Introduce fixed sys_sync_file_range2() syscall, implement on PowerPC and ARM

Not all the world is an i386. Many architectures need 64-bit arguments to be
aligned in suitable pairs of registers, and the original
sys_sync_file_range(int, loff_t, loff_t, int) was therefore wasting an
argument register for padding after the first integer. Since we don't
normally have more than 6 arguments for system calls, that left no room for
the final argument on some architectures.

Fix this by introducing sys_sync_file_range2(int, int, loff_t, loff_t) which
all fits nicely. In fact, ARM already had that, but called it
sys_arm_sync_file_range. Move it to fs/sync.c and rename it, then implement
the needed compatibility routine. And stop the missing syscall check from
bitching about the absence of sys_sync_file_range() if we've implemented
sys_sync_file_range2() instead.

Tested on PPC32 and with 32-bit and 64-bit userspace on PPC64.

Signed-off-by: David Woodhouse <[e-mail]>
Acked-by: Russell King <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/arm/kernel/calls.S

···
 		CALL(sys_set_robust_list)
 		CALL(sys_get_robust_list)
 /* 340 */	CALL(sys_splice)
-		CALL(sys_arm_sync_file_range)
+		CALL(sys_sync_file_range2)
 		CALL(sys_tee)
 		CALL(sys_vmsplice)
 		CALL(sys_move_pages)

arch/arm/kernel/sys_arm.c

···
 {
 	return sys_fadvise64_64(fd, offset, len, advice);
 }
-
-/*
- * Yet more syscall fsckage - we can't fit sys_sync_file_range's
- * arguments into the available registers with EABI.  So, let's
- * create an ARM specific syscall for this which has _sane_
- * arguments.  (This incidentally also has an ABI-independent
- * argument layout.)
- */
-asmlinkage long sys_arm_sync_file_range(int fd, unsigned int flags,
-					loff_t offset, loff_t nbytes)
-{
-	return sys_sync_file_range(fd, offset, nbytes, flags);
-}

arch/powerpc/kernel/sys_ppc32.c

···
 	return sys_request_key(_type, _description, _callout_info, destringid);
 }
 
+asmlinkage long compat_sys_sync_file_range2(int fd, unsigned int flags,
+				   unsigned offset_hi, unsigned offset_lo,
+				   unsigned nbytes_hi, unsigned nbytes_lo)
+{
+	loff_t offset = ((loff_t)offset_hi << 32) | offset_lo;
+	loff_t nbytes = ((loff_t)nbytes_hi << 32) | nbytes_lo;
+
+	return sys_sync_file_range(fd, offset, nbytes, flags);
+}

fs/sync.c

···
 	return ret;
 }
 
+/* It would be nice if people remember that not all the world's an i386
+   when they introduce new system calls */
+asmlinkage long sys_sync_file_range2(int fd, unsigned int flags,
+				     loff_t offset, loff_t nbytes)
+{
+	return sys_sync_file_range(fd, offset, nbytes, flags);
+}
+
 /*
  * `endbyte' is inclusive
  */

include/asm-arm/unistd.h

···
 #define __NR_get_robust_list		(__NR_SYSCALL_BASE+339)
 #define __NR_splice			(__NR_SYSCALL_BASE+340)
 #define __NR_arm_sync_file_range	(__NR_SYSCALL_BASE+341)
+#define __NR_sync_file_range2		__NR_arm_sync_file_range
 #define __NR_tee			(__NR_SYSCALL_BASE+342)
 #define __NR_vmsplice			(__NR_SYSCALL_BASE+343)
 #define __NR_move_pages			(__NR_SYSCALL_BASE+344)

include/asm-powerpc/systbl.h

···
 COMPAT_SYS_SPU(signalfd)
 COMPAT_SYS_SPU(timerfd)
 SYSCALL_SPU(eventfd)
+COMPAT_SYS_SPU(sync_file_range2)

include/asm-powerpc/unistd.h

···
 #define __NR_signalfd		305
 #define __NR_timerfd		306
 #define __NR_eventfd		307
+#define __NR_sync_file_range2	308
 
 #ifdef __KERNEL__
 
-#define __NR_syscalls		308
+#define __NR_syscalls		309
 
 #define __NR__exit __NR_exit
 #define NR_syscalls	__NR_syscalls

include/linux/syscalls.h

···
 
 asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 					unsigned int flags);
+asmlinkage long sys_sync_file_range2(int fd, unsigned int flags,
+				     loff_t offset, loff_t nbytes);
 asmlinkage long sys_get_robust_list(int pid,
 				    struct robust_list_head __user * __user *head_ptr,
 				    size_t __user *len_ptr);

scripts/checksyscalls.sh

···
 #define __IGNORE_setfsuid32
 #define __IGNORE_setfsgid32
 
+/* sync_file_range had a stupid ABI. Allow sync_file_range2 instead */
+#ifdef __NR_sync_file_range2
+#define __IGNORE_sync_file_range
+#endif
+
 /* Unmerged syscalls for AFS, STREAMS, etc. */
 #define __IGNORE_afs_syscall
 #define __IGNORE_getpmsg