Re: [PATCH v2 bpf-next 2/4] bpf: introduce helper bpf_get_task_stak()

On Fri, Jun 26, 2020 at 1:17 PM Andrii Nakryiko
[off-list ref] wrote:

On Thu, Jun 25, 2020 at 5:14 PM Song Liu [off-list ref] wrote:

quoted

Introduce helper bpf_get_task_stack(), which dumps stack trace of given
task. This is different to bpf_get_stack(), which gets stack track of
current task. One potential use case of bpf_get_task_stack() is to call
it from bpf_iter__task and dump all /proc/<pid>/stack to a seq_file.

bpf_get_task_stack() uses stack_trace_save_tsk() instead of
get_perf_callchain() for kernel stack. The benefit of this choice is that
stack_trace_save_tsk() doesn't require changes in arch/. The downside of
using stack_trace_save_tsk() is that stack_trace_save_tsk() dumps the
stack trace to unsigned long array. For 32-bit systems, we need to
translate it to u64 array.

Signed-off-by: Song Liu <redacted>
---

Looks great, I just think that there are cases where user doesn't
necessarily has valid task_struct pointer, just pid, so would be nice
to not artificially restrict such cases by having extra helper.

Acked-by: Andrii Nakryiko <redacted>

oh, please also fix a typo in the subject, it will make grepping more
frustrating

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