vfio: selftests: Fix out-of-tree build with make O=

The test programs are compiled via a static pattern rule that requires
intermediate .o files:

  $(TEST_GEN_PROGS): %: %.o $(LIBVFIO_O)

After lib.mk prefixes TEST_GEN_PROGS with $(OUTPUT), this creates
dependencies on .o files in the output directory (e.g.
$(OUTPUT)/vfio_dma_mapping_test.o). However, there is no rule to compile
these .o files from the source directory .c files when OUTPUT differs
from the source directory.

Add an explicit chain of pattern rules:
  $(OUTPUT)/% -> $(OUTPUT)/%.o -> %.c

Following the same pattern already used in libvfio.mk for the library
objects.

Fixes: 19faf6fd969c ("vfio: selftests: Add a helper library for VFIO selftests")
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v2-4ccc247e6aff+1d93-vfio_st_make_o_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
index 0684932d91bfcb2d116a0752cc93461030f86326..a19b75742342adf2fca962c779e6331e3cda154e 100644 (file)
--- a/tools/testing/selftests/vfio/Makefile
+++ b/tools/testing/selftests/vfio/Makefile
@@ -27,10 +27,13 @@ CFLAGS += $(EXTRA_CFLAGS)
 
 LDFLAGS += -pthread
 
-$(TEST_GEN_PROGS): %: %.o $(LIBVFIO_O)
+$(TEST_GEN_PROGS): $(OUTPUT)/%: $(OUTPUT)/%.o $(LIBVFIO_O)
        $(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $< $(LIBVFIO_O) $(LDLIBS) -o $@
 
 TEST_GEN_PROGS_O = $(patsubst %, %.o, $(TEST_GEN_PROGS))
+$(TEST_GEN_PROGS_O): $(OUTPUT)/%.o: %.c
+       $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
+
 TEST_DEP_FILES = $(patsubst %.o, %.d, $(TEST_GEN_PROGS_O) $(LIBVFIO_O))
 -include $(TEST_DEP_FILES)