linux-kernel - [PATCH 4.19 132/276] powerpc/64: Fix booting large kernels with STRICT_KERNEL

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Date:   Wed, 29 May 2019 20:04:50 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Russell Currey <ruscur@...sell.cc>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 132/276] powerpc/64: Fix booting large kernels with STRICT_KERNEL_RWX

[ Upstream commit 56c46bba9bbfe229b4472a5be313c44c5b714a39 ]

With STRICT_KERNEL_RWX enabled anything marked __init is placed at a 16M
boundary.  This is necessary so that it can be repurposed later with
different permissions.  However, in kernels with text larger than 16M,
this pushes early_setup past 32M, incapable of being reached by the
branch instruction.

Fix this by setting the CTR and branching there instead.

Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs")
Signed-off-by: Russell Currey <ruscur@...sell.cc>
[mpe: Fix it to work on BE by using DOTSYM()]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kernel/head_64.S | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 4898e9491a1cd..9168a247e24ff 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -970,7 +970,9 @@ start_here_multiplatform:
 
 	/* Restore parameters passed from prom_init/kexec */
 	mr	r3,r31
-	bl	early_setup		/* also sets r13 and SPRG_PACA */
+	LOAD_REG_ADDR(r12, DOTSYM(early_setup))
+	mtctr	r12
+	bctrl		/* also sets r13 and SPRG_PACA */
 
 	LOAD_REG_ADDR(r3, start_here_common)
 	ld	r4,PACAKMSR(r13)
-- 
2.20.1