[musl] Powerpc Linux 'scv' system call ABI proposal take 2

[Rich Felker]

On Thu, Apr 16, 2020 at 06:48:44AM +0200, Florian Weimer wrote:
> * Rich Felker:
> 
> > My preference would be that it work just like the i386 AT_SYSINFO
> > where you just replace "int $128" with "call *%%gs:16" and the kernel
> > provides a stub in the vdso that performs either scv or the old
> > mechanism with the same calling convention.
> 
> The i386 mechanism has received some criticism because it provides an
> effective means to redirect execution flow to anyone who can write to
> the TCB.  I am not sure if it makes sense to copy it.

Indeed that's a good point. Do you have ideas for making it equally
efficient without use of a function pointer in the TCB?

Rich