arm64: fix access to preempt_count from assembly code

preempt_count is defined as an int. Oddly enough, we access it
as a 64bit value. Things become interesting when running a BE
kernel, and looking at the current CPU number, which is stored
as an int next to preempt_count. Like in a per-cpu interrupt
handler, for example...

Using a 32bit access fixes the issue for good.

Cc: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 3881fd1..e116614 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -311,14 +311,14 @@ el1_irq:
 #endif
 #ifdef CONFIG_PREEMPT
        get_thread_info tsk
-       ldr     x24, [tsk, #TI_PREEMPT]         // get preempt count
-       add     x0, x24, #1                     // increment it
-       str     x0, [tsk, #TI_PREEMPT]
+       ldr     w24, [tsk, #TI_PREEMPT]         // get preempt count
+       add     w0, w24, #1                     // increment it
+       str     w0, [tsk, #TI_PREEMPT]
 #endif
        irq_handler
 #ifdef CONFIG_PREEMPT
-       str     x24, [tsk, #TI_PREEMPT]         // restore preempt count
-       cbnz    x24, 1f                         // preempt count != 0
+       str     w24, [tsk, #TI_PREEMPT]         // restore preempt count
+       cbnz    w24, 1f                         // preempt count != 0
        ldr     x0, [tsk, #TI_FLAGS]            // get flags
        tbz     x0, #TIF_NEED_RESCHED, 1f       // needs rescheduling?
        bl      el1_preempt
@@ -509,15 +509,15 @@ el0_irq_naked:
 #endif
        get_thread_info tsk
 #ifdef CONFIG_PREEMPT
-       ldr     x24, [tsk, #TI_PREEMPT]         // get preempt count
-       add     x23, x24, #1                    // increment it
-       str     x23, [tsk, #TI_PREEMPT]
+       ldr     w24, [tsk, #TI_PREEMPT]         // get preempt count
+       add     w23, w24, #1                    // increment it
+       str     w23, [tsk, #TI_PREEMPT]
 #endif
        irq_handler
 #ifdef CONFIG_PREEMPT
-       ldr     x0, [tsk, #TI_PREEMPT]
-       str     x24, [tsk, #TI_PREEMPT]
-       cmp     x0, x23
+       ldr     w0, [tsk, #TI_PREEMPT]
+       str     w24, [tsk, #TI_PREEMPT]
+       cmp     w0, w23
        b.eq    1f
        mov     x1, #0
        str     x1, [x1]                        // BUG