Re: IOKit KEXT Questions
Re: IOKit KEXT Questions
- Subject: Re: IOKit KEXT Questions
- From: Terry Lambert <email@hidden>
- Date: Wed, 15 Aug 2007 16:24:59 -0700
On Aug 15, 2007, at 3:21 PM, Matt Burnett wrote:
I have 2 questions regarding IOKit KEXTs.
- How does IOMemoryDescriptor deal with memory protection (mprotect/
vm_protect)? Is there a class available to check/change the
protection of certain pages in memory or should i use mprotect/
vm_protect?
- Why do IOKit KEXTs have issues resolving kernel symbols, and what
can i do to work around it. For example if i create a KEXT in C, i
can lookup the address of any symbol which is in /mach.sym, however
I get unresolved symbol errors if i do the same in a IOKit KEXT.
Example HelloIOKit.cpp Code:
...
extern "C" int execve(void *, void *, int *);
...
IOLog("Found execve at %p\n",execve);
...
Example kextload output:
kextload: extension HelloIOKit.kext appears to be valid
kld(): Undefined symbols:
_execve
...
We hide system calls so someone unscrupulous does not overwrite their
entry points with jump instructions to their own code, perhaps
thinking that we do not change locking or other implementations
details in software updates.
If you need to trap and/or prevent this type of operation for
legitimate reasons, use kauth instead.
-- Terry
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