[PATCH 3/3] powerpc: enable support for GCC plugins

[Andrew Donnellan <andrew.donnellan@au1.ibm.com>]

Enable support for GCC plugins on powerpc.

Add an additional version check in gcc-plugins-check to advise users to
upgrade to gcc 5.2+ on powerpc to avoid issues with header files (gcc <=
4.6) or missing copies of rs6000-cpus.def (4.8 to 5.1 on 64-bit targets).

Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>

---

Open to bikeshedding on the gcc version check.

Compile tested with all plugins enabled on gcc 4.6-6.2,
x86->ppc{32,64,64le} and 4.8-6.2 ppc64le->ppc{32,64,64le}. Thanks to
Chris Smart for help with this.

I think it's best to take this through powerpc#next with an ACK from
Kees/Emese?
---
 arch/powerpc/Kconfig         | 1 +
 scripts/Makefile.gcc-plugins | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 65fba4c..6efbc08 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -92,6 +92,7 @@ config PPC
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_GCC_PLUGINS
 	select SYSCTL_EXCEPTION_TRACE
 	select VIRT_TO_BUS if !PPC64
 	select HAVE_IDE
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 26c67b7..9835a75 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -47,6 +47,14 @@ gcc-plugins-check: FORCE
 ifdef CONFIG_GCC_PLUGINS
   ifeq ($(PLUGINCC),)
     ifneq ($(GCC_PLUGINS_CFLAGS),)
+      # Various gccs between 4.5 and 5.1 have bugs on powerpc due to missing
+      # header files. gcc <= 4.6 doesn't work at all, gccs from 4.8 to 5.1 have
+      # issues with 64-bit targets.
+      ifeq ($(ARCH),powerpc)
+        ifeq ($(call cc-ifversion, -le, 0501, y), y)
+	  @echo "Cannot use CONFIG_GCC_PLUGINS: plugin support on gcc <= 5.1 is buggy on powerpc, please upgrade to gcc 5.2 or newer" >&2 && exit 1
+        endif
+      endif
       ifeq ($(call cc-ifversion, -ge, 0405, y), y)
 	$(Q)$(srctree)/scripts/gcc-plugin.sh --show-error "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)" || true
 	@echo "Cannot use CONFIG_GCC_PLUGINS: your gcc installation does not support plugins, perhaps the necessary headers are missing?" >&2 && exit 1
-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited