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

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/20230210001210.395194-6-iii@linux.ibm.com

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

@@ -16,10 +16,10 @@ static noinline int autoattach_trigger_func(int arg1, int arg2, int arg3,
 
 void test_uprobe_autoattach(void)
 {
+	const char *devnull_str = "/dev/null";
 	struct test_uprobe_autoattach *skel;
 	int trigger_ret;
-	size_t malloc_sz = 1;
-	char *mem;
+	FILE *devnull;
 
 	skel = test_uprobe_autoattach__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "skel_open"))
@@ -36,16 +36,18 @@ void test_uprobe_autoattach(void)
 	skel->bss->test_pid = getpid();
 
 	/* trigger & validate shared library u[ret]probes attached by name */
-	mem = malloc(malloc_sz);
+	devnull = fopen(devnull_str, "r");
 
 	ASSERT_EQ(skel->bss->uprobe_byname_parm1, 1, "check_uprobe_byname_parm1");
 	ASSERT_EQ(skel->bss->uprobe_byname_ran, 1, "check_uprobe_byname_ran");
 	ASSERT_EQ(skel->bss->uretprobe_byname_rc, trigger_ret, "check_uretprobe_byname_rc");
 	ASSERT_EQ(skel->bss->uretprobe_byname_ret, trigger_ret, "check_uretprobe_byname_ret");
 	ASSERT_EQ(skel->bss->uretprobe_byname_ran, 2, "check_uretprobe_byname_ran");
-	ASSERT_EQ(skel->bss->uprobe_byname2_parm1, malloc_sz, "check_uprobe_byname2_parm1");
+	ASSERT_EQ(skel->bss->uprobe_byname2_parm1, (__u64)(long)devnull_str,
+		  "check_uprobe_byname2_parm1");
 	ASSERT_EQ(skel->bss->uprobe_byname2_ran, 3, "check_uprobe_byname2_ran");
-	ASSERT_EQ(skel->bss->uretprobe_byname2_rc, mem, "check_uretprobe_byname2_rc");
+	ASSERT_EQ(skel->bss->uretprobe_byname2_rc, (__u64)(long)devnull,
+		  "check_uretprobe_byname2_rc");
 	ASSERT_EQ(skel->bss->uretprobe_byname2_ran, 4, "check_uretprobe_byname2_ran");
 
 	ASSERT_EQ(skel->bss->a[0], 1, "arg1");
@@ -67,7 +69,7 @@ void test_uprobe_autoattach(void)
 	ASSERT_EQ(skel->bss->a[7], 8, "arg8");
 #endif
 
-	free(mem);
+	fclose(devnull);
 cleanup:
 	test_uprobe_autoattach__destroy(skel);
 }

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

@@ -13,9 +13,9 @@ int uprobe_byname_ran = 0;
 int uretprobe_byname_rc = 0;
 int uretprobe_byname_ret = 0;
 int uretprobe_byname_ran = 0;
-size_t uprobe_byname2_parm1 = 0;
+u64 uprobe_byname2_parm1 = 0;
 int uprobe_byname2_ran = 0;
-char *uretprobe_byname2_rc = NULL;
+u64 uretprobe_byname2_rc = 0;
 int uretprobe_byname2_ran = 0;
 
 int test_pid;
@@ -88,28 +88,28 @@ int BPF_URETPROBE(handle_uretprobe_byname, int ret)
 }
 
 
-SEC("uprobe/libc.so.6:malloc")
-int handle_uprobe_byname2(struct pt_regs *ctx)
+SEC("uprobe/libc.so.6:fopen")
+int BPF_UPROBE(handle_uprobe_byname2, const char *pathname, const char *mode)
 {
 	int pid = bpf_get_current_pid_tgid() >> 32;
 
 	/* ignore irrelevant invocations */
 	if (test_pid != pid)
 		return 0;
-	uprobe_byname2_parm1 = PT_REGS_PARM1_CORE(ctx);
+	uprobe_byname2_parm1 = (u64)(long)pathname;
 	uprobe_byname2_ran = 3;
 	return 0;
 }
 
-SEC("uretprobe/libc.so.6:malloc")
-int handle_uretprobe_byname2(struct pt_regs *ctx)
+SEC("uretprobe/libc.so.6:fopen")
+int BPF_URETPROBE(handle_uretprobe_byname2, void *ret)
 {
 	int pid = bpf_get_current_pid_tgid() >> 32;
 
 	/* ignore irrelevant invocations */
 	if (test_pid != pid)
 		return 0;
-	uretprobe_byname2_rc = (char *)PT_REGS_RC_CORE(ctx);
+	uretprobe_byname2_rc = (u64)(long)ret;
 	uretprobe_byname2_ran = 4;
 	return 0;
 }