From: Guenter Roeck Date: Tue, 12 Sep 2017 03:45:26 +0000 (-0700) Subject: nios2: time: Read timer in get_cycles only if initialized X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=65d1e3ddeae117f6a224535e10a09145f0f96508;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git nios2: time: Read timer in get_cycles only if initialized 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 Cc: Kees Cook Cc: Daniel Micay Signed-off-by: Guenter Roeck --- diff --git a/arch/nios2/kernel/time.c b/arch/nios2/kernel/time.c index 645129aaa9a0..20e86209ef2e 100644 --- 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);