bpf: selftests: Remove libcap usage from test_progs

This patch removes the libcap usage from test_progs.
bind_perm.c is the only user.  cap_*_effective() helpers added in the
earlier patch are directly used instead.

No other selftest binary is using libcap, so '-lcap' is also removed
from the Makefile.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20220316173835.2039334-1-kafai@fb.com

tools/testing/selftests/bpf/Makefile

@@ -25,7 +25,7 @@ CFLAGS += -g -O0 -rdynamic -Wall -Werror $(GENFLAGS) $(SAN_CFLAGS)	\
 	  -I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)		\
 	  -I$(TOOLSINCDIR) -I$(APIDIR) -I$(OUTPUT)
 LDFLAGS += $(SAN_CFLAGS)
-LDLIBS += -lcap -lelf -lz -lrt -lpthread
+LDLIBS += -lelf -lz -lrt -lpthread
 
 # Silence some warnings when compiled with clang
 ifneq ($(LLVM),)
@@ -480,7 +480,8 @@ TRUNNER_TESTS_DIR := prog_tests
 TRUNNER_BPF_PROGS_DIR := progs
 TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c	\
 			 network_helpers.c testing_helpers.c		\
-			 btf_helpers.c flow_dissector_load.h
+			 btf_helpers.c flow_dissector_load.h		\
+			 cap_helpers.c
 TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read $(OUTPUT)/bpf_testmod.ko	\
 		       ima_setup.sh					\
 		       $(wildcard progs/btf_dump_test_case_*.c)

tools/testing/selftests/bpf/prog_tests/bind_perm.c

@@ -4,9 +4,9 @@
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/socket.h>
-#include <sys/capability.h>
 
 #include "test_progs.h"
+#include "cap_helpers.h"
 #include "bind_perm.skel.h"
 
 static int duration;
@@ -49,41 +49,11 @@ void try_bind(int family, int port, int expected_errno)
 		close(fd);
 }
 
-bool cap_net_bind_service(cap_flag_value_t flag)
-{
-	const cap_value_t cap_net_bind_service = CAP_NET_BIND_SERVICE;
-	cap_flag_value_t original_value;
-	bool was_effective = false;
-	cap_t caps;
-
-	caps = cap_get_proc();
-	if (CHECK(!caps, "cap_get_proc", "errno %d", errno))
-		goto free_caps;
-
-	if (CHECK(cap_get_flag(caps, CAP_NET_BIND_SERVICE, CAP_EFFECTIVE,
-			       &original_value),
-		  "cap_get_flag", "errno %d", errno))
-		goto free_caps;
-
-	was_effective = (original_value == CAP_SET);
-
-	if (CHECK(cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_net_bind_service,
-			       flag),
-		  "cap_set_flag", "errno %d", errno))
-		goto free_caps;
-
-	if (CHECK(cap_set_proc(caps), "cap_set_proc", "errno %d", errno))
-		goto free_caps;
-
-free_caps:
-	CHECK(cap_free(caps), "cap_free", "errno %d", errno);
-	return was_effective;
-}
-
 void test_bind_perm(void)
 {
-	bool cap_was_effective;
+	const __u64 net_bind_svc_cap = 1ULL << CAP_NET_BIND_SERVICE;
 	struct bind_perm *skel;
+	__u64 old_caps = 0;
 	int cgroup_fd;
 
 	if (create_netns())
@@ -105,7 +75,8 @@ void test_bind_perm(void)
 	if (!ASSERT_OK_PTR(skel, "bind_v6_prog"))
 		goto close_skeleton;
 
-	cap_was_effective = cap_net_bind_service(CAP_CLEAR);
+	ASSERT_OK(cap_disable_effective(net_bind_svc_cap, &old_caps),
+		  "cap_disable_effective");
 
 	try_bind(AF_INET, 110, EACCES);
 	try_bind(AF_INET6, 110, EACCES);
@@ -113,8 +84,9 @@ void test_bind_perm(void)
 	try_bind(AF_INET, 111, 0);
 	try_bind(AF_INET6, 111, 0);
 
-	if (cap_was_effective)
-		cap_net_bind_service(CAP_SET);
+	if (old_caps & net_bind_svc_cap)
+		ASSERT_OK(cap_enable_effective(net_bind_svc_cap, NULL),
+			  "cap_enable_effective");
 
 close_skeleton:
 	bind_perm__destroy(skel);