[PATCH] selftests/rseq: Fix out-of-tree compilation

[Michael Ellerman]

Currently if you build with O=... the rseq tests don't build:

  $ make O=$PWD/output -C tools/testing/selftests/ TARGETS=rseq
  make: Entering directory '/linux/tools/testing/selftests'
  ...
  make[1]: Entering directory '/linux/tools/testing/selftests/rseq'
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./  -shared -fPIC rseq.c -lpthread -o /linux/output/rseq/librseq.so
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./  basic_test.c -lpthread -lrseq -o /linux/output/rseq/basic_test
  /usr/bin/ld: cannot find -lrseq
  collect2: error: ld returned 1 exit status

This is because the library search path points to the source
directory, not the output.

We can fix it by changing the library search path to $(OUTPUT).

Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
---

This works in all cases.

With O= set:

  $ make O=$PWD/output -C tools/testing/selftests/ TARGETS=rseq
  ...
  make[1]: Entering directory '/linux/tools/testing/selftests/rseq'
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/output/rseq -Wl,-rpath=./  basic_test.c -lpthread -lrseq -o /linux/output/rseq/basic_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/output/rseq -Wl,-rpath=./  basic_percpu_ops_test.c -lpthread -lrseq -o /linux/output/rseq/basic_percpu_ops_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/output/rseq -Wl,-rpath=./  param_test.c -lpthread -lrseq -o /linux/output/rseq/param_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/output/rseq -Wl,-rpath=./  -DBENCHMARK param_test.c -lpthread -lrseq -o /linux/output/rseq/param_test_benchmark
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/output/rseq -Wl,-rpath=./  -DRSEQ_COMPARE_TWICE param_test.c -lpthread -lrseq -o /linux/output/rseq/param_test_compare_twice
  make[1]: Leaving directory '/linux/tools/testing/selftests/rseq'
  make: Leaving directory '/linux/tools/testing/selftests'

And also without, in which case the selftest makefiles set OUTPUT to
the full path of the source directory:

  $ make -C tools/testing/selftests/ TARGETS=rseq
  ...
  make[1]: Entering directory '/linux/tools/testing/selftests/rseq'
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  -shared -fPIC rseq.c -lpthread -o /linux/tools/testing/selftests/rseq/librseq.so
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  basic_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/basic_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  basic_percpu_ops_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/basic_percpu_ops_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  param_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/param_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  -DBENCHMARK param_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/param_test_benchmark
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  -DRSEQ_COMPARE_TWICE param_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/param_test_compare_twice
  make[1]: Leaving directory '/linux/tools/testing/selftests/rseq'
  make: Leaving directory '/linux/tools/testing/selftests'

And finally, it also works if you build directly in the rseq
directory, eg:

  $ cd tools/testing/selftests/rseq
  $ make
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  -shared -fPIC rseq.c -lpthread -o /linux/tools/testing/selftests/rseq/librseq.so
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  basic_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/basic_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  basic_percpu_ops_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/basic_percpu_ops_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  param_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/param_test
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  -DBENCHMARK param_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/param_test_benchmark
  gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L/linux/tools/testing/selftests/rseq -Wl,-rpath=./  -DRSEQ_COMPARE_TWICE param_test.c -lpthread -lrseq -o /linux/tools/testing/selftests/rseq/param_test_compare_twice
---
 tools/testing/selftests/rseq/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
index d6469535630a..708c1b345245 100644
--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile
@@ -4,7 +4,7 @@ ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
 CLANG_FLAGS += -no-integrated-as
 endif
 
-CFLAGS += -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./ \
+CFLAGS += -O2 -Wall -g -I./ -I../../../../usr/include/ -L$(OUTPUT) -Wl,-rpath=./ \
 	  $(CLANG_FLAGS)
 LDLIBS += -lpthread
 

base-commit: 11a48a5a18c63fd7621bb050228cebf13566e4d8
-- 
2.21.1