From: Guenter Roeck <linux@xxxxxxxxxxxx>
commit 65d1e3ddeae117f6a224535e10a09145f0f96508 upstream.
Mainline crashes as follows when running nios2 images.
On node 0 totalpages: 65536
free_area_init_node: node 0, pgdat c8408fa0, node_mem_map c8726000
Normal zone: 512 pages used for memmap
Normal zone: 0 pages reserved
Normal zone: 65536 pages, LIFO batch:15
Unable to handle kernel NULL pointer dereference at virtual address 00000000
ea = c8003cb0, ra = c81cbf40, cause = 15
Kernel panic - not syncing: Oops
Problem is seen because get_cycles() is called before the timer it depends
on is initialized. Returning 0 in that situation fixes the problem.
Fixes: 33d72f3822d7 ("init/main.c: extract early boot entropy from the ..")
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Daniel Micay <danielmicay@xxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/nios2/kernel/time.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/nios2/kernel/time.c
+++ b/arch/nios2/kernel/time.c
@@ -107,7 +107,10 @@ static struct nios2_clocksource nios2_cs
cycles_t get_cycles(void)
{
- return nios2_timer_read(&nios2_cs.cs);
+ /* Only read timer if it has been initialized */
+ if (nios2_cs.timer.base)
+ return nios2_timer_read(&nios2_cs.cs);
+ return 0;
}
EXPORT_SYMBOL(get_cycles);
