[PATCH 4.4 15/38] MIPS: Fix BUILD_ROLLBACK_PROLOGUE for microMIPS

From: Greg Kroah-Hartman
Date: Mon Nov 23 2020 - 07:24:20 EST


From: Paul Burton <paul.burton@xxxxxxxxxx>

[ Upstream commit 1eefcbc89cf3a8e252e5aeb25825594699b47360 ]

When the kernel is built for microMIPS, branches targets need to be
known to be microMIPS code in order to result in bit 0 of the PC being
set. The branch target in the BUILD_ROLLBACK_PROLOGUE macro was simply
the end of the macro, which may be pointing at padding rather than at
code. This results in recent enough GNU linkers complaining like so:

mips-img-linux-gnu-ld: arch/mips/built-in.o: .text+0x3e3c: Unsupported branch between ISA modes.
mips-img-linux-gnu-ld: final link failed: Bad value
Makefile:936: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1

Fix this by changing the branch target to be the start of the
appropriate handler, skipping over any padding.

Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/14019/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/mips/kernel/genex.S | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index 7ffd158de76e5..1b837d6f73deb 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -142,9 +142,8 @@ LEAF(__r4k_wait)
PTR_LA k1, __r4k_wait
ori k0, 0x1f /* 32 byte rollback region */
xori k0, 0x1f
- bne k0, k1, 9f
+ bne k0, k1, \handler
MTC0 k0, CP0_EPC
-9:
.set pop
.endm

--
2.27.0