linux-kernel - Re: [PATCH v5 11/15] tools/bpf/bpftool: use TASK_COMM_LEN

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Date:   Thu, 21 Oct 2021 15:38:10 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Peter Ziljstra <peterz@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Valentin Schneider <valentin.schneider@....com>,
        qiang.zhang@...driver.com, robdclark@...omium.org,
        Christian Brauner <christian@...uner.io>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...hat.com>, juri.lelli@...hat.com,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        oliver.sang@...el.com, kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH v5 11/15] tools/bpf/bpftool: use TASK_COMM_LEN_16 instead
 of hard-coded 16

On Wed, Oct 20, 2021 at 8:46 PM Yafang Shao <laoar.shao@...il.com> wrote:
>
> Use TASK_COMM_LEN_16 instead of hard-coded 16 to make it more grepable.
> It uses bpf_probe_read_kernel() to get task comm, which may return a
> string without nul terminator. We should use bpf_probe_read_kernel_str()
> instead.
>
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Petr Mladek <pmladek@...e.com>
> ---
>  tools/bpf/bpftool/Makefile                | 1 +
>  tools/bpf/bpftool/main.h                  | 3 ++-
>  tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 4 ++--
>  tools/bpf/bpftool/skeleton/pid_iter.h     | 4 +++-
>  4 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index d73232be1e99..33fbde84993c 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -164,6 +164,7 @@ $(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF)
>         $(QUIET_CLANG)$(CLANG) \
>                 -I$(if $(OUTPUT),$(OUTPUT),.) \
>                 -I$(srctree)/tools/include/uapi/ \
> +               -I$(srctree)/tools/include/ \

bpftool shouldn't rely on internal kernel headers for compilation. If
you want to have TASK_COMM_LEN_16 constant for grep-ability, just
#define it where appropriate

>                 -I$(LIBBPF_PATH) \
>                 -I$(srctree)/tools/lib \
>                 -g -O2 -Wall -target bpf -c $< -o $@ && $(LLVM_STRIP) -g $@
> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> index 90caa42aac4c..5efa27188f68 100644
> --- a/tools/bpf/bpftool/main.h
> +++ b/tools/bpf/bpftool/main.h
> @@ -12,6 +12,7 @@
>  #include <linux/compiler.h>
>  #include <linux/kernel.h>
>  #include <linux/hashtable.h>
> +#include <linux/sched/task.h>
>  #include <tools/libc_compat.h>
>

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