Patch "ARM: avoid faulting on qemu" has been added to the 4.14-stable tree

Patch "ARM: avoid faulting on qemu" has been added to the 4.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ARM: avoid faulting on qemu

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-avoid-faulting-on-qemu.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 3aaf33bebda8d4ffcc0fc8ef39e6c1ac68823b11 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Mon, 27 Nov 2017 11:22:42 +0000
Subject: ARM: avoid faulting on qemu

From: Russell King <rmk+kernel@armlinux.org.uk>

commit 3aaf33bebda8d4ffcc0fc8ef39e6c1ac68823b11 upstream.

When qemu starts a kernel in a bare environment, the default SCR has
the AW and FW bits clear, which means that the kernel can't modify
the PSR A or PSR F bits, and means that FIQs and imprecise aborts are
always masked.

When running uboot under qemu, the AW and FW SCR bits are set, and the
kernel functions normally - and this is how real hardware behaves.

Fix this for qemu by ignoring the FIQ bit.

Fixes: 8bafae202c82 ("ARM: BUG if jumping to usermode address in kernel mode")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Alex Shi <alex.shi@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm/kernel/entry-header.S |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -300,7 +300,7 @@
 	mov	r2, sp
 	ldr	r1, [r2, #\offset + S_PSR]	@ get calling cpsr
 	ldr	lr, [r2, #\offset + S_PC]!	@ get pc
-	tst	r1, #0xcf
+	tst	r1, #PSR_I_BIT | 0x0f
 	bne	1f
 	msr	spsr_cxsf, r1			@ save in spsr_svc
 #if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
@@ -332,7 +332,7 @@
 	ldr	r1, [sp, #\offset + S_PSR]	@ get calling cpsr
 	ldr	lr, [sp, #\offset + S_PC]	@ get pc
 	add	sp, sp, #\offset + S_SP
-	tst	r1, #0xcf
+	tst	r1, #PSR_I_BIT | 0x0f
 	bne	1f
 	msr	spsr_cxsf, r1			@ save in spsr_svc
 


Patches currently in stable-queue which might be from rmk+kernel@armlinux.org.uk are

queue-4.14/arm-avoid-faulting-on-qemu.patch
queue-4.14/arm-bug-if-jumping-to-usermode-address-in-kernel-mode.patch