Subject: Re: [PATCH bpf-next v4 0/9] tools: bpftool: add probes for system and device

From: Stanislav Fomichev <[email-masked]>
Date: Wed, 16 Jan 2019 09:15:45 -0800

On 01/16, Quentin Monnet wrote:
> Hi,
> This set adds a new command to bpftool in order to dump a list of
> eBPF-related parameters for the system (or for a specific network
> device) to the console. Once again, this is based on a suggestion from
> Daniel.
> 
> At this time, output includes:
> 
>     - Availability of bpf() system call
>     - Availability of bpf() system call for unprivileged users
>     - JIT status (enabled or not, with or without debugging traces)
>     - JIT hardening status
>     - JIT kallsyms exports status
>     - Global memory limit for JIT compiler for unprivileged users
>     - Status of kernel compilation options related to BPF features
>     - Availability of known eBPF program types
>     - Availability of known eBPF map types
>     - Availability of known eBPF helper functions
> 
> There are three different ways to dump this information at this time:
> 
>     - Plain output dumps probe results in plain text. It is the most
>       flexible options for providing descriptive output to the user, but
>       should not be relied upon for parsing the output.
>     - JSON output is supported.
>     - A third mode, available through the "macros" keyword appended to the
>       command line, dumps some of those parameters (not all) as a series of
>       "#define" directives, that can be included into a C header file for
>       example.
> 
> Probes for supported program and map types, and supported helpers, are
> directly added to libbpf, so that other applications (or selftests) can
> reuse them as necessary.
> 
> If the user does not have root privileges (or more precisely, the
> CAP_SYS_ADMIN capability) detection will be erroneous for most
> parameters. Therefore, forbid non-root users to run the command.
> 
> v4:
> - Probe bpf_jit_limit parameter (patch 2).
> - Probe some additional kernel config options (patch 3).
> - Minor fixes on patch 6.
Looks great! For the whole series:

Reviewed-by: Stanislav Fomichev <[email-masked]>
> 
> v3:
> - Do not probe kernel version in bpftool (just retrieve it to probe support
>   for kprobes in libbpf).
> - Change the way results for helper support is displayed: now one list of
>   compatible helpers for each program type (and C-style output gets a
>   HAVE_PROG_TYPE_HELPER(prog_type, helper) macro to help with tests. See
>   patches 6, 7.
> - Address other comments from feedback from v2 (please refer to individual
>   patches' history).
> 
> v2 (please also refer to individual patches' history):
> - Move probes for prog/map types, helpers, from bpftool to libbpf.
> - Move C-style output as a separate patch, and restrict it to a subset of
>   collected information (bpf() availability, prog/map types, helpers).
> - Now probe helpers with all supported program types, and display a list of
>   compatible program types (as supported on the system) for each helper.
> - NOT addressed: grouping compilation options for kernel into subsections
>   (patch 3) (I don't see an easy way of grouping them at the moment, please
>   see also the discussion on v1 thread).
> 
> Cc: Arnaldo Carvalho de Melo <[email-masked]>
> Cc: Jesper Dangaard Brouer <[email-masked]>
> Cc: Stanislav Fomichev <[email-masked]>
> 
> Quentin Monnet (9):
>   tools: bpftool: add basic probe capability, probe syscall availability
>   tools: bpftool: add probes for /proc/ eBPF parameters
>   tools: bpftool: add probes for kernel configuration options
>   tools: bpftool: add probes for eBPF program types
>   tools: bpftool: add probes for eBPF map types
>   tools: bpftool: add probes for eBPF helper functions
>   tools: bpftool: add C-style "#define" output for probes
>   tools: bpftool: add probes for a network device
>   tools: bpftool: add bash completion for bpftool probes
> 
>  .../bpftool/Documentation/bpftool-cgroup.rst  |   1 +
>  .../bpftool/Documentation/bpftool-feature.rst |  85 ++
>  .../bpf/bpftool/Documentation/bpftool-map.rst |   1 +
>  .../bpf/bpftool/Documentation/bpftool-net.rst |   1 +
>  .../bpftool/Documentation/bpftool-perf.rst    |   1 +
>  .../bpftool/Documentation/bpftool-prog.rst    |   1 +
>  tools/bpf/bpftool/Documentation/bpftool.rst   |   1 +
>  tools/bpf/bpftool/bash-completion/bpftool     |  19 +
>  tools/bpf/bpftool/feature.c                   | 764 ++++++++++++++++++
>  tools/bpf/bpftool/main.c                      |   3 +-
>  tools/bpf/bpftool/main.h                      |   4 +
>  tools/bpf/bpftool/map.c                       |   4 +-
>  tools/lib/bpf/Build                           |   2 +-
>  tools/lib/bpf/libbpf.h                        |  14 +
>  tools/lib/bpf/libbpf.map                      |   3 +
>  tools/lib/bpf/libbpf_probes.c                 | 242 ++++++
>  16 files changed, 1143 insertions(+), 3 deletions(-)
>  create mode 100644 tools/bpf/bpftool/Documentation/bpftool-feature.rst
>  create mode 100644 tools/bpf/bpftool/feature.c
>  create mode 100644 tools/lib/bpf/libbpf_probes.c
> 
> -- 
> 2.17.1
>