This is a note to let you know that I've just added the patch titled
ARM: avoid faulting on qemu
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm-avoid-faulting-on-qemu.patch and it can be found in the queue-4.4 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 @@ -295,7 +295,7 @@ 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) @@ -327,7 +327,7 @@ 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-4.4/arm-avoid-faulting-on-qemu.patch queue-4.4/arm-bug-if-jumping-to-usermode-address-in-kernel-mode.patch