Canonicalize build system

* Respect user's CFLAGS/CPPFLAGS/LDFLAGS
* Respect $(MAKE)
* Remove CPPFLAGS from link rules

Note: for in-tree built test binaries, where we build --static,
  we do not apply LDFLAGS: we want to limit external
  dependencies in general; and users' LDFLAGS have a strong
  tendency to conflict with --static for linking.

Work in collaboration with David Seifert (ie, he wrote most of it).

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

6 files changed, 12 insertions, 20 deletions

diff --git a/contrib/bug400591/Makefile b/contrib/bug400591/Makefile
index 320610c..bb2e59d 100644
--- a/contrib/bug400591/Makefile
+++ b/contrib/bug400591/Makefile
@@ -1,8 +1,8 @@
 all: bug
 
 bug: bug.c ../../libcap Makefile
-	make -C ../../libcap
-	cc -g -I../../libcap/include --static -o $@ $< -L../../libcap -lcap
+	$(MAKE) -C ../../libcap
+	$(CC) $(CFLAGS) $(CPPFLAGS) -g -I../../libcap/include --static -o $@ $< -L../../libcap -lcap
 	./bug
 
 clean:
diff --git a/contrib/sucap/Makefile b/contrib/sucap/Makefile
index 91947af..8cd4cef 100644
--- a/contrib/sucap/Makefile
+++ b/contrib/sucap/Makefile
@@ -1,7 +1,7 @@
 all: su
 
 su: su.c
-	$(CC) -DPAM_APP_NAME=\"sucap\" -o $@ $< -lpam -lpam_misc -lcap
+	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -DPAM_APP_NAME=\"sucap\" -o $@ $< -lpam -lpam_misc -lcap
 	# to permit all ambient capabilities, this needs all permitted.
 	sudo setcap =p ./su
 
diff --git a/kdebug/Makefile b/kdebug/Makefile
index 0e8c11f..35a16d0 100644
--- a/kdebug/Makefile
+++ b/kdebug/Makefile
@@ -10,7 +10,7 @@ shell: exit
 	./test-kernel.sh
 
 exit: exit.c
-	$(CC) -O2 $< -o $@ --static
+	$(CC) $(CFLAGS) $(CPPFLAGS) $< -o $@ --static
 
 all:
 	@echo cd to kdebug to test a kernel build
diff --git a/libcap/Makefile b/libcap/Makefile
index 399aa66..4b96a0c 100644
--- a/libcap/Makefile
+++ b/libcap/Makefile
@@ -104,9 +104,6 @@ $(STAPSXLIBNAME): $(PSXOBJS) include/sys/psx_syscall.h
 
 ifeq ($(SHARED),yes)
 
-empty: empty.c
-	$(CC) -o $@ $<
-
 loader.txt: empty
 	$(OBJCOPY) --dump-section .interp=$@ $< /dev/null
 
@@ -134,7 +131,7 @@ cap_text.o: cap_text.c $(USE_GPERF_OUTPUT) $(INCLS)
 	$(CC) $(CFLAGS) $(CPPFLAGS) $(INCLUDE_GPERF_OUTPUT) -c $< -o $@
 
 cap_test: cap_test.c libcap.h $(CAPOBJS)
-	$(CC) $(CFLAGS) $(CPPFLAGS) $< $(CAPOBJS) -o $@
+	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $< $(CAPOBJS) -o $@
 
 libcapsotest: $(CAPLIBNAME)
 	./$(CAPLIBNAME)
diff --git a/pam_cap/Makefile b/pam_cap/Makefile
index 09083ea..b245307 100644
--- a/pam_cap/Makefile
+++ b/pam_cap/Makefile
@@ -55,20 +55,18 @@ lazylink.so: lazylink.c ../libcap/execable.h ../libcap/loader.txt
 endif
 endif
 
-pam_cap.o: pam_cap.c
-	$(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
-
 ../libcap/libcap.a:
 	$(MAKE) -C ../libcap libcap.a
 
+# Avoid $(LDFLAGS) here to avoid conflicts with --static for a in-tree
+# test binary.
 test_pam_cap: test_pam_cap.c pam_cap.c ../libcap/libcap.a
-	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -o $@ test_pam_cap.c $(LIBCAPLIB) --static
+	$(CC) $(CFLAGS) $(CPPFLAGS) -o $@ test_pam_cap.c $(LIBCAPLIB) --static
 
-testlink: test.c pam_cap.o
+testlink: test.o pam_cap.o
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $+ -lpam -ldl $(LIBCAPLIB)
 
 test: testlink test_pam_cap pam_cap.so
-	$(MAKE) testlink
 	./test_pam_cap
 	LD_LIBRARY_PATH=../libcap ./pam_cap.so
 	LD_LIBRARY_PATH=../libcap ./pam_cap.so --help
diff --git a/tests/Makefile b/tests/Makefile
index 770cffa..dd78432 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -105,20 +105,17 @@ run_exploit_test: exploit noexploit
 	@echo exploit should fail
 	$(SUDO) ./noexploit ; if [ $$? -eq 0 ]; then exit 0; else exit 1 ; fi
 
-exploit.o: exploit.c
-	$(CC) $(CFLAGS) $(CPPFLAGS) -c $<
-
 exploit: exploit.o $(DEPS)
-	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $< -o $@ $(LINKEXTRA) $(LIBCAPLIB) -lpthread
+	$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@ $(LINKEXTRA) $(LIBCAPLIB) -lpthread
 
 # Note, for some reason, the order of libraries is important to avoid
 # the exploit working for dynamic linking.
 noexploit: exploit.o $(DEPS)
-	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $< -o $@ $(LINKEXTRA) $(LIBPSXLIB) $(LIBCAPLIB)
+	$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@ $(LINKEXTRA) $(LIBPSXLIB) $(LIBCAPLIB)
 
 # This one runs in a chroot with no shared library files.
 noop: noop.c
-	$(CC) $(CFLAGS) $< -o $@ --static
+	$(CC) $(CFLAGS) $(CPPFLAGS) $< -o $@ --static
 
 clean:
 	rm -f psx_test libcap_psx_test libcap_launch_test uns_test *~