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Re: [PATCH, RFC] MIPS: Implement the getcontext API
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, âvsyscallâ,
> 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 â 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