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 <[email protected]>
> ---
>  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