On Fri, Jul 24, 2020 at 1:39 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> The program and map iterators work similar to seq_file-s.
> Once the program is pinned in bpffs it can be read with "cat" tool
> to print human readable output. In this case about BPF programs and maps.
> For example:
> $ cat /sys/fs/bpf/progs.debug
> id name attached
> 5 dump_bpf_map bpf_iter_bpf_map
> 6 dump_bpf_prog bpf_iter_bpf_prog
> $ cat /sys/fs/bpf/maps.debug
> id name pages
> 3 iterator.rodata 2
>
> To avoid kernel build dependency on clang 10 separate bpf skeleton generation
> into manual "make" step and instead check-in generated .skel.h into git.
>
> Unlike 'bpftool prog show' in-kernel BTF name is used (when available)
> to print full name of BPF program instead of 16-byte truncated name.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
Tiny bug below, otherwise looks good.
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
> kernel/bpf/preload/iterators/.gitignore | 2 +
> kernel/bpf/preload/iterators/Makefile | 57 +++
> kernel/bpf/preload/iterators/README | 4 +
> kernel/bpf/preload/iterators/iterators.bpf.c | 118 +++++
> kernel/bpf/preload/iterators/iterators.skel.h | 411 ++++++++++++++++++
> 5 files changed, 592 insertions(+)
> create mode 100644 kernel/bpf/preload/iterators/.gitignore
> create mode 100644 kernel/bpf/preload/iterators/Makefile
> create mode 100644 kernel/bpf/preload/iterators/README
> create mode 100644 kernel/bpf/preload/iterators/iterators.bpf.c
> create mode 100644 kernel/bpf/preload/iterators/iterators.skel.h
>
[...]
> +
> +static const char *get_name(struct btf *btf, long btf_id, const char *fallback)
> +{
> + struct btf_type **types, *t;
> + unsigned int name_off;
> + const char *str;
> +
> + if (!btf)
> + return fallback;
> + str = btf->strings;
> + types = btf->types;
> + bpf_probe_read_kernel(&t, sizeof(t), types + btf_id);
> + name_off = BPF_CORE_READ(t, name_off);
> + if (name_off > btf->hdr.str_len)
>= here?
> + return fallback;
> + return str + name_off;
> +}
> +
> +SEC("iter/bpf_map")
> +int dump_bpf_map(struct bpf_iter__bpf_map *ctx)
> +{
> + struct seq_file *seq = ctx->meta->seq;
> + __u64 seq_num = ctx->meta->seq_num;
> + struct bpf_map *map = ctx->map;
> +
> + if (!map)
> + return 0;
> +
> + if (seq_num == 0)
> + BPF_SEQ_PRINTF(seq, " id name pages\n");
> +
> + BPF_SEQ_PRINTF(seq, "%4u %-16s%6d\n", map->id, map->name, map->memory.pages);
map->memory.pages won't be meaningful, once Roman's patches removing
RLIMIT_MEMLOCK usage land, so might just drop them now
> + return 0;
> +}
> +
> +SEC("iter/bpf_prog")
> +int dump_bpf_prog(struct bpf_iter__bpf_prog *ctx)
> +{
> + struct seq_file *seq = ctx->meta->seq;
> + __u64 seq_num = ctx->meta->seq_num;
> + struct bpf_prog *prog = ctx->prog;
> + struct bpf_prog_aux *aux;
> +
> + if (!prog)
> + return 0;
> +
> + aux = prog->aux;
> + if (seq_num == 0)
> + BPF_SEQ_PRINTF(seq, " id name attached\n");
> +
> + BPF_SEQ_PRINTF(seq, "%4u %-16s %s %s\n", aux->id,
> + get_name(aux->btf, aux->func_info[0].type_id, aux->name),
> + aux->attach_func_name, aux->linked_prog->aux->name);
> + return 0;
> +}
> +char LICENSE[] SEC("license") = "GPL";
[...]
