MIPS: jump_label.c: Correct the span of the J instruction

Correct the check for the span of the 256MB segment addressable by the J
instruction according to this instruction's semantics.  The calculation
of the jump target is applied to the address of the delay-slot
instruction that immediately follows.  Adjust the check accordingly by
adding 4 to `e->code' that holds the address of the J instruction
itself.
Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8515/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/jump_label.c

@@ -27,8 +27,8 @@ void arch_jump_label_transform(struct jump_entry *e,
 	union mips_instruction *insn_p =
 		(union mips_instruction *)(unsigned long)e->code;
 
-	/* Jump only works within a 256MB aligned region. */
-	BUG_ON((e->target & ~J_RANGE_MASK) != (e->code & ~J_RANGE_MASK));
+	/* Jump only works within a 256MB aligned region of its delay slot. */
+	BUG_ON((e->target & ~J_RANGE_MASK) != ((e->code + 4) & ~J_RANGE_MASK));
 
 	/* Target must have 4 byte alignment. */
 	BUG_ON((e->target & 3) != 0);