On 07/29/2016 08:47 AM, Alexei Starovoitov wrote:
On Thu, Jul 28, 2016 at 05:42:21PM -0700, William Tu wrote:
The total size of value copy_to_user() writes to userspace should
be the (current number of cpu) * (value size), instead of
num_possible_cpus() * (value size). Found by samples/bpf/test_maps.c,
which always copies 512 byte to userspace, crashing the userspace
program stack.
hmm. I'm missing something. The sample code assumes no cpu hutplug,
so sysconf(_SC_NPROCESSORS_CONF) == num_possible_cpu == num_online_cpu,
unless there is crazy INIT_ALL_POSSIBLE config option is used.
Are you using ARM by chance? What is the count that you get in
user space and from kernel side?
http://lists.infradead.org/pipermail/linux-arm-kernel/2011-June/054177.html
