selftests/bpf: Add test to exercise typedef walking

Add new bpf_fentry_test_sinfo with skb_shared_info argument and try to
access frags.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20230626212522.2414485-2-sdf@google.com

net/bpf/test_run.c

@@ -555,6 +555,10 @@ __bpf_kfunc u32 bpf_fentry_test9(u32 *a)
 	return *a;
 }
 
+void noinline bpf_fentry_test_sinfo(struct skb_shared_info *sinfo)
+{
+}
+
 __bpf_kfunc int bpf_modify_return_test(int a, int *b)
 {
 	*b += 1;

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

@@ -58,6 +58,7 @@
 #include "verifier_stack_ptr.skel.h"
 #include "verifier_subprog_precision.skel.h"
 #include "verifier_subreg.skel.h"
+#include "verifier_typedef.skel.h"
 #include "verifier_uninit.skel.h"
 #include "verifier_unpriv.skel.h"
 #include "verifier_unpriv_perf.skel.h"
@@ -159,6 +160,7 @@ void test_verifier_spin_lock(void)            { RUN(verifier_spin_lock); }
 void test_verifier_stack_ptr(void)            { RUN(verifier_stack_ptr); }
 void test_verifier_subprog_precision(void)    { RUN(verifier_subprog_precision); }
 void test_verifier_subreg(void)               { RUN(verifier_subreg); }
+void test_verifier_typedef(void)              { RUN(verifier_typedef); }
 void test_verifier_uninit(void)               { RUN(verifier_uninit); }
 void test_verifier_unpriv(void)               { RUN(verifier_unpriv); }
 void test_verifier_unpriv_perf(void)          { RUN(verifier_unpriv_perf); }

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

+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+SEC("fentry/bpf_fentry_test_sinfo")
+__description("typedef: resolve")
+__success __retval(0)
+__naked void resolve_typedef(void)
+{
+	asm volatile ("					\
+	r1 = *(u64 *)(r1 +0);				\
+	r2 = *(u64 *)(r1 +%[frags_offs]);		\
+	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm_const(frags_offs,
+		      offsetof(struct skb_shared_info, frags))
+	: __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";