From 4b950bb9ac0c7246dcf75060040577c3de60c166 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 28 Jul 2019 20:27:41 +0200 Subject: Kbuild: Handle PREEMPT_RT for version string and magic Update the build scripts and the version magic to reflect when CONFIG_PREEMPT_RT is enabled in the same way as CONFIG_PREEMPT is treated. The resulting version strings: Linux m 5.3.0-rc1+ #100 SMP Fri Jul 26 ... Linux m 5.3.0-rc1+ #101 SMP PREEMPT Fri Jul 26 ... Linux m 5.3.0-rc1+ #102 SMP PREEMPT_RT Fri Jul 26 ... The module vermagic: 5.3.0-rc1+ SMP mod_unload modversions 5.3.0-rc1+ SMP preempt mod_unload modversions 5.3.0-rc1+ SMP preempt_rt mod_unload modversions Signed-off-by: Thomas Gleixner Signed-off-by: Masahiro Yamada --- include/linux/vermagic.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h index bae807eb2933..9aced11e9000 100644 --- a/include/linux/vermagic.h +++ b/include/linux/vermagic.h @@ -9,6 +9,8 @@ #endif #ifdef CONFIG_PREEMPT #define MODULE_VERMAGIC_PREEMPT "preempt " +#elif defined(CONFIG_PREEMPT_RT) +#define MODULE_VERMAGIC_PREEMPT "preempt_rt " #else #define MODULE_VERMAGIC_PREEMPT "" #endif -- cgit v1.2.3 From 6863f5643dd717376c2fdc85a47a00f9d738a834 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sat, 7 Sep 2019 11:52:36 +0900 Subject: kbuild: allow Clang to find unused static inline functions for W=1 build GCC and Clang have different policy for -Wunused-function; GCC does not warn unused static inline functions at all whereas Clang does if they are defined in source files instead of included headers although it has been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused static inline functions"). We often miss to delete unused functions where 'static inline' is used in *.c files since there is no tool to detect them. Unused code remains until somebody notices. For example, commit 075ddd75680f ("regulator: core: remove unused rdev_get_supply()"). Let's remove __maybe_unused from the inline macro to allow Clang to start finding unused static inline functions. For now, we do this only for W=1 build since it is not a good idea to sprinkle warnings for the normal build (e.g. 35 warnings for arch/x86/configs/x86_64_defconfig). My initial attempt was to add -Wno-unused-function for no W= build (https://lore.kernel.org/patchwork/patch/1120594/) Nathan Chancellor pointed out that would weaken Clang's checks since we would no longer get -Wunused-function without W=1. It is true GCC would catch unused static non-inline functions, but it would weaken Clang as a standalone compiler, at least. Hence, here is a counter implementation. The current problem is, W=... only controls compiler flags, which are globally effective. There is no way to address only 'static inline' functions. This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from the 'inline' macro. The new macro __inline_maybe_unused makes the code a bit uglier, so I hope we can remove it entirely after fixing most of the warnings. If you contribute to code clean-up, please run "make CC=clang W=1" and check -Wunused-function warnings. You will find lots of unused functions. Some of them are false-positives because the call-sites are disabled by #ifdef. I do not like to abuse the inline keyword for suppressing unused-function warnings because it is intended to be a hint for the compiler optimization. I prefer #ifdef around the definition, or __maybe_unused if #ifdef would make the code too ugly. Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor --- include/linux/compiler_types.h | 20 ++++++++++++++------ scripts/Makefile.extrawarn | 6 ++++++ 2 files changed, 20 insertions(+), 6 deletions(-) (limited to 'include') diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 599c27b56c29..b056a40116da 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -130,10 +130,6 @@ struct ftrace_likely_data { /* * Force always-inline if the user requests it so via the .config. - * GCC does not warn about unused static inline functions for - * -Wunused-function. This turns out to avoid the need for complex #ifdef - * directives. Suppress the warning in clang as well by using "unused" - * function attribute, which is redundant but not harmful for gcc. * Prefer gnu_inline, so that extern inline functions do not emit an * externally visible function. This makes extern inline behave as per gnu89 * semantics rather than c99. This prevents multiple symbol definition errors @@ -144,15 +140,27 @@ struct ftrace_likely_data { */ #if !defined(CONFIG_OPTIMIZE_INLINING) #define inline inline __attribute__((__always_inline__)) __gnu_inline \ - __maybe_unused notrace + __inline_maybe_unused notrace #else #define inline inline __gnu_inline \ - __maybe_unused notrace + __inline_maybe_unused notrace #endif #define __inline__ inline #define __inline inline +/* + * GCC does not warn about unused static inline functions for -Wunused-function. + * Suppress the warning in clang as well by using __maybe_unused, but enable it + * for W=1 build. This will allow clang to find unused functions. Remove the + * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings. + */ +#ifdef KBUILD_EXTRA_WARN1 +#define __inline_maybe_unused +#else +#define __inline_maybe_unused __maybe_unused +#endif + /* * Rather then using noinline to prevent stack consumption, use * noinline_for_stack instead. For documentation reasons. diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index 53eb7e0c6a5a..ecddf83ac142 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -36,6 +36,8 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) KBUILD_CFLAGS += -Wno-missing-field-initializers KBUILD_CFLAGS += -Wno-sign-compare +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 + else # Some diagnostics enabled by default are noisy. @@ -65,6 +67,8 @@ KBUILD_CFLAGS += -Wsign-compare KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 + endif # @@ -82,4 +86,6 @@ KBUILD_CFLAGS += -Wredundant-decls KBUILD_CFLAGS += -Wswitch-default KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 + endif -- cgit v1.2.3 From a0469f989fe1d051820cda7ead496f1a7371f3d8 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 9 Sep 2019 19:53:16 +0900 Subject: export.h: remove defined(__KERNEL__), which is no longer needed The conditional, define(__KERNEL__), was added by commit f235541699bc ("export.h: allow for per-symbol configurable EXPORT_SYMBOL()"). It was needed at that time to avoid the build error of modpost with CONFIG_TRIM_UNUSED_KSYMS=y. Since commit b2c5cdcfd4bc ("modpost: remove symbol prefix support"), modpost no longer includes linux/export.h, thus the define(__KERNEL__) is unneeded. Signed-off-by: Masahiro Yamada Acked-by: Nicolas Pitre --- include/linux/export.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/export.h b/include/linux/export.h index fd8711ed9ac4..cdd98a0d918c 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -20,7 +20,7 @@ extern struct module __this_module; #ifdef CONFIG_MODULES -#if defined(__KERNEL__) && !defined(__GENKSYMS__) +#if !defined(__GENKSYMS__) #ifdef CONFIG_MODVERSIONS /* Mark the CRC weak since genksyms apparently decides not to * generate a checksums for some symbols */ -- cgit v1.2.3 From 69a94abb82eed2789d52b58665ddf4b454d9adb9 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 9 Sep 2019 19:53:17 +0900 Subject: export.h, genksyms: do not make genksyms calculate CRC of trimmed symbols Arnd Bergmann reported false-positive modpost warnings detected by his randconfig testing of linux-next. Actually, this happens under the combination of CONFIG_MODVERSIONS and CONFIG_TRIM_UNUSED_KSYMS since commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions"). For example, arch/arm/config/multi_v7_defconfig + CONFIG_MODVERSIONS + CONFIG_TRIM_UNUSED_KSYMS 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 exported 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, orphan __crc* symbols are added to objects. It had been harmless until recently. With commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions"), it is now harmful because the bogus __crc* symbols make modpost call sym_update_crc() to add the symbols to the hash table, 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 Signed-off-by: Masahiro Yamada Tested-by: Arnd Bergmann --- include/linux/export.h | 42 ++++++++++++++++-------------------------- scripts/genksyms/keywords.c | 6 +----- 2 files changed, 17 insertions(+), 31 deletions(-) (limited to 'include') 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 }, -- cgit v1.2.3