On Wed, Mar 04, 2009 at 09:19:28AM +0100, Brian Foster wrote: > On Tuesday 03 March 2009 17:56:25 David Daney wrote: > >[ ... ] > > When (and if) we move the sigreturn trampoline to a vdso we should be > > able to maintain the ABI. > > it's more a matter of “when” rather than “if”. > there is still an intention here to use XI (we > have SmartMIPS), which requires not using the > signal (or FP) trampoline on the stack. > > moving the signal trampoline to a vdso (which > is(? was?) called, maybe misleadingly, ‘vsyscall’, > on other architectures) is the obvious solution to > that part of the puzzle. and yes, it is possible > to maintain the ABI; the signal trampoline is still > also put on the stack, and modulo XI, would work if > used — the trampoline-on-stack is simply not used > if there is a vdso with the signal trampoline. We generally want to get rid of stack trampolines. Trampolines require cacheflushing which especially on SMP systems can be a rather expensive operation. Ralf
