From owner-freebsd-bugs@freebsd.org Mon Nov 9 18:56:38 2020 Return-Path: Delivered-To: freebsd-bugs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 3172446ACE6 for ; Mon, 9 Nov 2020 18:56:38 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.nyi.freebsd.org (unknown [127.0.1.3]) by mx1.freebsd.org (Postfix) with ESMTP id 4CVKwQ0kzdz3lZF for ; Mon, 9 Nov 2020 18:56:38 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.nyi.freebsd.org (Postfix) id 1793D46ADE6; Mon, 9 Nov 2020 18:56:38 +0000 (UTC) Delivered-To: bugs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 175A646B02D for ; Mon, 9 Nov 2020 18:56:38 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4CVKwQ017Fz3lcg for ; Mon, 9 Nov 2020 18:56:38 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id E7BA316194 for ; Mon, 9 Nov 2020 18:56:37 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id 0A9Iub2I036632 for ; Mon, 9 Nov 2020 18:56:37 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 0A9IubeA036631 for bugs@FreeBSD.org; Mon, 9 Nov 2020 18:56:37 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 250954] ptrace(): weird ordering between inheriting debug registers and reporting a new thread Date: Mon, 09 Nov 2020 18:56:37 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 12.2-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: kib@FreeBSD.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Nov 2020 18:56:38 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D250954 --- Comment #13 from Konstantin Belousov --- (In reply to Micha=C5=82 G=C3=B3rny from comment #12) I believe the intended use of PT_SETDBREGS in combination with the new thre= ad tracking is to set debug registers to desired configuration on each PL_FLAG_BORN event. This should be most straight-forward. WRT to the race itself, trying to close it would affect normal operation of thread creation, as opposed to just causing minor inconvenience to the ptrace(2) consumers. We create thread, including the setup of all machine state, then we fire it running, up to the point of running at trampoline returning to t= he user space. This moment is when we report TBD_BORN to ptracestop(). It is important to do that stop from the context of the running new thread, so th= at we already know that all hardware state is copied as needed. Would we repo= rt TDB_BORN before copying, it means that copying should occur under process l= ock to guarantee consistency with potential modifications from debuggers, and we do not want this. Also I think existing consumers of TDB_BORN already expect that the event c= omes from the running thread, not from the embryo. So it really need be yet ano= ther event to not break API. --=20 You are receiving this mail because: You are the assignee for the bug.=