selftests/bpf: Tests with may_goto and jumps to the 1st insn

Add few tests with may_goto and jumps to the 1st insn.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240619011859.79334-2-alexei.starovoitov@gmail.com

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

@@ -307,6 +307,100 @@ int iter_limit_bug(struct __sk_buff *skb)
 	return 0;
 }
 
+SEC("socket")
+__success __retval(0)
+__naked void ja_and_may_goto(void)
+{
+	asm volatile ("			\
+l0_%=:	.byte 0xe5; /* may_goto */	\
+	.byte 0; /* regs */		\
+	.short 1; /* off 1 */		\
+	.long 0; /* imm */		\
+	goto l0_%=;			\
+	r0 = 0;				\
+	exit;				\
+"	::: __clobber_common);
+}
+
+SEC("socket")
+__success __retval(0)
+__naked void ja_and_may_goto2(void)
+{
+	asm volatile ("			\
+l0_%=:	r0 = 0;				\
+	.byte 0xe5; /* may_goto */	\
+	.byte 0; /* regs */		\
+	.short 1; /* off 1 */		\
+	.long 0; /* imm */		\
+	goto l0_%=;			\
+	r0 = 0;				\
+	exit;				\
+"	::: __clobber_common);
+}
+
+SEC("socket")
+__success __retval(0)
+__naked void jlt_and_may_goto(void)
+{
+	asm volatile ("			\
+l0_%=:	call %[bpf_jiffies64];		\
+	.byte 0xe5; /* may_goto */	\
+	.byte 0; /* regs */		\
+	.short 1; /* off 1 */		\
+	.long 0; /* imm */		\
+	if r0 < 10 goto l0_%=;		\
+	r0 = 0;				\
+	exit;				\
+"	:: __imm(bpf_jiffies64)
+	: __clobber_all);
+}
+
+#if (defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86) || \
+	(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64) || \
+	defined(__TARGET_ARCH_arm) || defined(__TARGET_ARCH_s390) || \
+	defined(__TARGET_ARCH_loongarch)) && \
+	__clang_major__ >= 18
+SEC("socket")
+__success __retval(0)
+__naked void gotol_and_may_goto(void)
+{
+	asm volatile ("			\
+l0_%=:	r0 = 0;				\
+	.byte 0xe5; /* may_goto */	\
+	.byte 0; /* regs */		\
+	.short 1; /* off 1 */		\
+	.long 0; /* imm */		\
+	gotol l0_%=;			\
+	r0 = 0;				\
+	exit;				\
+"	::: __clobber_common);
+}
+#endif
+
+SEC("socket")
+__success __retval(0)
+__naked void ja_and_may_goto_subprog(void)
+{
+	asm volatile ("			\
+	call subprog_with_may_goto;	\
+	exit;				\
+"	::: __clobber_all);
+}
+
+static __naked __noinline __used
+void subprog_with_may_goto(void)
+{
+	asm volatile ("			\
+l0_%=:	.byte 0xe5; /* may_goto */	\
+	.byte 0; /* regs */		\
+	.short 1; /* off 1 */		\
+	.long 0; /* imm */		\
+	goto l0_%=;			\
+	r0 = 0;				\
+	exit;				\
+"	::: __clobber_all);
+}
+
 #define ARR_SZ 1000000
 int zero;
 char arr[ARR_SZ];