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Re: Use of the PC value in interrupt/exception handlers

On Fri, Aug 02, 2013 at 10:46:31AM +0000, Piyus Kedia wrote:
> Dear all,
> We are working on developing a dynamic binary translator for the kernel.
> Towards this, we wanted to confirm if the interrupted PC value pushed on
> stack by an interrupt/exception is used by the interrupt/exception handlers?
> For example, is the PC value compared against a fixed address to determine
> the handler behaviour (like Linux's page fault handler compares the faulting
> PC against an exception table, to allow functions like copy_from_user to 
> fault).

IIRC i386 and amd64 both check the faulting PC for copyin() and copyout()
(and similar functions). Unlike linux these exist as proper functions
so there is only a single set of exception PC bounds (not one for every
call site.

There will also be checks that a user-space PC actually contains
a user address.

Also the signal information, coredump, and registers for GDB (etc)
contain the PC.


David Laight:

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