selftests/bpf: Attach to fopen()/fclose() in attach_probe

malloc() and free() may be completely replaced by sanitizers, use
fopen() and fclose() instead.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230210001210.395194-7-iii@linux.ibm.com

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

@@ -33,8 +33,8 @@ void test_attach_probe(void)
 	struct test_attach_probe* skel;
 	ssize_t uprobe_offset, ref_ctr_offset;
 	struct bpf_link *uprobe_err_link;
+	FILE *devnull;
 	bool legacy;
-	char *mem;
 
 	/* Check if new-style kprobe/uprobe API is supported.
 	 * Kernels that support new FD-based kprobe and uprobe BPF attachment
@@ -147,7 +147,7 @@ void test_attach_probe(void)
 	/* test attach by name for a library function, using the library
 	 * as the binary argument. libc.so.6 will be resolved via dlopen()/dlinfo().
 	 */
-	uprobe_opts.func_name = "malloc";
+	uprobe_opts.func_name = "fopen";
 	uprobe_opts.retprobe = false;
 	skel->links.handle_uprobe_byname2 =
 			bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe_byname2,
@@ -157,7 +157,7 @@ void test_attach_probe(void)
 	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname2, "attach_uprobe_byname2"))
 		goto cleanup;
 
-	uprobe_opts.func_name = "free";
+	uprobe_opts.func_name = "fclose";
 	uprobe_opts.retprobe = true;
 	skel->links.handle_uretprobe_byname2 =
 			bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe_byname2,
@@ -195,8 +195,8 @@ void test_attach_probe(void)
 	usleep(1);
 
 	/* trigger & validate shared library u[ret]probes attached by name */
-	mem = malloc(1);
-	free(mem);
+	devnull = fopen("/dev/null", "r");
+	fclose(devnull);
 
 	/* trigger & validate uprobe & uretprobe */
 	trigger_func();

tools/testing/selftests/bpf/progs/test_attach_probe.c

@@ -92,18 +92,19 @@ int handle_uretprobe_byname(struct pt_regs *ctx)
 }
 
 SEC("uprobe")
-int handle_uprobe_byname2(struct pt_regs *ctx)
+int BPF_UPROBE(handle_uprobe_byname2, const char *pathname, const char *mode)
 {
-	unsigned int size = PT_REGS_PARM1(ctx);
+	char mode_buf[2] = {};
 
-	/* verify malloc size */
-	if (size == 1)
+	/* verify fopen mode */
+	bpf_probe_read_user(mode_buf, sizeof(mode_buf), mode);
+	if (mode_buf[0] == 'r' && mode_buf[1] == 0)
 		uprobe_byname2_res = 7;
 	return 0;
 }
 
 SEC("uretprobe")
-int handle_uretprobe_byname2(struct pt_regs *ctx)
+int BPF_URETPROBE(handle_uretprobe_byname2, void *ret)
 {
 	uretprobe_byname2_res = 8;
 	return 0;