On Sat, 30 Jul 2016 08:51:25 -0500 Josh Poimboeuf <jpoim...@redhat.com> wrote:
> On Fri, Jul 29, 2016 at 10:20:36PM -0400, Steven Rostedt wrote: > > On Fri, 29 Jul 2016 19:50:59 -0500 > > Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > > > BTW, it would be really nice if ftrace_graph_ret_addr() were idempotent > > > so we could get the "real" return address without having to pass in a > > > state variable. > > > > > > For example we could add an "unsigned long *retp" pointer to > > > ftrace_ret_stack, which points to the return address on the stack. Then > > > we could get rid of the index state variable in ftrace_graph_ret_addr, > > > and also then there would never be a chance of the stack dump getting > > > out of sync with the ret_stack. > > > > > > What do you think? > > > > > > > I don't want to extend ret_stack as that is allocated 50 of these > > structures for every task. That said, we have the "fp" field that's > > used to check for frame pointer corruption when mcount is used. With > > CC_USING_FENTRY, that field is ignored. Perhaps we could overload that > > field for this. > > In that case, I guess we would need two versions of > ftrace_graph_ret_addr(), with the current implementation still needed > for mcount+HAVE_FUNCTION_GRAPH_FP_TEST. How hard would it be in that case? > > Or would you want to get rid of HAVE_FUNCTION_GRAPH_FP_TEST for x86? No, because there's gcc versions that we still support that mess up mcount, and could still cause issues with function graph. > > BTW, on a different note, should I put ftrace_graph_ret_addr() to > kernel/trace/trace_functions_graph.c so other arches can use it? > I guess you could. There doesn't seem to be any x86 specific code in that right? -- Steve
