Commit 4bd11e08 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

selftests/bpf: Add ref_ctr_offset selftests 



Extend attach_probe selftests to specify ref_ctr_offset for uprobe/uretprobe
and validate that its value is incremented from zero.

Turns out that once uprobe is attached with ref_ctr_offset, uretprobe for the
same location/function *has* to use ref_ctr_offset as well, otherwise
perf_event_open() fails with -EINVAL. So this test uses ref_ctr_offset for
both uprobe and uretprobe, even though for the purpose of test uprobe would be
enough.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210815070609.987780-17-andrii@kernel.org
parent 5e3b8356

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

+28 −11
Original line number Diff line number Diff line
@@ -2,14 +2,18 @@ 
#include <test_progs.h>

#include "test_attach_probe.skel.h"



/* this is how USDT semaphore is actually defined, except volatile modifier */

volatile unsigned short uprobe_ref_ctr __attribute__((unused)) __attribute((section(".probes")));



void test_attach_probe(void)

{

	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts);

	int duration = 0;

	struct bpf_link *kprobe_link, *kretprobe_link;

	struct bpf_link *uprobe_link, *uretprobe_link;

	struct test_attach_probe* skel;

	size_t uprobe_offset;

	ssize_t base_addr;

	ssize_t base_addr, ref_ctr_offset;



	base_addr = get_base_addr();

	if (CHECK(base_addr < 0, "get_base_addr",
@@ -17,6 +21,10 @@ void test_attach_probe(void) 
		return;

	uprobe_offset = get_uprobe_offset(&get_base_addr, base_addr);



	ref_ctr_offset = get_rel_offset((uintptr_t)&uprobe_ref_ctr);

	if (!ASSERT_GE(ref_ctr_offset, 0, "ref_ctr_offset"))

		return;



	skel = test_attach_probe__open_and_load();

	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))

		return;
@@ -37,20 +45,28 @@ void test_attach_probe(void) 
		goto cleanup;

	skel->links.handle_kretprobe = kretprobe_link;



	uprobe_link = bpf_program__attach_uprobe(skel->progs.handle_uprobe,

						 false /* retprobe */,

	ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_before");



	uprobe_opts.retprobe = false;

	uprobe_opts.ref_ctr_offset = ref_ctr_offset;

	uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe,

						      0 /* self pid */,

						      "/proc/self/exe",

						 uprobe_offset);

						      uprobe_offset,

						      &uprobe_opts);

	if (!ASSERT_OK_PTR(uprobe_link, "attach_uprobe"))

		goto cleanup;

	skel->links.handle_uprobe = uprobe_link;



	uretprobe_link = bpf_program__attach_uprobe(skel->progs.handle_uretprobe,

						    true /* retprobe */,

	ASSERT_GT(uprobe_ref_ctr, 0, "uprobe_ref_ctr_after");



	/* if uprobe uses ref_ctr, uretprobe has to use ref_ctr as well */

	uprobe_opts.retprobe = true;

	uprobe_opts.ref_ctr_offset = ref_ctr_offset;

	uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe,

							 -1 /* any pid */,

							 "/proc/self/exe",

						    uprobe_offset);

							 uprobe_offset, &uprobe_opts);

	if (!ASSERT_OK_PTR(uretprobe_link, "attach_uretprobe"))

		goto cleanup;

	skel->links.handle_uretprobe = uretprobe_link;
@@ -77,4 +93,5 @@ void test_attach_probe(void) 


cleanup:

	test_attach_probe__destroy(skel);

	ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_cleanup");

}

tools/testing/selftests/bpf/trace_helpers.c

+21 −0
Original line number Diff line number Diff line
@@ -202,3 +202,24 @@ ssize_t get_base_addr(void) 
	fclose(f);

	return -EINVAL;

}



ssize_t get_rel_offset(uintptr_t addr)

{

	size_t start, end, offset;

	char buf[256];

	FILE *f;



	f = fopen("/proc/self/maps", "r");

	if (!f)

		return -errno;



	while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &offset) == 4) {

		if (addr >= start && addr < end) {

			fclose(f);

			return (size_t)addr - start + offset;

		}

	}



	fclose(f);

	return -EINVAL;

}

tools/testing/selftests/bpf/trace_helpers.h

+1 −0
Original line number Diff line number Diff line
@@ -20,5 +20,6 @@ void read_trace_pipe(void); 


ssize_t get_uprobe_offset(const void *addr, ssize_t base);

ssize_t get_base_addr(void);

ssize_t get_rel_offset(uintptr_t addr);



#endif