Re: [design change] record-replay linux ABI level

[oza Pawandeep <oza.pawandeep@gmail.com>]

currently on i386 following is the function:

static enum gdb_syscall
i386_canonicalize_syscall (int syscall)
{
  enum { i386_syscall_max = 499 };

  if (syscall <= i386_syscall_max)
    return syscall;
  else
    return -1;
}

which is just straight mapping.

If we use generic enum defination, we will end up adding some
additional syscalls for ARM and

arm_canonicalize_syscall(int syscall)
end up having switch {case} and having one-to one mapping for some
syscalls and rest syscalls would be shift by 'n' position.
which looks clumsy to me.


I am trying to see if there is more generic way which would take care
of all archor move the defination to arch files.
will try to see what best could be done.

Regards,
Oza.



On Thu, May 10, 2012 at 7:09 PM, Tom Tromey <tromey@redhat.com> wrote:
> Oza> The definition of system call record maps fine to x86.  but arm
> Oza> syscall numbers are different. [partially] for e.g. on x86 sycall
> Oza> number for sys_epoll_create = 254 while on ARM it is 250.  the more
> Oza> we go down on defined system calls the more the numbers are
> Oza> differing on ARM and we loose one to one trivial mapping.
>
> My understanding of the current design is that the ARM code would see
> the syscall 250, and have a mapping to turn that into
> gdb_sys_epoll_create (== 254).  This can be done bidirectionally with
> two lookup tables.
>
> I suppose this could still not work in some scenarios.  One question is
> whether these occur in practice or are merely theoretical.
>
> I don't really care about this API either way.
> With a solid justification it is fine to change it.
>
> Tom