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module: add support for symbol namespaces.
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>
This commit is contained in:
Matthias Maennich
Jessica Yu
parent
ed13fc33f7
commit
8651ec01da
4 changed files with 125 additions and 21 deletions
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@ -17,11 +17,11 @@
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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 - .
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.long \val - ., \name - ., 0 - .
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#elif defined(CONFIG_64BIT)
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.quad \val, \name
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.quad \val, \name, 0
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#else
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.long \val, \name
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.long \val, \name, 0
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#endif
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.endm
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@ -20,6 +20,8 @@ extern struct module __this_module;
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#ifdef CONFIG_MODULES
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#define NS_SEPARATOR "."
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#if defined(__KERNEL__) && !defined(__GENKSYMS__)
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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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@ -29,13 +31,13 @@ extern struct module __this_module;
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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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" .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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" .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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@ -49,6 +51,16 @@ extern struct module __this_module;
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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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@ -56,32 +68,53 @@ extern struct module __this_module;
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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(sym, sec) \
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static const struct kernel_symbol __ksymtab_##sym \
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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 }
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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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/* For every exported symbol, place a struct in the __ksymtab section */
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#define ___EXPORT_SYMBOL(sym, sec) \
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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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__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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= #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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#if defined(__DISABLE_EXPORTS)
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@ -91,6 +124,7 @@ struct kernel_symbol {
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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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@ -117,18 +151,26 @@ struct kernel_symbol {
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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 ___EXPORT_SYMBOL_NS
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#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
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#endif
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#define EXPORT_SYMBOL(sym) \
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__EXPORT_SYMBOL(sym, "")
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#define EXPORT_SYMBOL_GPL(sym) \
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__EXPORT_SYMBOL(sym, "_gpl")
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#define EXPORT_SYMBOL_GPL_FUTURE(sym) \
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__EXPORT_SYMBOL(sym, "_gpl_future")
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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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@ -138,11 +180,28 @@ struct kernel_symbol {
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#define EXPORT_UNUSED_SYMBOL_GPL(sym)
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#endif
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#endif /* __GENKSYMS__ */
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#endif /* __KERNEL__ && !__GENKSYMS__ */
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#if defined(__GENKSYMS__)
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/*
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* When we're running genksyms, ignore the namespace and make the _NS
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* variants look like the normal ones. There are two reasons for this:
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* 1) In the normal definition of EXPORT_SYMBOL_NS, the 'ns' macro
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* argument is itself not expanded because it's always tokenized or
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* concatenated; but when running genksyms, a blank definition of the
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* macro does allow the argument to be expanded; if a namespace
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* happens to collide with a #define, this can cause issues.
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* 2) There's no need to modify genksyms to deal with the _NS variants
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*/
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#define EXPORT_SYMBOL_NS(sym, ns) EXPORT_SYMBOL(sym)
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#define EXPORT_SYMBOL_NS_GPL(sym, ns) EXPORT_SYMBOL_GPL(sym)
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#endif
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#else /* !CONFIG_MODULES... */
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#define EXPORT_SYMBOL(sym)
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#define EXPORT_SYMBOL_NS(sym, ns)
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#define EXPORT_SYMBOL_NS_GPL(sym, ns)
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#define EXPORT_SYMBOL_GPL(sym)
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#define EXPORT_SYMBOL_GPL_FUTURE(sym)
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#define EXPORT_UNUSED_SYMBOL(sym)
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@ -280,6 +280,8 @@ struct notifier_block;
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#ifdef CONFIG_MODULES
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#define MODULE_IMPORT_NS(ns) MODULE_INFO(import_ns, #ns)
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extern int modules_disabled; /* for sysctl */
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/* Get/put a kernel symbol (calls must be symmetric) */
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void *__symbol_get(const char *symbol);
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@ -544,6 +544,15 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
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#endif
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}
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static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
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{
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#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
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return offset_to_ptr(&sym->namespace_offset);
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#else
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return sym->namespace;
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#endif
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}
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static int cmp_name(const void *va, const void *vb)
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{
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const char *a;
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@ -1379,6 +1388,34 @@ static inline int same_magic(const char *amagic, const char *bmagic,
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}
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#endif /* CONFIG_MODVERSIONS */
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static char *get_modinfo(const struct load_info *info, const char *tag);
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static char *get_next_modinfo(const struct load_info *info, const char *tag,
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char *prev);
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static int verify_namespace_is_imported(const struct load_info *info,
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const struct kernel_symbol *sym,
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struct module *mod)
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{
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const char *namespace;
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char *imported_namespace;
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namespace = kernel_symbol_namespace(sym);
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if (namespace) {
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imported_namespace = get_modinfo(info, "import_ns");
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while (imported_namespace) {
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if (strcmp(namespace, imported_namespace) == 0)
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return 0;
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imported_namespace = get_next_modinfo(
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info, "import_ns", imported_namespace);
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}
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pr_err("%s: module uses symbol (%s) from namespace %s, but does not import it.\n",
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mod->name, kernel_symbol_name(sym), namespace);
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return -EINVAL;
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}
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return 0;
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}
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/* Resolve a symbol for this module. I.e. if we find one, record usage. */
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static const struct kernel_symbol *resolve_symbol(struct module *mod,
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const struct load_info *info,
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@ -1407,6 +1444,12 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
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goto getname;
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}
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err = verify_namespace_is_imported(info, sym, mod);
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if (err) {
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sym = ERR_PTR(err);
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goto getname;
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}
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err = ref_module(mod, owner);
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if (err) {
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sym = ERR_PTR(err);
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