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SubjectRE: [PATCH v2 2/2] tracing: Fix for non-continuous cpu ids
Date
On Monday, July 13, 2015 7:12 PM
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 9 Jun 2015 10:32:35 +0300
> Gil Fruchter <gilf@ezchip.com> wrote:
>
> > Currently exception occures due to access beyond buffer_iter range
> > while using index of cpu bigger than num_possible_cpus().
> > Below there is an example for such exception when we use cpus
> > 0,1,16,17.
> >
> > In order to fix buffer allocation size for non-continuous cpu ids we
> > allocate according to the max cpu id and not according to the amount
> > of possible cpus.
> >
> > Example:
> > $ cat /sys/kernel/debug/tracing/per_cpu/cpu1/trace
> > Path: /bin/busybox
> > CPU: 0 PID: 82 Comm: cat Not tainted 4.0.0 #29
> > task: 80734c80 ti: 80012000 task.ti: 80012000
> >
> > [ECR ]: 0x00220100 => Invalid Read @ 0x00000000 by insn @ 0x800abafc
> > [EFA ]: 0x00000000
> > [BLINK ]: ring_buffer_read_finish+0x24/0x64
> > [ERET ]: rb_check_pages+0x20/0x188
> > [STAT32]: 0x00001a00 :
> > BTA: 0x800abafc SP: 0x80013f0c FP: 0x57719cf8
> > LPS: 0x200036b4 LPE: 0x200036b8 LPC: 0x00000000
> > r00: 0x8002aca0 r01: 0x00001606 r02: 0x00000000
> > r03: 0x00000001 r04: 0x00000000 r05: 0x804b4954
> > r06: 0x00030003 r07: 0x8002a260 r08: 0x00000286
> > r09: 0x00080002 r10: 0x00001006 r11: 0x807351a4
> > r12: 0x00000001
> >
> > Stack Trace:
> > rb_check_pages+0x20/0x188
> > ring_buffer_read_finish+0x24/0x64
> > tracing_release+0x4e/0x170
> > __fput+0x62/0x158
> > task_work_run+0xa2/0xd4
> > do_notify_resume+0x52/0x7c
> > resume_user_mode_begin+0xdc/0xe0
> >
> > Signed-off-by: Noam Camus <noamc@ezchip.com>
>
> Why Noam's SoB tag? Did he author it?
>
> -- Steve
>

He didn't author it, but we worked on this issue together.

Gil.


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