November 2008 - Darwin-kernel

Safely reading Intel MSRs?
by Brent Burton 21 Nov '08

21 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:mime-version:content-type:content-transfer-encoding :content-disposition; bh=5DuGqwmK0scAG+K4x/jRnsew1xjm/L1cb+WJSgNiN+I=; b=IFoyv1flDeRQPm/Ux+HbhI+0hatxjyk5UOLUp7qWfc/vOo/BNBHPXA9vTUAbeOZGGF APkD0dZZ4Td3XznlQSkZKNCM9R3VQEx0VVQ/PUyEzy1x8RaEb66AhhpDhHdBHKXYFPwP JkDhWKABGWsHmwHoO0rGqkpWk1HZsh3xVmHsA= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:mime-version:content-type :content-transfer-encoding:content-disposition; b=od5IjzDlz9KSnsEIDKSRjCzAvNdXPRjhIE25ybzmzT75OEZoN9CNbmu/JqAzIM8XSj LQakNQozdZL6eO2YqRsPMlxsuME/nM2F6YVW7YXvG4tGkHZuEBiy9hj3aL/wE5V5mX+K KWubj/Wlct3tIJJ3BFbRHpP/D1R5tyC3kKse4= Hi all, I am writing some internal system software including a kernel extension that has the ability to read MSR values. While I have a runtime check for processor family and model, the mapping to valid MSR registers isn't finished (and of course, may have errors when it is finished). If an invalid MSR is read or written, it causes a kernel panic (via GPF), and I'd like to protect against this for all cases. Are there kernel functions, accessible from a kext, that provide safe reading of Intel MSRs? If not, one alternative is to (temporarily) redirect GPF handling. I don't particularly like this path, but I want to get more information on it. Where is documentation or headers that cover this, if any? thanks, -Brent _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: ACL handling for NFSv4
by Terry Lambert 20 Nov '08

20 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com And the fallback for extended attributes will create ._ files. Part of my problem is that I don't have extended attribute support in the server, so I don't have a way to store/retrieve the guid_t owner and group fields in kauth_filesec on the server, which leads me to... -- Terry _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… On Nov 19, 2008, at 7:48 AM, Michael Smith wrote: On Nov 13, 2008, at 12:38 PM, Rick Macklem wrote: I finally have an NFSv4 server that includes support for NFSv4 ACLs, so I was hoping to tweak my NFSv4 Leopard client (http://code.google.com/p/macnfsv4 ) to make use of them. (Note this is an experimental open source project using a Kext that already goes beyond the KPIs, so I realize that the internal interfaces may change at any time...) Looking at xnu-1228 sources, it seems that getting an ACL from a file system is done via vnode_getattr(), but is set via vn_setxattr() setting KAUTH_FILESEC_XATTR. Is that correct? No, the operations are symmetric. If vnode_setattr() returns without having claimed to have supported the ACL set, the fallback path will attempt to save the ACL using an extended attribute. Likewise if the ACL is requested and vnode_getattr() returns without claiming to have supported the request, the fallback will look for an EA. ACLs are dealt with in terms of filesec_t's, whise contents are intended to be considered opaque in user space, and for which there are no user space functions for setting certain parts of them. In practice, there is only check/read/modify/write, where if the check fails you do not do the read/modify/write, and if the check succeeds, you do the read/modify/write, and if you want to set one, you do a read/modify/write and the read cons's up the information that you can't create in user space, and you modify that to add the ACEs you want - the chmod and ls source code is a good reference. Best practice is to not use these fields, and to not set their validity flags when round-tripping in/out of filesec_t's (kauth_filesec's, in non-pointer references). NOTE TO CASUAL ARCHIVE READERS: UNLESS YOU ARE A FILESYSTEM IMPLEMENTOR RUNNING IN THE KERNEL, LEAVE THESE THE HECK ALONE!!! Check with Terry, however it's probably safe to either ignore these or ask the local system to translate the UID/GID you have into GUIDs. As long as these are not set, then they won't be an issue. The filesec_t is the contract between user space (libc POSIX 1003.1e, generally) and the kernel. Unless you return the values, the read/ modify/write from before won't set them, and so there will be no need to fake them up. What are the guid_t owner and group fields of a kauth_filesec and is there a way a client can map those to/from uid/gid or do they have to be stored/retrieved from the file system? (If I have to store/ retrieve them, I suspect I'm snookered.) There's a local translation service. See the kauth_* functions. Specifically, the kernel does not explicitly know about uuids/guids/ ntsids. The kernel know about integers, and it know how to ask that integers be translated to/from these things. All POSIX enforcement is based on integers, all credential information (other than MAC labels) is handled as integers, and you can't get at MAC labels and shouldn't try, due to scoping rules. So if I have an ACE I am trying to set, since the storage format *happens* to be GUID, then we translate the integer for the gid and uid of the current credential into a GUID for the purposes of storage. For the purposes of comparison on lookup, we then convert the current credential into a GUID (in general, the uid, since that is the primary identity in a credential), and compare the GUID to the GUID in the ACE. This is handled in xnu in bsd/kern/ kern_authorization.c:kauth_acl_evaluate(). Although there are support functions for translating the other direction, e.g. kauth_cred_guid2uid(), and kauth_cred_guid2gid() no one uses them, and I would, in fact, like to keep things that way. The only exception to this is kauth_cred_guid2gid() is used by kauth_cred_ismember_guid() when attempting to set a group owner on a file. This use is poorly supported by the rest of the code and should be avoided. Another thing to avoid is the (incorrect) assumption that because NTSIDs are permitted to be variable length that the functions to deal with their translation also expect variable length; while you are permitted to ask about shorter ones, you have to provide for storage of the largest possible one. Unless you are SMBFS or XSan, this should not be an issue for you, but it is a potential place where you'd write off the end of your memory during a copy/create operation (C99 prohibits the use of a variant array at the end of a structure embedded in a structure; gcc allows this if the first structure is at the end of the second, rather than in the middle, but this is technically a non-standard usage). This email sent to site_archiver(a)lists.apple.com

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Re: ACL handling for NFSv4
by Michael Smith 19 Nov '08

19 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Nov 13, 2008, at 12:38 PM, Rick Macklem wrote: Part of my problem is that I don't have extended attribute support in the server, so I don't have a way to store/retrieve the guid_t owner and group fields in kauth_filesec on the server, which leads me to... What are the guid_t owner and group fields of a kauth_filesec and is there a way a client can map those to/from uid/gid or do they have to be stored/retrieved from the file system? (If I have to store/retrieve them, I suspect I'm snookered.) There's a local translation service. See the kauth_* functions. = Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… I finally have an NFSv4 server that includes support for NFSv4 ACLs, so I was hoping to tweak my NFSv4 Leopard client (http://code.google.com/p/macnfsv4 ) to make use of them. (Note this is an experimental open source project using a Kext that already goes beyond the KPIs, so I realize that the internal interfaces may change at any time...) Looking at xnu-1228 sources, it seems that getting an ACL from a file system is done via vnode_getattr(), but is set via vn_setxattr() setting KAUTH_FILESEC_XATTR. Is that correct? No, the operations are symmetric. If vnode_setattr() returns without having claimed to have supported the ACL set, the fallback path will attempt to save the ACL using an extended attribute. Likewise if the ACL is requested and vnode_getattr() returns without claiming to have supported the request, the fallback will look for an EA. Check with Terry, however it's probably safe to either ignore these or ask the local system to translate the UID/GID you have into GUIDs. This email sent to site_archiver(a)lists.apple.com

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Re: Interrupt handling in multi-processor environment
by Rob Cas 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=gUHvbwaona1sKe/r1SZH3SZhC/R7eWcXG85DRGDxN5I=; b=Vo2I7TvGr1HwxPTJ7VfguroK26g8nM3/wD8jdCp97XCYt3zWWXe30jLslKbfpAyvC5 NmRDAT9HKehYMgQnigN6J3SSEAkVBnk4saGmAfxigM+NxRXqoFrTryto780gpi69IvkO ny+GkCvH0FUGLLXRturR5ubFionn0FJVvkxEc= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=eJvn3dF3mZiOqSJO45D4OpiXifBE3QanJd/wzrlMtkbbXqZy4OeUQgSffx5nAflV4z x0sikNcaAtQlJue2FLZQtqEiOAq9PKQQUUfGW5JCdYADYfteCkjEcKjyT5Srx+mfKq1K RaN6LJWic3YyiDVOU2d1PcJFkmauemVm8o2y8= On Tue, Nov 18, 2008 at 8:46 PM, Chris Suter <csuter(a)sutes.co.uk> wrote: <snip> > Is there a reason you need to use IOFilterInterruptEventSource rather than > IOInterruptEventSource? I mean, is performance that critical and will there > be a large number of ghost interrupts? > -- Chris I think filter event sources are appropriate (but am happy to stand corrected). Our device generates several different kinds of interrupt that are handled by different child IOService nubs containing their own filter event sources that test whether the interrupt is of concern to that nub. Additionally, being attached to a shared interrupt controller provided by our top nub's provider there appears to be interrupts generated every 10usec - most of which are not generated by our device and we should filter out and ignore. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Interrupt handling in multi-processor environment
by Chris Suter 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Interrupt handling in multi-processor environment
by Quinn 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com When the sti/cli instruction is executed by IOSimpleLockLockDisableInterrupts(), does it somehow have the effect of disabling interrupts across all CPUs (or specifically the 'interrupt handling CPU'), or just on the CPU executing the code? S+E -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Relations, Developer Technical Support, Core OS/Hardware _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… At 10:23 +1100 18/11/08, Rob Cas wrote: It only affects the calling CPU. This is pretty standard behaviour for a kernel-level spin lock. You need to disable interrupts on the calling CPU to prevent deadlocking against interrupt-level code running on the same CPU. Code running on other CPUs, either interrupt level or not, will spin on the lock. This email sent to site_archiver(a)lists.apple.com

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Re: Interrupt handling in multi-processor environment
by Chris Suter 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Where is asl_private.h?
by William Siegrist 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com http://darwinbuild.macosforge.org/ And when it doesnt work, it has a ticketing system and mailing lists. -Bill On Nov 17, 2008, at 4:44 PM, James C wrote: Regards, James. ASL/syslog are all userspace, so this isn't really a kernel issue. Good luck, Shantonu Sen ssen(a)apple.com Sent from my Mac Pro On Nov 18, 2008, at 1:05 PM, James C wrote: Hi All, In this list of Darwin kernel modules: http://www.opensource.apple.com/darwinsource/10.5.5/ the module: syslog-64 depends on a file asl_private.h, but does not contain it. How do I find the module that contains this file? Regards, James. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/wsiegrist%40apple.com ---- William Siegrist Mac OS Forge http://macosforge.org/ _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com darwinbuild can be used to automatically fetch dependencies in a clean build environment. Thanks; found it. Is there a better mailing list for what I'm trying to do? On Tue, Nov 18, 2008 at 1:10 PM, Shantonu Sen <ssen(a)apple.com> wrote: The relevant header is part of Libc (<http://www.opensource.apple.com/darwinsource/10.5.5/Libc-498.1.1/gen/ >) ps I'm trying to build syslogd with debug, to diagnose spinning while accessing asl.db, after shortages of cpu-time, which is suspect is triggered by a race condition. So far, Engineering have classified it as a fault in the most cpu-intensive application that I run, so I think I'll have to help myself. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/ssen %40apple.com This email sent to ssen(a)apple.com This email sent to wsiegrist(a)apple.com smime.p7s

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Re: Where is asl_private.h?
by James C 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=u4no5qdfeMMBJlqGkBzMVZoR6e2f1IfWyWRphWyDWeg=; b=pzphuV2CA+ZU4wnu3IY8fkST/Z6A+CkhFAOYztJBCsBNOEzE+Oag8CszKRyMHnjSyk BDYH36v2Lk0IG2Vz6rBkFCW9/DRtbwspscGPHsUC76u/25YW/wbzlX/9lSQpX79Et2Y7 UgiD50AzdO9YF0e4elQVjfa8x/q5NNNvUWY+8= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=vFxIGLrFs0udcene08sje2Q1wI4DOIi2A57fp8HLixNmUDJs5M3ZTn0EHh2no9EuNn MwrCGJnSl2d3v61zBimSKtvtbbGLAEpXxkypl2kvi9dPGT5hT0M3+zlZFSj+Qb19P/aZ FyQjsNOUL47Zy3h6fMgVUmq9kPhioi9GqyPjc= Thanks; found it. Is there a better mailing list for what I'm trying to do? Regards, James. On Tue, Nov 18, 2008 at 1:10 PM, Shantonu Sen <ssen(a)apple.com> wrote: > ASL/syslog are all userspace, so this isn't really a kernel issue. > > The relevant header is part of Libc > (<http://www.opensource.apple.com/darwinsource/10.5.5/Libc-498.1.1/gen/>) > > Good luck, > Shantonu Sen > ssen(a)apple.com > > Sent from my Mac Pro > > On Nov 18, 2008, at 1:05 PM, James C wrote: > >> Hi All, >> >> In this list of Darwin kernel modules: >> http://www.opensource.apple.com/darwinsource/10.5.5/ >> the module: >> syslog-64 >> depends on a file asl_private.h, but does not contain it. >> >> How do I find the module that contains this file? >> >> Regards, >> James. >> >> ps I'm trying to build syslogd with debug, to diagnose spinning while >> accessing asl.db, after shortages of cpu-time, which is suspect is >> triggered by a race condition. So far, Engineering have classified it >> as a fault in the most cpu-intensive application that I run, so I >> think I'll have to help myself. >> _______________________________________________ >> Do not post admin requests to the list. They will be ignored. >> Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) >> Help/Unsubscribe/Update your Subscription: >> http://lists.apple.com/mailman/options/darwin-kernel/ssen%40apple.com >> >> This email sent to ssen(a)apple.com > > _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Where is asl_private.h?
by Shantonu Sen 18 Nov '08

18 Nov '08

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com ASL/syslog are all userspace, so this isn't really a kernel issue. Good luck, Shantonu Sen ssen(a)apple.com Sent from my Mac Pro On Nov 18, 2008, at 1:05 PM, James C wrote: Hi All, In this list of Darwin kernel modules: http://www.opensource.apple.com/darwinsource/10.5.5/ the module: syslog-64 depends on a file asl_private.h, but does not contain it. How do I find the module that contains this file? Regards, James. ps I'm trying to build syslogd with debug, to diagnose spinning while accessing asl.db, after shortages of cpu-time, which is suspect is triggered by a race condition. So far, Engineering have classified it as a fault in the most cpu-intensive application that I run, so I think I'll have to help myself. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/ssen%40apple.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… The relevant header is part of Libc (<http://www.opensource.apple.com/darwinsource/10.5.5/Libc-498.1.1/gen/ >) This email sent to ssen(a)apple.com This email sent to site_archiver(a)lists.apple.com

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