From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sandelman.ca header.i=@sandelman.ca header.b="kRJL01DX" Received: from relay.sandelman.ca (relay.cooperix.net [IPv6:2a01:7e00:e000:2bb::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A7C73BE for ; Tue, 28 Nov 2023 01:43:39 -0800 (PST) Received: from dyas.sandelman.ca (dhcp-26-10.mtg.ripe.net [193.0.26.10]) by relay.sandelman.ca (Postfix) with ESMTPS id E3B881F4A5; Tue, 28 Nov 2023 09:43:37 +0000 (UTC) Authentication-Results: relay.sandelman.ca; dkim=pass (2048-bit key; secure) header.d=sandelman.ca header.i=@sandelman.ca header.b="kRJL01DX"; dkim-atps=neutral Received: by dyas.sandelman.ca (Postfix, from userid 1000) id 6972EA0EA4; Tue, 28 Nov 2023 10:43:36 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=sandelman.ca; s=dyas; t=1701164616; bh=V++t50RdFh97gfStfpihxNegajDRmjgxfyxc4gjCg8M=; h=From:To:Subject:In-reply-to:References:Date:From; b=kRJL01DXQBAFgrzSOih/I5DXJvXDHIronI6KSvDYFWmfdqTkIeSKqEr9BlktlSevY Y5dBn744SbHPGp5vL0T8pHzEkSIjpAMFO0iAPOZBDoi3JP3hmGBj7z/YrKp7Yd30P6 VQr9izeSBY2iyI5KzDoy7V9BOPHDXnzRXxr3r6eESrVZX8x/FhYqgjO9XirQx7qJcn KSKgR4Zwm6PMERmkJTRTYB9Qb9AtjnhjucD3BI/3mfUbvi6Jo7QSW//YtVH9Y3+Yrs FzKbHQNEIdmFZhb+4k7MNYTZrHCdImhQekFx5nmJ9RbLReGIgeBvzvBDXm2xE4aTTc ccQH77jbAzbHQ== Received: from dyas (localhost [127.0.0.1]) by dyas.sandelman.ca (Postfix) with ESMTP id 669A4A0EA2; Tue, 28 Nov 2023 10:43:36 +0100 (CET) From: Michael Richardson To: David Vernet , bpf@ietf.org, bpf@vger.kernel.org Subject: Re: [Bpf] IETF 118 BPF WG summary In-reply-to: <20231127201817.GB5421@maniforge> References: <20231127201817.GB5421@maniforge> Comments: In-reply-to David Vernet message dated "Mon, 27 Nov 2023 14:18:17 -0600." X-Mailer: MH-E 8.6+git; nmh 1.7+dev; GNU Emacs 26.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Date: Tue, 28 Nov 2023 10:43:36 +0100 Message-ID: <539475.1701164616@dyas> --=-=-= Content-Type: text/plain David Vernet wrote: > We had a productive BPF working group meeting at IETF 118, and we > wanted to provide a summary to recap what was discussed. David, this is a most excellent summary, thank you. (I wasn't there, I had a conflict) > subset. Existing language MMs do not properly handle control > dependencies, and suffer from issues such as OOTA (Out-of-Thin-Air) > reads. The presentation outlined the control dependencies proposed for > various types of BPF instructions, such as atomics, jumps, etc. I didn't know what an OOTA read was, but I think that hte first answer at: https://stackoverflow.com/questions/42588079/what-is-out-of-thin-air-safety explained it, but I just wnated to be sure that this was the same term. I think that we don't expect compilers emitting BPF code to do things like the tearing example: void threadA() { g = 0xAB00; // "tearing" g += 0x00CD; } but an underlying BPF JIT might do this kind of thing, and of course, the reads could be anywhere, and the variable could be written by C-code (or RUST!). -- Michael Richardson , Sandelman Software Works -= IPv6 IoT consulting =- *I*LIKE*TRAINS* --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQGzBAEBCgAdFiEEow/1qDVgAbWL2zxYcAKuwszYgEMFAmVltkgACgkQcAKuwszY gEMa/AwAhhnU4ksVpOS6W3Gi8BRUMYr8ZJRH7lWCBKFIlnqyzlRonLHtbRa5b9pY XVaj5aI/8os+O1xG1/B2aqXJ8OVz30DC/BVDMJjcOKBqP5lgzYwZrrXPSoGWaO+J gpV0XaWYjubyTwfwZCeuYmp1IN2ElTAYJVjFrrUFggIXfuKOKSqJ1xrjGikbnosH EO0zkjoSxFHyBnZh6C+0s0K2B+JdC33Ai15zFv9SA8hAFzfJP9/jK+rvwkrvJKWb AXLan3sYOAFKQZGftqwYhW2lx9KdSxu2raar1x7Vv751zQO4ILB3cGcOYYg/qGP7 nUCVHWRvfQizC7RSFBNhrmiaNdcDryL2/quRHP3ft7wK+CT6Kjzvc/UEhUpBwmxE M5t2GxHfCKfzNoP5Dzr4i7iHm79DKarFfnBdyjzY4WDSo91JsNy5lNAhum13v4dv KBY9PP1os2+kp6OQPHKS6G5+5dpc9cFDsp1zHGVMLPOzj1v4yEkhjoROlXvqOyTW puYGc4ZF =wl7o -----END PGP SIGNATURE----- --=-=-=-- From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; 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Tue, 28 Nov 2023 10:43:36 +0100 (CET) From: Michael Richardson To: David Vernet , bpf@ietf.org, bpf@vger.kernel.org In-reply-to: <20231127201817.GB5421@maniforge> References: <20231127201817.GB5421@maniforge> Comments: In-reply-to David Vernet message dated "Mon, 27 Nov 2023 14:18:17 -0600." X-Mailer: MH-E 8.6+git; nmh 1.7+dev; GNU Emacs 26.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Tue, 28 Nov 2023 10:43:36 +0100 Message-ID: <539475.1701164616@dyas> Archived-At: Subject: Re: [Bpf] IETF 118 BPF WG summary X-BeenThere: bpf@ietf.org X-Mailman-Version: 2.1.39 Precedence: list List-Archive: List-Post: List-Help: Content-Type: multipart/mixed; boundary="===============7133031010960809614==" Errors-To: bpf-bounces@ietf.org Sender: "Bpf" Message-ID: <20231128094336.hoSgvfkJy7GgxAhuODquDC3Y9XUGwlKWyI8seyBxLiE@z> --===============7133031010960809614== Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" --=-=-= Content-Type: text/plain David Vernet wrote: > We had a productive BPF working group meeting at IETF 118, and we > wanted to provide a summary to recap what was discussed. David, this is a most excellent summary, thank you. (I wasn't there, I had a conflict) > subset. Existing language MMs do not properly handle control > dependencies, and suffer from issues such as OOTA (Out-of-Thin-Air) > reads. The presentation outlined the control dependencies proposed for > various types of BPF instructions, such as atomics, jumps, etc. I didn't know what an OOTA read was, but I think that hte first answer at: https://stackoverflow.com/questions/42588079/what-is-out-of-thin-air-safety explained it, but I just wnated to be sure that this was the same term. I think that we don't expect compilers emitting BPF code to do things like the tearing example: void threadA() { g = 0xAB00; // "tearing" g += 0x00CD; } but an underlying BPF JIT might do this kind of thing, and of course, the reads could be anywhere, and the variable could be written by C-code (or RUST!). -- Michael Richardson , Sandelman Software Works -= IPv6 IoT consulting =- *I*LIKE*TRAINS* --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQGzBAEBCgAdFiEEow/1qDVgAbWL2zxYcAKuwszYgEMFAmVltkgACgkQcAKuwszY gEMa/AwAhhnU4ksVpOS6W3Gi8BRUMYr8ZJRH7lWCBKFIlnqyzlRonLHtbRa5b9pY XVaj5aI/8os+O1xG1/B2aqXJ8OVz30DC/BVDMJjcOKBqP5lgzYwZrrXPSoGWaO+J gpV0XaWYjubyTwfwZCeuYmp1IN2ElTAYJVjFrrUFggIXfuKOKSqJ1xrjGikbnosH EO0zkjoSxFHyBnZh6C+0s0K2B+JdC33Ai15zFv9SA8hAFzfJP9/jK+rvwkrvJKWb AXLan3sYOAFKQZGftqwYhW2lx9KdSxu2raar1x7Vv751zQO4ILB3cGcOYYg/qGP7 nUCVHWRvfQizC7RSFBNhrmiaNdcDryL2/quRHP3ft7wK+CT6Kjzvc/UEhUpBwmxE M5t2GxHfCKfzNoP5Dzr4i7iHm79DKarFfnBdyjzY4WDSo91JsNy5lNAhum13v4dv KBY9PP1os2+kp6OQPHKS6G5+5dpc9cFDsp1zHGVMLPOzj1v4yEkhjoROlXvqOyTW puYGc4ZF =wl7o -----END PGP SIGNATURE----- --=-=-=-- --===============7133031010960809614== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline -- Bpf mailing list Bpf@ietf.org https://www.ietf.org/mailman/listinfo/bpf --===============7133031010960809614==--