linux-kernel - [PATCH] bpf: verifier: allow arrays of progs to be used in sleepable context

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Message-Id: <20240422-sleepable_array_progs-v1-1-7c46ccbaa6e2@kernel.org>
Date: Mon, 22 Apr 2024 09:16:28 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 John Fastabend <john.fastabend@...il.com>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH] bpf: verifier: allow arrays of progs to be used in
 sleepable context

Arrays of progs are underlying using regular arrays, but they can only
be updated from a syscall.
Therefore, they should be safe to use while in a sleepable context.

This is required to be able to call bpf_tail_call() from a sleepable
tracing bpf program.

Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>
---
Hi,

a small patch to allow to have:

```
SEC("fmod_ret.s/__hid_bpf_tail_call_sleepable")
int BPF_PROG(hid_tail_call_sleepable, struct hid_bpf_ctx *hctx)
{
	bpf_tail_call(ctx, &hid_jmp_table, hctx->index);

	return 0;
}
```

This should allow me to add bpf hooks to functions that communicate with
the hardware.

Cheers,
Benjamin
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 68cfd6fc6ad4..880b32795136 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18171,6 +18171,7 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		case BPF_MAP_TYPE_QUEUE:
 		case BPF_MAP_TYPE_STACK:
 		case BPF_MAP_TYPE_ARENA:
+		case BPF_MAP_TYPE_PROG_ARRAY:
 			break;
 		default:
 			verbose(env,

---
base-commit: 735f5b8a7ccf383e50d76f7d1c25769eee474812
change-id: 20240422-sleepable_array_progs-e0c07b17cabb

Best regards,
-- 
Benjamin Tissoires <bentiss@...nel.org>