libbpf: Define s390x syscall regs spec in bpf_tracing.h

Define explicit table of registers used for syscall argument passing.
Note that we need custom overrides for PT_REGS_PARM1_[CORE_]SYSCALL
macros due to the need to use BPF CO-RE and custom local pt_regs
definitions to fetch orig_gpr2, storing 1st argument.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com> # s390x
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20230120200914.3008030-16-andrii@kernel.org

tools/lib/bpf/bpf_tracing.h

@@ -157,6 +157,10 @@
 
 #elif defined(bpf_target_s390)
 
+/*
+ * https://github.com/IBM/s390x-abi/releases/download/v1.6/lzsabi_s390x.pdf
+ */
+
 struct pt_regs___s390 {
 	unsigned long orig_gpr2;
 };
@@ -168,13 +172,22 @@ struct pt_regs___s390 {
 #define __PT_PARM3_REG gprs[4]
 #define __PT_PARM4_REG gprs[5]
 #define __PT_PARM5_REG gprs[6]
+
+#define __PT_PARM1_SYSCALL_REG orig_gpr2
+#define __PT_PARM2_SYSCALL_REG __PT_PARM2_REG
+#define __PT_PARM3_SYSCALL_REG __PT_PARM3_REG
+#define __PT_PARM4_SYSCALL_REG __PT_PARM4_REG
+#define __PT_PARM5_SYSCALL_REG __PT_PARM5_REG
+#define __PT_PARM6_SYSCALL_REG gprs[7]
+#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1_CORE_SYSCALL(x)
+#define PT_REGS_PARM1_CORE_SYSCALL(x) \
+	BPF_CORE_READ((const struct pt_regs___s390 *)(x), __PT_PARM1_SYSCALL_REG)
+
 #define __PT_RET_REG gprs[14]
 #define __PT_FP_REG gprs[11]	/* Works only with CONFIG_FRAME_POINTER */
 #define __PT_RC_REG gprs[2]
 #define __PT_SP_REG gprs[15]
 #define __PT_IP_REG psw.addr
-#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1_CORE_SYSCALL(x)
-#define PT_REGS_PARM1_CORE_SYSCALL(x) BPF_CORE_READ((const struct pt_regs___s390 *)(x), orig_gpr2)
 
 #elif defined(bpf_target_arm)