On 03.09.2003 at 11:06 AM, Jim Magee <jmagee@apple.com> wrote:
On Sep 3, 2003, at 10:23 AM, Geoffrey Schmit wrote:
I'm currently stuck trying to find a function that is accessible by a
kernel extension and that is equivalent to vm_read_overwrite in that
it will return an error if the specified address is inaccessible
rather than throwing a SIGSEGV signal.
So, a couple of questions:
Is there an example that captures a back trace in a kernel extension?
If so, where is it?
Are you trying to get a user-level backtrace or a kernel backtrace
from your kernel extension? And more importantly, why are you doing
this from a kernel extension in the first place?
I'm primarily interested in getting a kernel backtrace from my kernel extension. I'm porting a library that provides various services to other kernel extensions we develop. One of these services is to capture a backtrace. For example, we may capture a backtrace when a kernel extension detects an error in order to facilitate the debugging of that error condition. As another example, we may capture a backtrace when a kernel extension acquires a resource in order to later determine who acquired that resource if the resource is leaked. Ideally, it would be beneficial for the backtrace to eventually include the stack of the user-mode thread that initiated the transition to the kernel (in scenarios where this is the case). However, that is probably pushing my luck.... I'm not at all interested in developing a kernel extension to capture user-level backtraces from arbitrary processes.
In-kernel, if you access memory you don't have mapped, you're dead
(panic). You don't get a signal to respond to. And, besides, you can't
directly access any user-level memory at all. On PowerPC, user-memory
isn't mapped into the kernel's view of memory, since the kernel gets
it own 4GB address space. i386 is slightly different, but changing
more towards the PowerPC model than the other way around.
So, my problem is probably that as I walk the stack I eventually encounter an address from a user-mode thread and cause a panic. Is there a way to test if the address belongs to the kernel or otherwise determine that I should stop walking the stack? If further clarification would be helpful, please let me know. Thanks! geoff _______________________________________________ darwin-kernel mailing list | darwin-kernel@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.