diff options
authorGuenter Roeck <linux@roeck-us.net>2017-09-11 20:45:26 -0700
committerLey Foon Tan <ley.foon.tan@intel.com>2017-09-15 20:30:58 +0800
commit65d1e3ddeae117f6a224535e10a09145f0f96508 (patch)
parent8993d5e4662b16845492c413efe82ec162bf5370 (diff)
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 <labbott@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Daniel Micay <danielmicay@gmail.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
1 files changed, 4 insertions, 1 deletions
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;

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