ARM: avoid faulting on qemu

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>

diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 7f4d80c..0f07579 100644 (file)
--- 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