Call Gates
Fri, 20 Jun 1997 07:39:20 -0400 (EDT)

Hi there,

I am trying to understand how call gates work and as usual the Intel
documentation sucks. Can someone tell me or point me to a reference that
says EXACTLY what happens when a call gate is used, eg: from the moment
the CALL 0007:00000000 (for example) is executed to the time it is
handled. I was looking through another OS's source code and they use
0x07 as the designated call gate for system calls, however when looking
at how they initted the LDT, the table entry was the first line in the
descriptor array initialization. Is 0x07 an index into the LDT or is it
some other number (I dont think it is realted to the type, though). I
would think that once executed, the CALL makes the processor goto LDT[7]
and pull out that call gate then do the funky address computation and
stack change and do the other code...