From: Blaisorblade <blaisorblade@yahoo.it>
To: user-mode-linux-devel@lists.sourceforge.net,
user-mode-linux-user@lists.sourceforge.net,
Antoine Martin <antoine@nagafix.co.uk>,
Jeff Dike <jdike@addtoit.com>
Subject: [uml-devel] Using partially SKAS3 on x86_64 - news
Date: Mon, 20 Feb 2006 19:58:09 +0100 [thread overview]
Message-ID: <200602201958.10554.blaisorblade@yahoo.it> (raw)
Talking about 32-bit UMLs on AMD64 hosts: I've just discovered that on a
x86_64 platform you can use at least partially the SKAS3 patch.
Instead of adding "skas0" to the command line, to get a running UML it
suffices to use "noprocmm", if it's accepted by UML (I don't remember when
the patch was merged).
I've tested this with a Debian Sarge root_fs - as you already know, Slackware
root_fs already work in full SKAS3 mode.
As you can see at the beginning of the boot log, it won't use /proc/mm but it
will use PTRACE_FAULTINFO, which is the other part of SKAS3. Since this
addresses the biggest slowdown of SKAS0 (Jeff said SKAS0 is slightly slower
than TT for page fault handling), I expect the difference to be significant.
I've not done any benchmark yet, however.
Example startup:
$ kernels/vmlinux-2.6.15.3-bs2
ubd0=Root_images/Sarge-norm.rootfs.cow,Root_images/Sarge-norm.rootfs
rootfs=/dev/ubda noprocmm
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...missing
Checking PROT_EXEC mmap in /tmp...OK
Checking for the skas3 patch in the host:
- /proc/mm...found but disabled on command line
- PTRACE_FAULTINFO...found
- PTRACE_LDT...found
UML running in SKAS0 mode
....
--
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade
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reply other threads:[~2006-02-20 18:59 UTC|newest]
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