September 2009 - Darwin-kernel

Building a universal IOKit kext for 10.4 and up
by Ron Aldrich 17 Sep '09

17 Sep '09

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Hello, Thanks in advance, Ron Aldrich Software Architects, Inc. _______________________________________________ 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 have an IOKit kernel extension which needs to be compiled so that it runs on any operating system and architecture from Mac OS X 10.4 and up (including 64 bit Snow Leopard). Is there a document that describes the proper build settings for such a beast? If I build it using GCC 4.2 and the Mac OS X 10.6 SDK, will it be at all likely to run on 10.4? This email sent to site_archiver(a)lists.apple.com

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Re: A few low-level GDT/LDT K64 questions
by William Kucharski 17 Sep '09

17 Sep '09

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com User-agent: Thunderbird 2.0.0.23 (X11/20090910) 1. Is there an expectation within the kernel that the in-memory descriptor tables will be synchronized with the descriptor cache? That is, if the GDT or LDT is modified, can the descriptor cache hold stale values (beyond the local scope of the GDT/LDT modification)? 3. In general, can the following sequence expected to be idempotent with respect to the %fs descriptor cache: mov $IA32_FS_BASE, %ecx rdmsr mov %fs, %bx mov %bx, %fs wrmsr As long as you're in long mode, once the wrmsr has completed, yes. William Kucharski _______________________________________________ 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.… Actually, most of your questions are IA32e architecture rather than kernel questions per se, so aside from Apple chiming in with any Mac OS X-specific details: Of course it CAN; until the referencing segment registers are reloaded, the cache can be stale with respect to the GDT/LDT. This becomes even more entertaining in long mode because the descriptor cache for FS and GS are always "stale" with respect to the GDT/LDT if the MSRs have been used to set a 64-bit base value. Therefore one needs to be careful when porting code over from 32-bit mode that does a mov or pop to %fs or %gs as in long mode they'll leave the descriptor cache loaded with the 32-bit base value from the GDT/LDT, which in most cases is NOT likely to be the value you want. I didn't answer question (2) because in theory, yes the GDT or LDT could be modified so that existing selector indices are beyond the bounds of the descriptor table in question, but I'm unaware as to whether whatever routines Mac OS X has for manipulation of them enforces the validity of segment register indices. This email sent to site_archiver(a)lists.apple.com

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Hibernation
by Niklas Hoglund 17 Sep '09

17 Sep '09

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com User-agent: Thunderbird 2.0.0.23 (Windows/20090812) Hello, Any ideas? -- Niklas _______________________________________________ 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'm trying to implement a block driver that supports storing the hibernation file onto it. To do this, I need to subclass IOPolledInterface, as described in IOHibernateIO.cpp in the kernel, but I get unresolved references to its metaclass if I do. (__ZN17IOPolledInterface9metaClassE). I'm guessing this is because the symbol is in the _HIB section in the kernel. This email sent to site_archiver(a)lists.apple.com

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Re: A few low-level GDT/LDT K64 questions
by arwyn＠phasic.com 17 Sep '09

17 Sep '09

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Re: A few low-level GDT/LDT K64 questions
by Ben Gertzfield 17 Sep '09

17 Sep '09

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:sender:references:message-id :from:to:in-reply-to:content-type:content-transfer-encoding:x-mailer :mime-version:subject:date:cc; bh=PtfjVYljE4ahumRnbe97r5USjsQSyaBouqnV9INz3F8=; b=dmwP5nY6zicuqvOr6zwHXjeeRphuCjE/HtBVMBHKzDaH7zpcdg8tXOChTan7fHMoWh QonavG/6lYEUSt6pH1Z8Ryij7mBr/qcs8VmEqCrULpWdYNgROnirbgP0vsu/0MxqzaAz ofWn1/LR1dvEGLd/zJFlOX7/Rm/dGIXJzDMIQ= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:references:message-id:from:to:in-reply-to:content-type :content-transfer-encoding:x-mailer:mime-version:subject:date:cc; b=nokh3UB3hUVhJArS0O6bFjEq3CrcAAD/sQwmP6O425hUSoTFsHPBO+qC6Ug0zVzC4h yXgn3YdQ96PXx+ECy3ZQcG2ihh7RORUdMxs7k2ebmV8xj1eEFTTf/2h9N8T2yO4GzcRL RG7h7beMwYNQQWNM36OG+Aum/HHKu7qr7/Mk0= _______________________________________________ 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: A few low-level GDT/LDT K64 questions
by Michael Smith 17 Sep '09

17 Sep '09

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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A few low-level GDT/LDT K64 questions
by Ben Gertzfield 16 Sep '09

16 Sep '09

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:mime-version:sender:received:date :x-google-sender-auth:message-id:subject:from:to:content-type; bh=cPyNNrTd37TfG0/yfHWv2OQHkmyiaUPRLDlpaCabsBE=; b=xtNsSMyp2Y2q1eQqKEyd/CcCzZV2KYbrEWEJWVxg4yO0W8h+Tky2zssJEdYflw9a8c BlywKefsAhnrB08LW2lwbK4MIzHDSiFH2dIHEUT3QjK7R61WhQEdOVKk3lkrnLEd29pn hJGi0YD1zo7Pzze+wvQ7iZA1Kh0luoysHxs7A= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:date:x-google-sender-auth:message-id:subject :from:to:content-type; b=hJHk8RT1nf1FebYWDSZpm762cJLSydaQui4KACwA/AVjb6ySGzV7X/hCOFizUw2xHB RowExLeGwtvveKPVovn9DFx1P06XKwlpPIoc/xV0JDmowwHtxpB8+2a+bq/LpU2n8ypX vTzBuFGRahgpj/IjEdWdI8BFY8r0h/3g3Z4/g= Hi folks, Now that K64 is out there, we ran into a few interesting low-level questions about how the K64 (and K32) kernels handle the GDT and the LDT. These questions are in the context of a thread that's entered a K64 kernel extension via an ioctl. We ran into a few differences in the way the %fs and %gs registers are treated in K64, so we wanted to make sure we understood the expectations the kernel has with regards to the GDT and the LDT and these registers. 1. Is there an expectation within the kernel that the in-memory descriptor tables will be synchronized with the descriptor cache? That is, if the GDT or LDT is modified, can the descriptor cache hold stale values (beyond the local scope of the GDT/LDT modification)? 2. Is there an expectation within the kernel that the selector indices for all segment registers will always be within the bounds of the referenced descriptor table? That is, if the GDT or LDT shrinks in size, can a segment register hold a stale value that is now out of bounds for the referenced descriptor table (beyond the local scope of the GDT/LDT modification)? 3. In general, can the following sequence expected to be idempotent with respect to the %fs descriptor cache: mov $IA32_FS_BASE, %ecx rdmsr mov %fs, %bx mov %bx, %fs wrmsr Thanks so much, Ben _______________________________________________ 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: Thread sleep
by Eric Long 11 Sep '09

11 Sep '09

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Thread-index: Acoy9QqeaBJOH8bDzkS+3F3BR+W5ng== Thread-topic: Thread sleep User-agent: Microsoft-Entourage/12.20.0.090605 > Look at IOLockSleep and IOLockWakeup. You want code something like this: > > IOLockLock(&lock); > > while (!condition) > > IOLockSleep(&lock, &condition, 0); > > IOLockUnlock(&lock) > > > And in your other thread: > > IOLockLock(&lock); > > condition = true; > > IOLockUnlock(&lock); > > IOLockWakeup(&lock, &condition, true); > Wow, thanks Chris. I totally missed that. Thanks for pointing it out, showing usage, and not bashing me on the head. Eric _______________________________________________ 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: Thread sleep
by Chris Suter 10 Sep '09

10 Sep '09

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Re: Thread sleep
by Chris Suter 10 Sep '09

10 Sep '09

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Fri, Sep 11, 2009 at 6:44 AM, Eric Long <ericsmac(a)smithmicro.com> wrote: > I have a kext that sends data to a daemon via an IODataQueue. The daemon > processes the data and sends back a response to my IOUserClient. > > The thread that enqueues the data must have the response or time-out before > continuing. The response obviously comes on a separate thread. > > Ideally, the enque thread will go to sleep and be woken up by the response > handler. The problem is there is a window for a race condition between when > the enque thread is actually asleep and when the response arrives and the > handler wants to wake it up. This leaves the potential that the thread is > not asleep and therefore not ready to be woken up. > > The thread primitives that might allow me to check if the thread is sleeping > are not exposed in the kpi. > > Anyone with advice on how to reconcile this? Look at IOLockSleep and IOLockWakeup. You want code like this: IOLockLock(lock); while (!condition) _______________________________________________ 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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