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author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-20 20:42:41 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-20 20:42:41 +0300 |
commit | 5c40cd7db64a2949f268d7467b9be551a565d14b (patch) | |
tree | fb8a67f6edcb0c9922c256a598d675c1c04051d6 /Documentation/core-api/symbol-namespaces.rst | |
parent | 8bde384a2090759efc9b92f34300887d418a2a3a (diff) | |
parent | 25bf10be219d37d2fb221c93816a913f5f735530 (diff) | |
download | linux-rolling-stable.tar.xz |
Merge v6.16.2linux-rolling-stable
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/core-api/symbol-namespaces.rst')
-rw-r--r-- | Documentation/core-api/symbol-namespaces.rst | 47 |
1 files changed, 18 insertions, 29 deletions
diff --git a/Documentation/core-api/symbol-namespaces.rst b/Documentation/core-api/symbol-namespaces.rst index c6f59c5e2564..32fc73dc5529 100644 --- 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 @@ -31,15 +21,15 @@ its configuration, reject loading the module or warn about a missing import. Additionally, it is possible to put symbols into a module namespace, strictly limiting which modules are allowed to use these symbols. -2. How to define Symbol Namespaces -================================== +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 @@ -57,8 +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) @@ -86,8 +76,8 @@ 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. -2.3 Using the EXPORT_SYMBOL_GPL_FOR_MODULES() macro -=================================================== +Using the EXPORT_SYMBOL_GPL_FOR_MODULES() macro +----------------------------------------------- Symbols exported using this macro are put into a module namespace. This namespace cannot be imported. @@ -95,15 +85,15 @@ 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: +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. -3. How to use Symbols exported in Namespaces -============================================ +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 @@ -125,11 +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 @@ -140,8 +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 |