Merge branch 'bpf: Add helpers to access traced function arguments'

Jiri Olsa says:

====================
Add new helpers to access traced function arguments that
came out of the trampoline batch changes [1].

  Get n-th argument of the traced function:
    long bpf_get_func_arg(void *ctx, u32 n, u64 *value)

  Get return value of the traced function:
    long bpf_get_func_ret(void *ctx, u64 *value)

  Get arguments count of the traced funtion:
    long bpf_get_func_arg_cnt(void *ctx)

v2 changes:
  - added acks
  - updated stack diagram
  - return -EOPNOTSUPP instead of -EINVAL in bpf_get_func_ret
  - removed gpl_only for all helpers
  - added verifier fix to allow proper arguments checks,
    Andrii asked for checking also 'int *b' argument in
    bpf_modify_return_test programs and it turned out that it's currently
    not supported by verifier - we can't read argument that is int pointer,
    so I had to add verifier change to allow that + adding verifier selftest
  - checking all arguments in bpf_modify_return_test test programs
  - moved helpers proto gets in tracing_prog_func_proto with attach type check

thanks,
jirka

[1] https://lore.kernel.org/bpf/20211118112455.475349-1-jolsa@kernel.org/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/get_func_args_test.c b/tools/testing/selftests/bpf/prog_tests/get_func_args_test.c
new file mode 100644
index 000000000000..85c427119fe9
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/get_func_args_test.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "get_func_args_test.skel.h"
+
+void test_get_func_args_test(void)
+{
+	struct get_func_args_test *skel = NULL;
+	__u32 duration = 0, retval;
+	int err, prog_fd;
+
+	skel = get_func_args_test__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "get_func_args_test__open_and_load"))
+		return;
+
+	err = get_func_args_test__attach(skel);
+	if (!ASSERT_OK(err, "get_func_args_test__attach"))
+		goto cleanup;
+
+	/* This runs bpf_fentry_test* functions and triggers
+	 * fentry/fexit programs.
+	 */
+	prog_fd = bpf_program__fd(skel->progs.test1);
+	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+				NULL, NULL, &retval, &duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 0, "test_run");
+
+	/* This runs bpf_modify_return_test function and triggers
+	 * fmod_ret_test and fexit_test programs.
+	 */
+	prog_fd = bpf_program__fd(skel->progs.fmod_ret_test);
+	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+				NULL, NULL, &retval, &duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 1234, "test_run");
+
+	ASSERT_EQ(skel->bss->test1_result, 1, "test1_result");
+	ASSERT_EQ(skel->bss->test2_result, 1, "test2_result");
+	ASSERT_EQ(skel->bss->test3_result, 1, "test3_result");
+	ASSERT_EQ(skel->bss->test4_result, 1, "test4_result");
+
+cleanup:
+	get_func_args_test__destroy(skel);
+}