linux-kernel - [PATCH 4.4 15/38] MIPS: Fix BUILD_ROLLBACK

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Date:   Mon, 23 Nov 2020 13:22:01 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Burton <paul.burton@...tec.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 15/38] MIPS: Fix BUILD_ROLLBACK_PROLOGUE for microMIPS

From: Paul Burton <paul.burton@...tec.com>

[ 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@...tec.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14019/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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