[PATCH v2 1/2] perf build: Update build rule for generated files

[Namhyung Kim]

The bison and flex generate C files from the source (.y and .l)
files.  When O= option is used, they are saved in a separate directory
but the default build rule assumes the .C files are in the source
directory.  So it might read invalid file if there are generated files
from an old version.  The same is true for the pmu-events files.

For example, the following command would cause a build failure:

  $ git checkout v6.3
  $ make -C tools/perf  # build in the same directory

  $ git checkout v6.5-rc2
  $ mkdir build  # create a build directory
  $ make -C tools/perf O=build  # build in a different directory but it
                                # refers files in the source directory

Let's update the build rule to specify those cases explicitly to depend
on the files in the output directory.

Note that it's not a complete fix and it needs the next patch for the
include path too.

Fixes: 80eeb67fe577 ("perf jevents: Program to convert JSON file")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/build/Makefile.build  | 10 ++++++++++
 tools/perf/pmu-events/Build |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build
index 89430338a3d9..fac42486a8cf 100644
--- a/tools/build/Makefile.build
+++ b/tools/build/Makefile.build
@@ -117,6 +117,16 @@ $(OUTPUT)%.s: %.c FORCE
 	$(call rule_mkdir)
 	$(call if_changed_dep,cc_s_c)
 
+# bison and flex files are generated in the OUTPUT directory
+# so it needs a separate rule to depend on them properly
+$(OUTPUT)%-bison.o: $(OUTPUT)%-bison.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,$(host)cc_o_c)
+
+$(OUTPUT)%-flex.o: $(OUTPUT)%-flex.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,$(host)cc_o_c)
+
 # Gather build data:
 #   obj-y        - list of build objects
 #   subdir-y     - list of directories to nest
diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
index 150765f2baee..1d18bb89402e 100644
--- a/tools/perf/pmu-events/Build
+++ b/tools/perf/pmu-events/Build
@@ -35,3 +35,9 @@ $(PMU_EVENTS_C): $(JSON) $(JSON_TEST) $(JEVENTS_PY) $(METRIC_PY) $(METRIC_TEST_L
 	$(call rule_mkdir)
 	$(Q)$(call echo-cmd,gen)$(PYTHON) $(JEVENTS_PY) $(JEVENTS_ARCH) $(JEVENTS_MODEL) pmu-events/arch $@
 endif
+
+# pmu-events.c file is generated in the OUTPUT directory so it needs a
+# separate rule to depend on it properly
+$(OUTPUT)pmu-events/pmu-events.o: $(PMU_EVENTS_C)
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)
-- 
2.41.0.487.g6d72f3e995-goog