selftests/bpf: Uprobe tests should verify param/return values

uprobe/uretprobe tests don't do any validation of arguments/return values,
and without this we can't be sure we are attached to the right function,
or that we are indeed attached to a uprobe or uretprobe.  To fix this
record argument and return value for auto-attached functions and ensure
these match expectations.  Also need to filter by pid to ensure we do
not pick up stray malloc()s since auto-attach traces libc system-wide.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1649245431-29956-4-git-send-email-alan.maguire@oracle.com

1 files changed, 32 insertions, 11 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_uprobe_autoattach.c b/tools/testing/selftests/bpf/progs/test_uprobe_autoattach.c
index b442fb5ef54b..ab75522e2eeb 100644
--- a/tools/testing/selftests/bpf/progs/test_uprobe_autoattach.c
+++ b/tools/testing/selftests/bpf/progs/test_uprobe_autoattach.c
@@ -1,15 +1,22 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2022, Oracle and/or its affiliates. */
 
-#include <linux/ptrace.h>
-#include <linux/bpf.h>
+#include "vmlinux.h"
+
+#include <bpf/bpf_core_read.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-int uprobe_byname_res = 0;
-int uretprobe_byname_res = 0;
-int uprobe_byname2_res = 0;
-int uretprobe_byname2_res = 0;
+int uprobe_byname_parm1 = 0;
+int uprobe_byname_ran = 0;
+int uretprobe_byname_rc = 0;
+int uretprobe_byname_ran = 0;
+size_t uprobe_byname2_parm1 = 0;
+int uprobe_byname2_ran = 0;
+char *uretprobe_byname2_rc = NULL;
+int uretprobe_byname2_ran = 0;
+
+int test_pid;
 
 /* This program cannot auto-attach, but that should not stop other
  * programs from attaching.
@@ -23,14 +30,16 @@ int handle_uprobe_noautoattach(struct pt_regs *ctx)
 SEC("uprobe//proc/self/exe:autoattach_trigger_func")
 int handle_uprobe_byname(struct pt_regs *ctx)
 {
-	uprobe_byname_res = 1;
+	uprobe_byname_parm1 = PT_REGS_PARM1_CORE(ctx);
+	uprobe_byname_ran = 1;
 	return 0;
 }
 
 SEC("uretprobe//proc/self/exe:autoattach_trigger_func")
 int handle_uretprobe_byname(struct pt_regs *ctx)
 {
-	uretprobe_byname_res = 2;
+	uretprobe_byname_rc = PT_REGS_RC_CORE(ctx);
+	uretprobe_byname_ran = 2;
 	return 0;
 }
 
@@ -38,14 +47,26 @@ int handle_uretprobe_byname(struct pt_regs *ctx)
 SEC("uprobe/libc.so.6:malloc")
 int handle_uprobe_byname2(struct pt_regs *ctx)
 {
-	uprobe_byname2_res = 3;
+	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_ran = 3;
 	return 0;
 }
 
-SEC("uretprobe/libc.so.6:free")
+SEC("uretprobe/libc.so.6:malloc")
 int handle_uretprobe_byname2(struct pt_regs *ctx)
 {
-	uretprobe_byname2_res = 4;
+	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_ran = 4;
 	return 0;
 }