> On Wed, Nov 28, 2018 at 04:59:25PM +0100, Jan Hubicka wrote: > > Hi, > > I wonder how __return_loc sections work. In general it would be nice to > > You mean how it's used? It's for patching in/out return instrumentation > at runtime, and to find them we use the sections. > > > avoid direct output of assembler code in favour of adding instructions > > to rtl stream which should be possible to insert the call and return. > > That would be a full rewrite how all these hooks work. I was > hoping extending the existing frame work would be good enough for now.
Yep, it is ugly and it hits us ocassionaly as with the CET instrumentation, but I suppose we should care about this in stage1. > > > __return_loc seems harder, also I wonder if it makes unwind information > > possible? > > Do we need unwind information for calls? I thought it was only > for other stack manipulation. I just wonder if backtraces are right if something triggers in the extra code. If you make control flow to jump into separate section, I suppose backtraces won't be right. Not sure if that is necessarily issue? Honza > > -Andi
