On Wed, Jul 08, 2015 at 11:37:35AM -0500, Segher Boessenkool wrote: > On Wed, Jul 08, 2015 at 11:22:34AM -0500, Josh Poimboeuf wrote: > > > Writing the asm with a clobber of the stack pointer causes all stack > > > accesses to go via the frame pointer, which causes pretty horrible > > > code. > > > > As far as I can tell, most (but not all) kernel stack accesses already > > occur via the frame pointer anyway. Is that bad? Can you clarify what > > you mean by horrible code? > > If you already have a frame pointer anyway it won't get much worse, > sure :-) > > If you don't have one yet you will get one, and a stack frame, and > all that boilerplate. You don't want to force that if you don't > need it.
Ah. We're only clobbering the stack pointer when asm() has a call instruction. In that case we need to save and setup the frame pointer anyway. So I don't think it's a problem. -- Josh
