July 2002 - Darwin-kernel - lists.apple.com

Re: Remote Debug
by Justin C. Walker 26 Jul '02

26 Jul '02

On Thursday, July 25, 2002, at 03:11 PM, David Blanton wrote: Is it possible to debug a user land app and trace its transition to kernel land ? Two machine remote debug? Of course, it's possible; it's just not for the faint-of-heart. Doing this requires some understanding of the transition to kernel mode, and some faith in the implementation. It can't be done simply. Here's a way: Machine A: - run gdb and set up to debug Machine B Machine B: - hit the debug switch and wait for remote debugger Machine A: - connect to Machine B - plant appropriate breakpoints in the kernel - continue Machine B: - run gdb and start your user-mode application [depending on how you do the previous step, you may spend a lot of time typing 'c' on A] This setup will let you get control in the kernel as the user-mode program makes system calls. Is this what you had in mind (in spirit, if not in fact)? Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | Men are from Earth. | Women are from Earth. | Deal with it. *--------------------------------------*-------------------------------* _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: How do disk writes work these days?
by Justin C. Walker 26 Jul '02

26 Jul '02

On Wednesday, July 24, 2002, at 11:47 AM, Timothy A. Seufert wrote: "Justin C. Walker" <justin(a)mac.com> wrote: On Tuesday, July 23, 2002, at 07:18 AM, Wade Tregaskis wrote: [for background, I don't have any experience coding at the kernel level; I lurk on this list hoping to learn :)] This is probably a numbingly boring question, but what happens when the kernel gets handed data to write to disk, from say a userland app? I ask because I've begun covering this from a users point of view in my uni course, and they seem to indicate that the method, now as it was 30 years ago, is to block any disk write's and yield time to other processes. I don't recall any unix system in the past 30 years that did that. Disk writes are scheduled by the I/O subsystem, and the driver handles talking with the device to get the data there. All of this is generally asynchronous with respect to process activity. I think Wade meant "block [the calling process on] any disk writes and yield time to other processes". Which is in fact what happens, both now and 30 years ago. Just got back into town... I don't believe this is the case; writes have pretty much always been asynchronous, so that unless there is some serious blockage (e.g., out of buffers), the process can merrily go on its way after making the call (return happens after the data has been read; there are "edge cases", involving lots of data, where this doesn't happen, of course). Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | It's not whether you win or lose... | It's whether *I* win or lose. *--------------------------------------*-------------------------------* _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: How to debug kernel panic in boot
by Godfrey van der Linden 26 Jul '02

26 Jul '02

You can also get (non-synch) log output if your boot verbosely. sudo nvram boot-args=-'-v debug=0x146' This will set your system to boot verbosely and you can get system log messages directly on the screen. Godfrey At 9:10 -0400 02-7-26, Francis bouchard wrote: There are two different methods depending if your running 10.1.x or 10.2(prerelease) In both cases you will have to generate your symbols as "relocatable". 10.1.x kmodsyms or 10.2: kextload. Then you have to load(in the debugger) your symbol at the specific address you see in the panic. See in the Darwin dev list for a subject: How to read a backtrace/kernel panic It will give you a pretty good start. If your kext is not required at boot, you can load it manually after boot to see if your crash is a boot-time problem. Hope to help Francis On 26/07/02 08:17, "Tsuyoshi Tanaka" <tanaka(a)pixela.co.jp> wrote: Hello, When I put the original kernel extension in /System/Library/Extensions/, I 'm faced with the problem that Kernel panic happens in boot time. So, I 'd like to debug boot, but in the case of boot, I don't know how to create the symbol file for remote debug. And, in the case of Kernel panic, I can't get the system.log. > Does the method of debugging kernel panic in boot exist ? _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: How to debug kernel panic in boot
by Francis bouchard 26 Jul '02

26 Jul '02

There are two different methods depending if your running 10.1.x or 10.2(prerelease) In both cases you will have to generate your symbols as "relocatable". 10.1.x kmodsyms or 10.2: kextload. Then you have to load(in the debugger) your symbol at the specific address you see in the panic. See in the Darwin dev list for a subject: How to read a backtrace/kernel panic It will give you a pretty good start. If your kext is not required at boot, you can load it manually after boot to see if your crash is a boot-time problem. Hope to help Francis On 26/07/02 08:17, "Tsuyoshi Tanaka" <tanaka(a)pixela.co.jp> wrote: > Hello, > When I put the original kernel extension in /System/Library/Extensions/, > I 'm faced with the problem that Kernel panic happens in boot time. > So, I 'd like to debug boot, but in the case of boot, I don't know how > to create the symbol file for remote debug. > And, in the case of Kernel panic, I can't get the system.log. > Does the method of debugging kernel panic in boot exist ? > > Best Regards, > tusyoshi > _______________________________________________ > darwin-kernel mailing list | darwin-kernel(a)lists.apple.com > Help/Unsubscribe/Archives: > http://www.lists.apple.com/mailman/listinfo/darwin-kernel > Do not post admin requests to the list. They will be ignored. > -- Francis Bouchard francis.bouchard(a)matrox.com Groupe vidio Macintosh 1-514-822-6000 ext:2869 Matrox Electronic Systems Ltd. Montreal, Quibec, Canada _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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How to debug kernel panic in boot
by Tsuyoshi Tanaka 26 Jul '02

26 Jul '02

Hello, When I put the original kernel extension in /System/Library/Extensions/, I 'm faced with the problem that Kernel panic happens in boot time. So, I 'd like to debug boot, but in the case of boot, I don't know how to create the symbol file for remote debug. And, in the case of Kernel panic, I can't get the system.log. Does the method of debugging kernel panic in boot exist ? Best Regards, tusyoshi _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: Can I get KERNEL_DEBUG messages?
by Umesh Vaishampayan 26 Jul '02

26 Jul '02

On Thursday, July 25, 2002, at 02:51 PM, Scott Taggart wrote: How do you get the kernel buffer to dump out to the screen? Unfortunately, the tool to read the trace buffer, decode the raw trace and generate a report is not open sourced yet. :-( Look at xnu/bsd/kern/kdebug.c for the implementation details. You can use sysctl(3) to get at that buffer and get the raw trace data .... Look at xnu/bsd/kern/kern_sysctl.c for the implementation of "KERN_DEBUG" and kdebug_ops() for "KERN_KDENABLE", "KERN_KDSETBUF", "KERN_KDREADTR", etc... --Umesh At 01:19 PM 7/25/2002, Umesh Vaishampayan wrote: On Thursday, July 25, 2002, at 10:15 AM, Heiko Panther wrote: Hi! Some functions I use in the kernel (e.g. thread_funnel_set(), sosend()) sometimes fail and I want to know more about it. I see they have KERNEL_DEBUG/kernel_debug() calls built in, but I get no output to system.log. I have a 10.1.5 debug kernel, and I set kdebug_enable=true before I call the function in question. What should I do? Thanks Heiko Panther KERNEL_DEBUG() traces do not go to the system.log. They are logged into a kernel buffer. --Umesh -- Umesh Vaishampayan Apple Computer, Inc. Mac OS X Kernel Ph: (408) 974 0229 _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Remote Debug
by David Blanton 25 Jul '02

25 Jul '02

Is it possible to debug a user land app and trace its transition to kernel land ? Two machine remote debug? TIA, David Blanton "One man's mede is another man's persian." _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: Can I get KERNEL_DEBUG messages?
by Scott Taggart 25 Jul '02

25 Jul '02

How do you get the kernel buffer to dump out to the screen? At 01:19 PM 7/25/2002, Umesh Vaishampayan wrote: On Thursday, July 25, 2002, at 10:15 AM, Heiko Panther wrote: Hi! Some functions I use in the kernel (e.g. thread_funnel_set(), sosend()) sometimes fail and I want to know more about it. I see they have KERNEL_DEBUG/kernel_debug() calls built in, but I get no output to system.log. I have a 10.1.5 debug kernel, and I set kdebug_enable=true before I call the function in question. What should I do? Thanks Heiko Panther KERNEL_DEBUG() traces do not go to the system.log. They are logged into a kernel buffer. --Umesh -- Umesh Vaishampayan Apple Computer, Inc. Mac OS X Kernel Ph: (408) 974 0229 _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored. _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: Can I get KERNEL_DEBUG messages?
by Umesh Vaishampayan 25 Jul '02

25 Jul '02

On Thursday, July 25, 2002, at 10:15 AM, Heiko Panther wrote: Hi! Some functions I use in the kernel (e.g. thread_funnel_set(), sosend()) sometimes fail and I want to know more about it. I see they have KERNEL_DEBUG/kernel_debug() calls built in, but I get no output to system.log. I have a 10.1.5 debug kernel, and I set kdebug_enable=true before I call the function in question. What should I do? Thanks Heiko Panther KERNEL_DEBUG() traces do not go to the system.log. They are logged into a kernel buffer. --Umesh -- Umesh Vaishampayan Apple Computer, Inc. Mac OS X Kernel Ph: (408) 974 0229 _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Can I get KERNEL_DEBUG messages?
by Heiko Panther 25 Jul '02

25 Jul '02

Hi! Some functions I use in the kernel (e.g. thread_funnel_set(), sosend()) sometimes fail and I want to know more about it. I see they have KERNEL_DEBUG/kernel_debug() calls built in, but I get no output to system.log. I have a 10.1.5 debug kernel, and I set kdebug_enable=true before I call the function in question. What should I do? Thanks Heiko Panther _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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