[PATCH 3.16 04/86] MIPS: jump_label.c: Correct the span of the J instruction

Ben Hutchings
2019-05-16T16:03:45Z

From: "Maciej W. Rozycki" <macro@codesourcery.com>

commit 99436f7d69045800ffd1d66912f85d37150c7e2b upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/mips/kernel/jump_label.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/mips/kernel/jump_label.c
+++ b/arch/mips/kernel/jump_label.c
@@ -27,8 +27,8 @@ void arch_jump_label_transform(struct ju
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);