From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, HTML_MESSAGE,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 25482 invoked from network); 14 Jun 2020 15:53:15 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 14 Jun 2020 15:53:15 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 1901C9C26B; Mon, 15 Jun 2020 01:53:13 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 763719C1C8; Mon, 15 Jun 2020 01:52:42 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (2048-bit key; unprotected) header.d=bsdimp-com.20150623.gappssmtp.com header.i=@bsdimp-com.20150623.gappssmtp.com header.b="VKpxHOHQ"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id B3F569C1C8; Mon, 15 Jun 2020 01:52:38 +1000 (AEST) Received: from mail-qv1-f44.google.com (mail-qv1-f44.google.com [209.85.219.44]) by minnie.tuhs.org (Postfix) with ESMTPS id 1F993945D9 for ; Mon, 15 Jun 2020 01:52:38 +1000 (AEST) Received: by mail-qv1-f44.google.com with SMTP id p15so6651569qvr.9 for ; Sun, 14 Jun 2020 08:52:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=IF3oyEsp9vbEi3V6i0BnCpdmjox/5Ke7GF5e38VlK8A=; b=VKpxHOHQDfcNXtDJQQF9eQB/cS2IhEikwPp7R2byvv9JgrxijF9XkBWMe20qaYEVOa h8xf5eJ/56XOa4WWaj8mEuYQYeZPg2dxdpFJvpIx83/WjGaS6cyZQYD/H0Xg5giZ0wnm 1fCAVbehh1xbnkajdWTINXMBMLkPbE2o3v/HPkD2ayWIWRZhWGYzTu3c2MJQT61aNpz3 PVKYUr/8psN23VMYrSW+7Jhn9Yjnh2wNGfLWBiw+OYvuGzJmayyxa21oZW3isRgyiPrN 18koyFYYdSJlaHfo9qnociIZ9TC6EuvZgX1Vu8aTMkpghOtk5S2eCTXy/D8HkBbC2pvO PIBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=IF3oyEsp9vbEi3V6i0BnCpdmjox/5Ke7GF5e38VlK8A=; b=HrUO6WAlJew2s7fePlAsIFK3Th6dxq+WS1Si+IBCkWW3HPh4Ig/Dp5j6w1zNd+6y0R q0xqZcGKH0EG1m4H/VxwNH2UDhA7VhVuN7hlxEJAfBTu2xkgo3jlg251Q6whwcp4BwFW qOWotq0pH3KvIQtPslJKV2AVfrBK7fbP1Ei7j5+V2eMGhVqwVrIL/AHqFQVKbngPRqVF 3f81QZvi3Od7QI5G8tLqlgQ223dmY8elKinJOJ6JMxaRxJWlj979fgAn27fdxHAD4jnm +71AVvit+6EL7k2U7m+1B+h/8jO7lGWs/b2hZXgVr5Zp3BGFh9buhCqMrdagpOD0xVrZ J6Vw== X-Gm-Message-State: AOAM531v+HRQYurfXOGZ2g7jfZWeEMSGfsixRfgAznLL/i0yA25uVzcP JAAeu5jUQysX1UhT5GkP5rLeh6BrM6tdBY+pM1PI4Mq3 X-Google-Smtp-Source: ABdhPJx9NfEYHb9SZPDvulg9OeC4euG3pMUmfDqyPJF88swHQL/lSnDn5ouuC7kMjuE+aNm691yPTFvuUYS3Nrff7cg= X-Received: by 2002:a05:6214:bc5:: with SMTP id ff5mr21702330qvb.118.1592149956999; Sun, 14 Jun 2020 08:52:36 -0700 (PDT) MIME-Version: 1.0 References: <20200614144643.E4BBF18C09D@mercury.lcs.mit.edu> In-Reply-To: <20200614144643.E4BBF18C09D@mercury.lcs.mit.edu> From: Warner Losh Date: Sun, 14 Jun 2020 09:52:26 -0600 Message-ID: To: Noel Chiappa Content-Type: multipart/alternative; boundary="0000000000009dde4905a80d4c90" Subject: Re: [TUHS] Accessing the PDP-11/70 MMU registers and the kernel's u area X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: TUHS main list Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" --0000000000009dde4905a80d4c90 Content-Type: text/plain; charset="UTF-8" On Sun, Jun 14, 2020 at 8:47 AM Noel Chiappa wrote: > Not sure how different 2.11 is; I know it uses > one block of kernel address space to map in code overlays, but I don't know > all the details of how it works. > Yes. There's 1 8kB instruction segment that implements the overlays. The calls to these routines are bounced through thunks that flips the segment register if needed on the call. Each overlay is limited to 8k. The 2.11BSD kernel has about 70k of overlays these days... and they are all almost full, as is the text segment (which is limited to 56k). They get around this by running the TCP/IP stack in supervisor mode, kinda as a process.. This means the total size of the kernel and data for the kernel is 320k on a machine with a 128k address space :). I've been looking a lot at that code lately... I'm back to patch 0, but am missing ld.c and ranlib.c in my push to get back to the start since they were augmented between 2.10.1 and 2.11 for the new portable archive format... Once I solve those two, it's off to build testing in simh. Warner --0000000000009dde4905a80d4c90 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


=
On Sun, Jun 14, 2020 at 8:47 AM Noel = Chiappa <jnc@mercury.lcs.mit.= edu> wrote:
Not sure how different 2.11 is; I know it uses
one block of kernel address space to map in code overlays, but I don't = know
all the details of how it works.

=C2=A0= Yes. There's 1 8kB instruction segment that implements the overlays. Th= e calls to these routines are bounced through thunks that flips the segment= register if needed on the call. Each overlay is limited to 8k. The 2.11BSD= kernel has about 70k of overlays these days... and they are all almost ful= l, as is the text segment (which is limited to 56k). They get around this b= y running the TCP/IP stack in supervisor mode, kinda as a process..=C2=A0 T= his means the total size of the kernel and data for the kernel=C2=A0is 320k= on a machine with a 128k address space :).

I&= #39;ve been looking a lot at that code lately... I'm back to patch 0, b= ut am missing ld.c and ranlib.c in my push to get back to the start since t= hey were augmented between 2.10.1 and 2.11 for the new portable archive for= mat... Once I solve those two, it's off to build testing in simh.
=

Warner
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