netdev - Re: [PATCH bpf-next 4/9] samples: bpf: refactor task_fd

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Date:   Tue, 17 Nov 2020 22:15:50 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     "Daniel T. Lee" <danieltimlee@...il.com>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>, brakmo <brakmo@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        David Ahern <dsa@...ulusnetworks.com>,
        Yonghong Song <yhs@...com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Ira Weiny <ira.weiny@...el.com>, Thomas Graf <tgraf@...g.ch>,
        Jakub Kicinski <kuba@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        Xdp <xdp-newbies@...r.kernel.org>
Subject: Re: [PATCH bpf-next 4/9] samples: bpf: refactor task_fd_query
 program with libbpf

On Tue, Nov 17, 2020 at 02:56:39PM +0000, Daniel T. Lee wrote:
> This commit refactors the existing kprobe program with libbpf bpf
> loader. To attach bpf program, this uses generic bpf_program__attach()
> approach rather than using bpf_load's load_bpf_file().
> 
> To attach bpf to perf_event, instead of using previous ioctl method,
> this commit uses bpf_program__attach_perf_event since it manages the
> enable of perf_event and attach of BPF programs to it, which is much
> more intuitive way to achieve.
> 
> Also, explicit close(fd) has been removed since event will be closed
> inside bpf_link__destroy() automatically.
> 
> DEBUGFS macro from trace_helpers has been used to control uprobe events.
> Furthermore, to prevent conflict of same named uprobe events, O_TRUNC
> flag has been used to clear 'uprobe_events' interface.
> 
> Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
> ---
>  samples/bpf/Makefile             |   2 +-
>  samples/bpf/task_fd_query_user.c | 101 ++++++++++++++++++++++---------
>  2 files changed, 74 insertions(+), 29 deletions(-)
> 
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 7a643595ac6c..36b261c7afc7 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -107,7 +107,7 @@ xdp_adjust_tail-objs := xdp_adjust_tail_user.o
>  xdpsock-objs := xdpsock_user.o
>  xsk_fwd-objs := xsk_fwd.o
>  xdp_fwd-objs := xdp_fwd_user.o
> -task_fd_query-objs := bpf_load.o task_fd_query_user.o $(TRACE_HELPERS)
> +task_fd_query-objs := task_fd_query_user.o $(TRACE_HELPERS)
>  xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS)
>  ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
>  hbm-objs := hbm.o $(CGROUP_HELPERS) $(TRACE_HELPERS)
> diff --git a/samples/bpf/task_fd_query_user.c b/samples/bpf/task_fd_query_user.c
> index b68bd2f8fdc9..0891ef3a4779 100644
> --- a/samples/bpf/task_fd_query_user.c
> +++ b/samples/bpf/task_fd_query_user.c
> @@ -15,12 +15,15 @@
>  #include <sys/stat.h>
>  #include <linux/perf_event.h>
>  
> +#include <bpf/bpf.h>
>  #include <bpf/libbpf.h>
> -#include "bpf_load.h"
>  #include "bpf_util.h"
>  #include "perf-sys.h"
>  #include "trace_helpers.h"
>  
> +struct bpf_program *progs[2];
> +struct bpf_link *links[2];
static