selftests/bpf: Add notion of auxiliary programs for test_loader

In order to express test cases that use bpf_tail_call() intrinsic it
is necessary to have several programs to be loaded at a time.
This commit adds __auxiliary annotation to the set of annotations
supported by test_loader.c. Programs marked as auxiliary are always
loaded but are not treated as a separate test.

For example:

    void dummy_prog1(void);

    struct {
            __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
            __uint(max_entries, 4);
            __uint(key_size, sizeof(int));
            __array(values, void (void));
    } prog_map SEC(".maps") = {
            .values = {
                    [0] = (void *) &dummy_prog1,
            },
    };

    SEC("tc")
    __auxiliary
    __naked void dummy_prog1(void) {
            asm volatile ("r0 = 42; exit;");
    }

    SEC("tc")
    __description("reference tracking: check reference or tail call")
    __success __retval(0)
    __naked void check_reference_or_tail_call(void)
    {
            asm volatile (
            "r2 = %[prog_map] ll;"
            "r3 = 0;"
            "call %[bpf_tail_call];"
            "r0 = 0;"
            "exit;"
            :: __imm(bpf_tail_call),
            :  __clobber_all);
    }

Signed-off-by: Eduard Zingerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
index 3b307de8dab9..d3c1217ba79a 100644
--- a/tools/testing/selftests/bpf/progs/bpf_misc.h
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -53,6 +53,10 @@
  *                   - A numeric value.
  *                   Multiple __flag attributes could be specified, the final flags
  *                   value is derived by applying binary "or" to all specified values.
+ *
+ * __auxiliary         Annotated program is not a separate test, but used as auxiliary
+ *                     for some other test cases and should always be loaded.
+ * __auxiliary_unpriv  Same, but load program in unprivileged mode.
  */
 #define __msg(msg)		__attribute__((btf_decl_tag("comment:test_expect_msg=" msg)))
 #define __failure		__attribute__((btf_decl_tag("comment:test_expect_failure")))
@@ -65,6 +69,8 @@
 #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)))
+#define __auxiliary		__attribute__((btf_decl_tag("comment:test_auxiliary")))
+#define __auxiliary_unpriv	__attribute__((btf_decl_tag("comment:test_auxiliary_unpriv")))
 
 /* Convenience macro for use with 'asm volatile' blocks */
 #define __naked __attribute__((naked))