Re: [PATCH v1 bpf-next] bpf: new helper bpf_get_current_pcomm

On Wed, Aug 26, 2020 at 10:25:55PM -0700, Andrii Nakryiko wrote:

On Wed, Aug 26, 2020 at 9:06 AM Carlos Neira [off-list ref] wrote:

quoted

In multi-threaded applications bpf_get_current_comm is returning per-thread
names, this helper will return comm from real_parent.
This makes a difference for some Java applications, where get_current_comm is
returning per-thread names, but get_current_pcomm will return "java".

Why not bpf_probe_read_kernel_str(dst, 16, task->real_parent->comm)
for fentry/fexit/tp_btf/etc BTF-aware BPF programs or
BPF_CORE_READ_STR_INTO(dst, task, real_parent, comm) for any BPF
program that has bpf_probe_read_kernel[_str]() (which is pretty much
every BPF program nowadays, I think)?

Yes, CONFIG_DEBUG_INFO_BTF=y Kconfig is a requirement, but it's a good
idea to have that if you are using BPF anyways.

quoted

Signed-off-by: Carlos Neira <redacted>
---
 include/linux/bpf.h                           |  1 +
 include/uapi/linux/bpf.h                      | 15 ++++-
 kernel/bpf/core.c                             |  1 +
 kernel/bpf/helpers.c                          | 28 +++++++++
 kernel/trace/bpf_trace.c                      |  2 +
 tools/include/uapi/linux/bpf.h                | 15 ++++-
 .../selftests/bpf/prog_tests/current_pcomm.c  | 57 +++++++++++++++++++
 .../selftests/bpf/progs/test_current_pcomm.c  | 17 ++++++
 8 files changed, 134 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/current_pcomm.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_current_pcomm.c

[...]

Thanks Andrii,
I'll use bpf_probe_read_kernel_str(dst, 16, task->real_parent->comm),
I was not aware of that.

Bests!.