From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC09915DBB3 for ; Tue, 5 Nov 2024 16:33:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730824406; cv=none; b=l7I5x9Opb7e42woOONmqVSrca1jmJ7Yy8dLvywPadjwCGoyJ62kyuatjve7N4UACkhUuKPmA8x+v2OUA/lwWF3QbnwI1SwEuKgG94By5/lQnOWXsaU4w9YE1OiBpnFzJ+BUOm/v1OEK2jG7dQpXJ7K/Y4GFqQOpXXLUeiQBU6ZM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730824406; c=relaxed/simple; bh=+7Peqb5YWseDEkigRfa7wwqM/x2X4fk2REuNpPZyC0Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=e5XAHMkz2SMMXs/kUFpGgLGH26emLwwO7TSExzQty4bW+NY794jTnNVHVfFW9j1BfBwjy/D0W+w2RRAOHqxrYmUCrw5kpEWVVLHzsyGZaJxlFnyZ2JlTSTFVrAQDWkSJ0w7qKs4FYmgZMDRmbFd+PIXuo1KrVzQYJmj6bzwObvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=jeS2YHnZ; arc=none smtp.client-ip=95.215.58.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="jeS2YHnZ" Message-ID: <43dc0d7d-ca6e-4ba1-a831-e2a1e43f6311@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1730824403; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Qh70Angxv6P42eXAzDtoFyUntBGIhmcqR5D7QxYBQ58=; b=jeS2YHnZusS5LDqBB0fhHEXKXRHkU8Qujtns1vzVbZ2jtOfR1IdWCd7MVMQJZ1K0lpaiAQ wSHkYG2ZjJZDplAO5jEOrn0wGCBo8KSiEUt5ZPdGz2mBS+FmSO9yIalvvuz8RQeXqLFixd sQQadCQUcuOfnjCNTrRat9VyzvfIL1s= Date: Tue, 5 Nov 2024 08:33:17 -0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v9 02/10] bpf: Return false for bpf_prog_check_recur() default case Content-Language: en-GB To: Alexei Starovoitov Cc: bpf , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Kernel Team , Martin KaFai Lau , Tejun Heo References: <20241104193455.3241859-1-yonghong.song@linux.dev> <20241104193505.3242662-1-yonghong.song@linux.dev> <36294e71-4d0b-465d-9bf5-c5640aa3a089@linux.dev> <6c78f973-341e-4260-aed4-a5cb8e873acc@linux.dev> <29e2658c-02c9-4ef1-a633-ee5017e72bc3@linux.dev> <97ea8f52-96c3-4109-92b7-cf2631a34e2d@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 11/5/24 7:50 AM, Alexei Starovoitov wrote: > On Mon, Nov 4, 2024 at 10:02 PM Yonghong Song wrote: >>> I also don't understand the point of this patch 2. >>> The patch 3 can still do: >>> >>> + switch (prog->type) { >>> + case BPF_PROG_TYPE_KPROBE: >>> + case BPF_PROG_TYPE_TRACEPOINT: >>> + case BPF_PROG_TYPE_PERF_EVENT: >>> + case BPF_PROG_TYPE_RAW_TRACEPOINT: >>> + return PRIV_STACK_ADAPTIVE; >>> + default: >>> + break; >>> + } >>> + >>> + if (!bpf_prog_check_recur(prog)) >>> + return NO_PRIV_STACK; >>> >>> which would mean that iter, lsm, struct_ops will not be allowed >>> to use priv stack. >> One example is e.g. a TC prog. Since bpf_prog_check_recur(prog) >> will return true (means supporting recursion), and private stack >> does not really support TC prog, the logic will become more >> complicated. >> >> I am totally okay with removing patch 2 and go back to my >> previous approach to explicitly list prog types supporting >> private stack. > The point of reusing bpf_prog_check_recur() is that we don't > need to duplicate the logic. > We can still do something like: > switch (prog->type) { > case BPF_PROG_TYPE_KPROBE: > case BPF_PROG_TYPE_TRACEPOINT: > case BPF_PROG_TYPE_PERF_EVENT: > case BPF_PROG_TYPE_RAW_TRACEPOINT: > return PRIV_STACK_ADAPTIVE; > case BPF_PROG_TYPE_TRACING: > case BPF_PROG_TYPE_LSM: > case BPF_PROG_TYPE_STRUCT_OPS: > if (bpf_prog_check_recur()) > return PRIV_STACK_ADAPTIVE; > /* fallthrough */ > default: > return NO_PRIV_STACK; > } Right. Listing trampoline related prog types explicitly and using bpf_prog_check_recur() will be safe. One thing is for BPF_PROG_TYPE_STRUCT_OPS, PRIV_STACK_ALWAYS will be returned. I will make adjustment like switch (prog->type) { case BPF_PROG_TYPE_KPROBE: case BPF_PROG_TYPE_TRACEPOINT: case BPF_PROG_TYPE_PERF_EVENT: case BPF_PROG_TYPE_RAW_TRACEPOINT: return PRIV_STACK_ADAPTIVE; case BPF_PROG_TYPE_TRACING: case BPF_PROG_TYPE_LSM: case BPF_PROG_TYPE_STRUCT_OPS: if (bpf_prog_check_recur()) { if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) return PRIV_STACK_ALWAYS; else return PRIV_STACK_ADAPTIVE; } /* fallthrough */ default: return NO_PRIV_STACK; }