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e070355664
Summary of modules changes for the 5.4 merge window:
- Introduce exported symbol namespaces.
This new feature allows subsystem maintainers to partition and
categorize their exported symbols into explicit namespaces. Module
authors are now required to import the namespaces they need.
Some of the main motivations of this feature include: allowing kernel
developers to better manage the export surface, allow subsystem
maintainers to explicitly state that usage of some exported symbols
should only be limited to certain users (think: inter-module or
inter-driver symbols, debugging symbols, etc), as well as more easily
limiting the availability of namespaced symbols to other parts of the
kernel. With the module import requirement, it is also easier to spot
the misuse of exported symbols during patch review. Two new macros are
introduced: EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL(). The API is
thoroughly documented in Documentation/kbuild/namespaces.rst.
- Some small code and kbuild cleanups here and there.
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Merge tag 'modules-for-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux
Pull modules updates from Jessica Yu:
"The main bulk of this pull request introduces a new exported symbol
namespaces feature. The number of exported symbols is increasingly
growing with each release (we're at about 31k exports as of 5.3-rc7)
and we currently have no way of visualizing how these symbols are
"clustered" or making sense of this huge export surface.
Namespacing exported symbols allows kernel developers to more
explicitly partition and categorize exported symbols, as well as more
easily limiting the availability of namespaced symbols to other parts
of the kernel. For starters, we have introduced the USB_STORAGE
namespace to demonstrate the API's usage. I have briefly summarized
the feature and its main motivations in the tag below.
Summary:
- Introduce exported symbol namespaces.
This new feature allows subsystem maintainers to partition and
categorize their exported symbols into explicit namespaces. Module
authors are now required to import the namespaces they need.
Some of the main motivations of this feature include: allowing
kernel developers to better manage the export surface, allow
subsystem maintainers to explicitly state that usage of some
exported symbols should only be limited to certain users (think:
inter-module or inter-driver symbols, debugging symbols, etc), as
well as more easily limiting the availability of namespaced symbols
to other parts of the kernel.
With the module import requirement, it is also easier to spot the
misuse of exported symbols during patch review.
Two new macros are introduced: EXPORT_SYMBOL_NS() and
EXPORT_SYMBOL_NS_GPL(). The API is thoroughly documented in
Documentation/kbuild/namespaces.rst.
- Some small code and kbuild cleanups here and there"
* tag 'modules-for-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
module: Remove leftover '#undef' from export header
module: remove unneeded casts in cmp_name()
module: move CONFIG_UNUSED_SYMBOLS to the sub-menu of MODULES
module: remove redundant 'depends on MODULES'
module: Fix link failure due to invalid relocation on namespace offset
usb-storage: export symbols in USB_STORAGE namespace
usb-storage: remove single-use define for debugging
docs: Add documentation for Symbol Namespaces
scripts: Coccinelle script for namespace dependencies.
modpost: add support for generating namespace dependencies
export: allow definition default namespaces in Makefiles or sources
module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
modpost: add support for symbol namespaces
module: add support for symbol namespaces.
export: explicitly align struct kernel_symbol
module: support reading multiple values per modinfo tag
200 lines
6.3 KiB
C
200 lines
6.3 KiB
C
#ifndef _LINUX_EXPORT_H
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#define _LINUX_EXPORT_H
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/*
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* Export symbols from the kernel to modules. Forked from module.h
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* to reduce the amount of pointless cruft we feed to gcc when only
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* exporting a simple symbol or two.
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*
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* Try not to add #includes here. It slows compilation and makes kernel
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* hackers place grumpy comments in header files.
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*/
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#ifndef __ASSEMBLY__
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#ifdef MODULE
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extern struct module __this_module;
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#define THIS_MODULE (&__this_module)
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#else
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#define THIS_MODULE ((struct module *)0)
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#endif
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#define NS_SEPARATOR "."
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#ifdef CONFIG_MODVERSIONS
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/* Mark the CRC weak since genksyms apparently decides not to
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* generate a checksums for some symbols */
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#if defined(CONFIG_MODULE_REL_CRCS)
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#define __CRC_SYMBOL(sym, sec) \
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asm(" .section \"___kcrctab" sec "+" #sym "\", \"a\" \n" \
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" .weak __crc_" #sym " \n" \
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" .long __crc_" #sym " - . \n" \
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" .previous \n")
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#else
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#define __CRC_SYMBOL(sym, sec) \
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asm(" .section \"___kcrctab" sec "+" #sym "\", \"a\" \n" \
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" .weak __crc_" #sym " \n" \
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" .long __crc_" #sym " \n" \
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" .previous \n")
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#endif
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#else
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#define __CRC_SYMBOL(sym, sec)
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#endif
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#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
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#include <linux/compiler.h>
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/*
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* Emit the ksymtab entry as a pair of relative references: this reduces
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* the size by half on 64-bit architectures, and eliminates the need for
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* absolute relocations that require runtime processing on relocatable
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* kernels.
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*/
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#define __KSYMTAB_ENTRY_NS(sym, sec, ns) \
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__ADDRESSABLE(sym) \
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asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
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" .balign 4 \n" \
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"__ksymtab_" #sym NS_SEPARATOR #ns ": \n" \
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" .long " #sym "- . \n" \
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" .long __kstrtab_" #sym "- . \n" \
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" .long __kstrtab_ns_" #sym "- . \n" \
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" .previous \n")
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#define __KSYMTAB_ENTRY(sym, sec) \
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__ADDRESSABLE(sym) \
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asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
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" .balign 4 \n" \
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"__ksymtab_" #sym ": \n" \
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" .long " #sym "- . \n" \
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" .long __kstrtab_" #sym "- . \n" \
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" .long 0 \n" \
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" .previous \n")
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struct kernel_symbol {
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int value_offset;
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int name_offset;
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int namespace_offset;
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};
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#else
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#define __KSYMTAB_ENTRY_NS(sym, sec, ns) \
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static const struct kernel_symbol __ksymtab_##sym##__##ns \
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asm("__ksymtab_" #sym NS_SEPARATOR #ns) \
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__attribute__((section("___ksymtab" sec "+" #sym), used)) \
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__aligned(sizeof(void *)) \
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= { (unsigned long)&sym, __kstrtab_##sym, __kstrtab_ns_##sym }
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#define __KSYMTAB_ENTRY(sym, sec) \
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static const struct kernel_symbol __ksymtab_##sym \
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asm("__ksymtab_" #sym) \
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__attribute__((section("___ksymtab" sec "+" #sym), used)) \
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__aligned(sizeof(void *)) \
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= { (unsigned long)&sym, __kstrtab_##sym, NULL }
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struct kernel_symbol {
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unsigned long value;
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const char *name;
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const char *namespace;
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};
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#endif
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#ifdef __GENKSYMS__
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#define ___EXPORT_SYMBOL(sym,sec) __GENKSYMS_EXPORT_SYMBOL(sym)
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#define ___EXPORT_SYMBOL_NS(sym,sec,ns) __GENKSYMS_EXPORT_SYMBOL(sym)
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#else
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#define ___export_symbol_common(sym, sec) \
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extern typeof(sym) sym; \
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__CRC_SYMBOL(sym, sec); \
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static const char __kstrtab_##sym[] \
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__attribute__((section("__ksymtab_strings"), used, aligned(1))) \
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= #sym \
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/* For every exported symbol, place a struct in the __ksymtab section */
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#define ___EXPORT_SYMBOL_NS(sym, sec, ns) \
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___export_symbol_common(sym, sec); \
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static const char __kstrtab_ns_##sym[] \
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__attribute__((section("__ksymtab_strings"), used, aligned(1))) \
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= #ns; \
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__KSYMTAB_ENTRY_NS(sym, sec, ns)
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#define ___EXPORT_SYMBOL(sym, sec) \
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___export_symbol_common(sym, sec); \
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__KSYMTAB_ENTRY(sym, sec)
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#endif
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#if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS)
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/*
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* Allow symbol exports to be disabled completely so that C code may
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* be reused in other execution contexts such as the UEFI stub or the
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* decompressor.
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*/
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#define __EXPORT_SYMBOL_NS(sym, sec, ns)
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#define __EXPORT_SYMBOL(sym, sec)
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#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
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#include <generated/autoksyms.h>
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/*
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* For fine grained build dependencies, we want to tell the build system
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* about each possible exported symbol even if they're not actually exported.
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* We use a symbol pattern __ksym_marker_<symbol> that the build system filters
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* from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
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* discarded in the final link stage.
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*/
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#define __ksym_marker(sym) \
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static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
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#define __EXPORT_SYMBOL(sym, sec) \
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__ksym_marker(sym); \
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__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
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#define __cond_export_sym(sym, sec, conf) \
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___cond_export_sym(sym, sec, conf)
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#define ___cond_export_sym(sym, sec, enabled) \
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__cond_export_sym_##enabled(sym, sec)
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#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
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#define __cond_export_sym_0(sym, sec) /* nothing */
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#define __EXPORT_SYMBOL_NS(sym, sec, ns) \
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__ksym_marker(sym); \
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__cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
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#define __cond_export_ns_sym(sym, sec, ns, conf) \
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___cond_export_ns_sym(sym, sec, ns, conf)
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#define ___cond_export_ns_sym(sym, sec, ns, enabled) \
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__cond_export_ns_sym_##enabled(sym, sec, ns)
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#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
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#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
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#else
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#define __EXPORT_SYMBOL_NS(sym,sec,ns) ___EXPORT_SYMBOL_NS(sym,sec,ns)
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#define __EXPORT_SYMBOL(sym,sec) ___EXPORT_SYMBOL(sym,sec)
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#endif /* CONFIG_MODULES */
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#ifdef DEFAULT_SYMBOL_NAMESPACE
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#undef __EXPORT_SYMBOL
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#define __EXPORT_SYMBOL(sym, sec) \
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__EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
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#endif
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#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
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#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
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#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
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#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL_NS(sym, "", ns)
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#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL_NS(sym, "_gpl", ns)
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#ifdef CONFIG_UNUSED_SYMBOLS
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#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
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#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
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#else
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#define EXPORT_UNUSED_SYMBOL(sym)
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#define EXPORT_UNUSED_SYMBOL_GPL(sym)
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#endif
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#endif /* !__ASSEMBLY__ */
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#endif /* _LINUX_EXPORT_H */
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