[Autogenerated] Here, is my local kernel debugging session here,
I'm going to Use the ID T command.
To show the inter up dispatch table.
We've looked at interrupting the previous module but
now we can focus more on exceptions.
In fact, the beginning of this table,
is all about exceptions or mostly about exceptions.
For example, the exception index zero here, is about dividing by zero.
And this number zero,
is the one provided by intel specifying that this is going to be The
exception raised when the C P U is forced to divide by zero.
So it's not about what Windows want it's about how the C P U behaves.
Windows has to provide an appropriate handler for this particular case.
Another example, is this invalid up code fault.
So what happens when the processor encounters an instruction,
that doesn't exist.
It always raises an exception with the value of six and This is
the kernels handler for that kind of exception.
In some cases you'll find that You have these stack value here.
This indicates that There's another stack being
used while that kind of exception.
Is being handed for safety purposes.
Another common example, is index number three,
which is usually encountered as an in three instruction,
which is a break point, and this is the breakpoint handler,
that the kernel provides for this kind of case we have the page fault example
here which happens when the C P U tries to access memory,
that is currently not mapped into physical memory.
The C P U has no idea what this is or what virtual memory exactly.
Is In terms of where that might be stored.
The only thing it knows is that it, is not mapped into physical memory.
And In this case, just raises the page fault exception,
and hopes,
that the underlying operating system knows what to do with that So
these are exception handlers essentially and Of course,
they can be also invoked using the in instruction just directly
invoking that as an inter up But in fact,
it's done synchronously.
For example, if we, if we, want to to process,
D, PCs In fact,
this is called internally by the kernel where D PCs need to be handled,
then This is the index being used index,
two F here, the index,
two E might be something you may be familiar with because this is the
classic way of invoking system calls in newer process.
Source we have the CSS ss, call instruction,
but in the old X, 86 process, source before Intune two there,
was no,
CSS center instruction at the time which was the
32-bit equivalent of CSS call instead, a CSS software,
interact, was used which was exactly.
That entry, two E, and In fact, this is still something.
That is supported today, at least for compatibility reasons,
but perhaps there are some other reasons.
To keep that in place, obviously, CSS call is more efficient,
but even end two E would work.
To invoke system calls.