Re: Returning Properly from Assembly .lib
- From: hypervista@xxxxxxxxxxxxxxxxx <hypervistanewsgroupsnospam@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 10 Jan 2007 05:11:01 -0800
Ahhhhh..... Thanks! If I understand correctly, and for example, my CPUID
routine should include a cmp, which results in either 1 or 0. In my driver
..c code I would write something like, "if(!mycpuid()) {blahblahblah;} else
{taaadaaaataaa;}.
"Skywing [MVP]" wrote:
As in you don't call subfunctions from within your assembly functions..
--
Ken Johnson (Skywing)
Windows SDK MVP
http://www.nynaeve.net
"hypervista@xxxxxxxxxxxxxxxxx"
<hypervistanewsgroupsnospam@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:26CF5778-4C3C-4B77-B5D3-4064B7F8CCDF@xxxxxxxxxxxxxxxx
Thank you Ivan. I searched leaf functions, but afraid I'm a bit lost in
this
regard. Can you give me a link to an example of a leaf function, or could
you outline a brief leaf function to get me started. Thanks again.
"Ivan Brugiolo [MSFT]" wrote:
It's likely to be a mismatched calling convention when you invoke
DbgPrint in you ASM file.
I would recomend to make the ASM functions `leaf` functions
(AKA: they do not call anything else), and, instead, calling your
DbgPrint
from a C code, where the compiler knows how to pop the params off the
stack.
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"hypervista@xxxxxxxxxxxxxxxxx"
<hypervistanewsgroupsnospam@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:8B83D53F-07F7-48D6-9CCE-D6DA57B12439@xxxxxxxxxxxxxxxx
Hello - I think I need asistance in returning properly from my asm
code,
which I have linked into my driver via a .lib file.
For now, the .asm file simpy calls a CPUID function and returns.
Later, I
need to RDMSR and WRMSR, but thought I'd start out with the relatively
easy
CPUID portion of my project.
I've included a call to DbgPrint in my .asm code so I can see if things
are
going as planned. Immediately after my call to DbgPrint, I exit and
return.
During Windbg session, I see my DbgPrint message and then the driver
immediately crashes. Fyi, my driver name is hypervista. The error
immediately following my DbgPrint message is:
Access violation - code c0000005 (!!! second chance !!!)
hypervista!__security_cookie <PERF> (hypervista+0xa00):
f81aba00 0000 add [eax],al
The a portion of the verbose analysis is:
FAULTING_IP:
hypervista!__security_cookie <PERF> (hypervista+0xa00)+0
f81aba00 0000 add [eax],al
EXCEPTION_RECORD: ffffffff -- (.exr ffffffffffffffff)
ExceptionAddress: f81aba00 (hypervista!__security_cookie <PERF>
(hypervista+0xa00))
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000001
Parameter[1]: 00000000
Attempt to write to address 00000000
ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at "0x%08lx"
referenced
memory at "0x%08lx". The memory could not be "%s".
WRITE_ADDRESS: 00000000
I think I'm either not returning properly or not fixing up the
registers/memory, but not really sure.
Your help is greatly appreciated. Thanks.
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