On Tue, Dec 13, 2016 at 04:51:34PM +0100, Florian Weimer wrote: > On 12/13/2016 04:41 PM, Jeff Law wrote: > >On 12/13/2016 12:13 AM, Florian Weimer wrote: > >>Is it possible to use the stack from inline assembly? I'm particularly > >>interested in i386 and x86_64, and push/pop instructions and function > >>calls. > >You can push/pop and perform a function call. Obviously you have to > >express what's going on from a dataflow standpoint if you use a new > >style asm -- that includes notifying GCC of the registers clobbered at > >the call point and the memory usage. > > How do I express that? It's not that %rsp is clobbered, its unchanged. > How can I express a clobber on memory which does not even have an > address as far as C is concerned? Clobbering "memory" does not work here. Clobbering "rsp" however seems to work. But, "seems to", I don't think there is a guarantee anywhere. Clobbering the stack pointer forces the use of the frame pointer, but is that guaranteed even? Segher
