On Fri, Jul 17, 2020 at 10:36 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Fri, 17 Jul 2020 10:28:13 -0700 > Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote: > > > On Fri, Jun 26, 2020 at 4:29 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > > On Thu, Jun 25, 2020 at 03:40:42PM -0700, Sami Tolvanen wrote: > > > > > > > > Not boot tested, but it generates the required sections and they look > > > > > more or less as expected, ymmv. > > > > > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > > > > index a291823f3f26..189575c12434 100644 > > > > > --- a/arch/x86/Kconfig > > > > > +++ b/arch/x86/Kconfig > > > > > @@ -174,7 +174,6 @@ config X86 > > > > > select HAVE_EXIT_THREAD > > > > > select HAVE_FAST_GUP > > > > > select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE > > > > > - select HAVE_FTRACE_MCOUNT_RECORD > > > > > select HAVE_FUNCTION_GRAPH_TRACER > > > > > select HAVE_FUNCTION_TRACER > > > > > select HAVE_GCC_PLUGINS > > > > > > > > This breaks DYNAMIC_FTRACE according to kernel/trace/ftrace.c: > > > > > > > > #ifndef CONFIG_FTRACE_MCOUNT_RECORD > > > > # error Dynamic ftrace depends on MCOUNT_RECORD > > > > #endif > > > > > > > > And the build errors after that seem to confirm this. It looks like we might > > > > need another flag to skip recordmcount. > > > > > > Hurm, Steve, how you want to do that? > > > > Steven, did you have any thoughts about this? Moving recordmcount to > > an objtool pass that knows about call sites feels like a much cleaner > > solution than annotating kernel code to avoid unwanted relocations. > > > > Bah, I started to reply to this then went to look for details, got > distracted, forgot about it, my laptop crashed (due to a zoom call), > and I lost the email I was writing (haven't looked in the drafts > folder, but my idea about this has changed since anyway). > > So the problem is that we process mcount references in other areas and > that confuses the ftrace modification portion? Correct. > Someone just submitted a patch for arm64 for this: > > https://lore.kernel.org/r/20200717143338.19302-1-gregory.herrero@xxxxxxxxxx > > Is that what you want? That looks like the same issue, but we need to fix this on x86 instead. Sami
