[tip: perf/urgent] perf tools: Support Python 3.8+ in Makefile

[tip-bot2 for Sam Lunt]

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     b9c9ce4e598e012ca7c1813fae2f4d02395807de
Gitweb:        https://git.kernel.org/tip/b9c9ce4e598e012ca7c1813fae2f4d02395807de
Author:        Sam Lunt <samueljlunt@xxxxxxxxx>
AuthorDate:    Fri, 31 Jan 2020 12:11:23 -06:00
Committer:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitterDate: Fri, 03 Apr 2020 10:03:44 -03:00

perf tools: Support Python 3.8+ in Makefile

Python 3.8 changed the output of 'python-config --ldflags' to no longer
include the '-lpythonX.Y' flag (this apparently fixed an issue loading
modules with a statically linked Python executable).  The libpython
feature check in linux/build/feature fails if the Python library is not
included in FEATURE_CHECK_LDFLAGS-libpython variable.

This adds a check in the Makefile to determine if PYTHON_CONFIG accepts
the '--embed' flag and passes that flag alongside '--ldflags' if so.

tools/perf is the only place the libpython feature check is used.

Signed-off-by: Sam Lunt <samuel.j.lunt@xxxxxxxxx>
Tested-by: He Zhe <zhe.he@xxxxxxxxxxxxx>
Link: http://lore.kernel.org/lkml/c56be2e1-8111-9dfe-8298-f7d0f9ab7431@xxxxxxxxxxxxx
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: trivial@xxxxxxxxxx
Cc: stable@xxxxxxxxxx
Link: http://lore.kernel.org/lkml/20200131181123.tmamivhq4b7uqasr@xxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/Makefile.config | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index eb95c0c..12a8204 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -228,8 +228,17 @@ strip-libs  = $(filter-out -l%,$(1))
 
 PYTHON_CONFIG_SQ := $(call shell-sq,$(PYTHON_CONFIG))
 
+# Python 3.8 changed the output of `python-config --ldflags` to not include the
+# '-lpythonX.Y' flag unless '--embed' is also passed. The feature check for
+# libpython fails if that flag is not included in LDFLAGS
+ifeq ($(shell $(PYTHON_CONFIG_SQ) --ldflags --embed 2>&1 1>/dev/null; echo $$?), 0)
+  PYTHON_CONFIG_LDFLAGS := --ldflags --embed
+else
+  PYTHON_CONFIG_LDFLAGS := --ldflags
+endif
+
 ifdef PYTHON_CONFIG
-  PYTHON_EMBED_LDOPTS := $(shell $(PYTHON_CONFIG_SQ) --ldflags 2>/dev/null)
+  PYTHON_EMBED_LDOPTS := $(shell $(PYTHON_CONFIG_SQ) $(PYTHON_CONFIG_LDFLAGS) 2>/dev/null)
   PYTHON_EMBED_LDFLAGS := $(call strip-libs,$(PYTHON_EMBED_LDOPTS))
   PYTHON_EMBED_LIBADD := $(call grep-libs,$(PYTHON_EMBED_LDOPTS)) -lutil
   PYTHON_EMBED_CCOPTS := $(shell $(PYTHON_CONFIG_SQ) --includes 2>/dev/null)