABI_EX_H__ */
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@ -287,10 +287,12 @@ void generate_symtypes_and_versions(FILE *file);
 * kabi.c
 */

+bool kabi_get_byte_size(const char *fqn, unsigned long *value);
 bool kabi_is_enumerator_ignored(const char *fqn, const char *field);
 bool kabi_get_enumerator_value(const char *fqn, const char *field,
 			       unsigned long *value);
 bool kabi_is_declonly(const char *fqn);
+bool kabi_get_type_string(const char *type, const char **str);

 void kabi_read_rules(int fd);
 void kabi_free(void);
--- a/scripts/gendwarfksyms/kabi.c
+++ b/scripts/gendwarfksyms/kabi.c
@ -54,11 +54,27 @@
 */
 #define KABI_RULE_TAG_ENUMERATOR_VALUE "enumerator_value"

+/*
+ * Rule: byte_size
+ * - For the fqn_field in the target field, set the byte_size
+ *   attribute to the value in the value field.
+ */
+#define KABI_RULE_TAG_BYTE_SIZE "byte_size"
+
+/*
+ * Rule: type_string
+ * - For the type reference in the fqn field, use the type string
+ *   in the value field.
+ */
+#define KABI_RULE_TAG_TYPE_STRING "type_string"
+
 enum kabi_rule_type {
 	KABI_RULE_TYPE_UNKNOWN,
 	KABI_RULE_TYPE_DECLONLY,
 	KABI_RULE_TYPE_ENUMERATOR_IGNORE,
 	KABI_RULE_TYPE_ENUMERATOR_VALUE,
+	KABI_RULE_TYPE_BYTE_SIZE,
+	KABI_RULE_TYPE_TYPE_STRING,
 };

 #define RULE_HASH_BITS 7
@ -127,6 +143,14 @@ void kabi_read_rules(int fd)
 			.type = KABI_RULE_TYPE_ENUMERATOR_VALUE,
 			.tag = KABI_RULE_TAG_ENUMERATOR_VALUE,
 		},
+		{
+			.type = KABI_RULE_TYPE_BYTE_SIZE,
+			.tag = KABI_RULE_TAG_BYTE_SIZE,
+		},
+		{
+			.type = KABI_RULE_TYPE_TYPE_STRING,
+			.tag = KABI_RULE_TAG_TYPE_STRING,
+		},
 	};

 	if (!stable)
@ -222,25 +246,6 @@ void kabi_read_rules(int fd)
 	check(elf_end(elf));
 }

-bool kabi_is_declonly(const char *fqn)
-{
-	struct rule *rule;
-
-	if (!stable)
-		return false;
-	if (!fqn || !*fqn)
-		return false;
-
-	hash_for_each_possible(rules, rule, hash,
-			       rule_values_hash(KABI_RULE_TYPE_DECLONLY, fqn)) {
-		if (rule->type == KABI_RULE_TYPE_DECLONLY &&
-		    !strcmp(fqn, rule->target))
-			return true;
-	}
-
-	return false;
-}
-
 static char *get_enumerator_target(const char *fqn, const char *field)
 {
 	char *target = NULL;
@ -251,6 +256,47 @@ static char *get_enumerator_target(const char *fqn, const char *field)
 	return target;
 }

+static struct rule *find_rule(enum kabi_rule_type type, const char *target)
+{
+	struct rule *rule;
+
+	if (!stable)
+		return NULL;
+	if (!target || !*target)
+		return NULL;
+
+	hash_for_each_possible(rules, rule, hash,
+			       rule_values_hash(type, target)) {
+		if (rule->type == type && !strcmp(target, rule->target))
+			return rule;
+	}
+
+	return NULL;
+}
+
+static struct rule *find_enumerator_rule(enum kabi_rule_type type,
+					 const char *fqn, const char *field)
+{
+	struct rule *rule;
+	char *target;
+
+	if (!stable)
+		return NULL;
+	if (!fqn || !*fqn || !field || !*field)
+		return NULL;
+
+	target = get_enumerator_target(fqn, field);
+	rule = find_rule(type, target);
+
+	free(target);
+	return rule;
+}
+
+bool kabi_is_declonly(const char *fqn)
+{
+	return !!find_rule(KABI_RULE_TYPE_DECLONLY, fqn);
+}
+
 static unsigned long get_ulong_value(const char *value)
 {
 	unsigned long result = 0;
@ -267,58 +313,49 @@ static unsigned long get_ulong_value(const char *value)

 bool kabi_is_enumerator_ignored(const char *fqn, const char *field)
 {
-	bool match = false;
-	struct rule *rule;
-	char *target;
-
-	if (!stable)
-		return false;
-	if (!fqn || !*fqn || !field || !*field)
-		return false;
-
-	target = get_enumerator_target(fqn, field);
-
-	hash_for_each_possible(
-		rules, rule, hash,
-		rule_values_hash(KABI_RULE_TYPE_ENUMERATOR_IGNORE, target)) {
-		if (rule->type == KABI_RULE_TYPE_ENUMERATOR_IGNORE &&
-		    !strcmp(target, rule->target)) {
-			match = true;
-			break;
-		}
-	}
-
-	free(target);
-	return match;
+	return !!find_enumerator_rule(KABI_RULE_TYPE_ENUMERATOR_IGNORE, fqn,
+				      field);
 }

 bool kabi_get_enumerator_value(const char *fqn, const char *field,
 			       unsigned long *value)
 {
-	bool match = false;
 	struct rule *rule;
-	char *target;

-	if (!stable)
-		return false;
-	if (!fqn || !*fqn || !field || !*field)
-		return false;
-
-	target = get_enumerator_target(fqn, field);
-
-	hash_for_each_possible(rules, rule, hash,
-			       rule_values_hash(KABI_RULE_TYPE_ENUMERATOR_VALUE,
-						target)) {
-		if (rule->type == KABI_RULE_TYPE_ENUMERATOR_VALUE &&
-		    !strcmp(target, rule->target)) {
-			*value = get_ulong_value(rule->value);
-			match = true;
-			break;
-		}
+	rule = find_enumerator_rule(KABI_RULE_TYPE_ENUMERATOR_VALUE, fqn,
+				    field);
+	if (rule) {
+		*value = get_ulong_value(rule->value);
+		return true;
 	}

-	free(target);
-	return match;
+	return false;
+}
+
+bool kabi_get_byte_size(const char *fqn, unsigned long *value)
+{
+	struct rule *rule;
+
+	rule = find_rule(KABI_RULE_TYPE_BYTE_SIZE, fqn);
+	if (rule) {
+		*value = get_ulong_value(rule->value);
+		return true;
+	}
+
+	return false;
+}
+
+bool kabi_get_type_string(const char *type, const char **str)
+{
+	struct rule *rule;
+
+	rule = find_rule(KABI_RULE_TYPE_TYPE_STRING, type);
+	if (rule) {
+		*str = rule->value;
+		return true;
+	}
+
+	return false;
 }

 void kabi_free(void)
--- a/scripts/gendwarfksyms/types.c
+++ b/scripts/gendwarfksyms/types.c
@ -100,7 +100,7 @@ static void type_expansion_append(struct type_expansion *type, const char *s,
 #define TYPE_HASH_BITS 12
 static HASHTABLE_DEFINE(type_map, 1 << TYPE_HASH_BITS);

-static int type_map_get(const char *name, struct type_expansion **res)
+static int __type_map_get(const char *name, struct type_expansion **res)
 {
 	struct type_expansion *e;

@ -114,11 +114,12 @@ static int type_map_get(const char *name, struct type_expansion **res)
 	return -1;
 }

-static void type_map_add(const char *name, struct type_expansion *type)
+static struct type_expansion *type_map_add(const char *name,
+					   struct type_expansion *type)
 {
 	struct type_expansion *e;

-	if (type_map_get(name, &e)) {
+	if (__type_map_get(name, &e)) {
 		e = xmalloc(sizeof(struct type_expansion));
 		type_expansion_init(e);
 		e->name = xstrdup(name);
@ -130,7 +131,7 @@ static void type_map_add(const char *name, struct type_expansion *type)
 	} else {
 		/* Use the longest available expansion */
 		if (type->len <= e->len)
-			return;
+			return e;

 		type_list_free(&e->expanded);

@ -148,6 +149,34 @@ static void type_map_add(const char *name, struct type_expansion *type)
 		type_list_write(&e->expanded, stderr);
 		checkp(fputs("\n", stderr));
 	}
+
+	return e;
+}
+
+static void type_parse(const char *name, const char *str,
+		       struct type_expansion *type);
+
+static int type_map_get(const char *name, struct type_expansion **res)
+{
+	struct type_expansion type;
+	const char *override;
+
+	if (!__type_map_get(name, res))
+		return 0;
+
+	/*
+	 * If die_map didn't contain a type, we might still have
+	 * a type_string kABI rule that defines it.
+	 */
+	if (stable && kabi_get_type_string(name, &override)) {
+		type_expansion_init(&type);
+		type_parse(name, override, &type);
+		*res = type_map_add(name, &type);
+		type_expansion_free(&type);
+		return 0;
+	}
+
+	return -1;
 }

 static void type_map_write(FILE *file)
@ -267,15 +296,18 @@ static char *get_type_name(struct die *cache)
 	return name;
 }

-static void __calculate_version(struct version *version, struct list_head *list)
+static void __calculate_version(struct version *version,
+				struct type_expansion *type)
 {
 	struct type_list_entry *entry;
 	struct type_expansion *e;

 	/* Calculate a CRC over an expanded type string */
-	list_for_each_entry(entry, list, list) {
+	list_for_each_entry(entry, &type->expanded, list) {
 		if (is_type_prefix(entry->str)) {
-			check(type_map_get(entry->str, &e));
+			if (type_map_get(entry->str, &e))
+				error("unknown type reference to '%s' when expanding '%s'",
+				      entry->str, type->name);

 			/*
 			 * It's sufficient to expand each type reference just
@ -285,7 +317,7 @@ static void __calculate_version(struct version *version, struct list_head *list)
 				version_add(version, entry->str);
 			} else {
 				cache_mark_expanded(&expansion_cache, e);
-				__calculate_version(version, &e->expanded);
+				__calculate_version(version, e);
 			}
 		} else {
 			version_add(version, entry->str);
@ -293,10 +325,11 @@ static void __calculate_version(struct version *version, struct list_head *list)
 	}
 }

-static void calculate_version(struct version *version, struct list_head *list)
+static void calculate_version(struct version *version,
+			      struct type_expansion *type)
 {
 	version_init(version);
-	__calculate_version(version, list);
+	__calculate_version(version, type);
 	cache_free(&expansion_cache);
 }

@ -372,9 +405,80 @@ static void type_expand(struct die *cache, struct type_expansion *type,
 	cache_free(&expansion_cache);
 }

+static void type_parse(const char *name, const char *str,
+		       struct type_expansion *type)
+{
+	char *fragment;
+	size_t start = 0;
+	size_t end;
+	size_t pos;
+
+	if (!*str)
+		error("empty type string override for '%s'", name);
+
+	type_expansion_init(type);
+
+	for (pos = 0; str[pos]; ++pos) {
+		bool empty;
+		char marker = ' ';
+
+		if (!is_type_prefix(&str[pos]))
+			continue;
+
+		end = pos + 2;
+
+		/*
+		 * Find the end of the type reference. If the type name contains
+		 * spaces, it must be in single quotes.
+		 */
+		if (str[end] == '\'') {
+			marker = '\'';
+			++end;
+		}
+		while (str[end] && str[end] != marker)
+			++end;
+
+		/* Check that we have a non-empty type name */
+		if (marker == '\'') {
+			if (str[end] != marker)
+				error("incomplete %c# type reference for '%s' (string : '%s')",
+				      str[pos], name, str);
+			empty = end == pos + 3;
+			++end;
+		} else {
+			empty = end == pos + 2;
+		}
+		if (empty)
+			error("empty %c# type name for '%s' (string: '%s')",
+			      str[pos], name, str);
+
+		/* Append the part of the string before the type reference */
+		if (pos > start) {
+			fragment = xstrndup(&str[start], pos - start);
+			type_expansion_append(type, fragment, fragment);
+		}
+
+		/*
+		 * Append the type reference -- note that if the reference
+		 * is invalid, i.e. points to a non-existent type, we will
+		 * print out an error when calculating versions.
+		 */
+		fragment = xstrndup(&str[pos], end - pos);
+		type_expansion_append(type, fragment, fragment);
+
+		start = end;
+		pos = end - 1;
+	}
+
+	/* Append the rest of the type string, if there's any left */
+	if (str[start])
+		type_expansion_append(type, &str[start], NULL);
+}
+
 static void expand_type(struct die *cache, void *arg)
 {
 	struct type_expansion type;
+	const char *override;
 	char *name;

 	if (cache->mapped)
@ -399,9 +503,13 @@ static void expand_type(struct die *cache, void *arg)
 		return;

 	debug("%s", name);
-	type_expand(cache, &type, true);
-	type_map_add(name, &type);

+	if (stable && kabi_get_type_string(name, &override))
+		type_parse(name, override, &type);
+	else
+		type_expand(cache, &type, true);
+
+	type_map_add(name, &type);
 	type_expansion_free(&type);
 	free(name);
 }
@ -410,6 +518,7 @@ static void expand_symbol(struct symbol *sym, void *arg)
 {
 	struct type_expansion type;
 	struct version version;
+	const char *override;
 	struct die *cache;

 	/*
@ -423,11 +532,14 @@ static void expand_symbol(struct symbol *sym, void *arg)
 	if (__die_map_get(sym->die_addr, DIE_SYMBOL, &cache))
 		return; /* We'll warn about missing CRCs later. */

-	type_expand(cache, &type, false);
+	if (stable && kabi_get_type_string(sym->name, &override))
+		type_parse(sym->name, override, &type);
+	else
+		type_expand(cache, &type, false);

 	/* If the symbol already has a version, don't calculate it again. */
 	if (sym->state != SYMBOL_PROCESSED) {
-		calculate_version(&version, &type.expanded);
+		calculate_version(&version, &type);
 		symbol_set_crc(sym, version.crc);
 		debug("%s = %lx", sym->name, version.crc);

--- a/scripts/genksyms/genksyms.c
+++ b/scripts/genksyms/genksyms.c
@ -181,13 +181,9 @@ static int is_unknown_symbol(struct symbol *sym)
 			strcmp(defn->string, "{") == 0);
 }

-static struct symbol *__add_symbol(const char *name, enum symbol_type type,
-			    struct string_list *defn, int is_extern,
-			    int is_reference)
+static struct string_list *process_enum(const char *name, enum symbol_type type,
+					struct string_list *defn)
 {
-	unsigned long h;
-	struct symbol *sym;
-	enum symbol_status status = STATUS_UNCHANGED;
 	/* The parser adds symbols in the order their declaration completes,
 	 * so it is safe to store the value of the previous enum constant in
 	 * a static variable.
@ -216,7 +212,7 @@ static struct symbol *__add_symbol(const char *name, enum symbol_type type,
 				defn = mk_node(buf);
 			}
 		}
-	} else if (type == SYM_ENUM) {
+	} else {
 		free_list(last_enum_expr, NULL);
 		last_enum_expr = NULL;
 		enum_counter = 0;
@ -225,6 +221,23 @@ static struct symbol *__add_symbol(const char *name, enum symbol_type type,
 			return NULL;
 	}

+	return defn;
+}
+
+static struct symbol *__add_symbol(const char *name, enum symbol_type type,
+			    struct string_list *defn, int is_extern,
+			    int is_reference)
+{
+	unsigned long h;
+	struct symbol *sym;
+	enum symbol_status status = STATUS_UNCHANGED;
+
+	if ((type == SYM_ENUM_CONST || type == SYM_ENUM) && !is_reference) {
+		defn = process_enum(name, type, defn);
+		if (defn == NULL)
+			return NULL;
+	}
+
 	h = crc32(name);
 	hash_for_each_possible(symbol_hashtable, sym, hnode, h) {
 		if (map_to_ns(sym->type) != map_to_ns(type) ||
--- a/scripts/kconfig/expr.h
+++ b/scripts/kconfig/expr.h
@ -205,15 +205,26 @@ struct property {
 	for (st = sym->prop; st; st = st->next) \
 		if (st->text)

+enum menu_type {
+	M_CHOICE,  // "choice"
+	M_COMMENT, // "comment"
+	M_IF,      // "if"
+	M_MENU,    // "mainmenu", "menu", "menuconfig"
+	M_NORMAL,  // others, i.e., "config"
+};
+
 /*
 * Represents a node in the menu tree, as seen in e.g. menuconfig (though used
 * for all front ends). Each symbol, menu, etc. defined in the Kconfig files
 * gets a node. A symbol defined in multiple locations gets one node at each
 * location.
 *
+ * @type: type of the menu entry
 * @choice_members: list of choice members with priority.
 */
 struct menu {
+	enum menu_type type;
+
 	/* The next menu node at the same level */
 	struct menu *next;

--- a/scripts/kconfig/lkc.h
+++ b/scripts/kconfig/lkc.h
@ -81,7 +81,7 @@ void _menu_init(void);
 void menu_warn(const struct menu *menu, const char *fmt, ...);
 struct menu *menu_add_menu(void);
 void menu_end_menu(void);
-void menu_add_entry(struct symbol *sym);
+void menu_add_entry(struct symbol *sym, enum menu_type type);
 void menu_add_dep(struct expr *dep);
 void menu_add_visibility(struct expr *dep);
 struct property *menu_add_prompt(enum prop_type type, const char *prompt,
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@ -15,7 +15,7 @@

 static const char nohelp_text[] = "There is no help available for this option.";

-struct menu rootmenu;
+struct menu rootmenu = { .type = M_MENU };
 static struct menu **last_entry_ptr;

 /**
@ -65,12 +65,13 @@ void _menu_init(void)
 	last_entry_ptr = &rootmenu.list;
 }

-void menu_add_entry(struct symbol *sym)
+void menu_add_entry(struct symbol *sym, enum menu_type type)
 {
 	struct menu *menu;

 	menu = xmalloc(sizeof(*menu));
 	memset(menu, 0, sizeof(*menu));
+	menu->type = type;
 	menu->sym = sym;
 	menu->parent = current_menu;
 	menu->filename = cur_filename;
--- a/scripts/kconfig/parser.y
+++ b/scripts/kconfig/parser.y
@ -139,7 +139,7 @@ stmt_list_in_choice:

 config_entry_start: T_CONFIG nonconst_symbol T_EOL
 {
-	menu_add_entry($2);
+	menu_add_entry($2, M_NORMAL);
 	printd(DEBUG_PARSE, "%s:%d:config %s\n", cur_filename, cur_lineno, $2->name);
 };

@ -173,7 +173,7 @@ config_stmt: config_entry_start config_option_list

 menuconfig_entry_start: T_MENUCONFIG nonconst_symbol T_EOL
 {
-	menu_add_entry($2);
+	menu_add_entry($2, M_MENU);
 	printd(DEBUG_PARSE, "%s:%d:menuconfig %s\n", cur_filename, cur_lineno, $2->name);
 };

@ -246,7 +246,7 @@ choice: T_CHOICE T_EOL
 {
 	struct symbol *sym = sym_lookup(NULL, 0);

-	menu_add_entry(sym);
+	menu_add_entry(sym, M_CHOICE);
 	menu_set_type(S_BOOLEAN);
 	INIT_LIST_HEAD(&current_entry->choice_members);

@ -315,7 +315,7 @@ default:
 if_entry: T_IF expr T_EOL
 {
 	printd(DEBUG_PARSE, "%s:%d:if\n", cur_filename, cur_lineno);
-	menu_add_entry(NULL);
+	menu_add_entry(NULL, M_IF);
 	menu_add_dep($2);
 	$$ = menu_add_menu();
 };
@ -338,7 +338,7 @@ if_stmt_in_choice: if_entry stmt_list_in_choice if_end

 menu: T_MENU T_WORD_QUOTE T_EOL
 {
-	menu_add_entry(NULL);
+	menu_add_entry(NULL, M_MENU);
 	menu_add_prompt(P_MENU, $2, NULL);
 	printd(DEBUG_PARSE, "%s:%d:menu\n", cur_filename, cur_lineno);
 };
@ -376,7 +376,7 @@ source_stmt: T_SOURCE T_WORD_QUOTE T_EOL

 comment: T_COMMENT T_WORD_QUOTE T_EOL
 {
-	menu_add_entry(NULL);
+	menu_add_entry(NULL, M_COMMENT);
 	menu_add_prompt(P_COMMENT, $2, NULL);
 	printd(DEBUG_PARSE, "%s:%d:comment\n", cur_filename, cur_lineno);
 };
--- a/scripts/misc-check
+++ b/scripts/misc-check
@ -3,17 +3,65 @@

 set -e

-# Detect files that are tracked but ignored by git. This is checked only when
-# ${KBUILD_EXTRA_WARN} contains 1, git is installed, and the source tree is
-# tracked by git.
+# Detect files that are tracked but ignored by git.
 check_tracked_ignored_files () {
-	case "${KBUILD_EXTRA_WARN}" in
-	*1*) ;;
-	*) return;;
-	esac
-
-	git -C ${srctree:-.} ls-files -i -c --exclude-per-directory=.gitignore 2>/dev/null |
+	git -C "${srctree:-.}" ls-files -i -c --exclude-per-directory=.gitignore 2>/dev/null |
 		sed 's/$/: warning: ignored by one of the .gitignore files/' >&2
 }

+# Check for missing #include <linux/export.h>
+#
+# The rule for including <linux/export.h> is very simple:
+# Include <linux/export.h> only when you use EXPORT_SYMBOL(). That's it.
+#
+# However, some headers include <linux/export.h> even though they are completely
+# unrelated to EXPORT_SYMBOL().
+#
+# One example is include/linux/module.h. Please note <linux/module.h> and
+# <linux/export.h> are orthogonal. <linux/module.h> should be included by files
+# that can be compiled as modules. In other words, <linux/module.h> should be
+# included by EXPORT_SYMBOL consumers. In contrast, <linux/export.h> should be
+# included from EXPORT_SYMBOL providers, which may or may not be modular.
+# Hence, include/linux/module.h should *not* include <linux/export.h>.
+#
+# Another example is include/linux/linkage.h, which is completely unrelated to
+# EXPORT_SYMBOL(). Worse, it is included by most C files, which means, most C
+# files end up including <linux/export.h>, even though only some of them
+# actually export symbols. Hence, include/linux/linkage.h should *not* include
+# <linux/export.h>.
+#
+# Before fixing such headers, we must ensure that C files using EXPORT_SYMBOL()
+# include <linux/export.h> directly, since many C files currently rely on
+# <linux/export.h> being included indirectly (likely, via <linux/linkage> etc.).
+#
+# Therefore, this check.
+#
+# The problem is simple - the warned files use EXPORT_SYMBOL(), but do not
+# include <linux/export.h>. Please add #include <linux/export.h> to them.
+#
+# If the included headers are sorted alphabetically, please insert
+# <linux/export.h> in the appropriate position to maintain the sort order.
+# For this reason, this script only checks missing <linux/export.h>, but
+# does not automatically fix it.
+check_missing_include_linux_export_h () {
+
+	git -C "${srctree:-.}" grep --files-with-matches -E 'EXPORT_SYMBOL((_NS)?(_GPL)?|_GPL_FOR_MODULES)\(.*\)' \
+	    -- '*.[ch]' :^tools/ :^include/linux/export.h |
+	xargs -r git -C "${srctree:-.}" grep --files-without-match '#include[[:space:]]*<linux/export\.h>' |
+	xargs -r printf "%s: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing\n" >&2
+}
+
+# If you do not use EXPORT_SYMBOL(), please do not include <linux/export.h>.
+# Currently, this is checked for *.c files, but not for *.h files, because some
+# *.c files rely on <linux/export.h> being included indirectly.
+check_unnecessary_include_linux_export_h () {
+
+	git -C "${srctree:-.}" grep --files-with-matches '#include[[:space:]]*<linux/export\.h>' \
+	    -- '*.[c]' :^tools/ |
+	xargs -r git -C "${srctree:-.}" grep --files-without-match -E 'EXPORT_SYMBOL((_NS)?(_GPL)?|_GPL_FOR_MODULES)\(.*\)' |
+	xargs -r printf "%s: warning: EXPORT_SYMBOL() is not used, but #include <linux/export.h> is present\n" >&2
+}
+
 check_tracked_ignored_files
+check_missing_include_linux_export_h
+check_unnecessary_include_linux_export_h
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@ -28,6 +28,8 @@
 #include "modpost.h"
 #include "../../include/linux/license.h"

+#define MODULE_NS_PREFIX "module:"
+
 static bool module_enabled;
 /* Are we using CONFIG_MODVERSIONS? */
 static bool modversions;
@ -1595,11 +1597,14 @@ static void read_symbols(const char *modname)
 			license = get_next_modinfo(&info, "license", license);
 		}

-		namespace = get_modinfo(&info, "import_ns");
-		while (namespace) {
+		for (namespace = get_modinfo(&info, "import_ns");
+		     namespace;
+		     namespace = get_next_modinfo(&info, "import_ns", namespace)) {
+			if (strstarts(namespace, MODULE_NS_PREFIX))
+				error("%s: explicitly importing namespace \"%s\" is not allowed.\n",
+				      mod->name, namespace);
+
 			add_namespace(&mod->imported_namespaces, namespace);
-			namespace = get_next_modinfo(&info, "import_ns",
-						     namespace);
 		}

 		if (!get_modinfo(&info, "description"))
@ -1684,6 +1689,46 @@ void buf_write(struct buffer *buf, const char *s, int len)
 	buf->pos += len;
 }

+/**
+ * verify_module_namespace() - does @modname have access to this symbol's @namespace
+ * @namespace: export symbol namespace
+ * @modname: module name
+ *
+ * If @namespace is prefixed with "module:" to indicate it is a module namespace
+ * then test if @modname matches any of the comma separated patterns.
+ *
+ * The patterns only support tail-glob.
+ */
+static bool verify_module_namespace(const char *namespace, const char *modname)
+{
+	size_t len, modlen = strlen(modname);
+	const char *prefix = "module:";
+	const char *sep;
+	bool glob;
+
+	if (!strstarts(namespace, prefix))
+		return false;
+
+	for (namespace += strlen(prefix); *namespace; namespace = sep) {
+		sep = strchrnul(namespace, ',');
+		len = sep - namespace;
+
+		glob = false;
+		if (sep[-1] == '*') {
+			len--;
+			glob = true;
+		}
+
+		if (*sep)
+			sep++;
+
+		if (strncmp(namespace, modname, len) == 0 && (glob || len == modlen))
+			return true;
+	}
+
+	return false;
+}
+
 static void check_exports(struct module *mod)
 {
 	struct symbol *s, *exp;
@ -1711,7 +1756,8 @@ static void check_exports(struct module *mod)

 		basename = get_basename(mod->name);

-		if (!contains_namespace(&mod->imported_namespaces, exp->namespace)) {
+		if (!verify_module_namespace(exp->namespace, basename) &&
+		    !contains_namespace(&mod->imported_namespaces, exp->namespace)) {
 			modpost_log(!allow_missing_ns_imports,
 				    "module %s uses symbol %s from namespace %s, but does not import it.\n",
 				    basename, exp->name, exp->namespace);
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@ -344,7 +344,7 @@ case "$1" in

 	"tags")
 		rm -f tags
-		xtags ctags
+		xtags ${CTAGS:-ctags}
 		remove_structs=y
 		;;