Re: signal/syscall/swapcontext fixes

David Woodhouse writes:

The 64-bit version (bl .save_nvgprs) is prettier than the 32-bit version
(doing it longhand), and they're still gratuitously different. We should
probably fix that.

There's also the difference where ret_from_except in 32-bit does what
ret_from_except_lite does in 64-bit, and the 32-bit
ret_from_except_full is approximately the same as the 64-bit
ret_from_except. :)

On a similar note, we should also do a ptrace stop when we deliver
signals, to ensure that the debugger gets a stop _on_ the first
instruction of the handler. Once upon a time there was a stop in
handle_rt_signal() and handle_signal(), but doing it that way gave a
_double_ stop when we ended up in a signal handler from sigsuspend(),
because the syscall stop you just fixed for ppc32 happened too.

Do we have a fix for this for 2.6.16, or will we leave it until
2.6.17?

On a purely cosmetic note I'm not sure about this though -- it was
slightly easier to follow when it was more explicit:
-       andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_SAVE_NVGPRS|_TIF_NOERROR|_TIF_RESTORE_SIGMASK)
+       andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)

I did it that way because we are clearing _TIF_PERSYSCALL_MASK further
down.  If we expand one we should expand both.

Paul.