ARM: 7839/1: entry: fix tracing of ARM-private syscalls

Commit 377747c406 ("ARM: entry: allow ARM-private syscalls to be
restarted") reworked the low-level syscall dispatcher to allow
restarting of ARM-private syscalls. Unfortunately, this relocated the
label used to dispatch a private syscall from the trace path, so that
the invocation would be bypassed altogether!

This causes applications to fail under strace as soon as they rely on
a private syscall (e.g. set_tls):

  set_tls(0xb6fad4c0, 0xb6fadb98, 0xb6fb1050, 0xb6fad4c0, 0xb6fb1050)
      = -1 ENOSYS (Function not implemented)

This patch fixes the label so that we correctly dispatch private
syscalls from the trace path.

Reported-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Tested-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/entry-common.S

@@ -442,10 +442,10 @@ local_restart:
 	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
 
 	add	r1, sp, #S_OFF
-	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
+2:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
 	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
 	bcs	arm_syscall
-2:	mov	why, #0				@ no longer a real syscall
+	mov	why, #0				@ no longer a real syscall
 	b	sys_ni_syscall			@ not private func
 
 #if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)