On Mon, Jan 21, 2002 at 10:52:53AM -0800, H . J . Lu wrote:
> On Mon, Jan 21, 2002 at 10:36:26AM -0800, Ulrich Drepper wrote:
> > "H . J . Lu" <email@example.com> writes:
> > > Ulrich, should applciations have access to thread register directly?
> > It doesn't matter. The value isn't changed in the lifetime of a
> > thread. So the overhead of a syscall wouldn't be too much. And
> > protection against programs overwriting the register isn't necessary.
> > It's the program's fault if that happens.
> Thq question is if we should reserve $23 outside of glibc. $23 is
> a saved register in the MIPS ABI. It doesn't change across function
> calls. If applications outside of glibc don't need to access the
> thread register directly, that means $23 can be used as a saved
> register. We don't have to change anything when compiling applications.
> We only need to compile glibc with $23 reserved as the thread register.
That's not right. If it is call-saved in the application, that means
the application can use it. Main may have to restore it before it
returns to __libc_start_main, but that doesn't do you any good.
It doesn't change across function calls, but it does change inside
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer