RE: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor

From: Mark Rutland

Sent: 31 July 2020 19:32

...

quoted

It requires PC-relative data references. I have not worked on all architectures.
So, I need to study this. But do all ISAs support PC-relative data references?

Not all do, but pretty much any recent ISA will as it's a practical
necessity for fast position-independent code.

i386 has neither PC-relative addressing nor moves from %pc.
The cpu architecture knows that the sequence:
	call	1f  
1:	pop	%reg  
is used to get the %pc value so is treated specially so that
it doesn't 'trash' the return stack.

So PIC code isn't too bad, but you have to use the correct
sequence.

	David

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