Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor | Date | Mon, 3 Aug 2020 08:27:25 +0000 |
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From: Mark Rutland > Sent: 31 July 2020 19:32 ... > > 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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