On 24-Apr-2002 Kenneth Culver wrote:
>> Brandon S Allbery KF8NH writes:
>>  > On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote:
>>  > > Maybe the argument isn't where you expect it to be, but is there.
>>  > > Can you make a test program which calls mmap2 with its 6th arg as
>>  > > something unique like 0xdeadbeef?  Then print out (in hex :) the
>>  > > trapframe
>>  > > from the linux prepsyscall routine & see if you can find the deadbeef.
>>  >
>>  > My recollection is that beyond 5 arguments, a pointer to the remaining
>>  > ones is passed.  (But my recollection may be wrong and I don't wish to
>>  > subject myself to the source cesspool at the moment....)
>>  >
>> I think that's how it used to work.  Apparently, they've changed it
>> recently and they now pass 6 args in registers.  Eg, in the linux
>> kernel sources, old_mmap() fetches its args via copy_from_user(),
>> whereas the newer sys_mmap2() doesn't.
>> Drew
> Yep, according to the docs and source code I looked at in the linux
> kernel, the sixth arg is in the ebp register. I've looked all over the
> FreeBSD kernel and the linux emulator for the place that actually sets
> these, and unfortunately, due to my lack of asm coding knowledge, I can't
> find anything.

libc sets it before it enters the kernel.  Then on kernel entry we save ebp
in the trapframe.


John Baldwin <[EMAIL PROTECTED]>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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