Arnd Bergmann reported false-positive modpost warnings detected by his randconfig testing of linux-next: https://lkml.org/lkml/2019/9/6/619 Actually, this happens under the combination of CONFIG_MODVERSIONS=y and CONFIG_TRIM_UNUSED_KSYMS=y since commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions"). For example, arch/arm/config/multi_v7_defconfig + CONFIG_MODVERSIONS=y + CONFIG_TRIM_UNUSED_KSYMS=y produces the following false-positives: WARNING: "__lshrdi3" [vmlinux] is a static (unknown) WARNING: "__ashrdi3" [vmlinux] is a static (unknown) WARNING: "__aeabi_lasr" [vmlinux] is a static (unknown) WARNING: "__aeabi_llsr" [vmlinux] is a static (unknown) WARNING: "ftrace_set_clr_event" [vmlinux] is a static (unknown) WARNING: "__muldi3" [vmlinux] is a static (unknown) WARNING: "__aeabi_ulcmp" [vmlinux] is a static (unknown) WARNING: "__ucmpdi2" [vmlinux] is a static (unknown) WARNING: "__aeabi_lmul" [vmlinux] is a static (unknown) WARNING: "__bswapsi2" [vmlinux] is a static (unknown) WARNING: "__bswapdi2" [vmlinux] is a static (unknown) WARNING: "__ashldi3" [vmlinux] is a static (unknown) WARNING: "__aeabi_llsl" [vmlinux] is a static (unknown) The root cause of the problem is not in the modpost, but in the implementation of CONFIG_TRIM_UNUSED_KSYMS. If there is at least one untrimmed symbol in the file, genksyms is invoked to calculate CRC of *all* the symbols in that file even if some of them have been trimmed due to no caller existing. As a result, .tmp_*.ver files contain CRC of trimmed symbols, thus unneeded __crc* symbols are added to objects. It has been harmless until recently. Since commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions"), it is harmful because the bogus __crc* symbols make modpost call sym_update_crc(), and then new_symbol(), but there is no one that clears the ->is_static member. I gave Fixes to the first commit that uncovered the issue, but the potential problem has long existed since commit f235541699bc ("export.h: allow for per-symbol configurable EXPORT_SYMBOL()"). Fixes: 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions") Reported-by: Arnd Bergmann <arnd@xxxxxxxx> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> --- include/linux/export.h | 42 ++++++++++++++----------------------- scripts/genksyms/keywords.c | 6 +----- 2 files changed, 17 insertions(+), 31 deletions(-) diff --git a/include/linux/export.h b/include/linux/export.h index cdd98a0d918c..7d8c112a8b61 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -18,9 +18,6 @@ extern struct module __this_module; #define THIS_MODULE ((struct module *)0) #endif -#ifdef CONFIG_MODULES - -#if !defined(__GENKSYMS__) #ifdef CONFIG_MODVERSIONS /* Mark the CRC weak since genksyms apparently decides not to * generate a checksums for some symbols */ @@ -74,6 +71,12 @@ struct kernel_symbol { }; #endif +#ifdef __GENKSYMS__ + +#define ___EXPORT_SYMBOL(sym, sec) __GENKSYMS_EXPORT_SYMBOL(sym) + +#else + /* For every exported symbol, place a struct in the __ksymtab section */ #define ___EXPORT_SYMBOL(sym, sec) \ extern typeof(sym) sym; \ @@ -83,7 +86,9 @@ struct kernel_symbol { = #sym; \ __KSYMTAB_ENTRY(sym, sec) -#if defined(__DISABLE_EXPORTS) +#endif + +#if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS) /* * Allow symbol exports to be disabled completely so that C code may @@ -117,37 +122,22 @@ struct kernel_symbol { #define __cond_export_sym_0(sym, sec) /* nothing */ #else -#define __EXPORT_SYMBOL ___EXPORT_SYMBOL -#endif -#define EXPORT_SYMBOL(sym) \ - __EXPORT_SYMBOL(sym, "") +#define __EXPORT_SYMBOL(sym, sec) ___EXPORT_SYMBOL(sym, sec) -#define EXPORT_SYMBOL_GPL(sym) \ - __EXPORT_SYMBOL(sym, "_gpl") - -#define EXPORT_SYMBOL_GPL_FUTURE(sym) \ - __EXPORT_SYMBOL(sym, "_gpl_future") +#endif /* CONFIG_MODULES */ +#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "") +#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl") +#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future") #ifdef CONFIG_UNUSED_SYMBOLS -#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused") -#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl") +#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused") +#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl") #else #define EXPORT_UNUSED_SYMBOL(sym) #define EXPORT_UNUSED_SYMBOL_GPL(sym) #endif -#endif /* __GENKSYMS__ */ - -#else /* !CONFIG_MODULES... */ - -#define EXPORT_SYMBOL(sym) -#define EXPORT_SYMBOL_GPL(sym) -#define EXPORT_SYMBOL_GPL_FUTURE(sym) -#define EXPORT_UNUSED_SYMBOL(sym) -#define EXPORT_UNUSED_SYMBOL_GPL(sym) - -#endif /* CONFIG_MODULES */ #endif /* !__ASSEMBLY__ */ #endif /* _LINUX_EXPORT_H */ diff --git a/scripts/genksyms/keywords.c b/scripts/genksyms/keywords.c index c586d32dd2c3..7a85c4e21175 100644 --- a/scripts/genksyms/keywords.c +++ b/scripts/genksyms/keywords.c @@ -3,11 +3,7 @@ static struct resword { const char *name; int token; } keywords[] = { - { "EXPORT_SYMBOL", EXPORT_SYMBOL_KEYW }, - { "EXPORT_SYMBOL_GPL", EXPORT_SYMBOL_KEYW }, - { "EXPORT_SYMBOL_GPL_FUTURE", EXPORT_SYMBOL_KEYW }, - { "EXPORT_UNUSED_SYMBOL", EXPORT_SYMBOL_KEYW }, - { "EXPORT_UNUSED_SYMBOL_GPL", EXPORT_SYMBOL_KEYW }, + { "__GENKSYMS_EXPORT_SYMBOL", EXPORT_SYMBOL_KEYW }, { "__asm", ASM_KEYW }, { "__asm__", ASM_KEYW }, { "__attribute", ATTRIBUTE_KEYW }, -- 2.17.1
