4.4-stable review patch. If anyone has any objections, please let me know.
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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