DEBUG: selftests/bpf: Show lskel attach broken (ringbuf_overwrite)

Attaching BPF kprobe program via lskel fails silently on armhf 32-bit: the
program is never called when triggered and results in many strange test
failures, especially since testcode often neglects unhappy paths.

Before:

root@qemu-armhf: # ./test_progs -a ringbuf/ringbuf_overwrite_mode
Process ./test_progs created; pid = 125
ringbuf_overwrite_mode_subtest:PASS:skel_open 0 nsec
ringbuf_overwrite_mode_subtest:PASS:skel_load 0 nsec
ringbuf_overwrite_mode_subtest:PASS:skel_attach 0 nsec
ringbuf_overwrite_mode_subtest:PASS:reserve 1 0 nsec
ringbuf_overwrite_mode_subtest:PASS:reserve 2 0 nsec
ringbuf_overwrite_mode_subtest:FAIL:reserve 3 unexpected reserve 3: actual 0 != expected 1
ringbuf_overwrite_mode_subtest:PASS:reserve 4 0 nsec
ringbuf_overwrite_mode_subtest:PASS:reserve 5 0 nsec
ringbuf_overwrite_mode_subtest:FAIL:check_ring_size unexpected check_ring_size: actual 0 != expected 4096
ringbuf_overwrite_mode_subtest:FAIL:check_avail_size unexpected check_avail_size: actual 0 != expected 3040
ringbuf_overwrite_mode_subtest:PASS:check_cons_pos 0 nsec
ringbuf_overwrite_mode_subtest:FAIL:check_prod_pos unexpected check_prod_pos: actual 0 != expected 5096
ringbuf_overwrite_mode_subtest:FAIL:check_over_pos unexpected check_over_pos: actual 0 != expected 2056
torvalds#358/5   ringbuf/ringbuf_overwrite_mode:FAIL
torvalds#358     ringbuf:FAIL

After patch switching to use libbpf skel instead of lskel:

root@qemu-armhf: # ./test_progs -a ringbuf/ringbuf_overwrite_mode
torvalds#358/5   ringbuf/ringbuf_overwrite_mode:OK
torvalds#358     ringbuf:OK

Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>

Author: guidosarducci

tools/testing/selftests/bpf/Makefile

@@ -507,8 +507,7 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
 
 LSKELS := fexit_sleep.c trace_printk.c trace_vprintk.c map_ptr_kern.c 	\
 	core_kern.c core_kern_overflow.c test_ringbuf.c			\
-	test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c    \
-	test_ringbuf_overwrite.c
+	test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c
 
 LSKELS_SIGNED := fentry_test.c fexit_test.c atomics.c
 

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

@@ -17,7 +17,7 @@
 #include "test_ringbuf_n.lskel.h"
 #include "test_ringbuf_map_key.lskel.h"
 #include "test_ringbuf_write.lskel.h"
-#include "test_ringbuf_overwrite.lskel.h"
+#include "test_ringbuf_overwrite.skel.h"
 
 #define EDONE 7777
 
@@ -502,11 +502,11 @@ static void ringbuf_overwrite_mode_subtest(void)
 {
 	unsigned long size, len1, len2, len3, len4, len5;
 	unsigned long expect_avail_data, expect_prod_pos, expect_over_pos;
-	struct test_ringbuf_overwrite_lskel *skel;
+	struct test_ringbuf_overwrite *skel;
 	int page_size = getpagesize();
 	int err;
 
-	skel = test_ringbuf_overwrite_lskel__open();
+	skel = test_ringbuf_overwrite__open();
 	if (!ASSERT_OK_PTR(skel, "skel_open"))
 		return;
 
@@ -517,7 +517,7 @@ static void ringbuf_overwrite_mode_subtest(void)
 	len4 = len3 - 8;
 	len5 = len3; /* retry with len3 */
 
-	skel->maps.ringbuf.max_entries = size;
+	bpf_map__set_max_entries(skel->maps.ringbuf, size);
 	skel->rodata->LEN1 = len1;
 	skel->rodata->LEN2 = len2;
 	skel->rodata->LEN3 = len3;
@@ -526,11 +526,11 @@ static void ringbuf_overwrite_mode_subtest(void)
 
 	skel->bss->pid = getpid();
 
-	err = test_ringbuf_overwrite_lskel__load(skel);
+	err = test_ringbuf_overwrite__load(skel);
 	if (!ASSERT_OK(err, "skel_load"))
 		goto cleanup;
 
-	err = test_ringbuf_overwrite_lskel__attach(skel);
+	err = test_ringbuf_overwrite__attach(skel);
 	if (!ASSERT_OK(err, "skel_attach"))
 		goto cleanup;
 
@@ -555,9 +555,9 @@ static void ringbuf_overwrite_mode_subtest(void)
 	expect_over_pos = len1 + BPF_RINGBUF_HDR_SZ;
 	ASSERT_EQ(skel->bss->over_pos, expect_over_pos, "check_over_pos");
 
-	test_ringbuf_overwrite_lskel__detach(skel);
+	test_ringbuf_overwrite__detach(skel);
 cleanup:
-	test_ringbuf_overwrite_lskel__destroy(skel);
+	test_ringbuf_overwrite__destroy(skel);
 }
 
 void test_ringbuf(void)