netdev - Re: [PATCH bpf-next] bpf: Add bpf

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Date:   Wed, 1 Jul 2020 22:23:51 -0700
From:   Yonghong Song <yhs@...com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        <davem@...emloft.net>
CC:     <daniel@...earbox.net>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <kernel-team@...com>
Subject: Re: [PATCH bpf-next] bpf: Add bpf_prog iterator



On 7/1/20 6:40 PM, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@...nel.org>
> 
> It's mostly a copy paste of commit 6086d29def80 ("bpf: Add bpf_map iterator")
> that is use to implement bpf_seq_file opreations to traverse all bpf programs.

Thanks for implementing bpf iter for bpf_progs!

> 
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---
> No selftests?!
> They're coming as part of "usermode_driver for iterators" set.
> This patch is trivial and independent, so sending it first.

Okay. Ack only with a few nits.
Acked-by: Yonghong Song <yhs@...com>

> 
>   include/linux/bpf.h    |   1 +
>   kernel/bpf/Makefile    |   2 +-
>   kernel/bpf/prog_iter.c | 102 +++++++++++++++++++++++++++++++++++++++++
>   kernel/bpf/syscall.c   |  19 ++++++++
>   4 files changed, 123 insertions(+), 1 deletion(-)
>   create mode 100644 kernel/bpf/prog_iter.c
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 0cd7f6884c5c..3c659f36591d 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1112,6 +1112,7 @@ int  generic_map_delete_batch(struct bpf_map *map,
>   			      const union bpf_attr *attr,
>   			      union bpf_attr __user *uattr);
>   struct bpf_map *bpf_map_get_curr_or_next(u32 *id);
> +struct bpf_prog *bpf_prog_get_curr_or_next(u32 *id);
>   
>   extern int sysctl_unprivileged_bpf_disabled;
>   
> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> index 1131a921e1a6..e6eb9c0402da 100644
> --- a/kernel/bpf/Makefile
> +++ b/kernel/bpf/Makefile
> @@ -2,7 +2,7 @@
>   obj-y := core.o
>   CFLAGS_core.o += $(call cc-disable-warning, override-init)
>   
> -obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o
> +obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o
>   obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
>   obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
>   obj-$(CONFIG_BPF_SYSCALL) += disasm.o
> diff --git a/kernel/bpf/prog_iter.c b/kernel/bpf/prog_iter.c
> new file mode 100644
> index 000000000000..3080abd4d8ad
> --- /dev/null
> +++ b/kernel/bpf/prog_iter.c
> @@ -0,0 +1,102 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2020 Facebook */
> +#include <linux/bpf.h>
> +#include <linux/fs.h>
> +#include <linux/filter.h>
> +#include <linux/kernel.h>
> +
> +struct bpf_iter_seq_prog_info {
> +	u32 mid;

original field name "mid" is for "map_id".
Here, "pid" is a little bit misleading, maybe "prog_id"?

> +};
> +
> +static void *bpf_prog_seq_start(struct seq_file *seq, loff_t *pos)
> +{
> +	struct bpf_iter_seq_prog_info *info = seq->private;
> +	struct bpf_prog *prog;
> +
> +	prog = bpf_prog_get_curr_or_next(&info->mid);
> +	if (!prog)
> +		return NULL;
> +
> +	++*pos;
> +	return prog;
> +}
> +
> +static void *bpf_prog_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> +{
> +	struct bpf_iter_seq_prog_info *info = seq->private;
> +	struct bpf_prog *prog;
> +
> +	++*pos;
> +	++info->mid;
> +	bpf_prog_put((struct bpf_prog *)v);
> +	prog = bpf_prog_get_curr_or_next(&info->mid);
> +	if (!prog)
> +		return NULL;
> +
> +	return prog;

You can just do "return bpf_prog_get_curr_or_next(&info->prog_id);"
"struct bpf_prog *prog" is not needed any more.

bpf_map_seq_next() has the same inefficiency. I think after a few 
revisions I lost the sight.

> +}
> +
> +struct bpf_iter__bpf_prog {
> +	__bpf_md_ptr(struct bpf_iter_meta *, meta);
> +	__bpf_md_ptr(struct bpf_prog *, prog);
> +};
> +
> +DEFINE_BPF_ITER_FUNC(bpf_prog, struct bpf_iter_meta *meta, struct bpf_prog *prog)
> +
> +static int __bpf_prog_seq_show(struct seq_file *seq, void *v, bool in_stop)
> +{
> +	struct bpf_iter__bpf_prog ctx;
> +	struct bpf_iter_meta meta;
> +	struct bpf_prog *prog;
> +	int ret = 0;
> +
> +	ctx.meta = &meta;
> +	ctx.prog = v;
> +	meta.seq = seq;
> +	prog = bpf_iter_get_info(&meta, in_stop);
> +	if (prog)
> +		ret = bpf_iter_run_prog(prog, &ctx);
> +
> +	return ret;
> +}
> +
[...]