From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (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 36FB328CF74 for ; Thu, 19 Jun 2025 17:55:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750355758; cv=none; b=Q8RTC4Vn9XW0QdLLr/e8YMPPs3A318Lr7gVcFp5drHAboMaemW5yURS0oLAx6TvCd+SCwjzJX5FrzJoZ2O1jO+3OPCyjlapkTeC7TEpX/IZdJ+UFbyhcWBeC+zT0eJUpION1So2si7WkysV9qLPrQNbl2a8h8UE8dJQcqm9RZEY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750355758; c=relaxed/simple; bh=SYjKbPsZzWTBPQPSXyX+CXzx5n5UoGWPVDeE3a2YoPE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Eem4q9MTOLJ/agWOCLwCkCjhuMwTVIARCxRnlHoQPVke0WKBM+fF9vPUnoVhPogi4b6J/pg41xO3pFU1XIJbDhfhkfoFUM9SLk8Pu/2bGer51TDt6HfFf7mOJK/UjleYTDTfsPeU9/tdZ3L2lj1kvKvUo2cwS/5qBcPp8/pVRwk= 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=m95zovZk; arc=none smtp.client-ip=91.218.175.183 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="m95zovZk" Message-ID: <7e7e4056-e2b8-41a5-a6b2-a2fbe0a94f4c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1750355754; 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=EtgKYGBD8XnCA4CkCmGywoXIEBd2GbqL6X0bRSIikNg=; b=m95zovZkH/B5W19xWC5cj8LhnlawottZq3MH/S44erR8gbzI5rX/TfJ0nYjq0QQ1ENIMNK 4NKFwgYiV5W5G3Y4tHm5++esO+xCqNOY49J3ubLtTlNuieOyFXkMTz/nyJHRkcVMkxmAX6 zy4lMUceWQXI8KXMdwBeX6Ou5d/std4= Date: Thu, 19 Jun 2025 10:55:49 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next 1/2] bpf: add bpf_dynptr_memset() kfunc To: Eduard Zingerman , Mykyta Yatsenko , andrii@kernel.org Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, mykolal@fb.com, kernel-team@meta.com References: <20250618223310.3684760-1-isolodrai@meta.com> <45390c6c-bd2a-4962-8222-1ad346f9908c@linux.dev> <7852f30ba177dc5b811bb0840ca0f301df2a8b58.camel@gmail.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ihor Solodrai In-Reply-To: <7852f30ba177dc5b811bb0840ca0f301df2a8b58.camel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 6/19/25 10:19 AM, Eduard Zingerman wrote: > On Thu, 2025-06-19 at 10:09 -0700, Ihor Solodrai wrote: > > [...] > >> But then, does memset even make sense for xdp/skb buffers? > > Why not? I was thinking that in a BPF program you'd usually be reading xdp/skb and not writing to it, especially not via memset. But never mind, I am likely wrong. > >> Maybe -ENOTSUPP is more appropriate? >> >> I'd appreciate any hints. > > I think Mykyta has kernel/trace/bpf_trace.c:__bpf_dynptr_copy_str() in mind. Thanks for the pointer. So it looks like memset can use bpf_dynptr_slice_rdwr() to handle xdp/skb cases. Something like: void *ptr = bpf_dynptr_slice_rdwr(&dynptr, 0, buffer, sizeof(buffer)); if (!ptr) return -EINVAL; memset(ptr, val, n); if (ptr == buffer) bpf_dynptr_write(&dynptr, 0, buffer, sizeof(buffer), 0); >