lkml.org 
[lkml]   [2017]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] nios2: time: Read timer in get_cycles only if initialized
Date
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>
---
Taking a stab at the problem. Fix works for my qemu test.

arch/nios2/kernel/time.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

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);

--
2.7.4
\
 
 \ /
  Last update: 2017-09-12 05:46    [W:0.031 / U:2.272 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site