| Message ID | 20230914-nolibc-syscall-nr-v1-2-e50df410da11@weissschuh.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | tools/nolibc: cleanups for syscall fallbacks | expand |
On Thu, Sep 14, 2023 at 06:01:18PM +0200, Thomas Weißschuh wrote: > The ENOSYS fallback code does not use its functions parameters. > This can lead to compiler warnings about unused parameters. > > Explicitly avoid these warnings. Just out of curiosity, did you find a valid case for enabling this warning or were you trying various combinations ? I'm asking because I've never seen it enabled anywhere given that it's probably the most useless and unusable warning: as soon as you're dealing with function pointers, you start to have multiple functions with a similar prototype, some of which just don't need certain arguments, and the only way to shut the warning is to significantly uglify the code. If really needed, I'm wondering if instead we shouldn't have an "no_syscall*" set of macros, that would have the same signature as my_syscall* to just consume all args in the same order and return -ENOSYS. E.g, consider the following: @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva #endif return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout); #else + (void)nfds; + (void)rfds; + (void)wfds; + (void)efds; + (void)timeout; return -ENOSYS; #endif It would become: @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva #endif return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout); #else + return no_syscall5(nfds, rfds, wfds, efds, timeout); - return -ENOSYS; #endif What do you think ? Thanks! Willy
On 2023-09-17 04:58:51+0200, Willy Tarreau wrote: > On Thu, Sep 14, 2023 at 06:01:18PM +0200, Thomas Weißschuh wrote: > > The ENOSYS fallback code does not use its functions parameters. > > This can lead to compiler warnings about unused parameters. > > > > Explicitly avoid these warnings. > > Just out of curiosity, did you find a valid case for enabling this > warning or were you trying various combinations ? I'm asking because > I've never seen it enabled anywhere given that it's probably the most > useless and unusable warning: as soon as you're dealing with function > pointers, you start to have multiple functions with a similar > prototype, some of which just don't need certain arguments, and the > only way to shut the warning is to significantly uglify the code. nolibc-test uses it currently and I also used it in some projects. > If really needed, I'm wondering if instead we shouldn't have an > "no_syscall*" set of macros, that would have the same signature > as my_syscall* to just consume all args in the same order and > return -ENOSYS. E.g, consider the following: > > @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva > #endif > return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout); > #else > + (void)nfds; > + (void)rfds; > + (void)wfds; > + (void)efds; > + (void)timeout; > return -ENOSYS; > #endif > > It would become: > > @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva > #endif > return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout); > #else > + return no_syscall5(nfds, rfds, wfds, efds, timeout); > - return -ENOSYS; > #endif > > What do you think ? The idea sounds good. But "no_syscall5" sounds a bit non-obvious to me. Maybe the macro-equivalent of this? static inline int __nolibc_enosys(...) { return -ENOSYS; } The only-vararg function unfortunately needs C23 so we can't use it. It's clear to the users that this is about ENOSYS and we don't need a bunch of new macros similar. I'll check if it is cleaner to implement a generic macro or a few numbered ones. Thomas
On Sun, Sep 17, 2023 at 07:49:57AM +0200, Thomas Weißschuh wrote: > On 2023-09-17 04:58:51+0200, Willy Tarreau wrote: > > On Thu, Sep 14, 2023 at 06:01:18PM +0200, Thomas Weißschuh wrote: > > > The ENOSYS fallback code does not use its functions parameters. > > > This can lead to compiler warnings about unused parameters. > > > > > > Explicitly avoid these warnings. > > > > Just out of curiosity, did you find a valid case for enabling this > > warning or were you trying various combinations ? I'm asking because > > I've never seen it enabled anywhere given that it's probably the most > > useless and unusable warning: as soon as you're dealing with function > > pointers, you start to have multiple functions with a similar > > prototype, some of which just don't need certain arguments, and the > > only way to shut the warning is to significantly uglify the code. > > nolibc-test uses it currently and I also used it in some projects. OK then let's handle it. > > @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva > > #endif > > return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout); > > #else > > + return no_syscall5(nfds, rfds, wfds, efds, timeout); > > - return -ENOSYS; > > #endif > > > > What do you think ? > > The idea sounds good. But "no_syscall5" sounds a bit non-obvious to me. Of course, I was just trying to illustrate. I'm never good at giving names. > Maybe the macro-equivalent of this? > > static inline int __nolibc_enosys(...) > { > return -ENOSYS; > } > > The only-vararg function unfortunately needs C23 so we can't use it. > > It's clear to the users that this is about ENOSYS and we don't need a > bunch of new macros similar. I like it, I didn't think about varargs, it's an excellent idea! Let's just do simpler, start with a first arg "syscall_num" that we may later reuse for debugging, and just mark this one unused: static inline int __nolibc_enosys(int syscall_num, ...) { (void)syscall_num; return -ENOSYS; } Willy
On 2023-09-17 11:48:27+0200, Willy Tarreau wrote: > [..] > > Maybe the macro-equivalent of this? > > > > static inline int __nolibc_enosys(...) > > { > > return -ENOSYS; > > } > > > > The only-vararg function unfortunately needs C23 so we can't use it. > > > > It's clear to the users that this is about ENOSYS and we don't need a > > bunch of new macros similar. > > I like it, I didn't think about varargs, it's an excellent idea! Let's > just do simpler, start with a first arg "syscall_num" that we may later > reuse for debugging, and just mark this one unused: > > static inline int __nolibc_enosys(int syscall_num, ...) > { > (void)syscall_num; > return -ENOSYS; > } But which syscall_num to use, as the point of __nolibc_enosys() would be that no syscall number is available and the defines are missing. For debugging we could add a string argument, though.
On Sun, Sep 17, 2023 at 05:07:18PM +0200, Thomas Weißschuh wrote: > On 2023-09-17 11:48:27+0200, Willy Tarreau wrote: > > [..] > > > Maybe the macro-equivalent of this? > > > > > > static inline int __nolibc_enosys(...) > > > { > > > return -ENOSYS; > > > } > > > > > > The only-vararg function unfortunately needs C23 so we can't use it. > > > > > > It's clear to the users that this is about ENOSYS and we don't need a > > > bunch of new macros similar. > > > > I like it, I didn't think about varargs, it's an excellent idea! Let's > > just do simpler, start with a first arg "syscall_num" that we may later > > reuse for debugging, and just mark this one unused: > > > > static inline int __nolibc_enosys(int syscall_num, ...) > > { > > (void)syscall_num; > > return -ENOSYS; > > } > > But which syscall_num to use, as the point of __nolibc_enosys() would be > that no syscall number is available and the defines are missing. good point :-) > For debugging we could add a string argument, though. That works for me. Willy
diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index b478750c9004..bc56310c6bdf 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -133,6 +133,8 @@ int sys_chmod(const char *path, mode_t mode) #elif defined(__NR_chmod) return my_syscall2(__NR_chmod, path, mode); #else + (void)path; + (void)mode; return -ENOSYS; #endif } @@ -156,6 +158,9 @@ int sys_chown(const char *path, uid_t owner, gid_t group) #elif defined(__NR_chown) return my_syscall3(__NR_chown, path, owner, group); #else + (void)path; + (void)owner; + (void)group; return -ENOSYS; #endif } @@ -230,6 +235,8 @@ int sys_dup2(int old, int new) #elif defined(__NR_dup2) return my_syscall2(__NR_dup2, old, new); #else + (void)old; + (void)new; return -ENOSYS; #endif } @@ -486,6 +493,8 @@ int sys_gettimeofday(struct timeval *tv, struct timezone *tz) #ifdef __NR_gettimeofday return my_syscall2(__NR_gettimeofday, tv, tz); #else + (void)tv; + (void)tz; return -ENOSYS; #endif } @@ -563,6 +572,8 @@ int sys_link(const char *old, const char *new) #elif defined(__NR_link) return my_syscall2(__NR_link, old, new); #else + (void)old; + (void)new; return -ENOSYS; #endif } @@ -584,6 +595,9 @@ off_t sys_lseek(int fd, off_t offset, int whence) #ifdef __NR_lseek return my_syscall3(__NR_lseek, fd, offset, whence); #else + (void)fd; + (void)offset; + (void)whence; return -ENOSYS; #endif } @@ -607,6 +621,8 @@ int sys_mkdir(const char *path, mode_t mode) #elif defined(__NR_mkdir) return my_syscall2(__NR_mkdir, path, mode); #else + (void)path; + (void)mode; return -ENOSYS; #endif } @@ -629,6 +645,7 @@ int sys_rmdir(const char *path) #elif defined(__NR_unlinkat) return my_syscall3(__NR_unlinkat, AT_FDCWD, path, AT_REMOVEDIR); #else + (void)path; return -ENOSYS; #endif } @@ -652,6 +669,9 @@ long sys_mknod(const char *path, mode_t mode, dev_t dev) #elif defined(__NR_mknod) return my_syscall3(__NR_mknod, path, mode, dev); #else + (void)path; + (void)mode; + (void)dev; return -ENOSYS; #endif } @@ -742,6 +762,9 @@ int sys_open(const char *path, int flags, mode_t mode) #elif defined(__NR_open) return my_syscall3(__NR_open, path, flags, mode); #else + (void)path; + (void)flags; + (void)mode; return -ENOSYS; #endif } @@ -842,6 +865,9 @@ int sys_poll(struct pollfd *fds, int nfds, int timeout) #elif defined(__NR_poll) return my_syscall3(__NR_poll, fds, nfds, timeout); #else + (void)fds; + (void)nfds; + (void)timeout; return -ENOSYS; #endif } @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva #endif return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout); #else + (void)nfds; + (void)rfds; + (void)wfds; + (void)efds; + (void)timeout; return -ENOSYS; #endif }
The ENOSYS fallback code does not use its functions parameters. This can lead to compiler warnings about unused parameters. Explicitly avoid these warnings. Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> --- tools/include/nolibc/sys.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)