| Message ID | 20171114114109.257057-1-arnd@arndb.de |
|---|---|
| State | Accepted |
| Commit | f50caa9b517a2542ae9769fc17ad84110ae07c8b |
| Headers | show |
| Series | debugfs: fix debugfs_real_fops() build error | expand |
On Tue, Nov 14, 2017 at 12:40:31PM +0100, Arnd Bergmann wrote: > Some drivers use debugfs_real_fops() even when CONFIG_DEBUG_FS is disabled, > which now leads to a build error: > > In file included from include/linux/list.h:9:0, > from include/linux/wait.h:7, > from include/linux/wait_bit.h:8, > from include/linux/fs.h:6, > from drivers/net/wireless/broadcom/b43legacy/debugfs.c:26: > drivers/net/wireless/broadcom/b43legacy/debugfs.c: In function 'b43legacy_debugfs_read': > drivers/net/wireless/broadcom/b43legacy/debugfs.c:224:23: error: implicit declaration of function 'debugfs_real_fops'; did you mean 'debugfs_create_bool'? [-Werror=implicit-function-declaration] > > My first impulse was to add another 'static inline' dummy function > returning NULL for it, which would work fine. However, most callers > feed the pointer into container_of(), so it seems a little dangerous > here. Since all the callers are inside of a read/write file operation > that gets eliminated in this configuration, so having an 'extern' > declaration seems better here. If it ever gets used in a dangerous > way, that will now result in a link error. Ok, but does your patch really "fix" anything? The linker should now complain, not the compiler, for these types of configurations? thanks, greg k-h
On Tue, Nov 14, 2017 at 12:50 PM, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > On Tue, Nov 14, 2017 at 12:40:31PM +0100, Arnd Bergmann wrote: >> Some drivers use debugfs_real_fops() even when CONFIG_DEBUG_FS is disabled, >> which now leads to a build error: >> >> In file included from include/linux/list.h:9:0, >> from include/linux/wait.h:7, >> from include/linux/wait_bit.h:8, >> from include/linux/fs.h:6, >> from drivers/net/wireless/broadcom/b43legacy/debugfs.c:26: >> drivers/net/wireless/broadcom/b43legacy/debugfs.c: In function 'b43legacy_debugfs_read': >> drivers/net/wireless/broadcom/b43legacy/debugfs.c:224:23: error: implicit declaration of function 'debugfs_real_fops'; did you mean 'debugfs_create_bool'? [-Werror=implicit-function-declaration] >> >> My first impulse was to add another 'static inline' dummy function >> returning NULL for it, which would work fine. However, most callers >> feed the pointer into container_of(), so it seems a little dangerous >> here. Since all the callers are inside of a read/write file operation >> that gets eliminated in this configuration, so having an 'extern' >> declaration seems better here. If it ever gets used in a dangerous >> way, that will now result in a link error. > > Ok, but does your patch really "fix" anything? The linker should now > complain, not the compiler, for these types of configurations? As I said, all calls to debugfs_real_fops() are from a read/write file operation, which gets discarded when CONFIG_DEBUG_FS is disabled, because debugfs_create_file() and similar functions don't use the file_operations structure pointing to them. There is no link error, unless someone uses debugfs_real_fops() in a function that does not get discarded. If we ever get a function calling debugfs_real_fops() when DEBUG_FS is turned off and we call that function from somewhere else, we definitely want to get the link error over dereferencing container_of(NULL, type, member). Arnd
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h index f36ecc2a5712..3b0ba54cc4d5 100644 --- a/include/linux/debugfs.h +++ b/include/linux/debugfs.h @@ -216,6 +216,8 @@ static inline void debugfs_remove(struct dentry *dentry) static inline void debugfs_remove_recursive(struct dentry *dentry) { } +const struct file_operations *debugfs_real_fops(const struct file *filp); + static inline int debugfs_file_get(struct dentry *dentry) { return 0;
Some drivers use debugfs_real_fops() even when CONFIG_DEBUG_FS is disabled, which now leads to a build error: In file included from include/linux/list.h:9:0, from include/linux/wait.h:7, from include/linux/wait_bit.h:8, from include/linux/fs.h:6, from drivers/net/wireless/broadcom/b43legacy/debugfs.c:26: drivers/net/wireless/broadcom/b43legacy/debugfs.c: In function 'b43legacy_debugfs_read': drivers/net/wireless/broadcom/b43legacy/debugfs.c:224:23: error: implicit declaration of function 'debugfs_real_fops'; did you mean 'debugfs_create_bool'? [-Werror=implicit-function-declaration] My first impulse was to add another 'static inline' dummy function returning NULL for it, which would work fine. However, most callers feed the pointer into container_of(), so it seems a little dangerous here. Since all the callers are inside of a read/write file operation that gets eliminated in this configuration, so having an 'extern' declaration seems better here. If it ever gets used in a dangerous way, that will now result in a link error. Fixes: 7c8d469877b1 ("debugfs: add support for more elaborate ->d_fsdata") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- include/linux/debugfs.h | 2 ++ 1 file changed, 2 insertions(+) -- 2.9.0