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The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to export a symbol to a specific namespace. There are no _GPL_FUTURE and _UNUSED variants because these are currently unused, and I'm not sure they are necessary. I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the namespace of ASM exports to NULL by default. In case of relative references, it will be relocatable to NULL. If there's a need, this should be pretty easy to add. A module that wants to use a symbol exported to a namespace must add a MODULE_IMPORT_NS() statement to their module code; otherwise, modpost will complain when building the module, and the kernel module loader will emit an error and fail when loading the module. MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That tag can be observed by the modinfo command, modpost and kernel/module.c at the time of loading the module. The ELF symbols are renamed to include the namespace with an asm label; for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes 'usb_stor_suspend.USB_STORAGE'. This allows modpost to do namespace checking, without having to go through all the effort of parsing ELF and relocation records just to get to the struct kernel_symbols. On x86_64 I saw no difference in binary size (compression), but at runtime this will require a word of memory per export to hold the namespace. An alternative could be to store namespaced symbols in their own section and use a separate 'struct namespaced_kernel_symbol' for that section, at the cost of making the module loader more complex. Co-developed-by: Martijn Coenen <maco@android.com> Signed-off-by: Martijn Coenen <maco@android.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Matthias Maennich <maennich@google.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
95 lines
2.2 KiB
C
95 lines
2.2 KiB
C
#ifndef __ASM_GENERIC_EXPORT_H
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#define __ASM_GENERIC_EXPORT_H
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#ifndef KSYM_FUNC
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#define KSYM_FUNC(x) x
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#endif
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#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
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#define KSYM_ALIGN 4
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#elif defined(CONFIG_64BIT)
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#define KSYM_ALIGN 8
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#else
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#define KSYM_ALIGN 4
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#endif
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#ifndef KCRC_ALIGN
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#define KCRC_ALIGN 4
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#endif
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.macro __put, val, name
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#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
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.long \val - ., \name - ., 0 - .
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#elif defined(CONFIG_64BIT)
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.quad \val, \name, 0
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#else
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.long \val, \name, 0
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#endif
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.endm
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/*
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* note on .section use: @progbits vs %progbits nastiness doesn't matter,
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* since we immediately emit into those sections anyway.
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*/
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.macro ___EXPORT_SYMBOL name,val,sec
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#ifdef CONFIG_MODULES
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.globl __ksymtab_\name
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.section ___ksymtab\sec+\name,"a"
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.balign KSYM_ALIGN
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__ksymtab_\name:
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__put \val, __kstrtab_\name
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.previous
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.section __ksymtab_strings,"a"
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__kstrtab_\name:
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.asciz "\name"
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.previous
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#ifdef CONFIG_MODVERSIONS
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.section ___kcrctab\sec+\name,"a"
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.balign KCRC_ALIGN
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__kcrctab_\name:
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#if defined(CONFIG_MODULE_REL_CRCS)
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.long __crc_\name - .
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#else
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.long __crc_\name
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#endif
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.weak __crc_\name
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.previous
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#endif
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#endif
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.endm
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#undef __put
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#if defined(CONFIG_TRIM_UNUSED_KSYMS)
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#include <linux/kconfig.h>
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#include <generated/autoksyms.h>
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.macro __ksym_marker sym
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.section ".discard.ksym","a"
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__ksym_marker_\sym:
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.previous
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.endm
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#define __EXPORT_SYMBOL(sym, val, sec) \
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__ksym_marker sym; \
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__cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
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#define __cond_export_sym(sym, val, sec, conf) \
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___cond_export_sym(sym, val, sec, conf)
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#define ___cond_export_sym(sym, val, sec, enabled) \
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__cond_export_sym_##enabled(sym, val, sec)
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#define __cond_export_sym_1(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
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#define __cond_export_sym_0(sym, val, sec) /* nothing */
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#else
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#define __EXPORT_SYMBOL(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
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#endif
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#define EXPORT_SYMBOL(name) \
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__EXPORT_SYMBOL(name, KSYM_FUNC(name),)
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#define EXPORT_SYMBOL_GPL(name) \
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__EXPORT_SYMBOL(name, KSYM_FUNC(name), _gpl)
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#define EXPORT_DATA_SYMBOL(name) \
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__EXPORT_SYMBOL(name, name,)
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#define EXPORT_DATA_SYMBOL_GPL(name) \
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__EXPORT_SYMBOL(name, name,_gpl)
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#endif
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