samples: bpf: syscall_nrs: use mmap2 if defined

For arm32 xdp sockets mmap2 is preferred, so use it if it's defined.
Declaration of __NR_mmap can be skipped and it breaks build.

Signed-off-by: Ivan Khoronzhuk <[e-mail]>
Acked-by: Jonathan Lemon <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

samples/bpf/syscall_nrs.c

···
 	COMMENT("Linux system call numbers.");
 	SYSNR(__NR_write);
 	SYSNR(__NR_read);
+#ifdef __NR_mmap2
+	SYSNR(__NR_mmap2);
+#endif
+#ifdef __NR_mmap
 	SYSNR(__NR_mmap);
+#endif
+
 }

samples/bpf/tracex5_kern.c

···
 	return 0;
 }
 
-PROG(SYS__NR_mmap)(struct pt_regs *ctx)
+#ifdef __NR_mmap2
+PROG(SYS__NR_mmap2)(struct pt_regs *ctx)
 {
-	char fmt[] = "mmap\n";
+	char fmt[] = "mmap2\n";
+
 	bpf_trace_printk(fmt, sizeof(fmt));
 	return 0;
 }
+#endif
+
+#ifdef __NR_mmap
+PROG(SYS__NR_mmap)(struct pt_regs *ctx)
+{
+	char fmt[] = "mmap\n";
+
+	bpf_trace_printk(fmt, sizeof(fmt));
+	return 0;
+}
+#endif
 
 char _license[] SEC("license") = "GPL";
 u32 _version SEC("version") = LINUX_VERSION_CODE;