Re: [PATCH v2] bpf: restore the ebpf program ID for BPF_AUDIT_UNLOAD and PERF_BPF_EVENT_PROG_UNLOAD

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, Dec 23, 2022 at 01:55:31PM -0500, Paul Moore wrote:

SNIP

> diff --git a/drivers/net/netdevsim/bpf.c b/drivers/net/netdevsim/bpf.c
> index 50854265864d..2795f03f5f34 100644
> --- a/drivers/net/netdevsim/bpf.c
> +++ b/drivers/net/netdevsim/bpf.c
> @@ -109,7 +109,7 @@ nsim_bpf_offload(struct netdevsim *ns, struct bpf_prog *prog, bool oldprog)
>  	     "bad offload state, expected offload %sto be active",
>  	     oldprog ? "" : "not ");
>  	ns->bpf_offloaded = prog;
> -	ns->bpf_offloaded_id = prog ? prog->aux->id : 0;
> +	ns->bpf_offloaded_id = prog ? bpf_prog_get_id(prog) : 0;
>  	nsim_prog_set_loaded(prog, true);
>  
>  	return 0;
> @@ -221,6 +221,7 @@ static int nsim_bpf_create_prog(struct nsim_dev *nsim_dev,
>  	struct nsim_bpf_bound_prog *state;
>  	char name[16];
>  	int ret;
> +	u32 id;
>  
>  	state = kzalloc(sizeof(*state), GFP_KERNEL);
>  	if (!state)
> @@ -239,7 +240,8 @@ static int nsim_bpf_create_prog(struct nsim_dev *nsim_dev,
>  		return ret;
>  	}
>  
> -	debugfs_create_u32("id", 0400, state->ddir, &prog->aux->id);
> +	id = bpf_prog_get_id(prog);
> +	debugfs_create_u32("id", 0400, state->ddir, &id);
>  	debugfs_create_file("state", 0400, state->ddir,
>  			    &state->state, &nsim_bpf_string_fops);
>  	debugfs_create_bool("loaded", 0400, state->ddir, &state->is_loaded);
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 9e7d46d16032..18e965bd7db9 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1102,7 +1102,7 @@ struct bpf_prog_aux {
>  	u32 max_pkt_offset;
>  	u32 max_tp_access;
>  	u32 stack_depth;
> -	u32 id;
> +	u32 __id; /* access via bpf_prog_get_id() to check bpf_prog::valid_id */

it breaks bpftool that uses

  BPF_CORE_READ((struct bpf_prog *)ent, aux, id);

and bpffs selftest because of preload iter object uses aux->id

  kernel/bpf/preload/iterators/iterators.bpf.c

it'd be great to have a solution that keep 'id' field,
because it's probably used in many bpf programs already

jirka

>  	u32 func_cnt; /* used by non-func prog as the number of func progs */
>  	u32 func_idx; /* 0 for non-func prog, the index in func array for func prog */
>  	u32 attach_btf_id; /* in-kernel BTF type id to attach to */
> @@ -1197,7 +1197,8 @@ struct bpf_prog {
>  				enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
>  				call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
>  				call_get_func_ip:1, /* Do we call get_func_ip() */
> -				tstamp_type_access:1; /* Accessed __sk_buff->tstamp_type */
> +				tstamp_type_access:1, /* Accessed __sk_buff->tstamp_type */
> +				valid_id:1; /* Is bpf_prog::aux::__id valid? */
>  	enum bpf_prog_type	type;		/* Type of BPF program */
>  	enum bpf_attach_type	expected_attach_type; /* For some prog types */
>  	u32			len;		/* Number of filter blocks */
> @@ -1688,6 +1689,12 @@ void bpf_prog_inc(struct bpf_prog *prog);
>  struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog);
>  void bpf_prog_put(struct bpf_prog *prog);
>  

SNIP