On Wed, Sep 23, 2020 at 05:38:31PM +0100, Al Viro wrote: > On Wed, Sep 23, 2020 at 03:59:01PM +0100, Al Viro wrote: > > > > That's a very good question. But it does not just compile but actually > > > works. Probably because all the syscall wrappers mean that we don't > > > actually generate the normal names. I just tried this: > > > > > > --- a/include/linux/syscalls.h > > > +++ b/include/linux/syscalls.h > > > @@ -468,7 +468,7 @@ asmlinkage long sys_lseek(unsigned int fd, off_t offset, > > > asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count); > > > asmlinkage long sys_write(unsigned int fd, const char __user *buf, > > > size_t count); > > > -asmlinkage long sys_readv(unsigned long fd, > > > +asmlinkage long sys_readv(void *fd, > > > > > > for fun, and the compiler doesn't care either.. > > > > Try to build it for sparc or ppc... > > FWIW, declarations in syscalls.h used to serve 4 purposes: > 1) syscall table initializers needed symbols declared > 2) direct calls needed the same > 3) catching mismatches between the declarations and definitions > 4) centralized list of all syscalls > > (2) has been (thankfully) reduced for some time; in any case, ksys_... is > used for the remaining ones. > > (1) and (3) are served by syscalls.h in architectures other than x86, arm64 > and s390. On those 3 (1) is done otherwise (near the syscall table initializer) > and (3) is not done at all. > > I wonder if we should do something like > > SYSCALL_DECLARE3(readv, unsigned long, fd, const struct iovec __user *, vec, > unsigned long, vlen); > in syscalls.h instead, and not under that ifdef. > > Let it expand to declaration of sys_...() in generic case and, on x86, into > __do_sys_...() and __ia32_sys_...()/__x64_sys_...(), with types matching > what SYSCALL_DEFINE ends up using. > > Similar macro would cover compat_sys_...() declarations. That would > restore mismatch checking for x86 and friends. AFAICS, the cost wouldn't > be terribly high - cpp would have more to chew through in syscalls.h, > but it shouldn't be all that costly. Famous last words, of course... > > Does anybody see fundamental problems with that? Just to make it clear - I do not propose to fold that into this series; there we just need to keep those declarations in sync with fs/read_write.c
