On Thu, 1 Nov 2018, Florian Weimer wrote:
* Andy Lutomirski:
The basic idea would be to allow libc, or maybe even any library, to
register a handler that gets a chance to act on an exception caused by
a user instruction before a signal is delivered. As a straw-man
example for how this could work, there could be a new syscall:
long register_exception_handler(void (*handler)(int, siginfo_t *, void *));
If a handler is registered, then, if a synchronous exception happens
(page fault, etc), the kernel would set up an exception frame as usual
but, rather than checking for signal handlers, it would just call the
registered handler. That handler is expected to either handle the
exception entirely on its own or to call one of two new syscalls to
ask for normal signal delivery or to ask to retry the faulting
instruction.
Would the exception handler be a per-thread resource?
For SGX purposes it would *need* to be per-thread resource so that the
run-time (not just Intel but any user space support code for SGX) is
able to act on thread that caused this exception inside the enclave.
/Jarkko
