selftests/bpf: Tests execution support for test_loader.c

Extends test_loader.c:test_loader__run_subtests() by allowing to
execute BPF_PROG_TEST_RUN bpf command for selected programs.
This is similar to functionality provided by test_verifier.

Adds the following new attributes controlling test_loader behavior:

  __retval(...)
  __retval_unpriv(...)

* If any of these attributes is present, the annotated program would
  be executed using libbpf's bpf_prog_test_run_opts() function.
* If __retval is present, the test run would be done for program
  loaded in privileged mode.
* If __retval_unpriv is present, the test run would be done for
  program loaded in unprivileged mode.
* To mimic test_verifier behavior, the actual run is initiated in
  privileged mode.
* The value returned by a test run is compared against retval
  parameter.

The retval attribute takes one of the following parameters:
- a decimal number
- a hexadecimal number (must start from '0x')
- any of a three special literals (provided for compatibility with
  test_verifier):
  - INT_MIN
  - POINTER_VALUE
  - TEST_DATA_LEN

An example of the attribute usage:

  SEC("socket")
  __description("return 42")
  __success __success_unpriv __retval(42)
  __naked void the_42_test(void)
  {
          asm volatile ("                                 \
          r0 = 42;                                        \
          exit;                                           \
  "       ::: __clobber_all);
  }

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20230325025524.144043-5-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
index 9defc217a5bd..6e3b4903c541 100644
--- a/tools/testing/selftests/bpf/progs/bpf_misc.h
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -30,6 +30,15 @@
  * __failure         Expect program load failure in privileged mode.
  * __failure_unpriv  Expect program load failure in unprivileged mode.
  *
+ * __retval          Execute the program using BPF_PROG_TEST_RUN command,
+ *                   expect return value to match passed parameter:
+ *                   - a decimal number
+ *                   - a hexadecimal number, when starts from 0x
+ *                   - literal INT_MIN
+ *                   - literal POINTER_VALUE (see definition below)
+ *                   - literal TEST_DATA_LEN (see definition below)
+ * __retval_unpriv   Same, but load program in unprivileged mode.
+ *
  * __description     Text to be used instead of a program name for display
  *                   and filtering purposes.
  *
@@ -54,6 +63,8 @@
 #define __success_unpriv	__attribute__((btf_decl_tag("comment:test_expect_success_unpriv")))
 #define __log_level(lvl)	__attribute__((btf_decl_tag("comment:test_log_level="#lvl)))
 #define __flag(flag)		__attribute__((btf_decl_tag("comment:test_prog_flags="#flag)))
+#define __retval(val)		__attribute__((btf_decl_tag("comment:test_retval="#val)))
+#define __retval_unpriv(val)	__attribute__((btf_decl_tag("comment:test_retval_unpriv="#val)))
 
 /* Convenience macro for use with 'asm volatile' blocks */
 #define __naked __attribute__((naked))
@@ -65,6 +76,10 @@
 #define __imm_ptr(name) [name]"p"(&name)
 #define __imm_insn(name, expr) [name]"i"(*(long *)&(expr))
 
+/* Magic constants used with __retval() */
+#define POINTER_VALUE	0xcafe4all
+#define TEST_DATA_LEN	64
+
 #if defined(__TARGET_ARCH_x86)
 #define SYSCALL_WRAPPER 1
 #define SYS_PREFIX "__x64_"