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Re: Kernel stack size and kernel memory debugger
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Re: Kernel stack size and kernel memory debugger

  • Subject: Re: Kernel stack size and kernel memory debugger
  • From: Godfrey van der Linden <email@hidden>
  • Date: Tue, 01 Dec 2009 13:44:26 +1100
You do know the most common reason for kernel allocation returning bad addresses is scribbling on a 'free-ed' pointer.  I'd really, really carefully examine your free data paths and make sure the isn't a teardown race.  It is very unlikely that malloc has a problem that only your driver uncovers.

Good Luck

Godfrey

On 2009-12-01, at 7:31 AM, mogambo wrote:

And, while I am on the subject of corruption, is there a kernel memory debugger in Mac OS/bsd?  I have seen this questions being asked on the forum, but did not find any answers.

Are you looking for something other than two-machine debugging with gdb?  This is the relevant section of the (somewhat outdated) Kernel Extension Programming Topics.

I was wondering if there were any debug flags or something to turn on some sort of memory fencing.  I am debugging a problem where the pointer returned by _MALLOC is invalid (e.g. 0x122aae48) and I get a trap fault.  The size of allocation is 56 bytes, so I would expect allocation out of kalloc.64 zone.  zprint in gdb shows the following for kalloc.64:

ZONE                 COUNT   TOT_SZ   MAX_SZ ELT_SZ ALLOC_SZ NAME
0xffffff80031105c8   56461   3aa000   445800     64     1000 kalloc.64 CX

Thanks!
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References: 
 >Kernel stack size and kernel memory debugger (From: mogambo <email@hidden>)
 >Re: Kernel stack size and kernel memory debugger (From: Andrew Myrick <email@hidden>)
 >Re: Kernel stack size and kernel memory debugger (From: mogambo <email@hidden>)

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