| From a6e60d84989fa0e91db7f236eda40453b0e44afa Mon Sep 17 00:00:00 2001 |
| From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> |
| Date: Sat, 19 Jan 2019 20:59:34 +0100 |
| Subject: include/linux/module.h: copy __init/__exit attrs to init/cleanup_module |
| |
| From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> |
| |
| commit a6e60d84989fa0e91db7f236eda40453b0e44afa upstream. |
| |
| The upcoming GCC 9 release extends the -Wmissing-attributes warnings |
| (enabled by -Wall) to C and aliases: it warns when particular function |
| attributes are missing in the aliases but not in their target. |
| |
| In particular, it triggers for all the init/cleanup_module |
| aliases in the kernel (defined by the module_init/exit macros), |
| ending up being very noisy. |
| |
| These aliases point to the __init/__exit functions of a module, |
| which are defined as __cold (among other attributes). However, |
| the aliases themselves do not have the __cold attribute. |
| |
| Since the compiler behaves differently when compiling a __cold |
| function as well as when compiling paths leading to calls |
| to __cold functions, the warning is trying to point out |
| the possibly-forgotten attribute in the alias. |
| |
| In order to keep the warning enabled, we decided to silence |
| this case. Ideally, we would mark the aliases directly |
| as __init/__exit. However, there are currently around 132 modules |
| in the kernel which are missing __init/__exit in their init/cleanup |
| functions (either because they are missing, or for other reasons, |
| e.g. the functions being called from somewhere else); and |
| a section mismatch is a hard error. |
| |
| A conservative alternative was to mark the aliases as __cold only. |
| However, since we would like to eventually enforce __init/__exit |
| to be always marked, we chose to use the new __copy function |
| attribute (introduced by GCC 9 as well to deal with this). |
| With it, we copy the attributes used by the target functions |
| into the aliases. This way, functions that were not marked |
| as __init/__exit won't have their aliases marked either, |
| and therefore there won't be a section mismatch. |
| |
| Note that the warning would go away marking either the extern |
| declaration, the definition, or both. However, we only mark |
| the definition of the alias, since we do not want callers |
| (which only see the declaration) to be compiled as if the function |
| was __cold (and therefore the paths leading to those calls |
| would be assumed to be unlikely). |
| |
| Link: https://lore.kernel.org/lkml/20190123173707.GA16603@gmail.com/ |
| Link: https://lore.kernel.org/lkml/20190206175627.GA20399@gmail.com/ |
| Suggested-by: Martin Sebor <msebor@gcc.gnu.org> |
| Acked-by: Jessica Yu <jeyu@kernel.org> |
| Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> |
| Signed-off-by: Stefan Agner <stefan@agner.ch> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| include/linux/module.h | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/include/linux/module.h |
| +++ b/include/linux/module.h |
| @@ -130,13 +130,13 @@ extern void cleanup_module(void); |
| #define module_init(initfn) \ |
| static inline initcall_t __maybe_unused __inittest(void) \ |
| { return initfn; } \ |
| - int init_module(void) __attribute__((alias(#initfn))); |
| + int init_module(void) __copy(initfn) __attribute__((alias(#initfn))); |
| |
| /* This is only required if you want to be unloadable. */ |
| #define module_exit(exitfn) \ |
| static inline exitcall_t __maybe_unused __exittest(void) \ |
| { return exitfn; } \ |
| - void cleanup_module(void) __attribute__((alias(#exitfn))); |
| + void cleanup_module(void) __copy(exitfn) __attribute__((alias(#exitfn))); |
| |
| #endif |
| |