On Wed, Mar 04, 2009 at 09:19:28AM +0100, Brian Foster wrote: > 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. That won't quite retain the ABI: you need to make sure everyone locates it by using the stack pointer instead of the return pc. Fortunately, GCC uses the return PC only for instruction matching today. I have a vague memory it used to use the stack pointer but this was more reliable. They don't necessarily have to go into the vdso; other architectures have moved them off the stack directly to glibc. -- Daniel Jacobowitz CodeSourcery
