compat: let architectures define __ARCH_WANT_COMPAT_SYS_GETDENTS64

For architecture dependent compat syscalls in common code an architecture
must define something like __ARCH_WANT_<WHATEVER> if it wants to use the
code.
This however is not true for compat_sys_getdents64 for which architectures
must define __ARCH_OMIT_COMPAT_SYS_GETDENTS64 if they do not want the code.

This leads to the situation where all architectures, except mips, get the
compat code but only x86_64, arm64 and the generic syscall architectures
actually use it.

So invert the logic, so that architectures actively must do something to
get the compat code.

This way a couple of architectures get rid of otherwise dead code.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

2 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 3f448c65511b..beded18f992d 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -502,9 +502,11 @@ asmlinkage long compat_sys_old_readdir(unsigned int fd,
 asmlinkage long compat_sys_getdents(unsigned int fd,
                                     struct compat_linux_dirent __user *dirent,
                                     unsigned int count);
+#ifdef __ARCH_WANT_COMPAT_SYS_GETDENTS64
 asmlinkage long compat_sys_getdents64(unsigned int fd,
                                       struct linux_dirent64 __user *dirent,
                                       unsigned int count);
+#endif
 asmlinkage long compat_sys_vmsplice(int fd, const struct compat_iovec __user *,
                                     unsigned int nr_segs, unsigned int flags);
 asmlinkage long compat_sys_open(const char __user *filename, int flags,
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index dde8041f40d2..6db66783d268 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -191,6 +191,7 @@ __SYSCALL(__NR_quotactl, sys_quotactl)
 
 /* fs/readdir.c */
 #define __NR_getdents64 61
+#define __ARCH_WANT_COMPAT_SYS_GETDENTS64
 __SC_COMP(__NR_getdents64, sys_getdents64, compat_sys_getdents64)
 
 /* fs/read_write.c */