pc-bios/s390-ccw: Add core files for the network bootloading program

This is just a preparation for the next steps: Add a makefile and a
stripped down copy of pc-bios/s390-ccw/main.c as a basis for the network
bootloader program, linked against the libc from SLOF already (which we
will need for SLOF's libnet). The networking code is not included yet.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1499863793-18627-10-git-send-email-thuth@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

pc-bios/s390-ccw/netmain.c

@@ -0,0 +1,136 @@
+/*
+ * S390 virtio-ccw network boot loading program
+ *
+ * Copyright 2017 Thomas Huth, Red Hat Inc.
+ *
+ * Based on the S390 virtio-ccw loading program (main.c)
+ * Copyright (c) 2013 Alexander Graf <agraf@suse.de>
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+
+#include "s390-ccw.h"
+#include "virtio.h"
+
+extern char _start[];
+
+char stack[PAGE_SIZE * 8] __attribute__((aligned(PAGE_SIZE)));
+IplParameterBlock iplb __attribute__((aligned(PAGE_SIZE)));
+
+static SubChannelId net_schid = { .one = 1 };
+static uint64_t dest_timer;
+
+static uint64_t get_timer_ms(void)
+{
+    uint64_t clk;
+
+    asm volatile(" stck %0 " : : "Q"(clk) : "memory");
+
+    /* Bit 51 is incremented each microsecond */
+    return (clk >> (63 - 51)) / 1000;
+}
+
+void set_timer(int val)
+{
+    dest_timer = get_timer_ms() + val;
+}
+
+int get_timer(void)
+{
+    return dest_timer - get_timer_ms();
+}
+
+int get_sec_ticks(void)
+{
+    return 1000;    /* number of ticks in 1 second */
+}
+
+void panic(const char *string)
+{
+    sclp_print(string);
+    for (;;) {
+        disabled_wait();
+    }
+}
+
+static bool find_net_dev(Schib *schib, int dev_no)
+{
+    int i, r;
+
+    for (i = 0; i < 0x10000; i++) {
+        net_schid.sch_no = i;
+        r = stsch_err(net_schid, schib);
+        if (r == 3 || r == -EIO) {
+            break;
+        }
+        if (!schib->pmcw.dnv) {
+            continue;
+        }
+        if (!virtio_is_supported(net_schid)) {
+            continue;
+        }
+        if (virtio_get_device_type() != VIRTIO_ID_NET) {
+            continue;
+        }
+        if (dev_no < 0 || schib->pmcw.dev == dev_no) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static void virtio_setup(void)
+{
+    Schib schib;
+    int ssid;
+    bool found = false;
+    uint16_t dev_no;
+
+    /*
+     * We unconditionally enable mss support. In every sane configuration,
+     * this will succeed; and even if it doesn't, stsch_err() can deal
+     * with the consequences.
+     */
+    enable_mss_facility();
+
+    if (store_iplb(&iplb)) {
+        IPL_assert(iplb.pbt == S390_IPL_TYPE_CCW, "IPL_TYPE_CCW expected");
+        dev_no = iplb.ccw.devno;
+        debug_print_int("device no. ", dev_no);
+        net_schid.ssid = iplb.ccw.ssid & 0x3;
+        debug_print_int("ssid ", net_schid.ssid);
+        found = find_net_dev(&schib, dev_no);
+    } else {
+        for (ssid = 0; ssid < 0x3; ssid++) {
+            net_schid.ssid = ssid;
+            found = find_net_dev(&schib, -1);
+            if (found) {
+                break;
+            }
+        }
+    }
+
+    IPL_assert(found, "No virtio net device found");
+}
+
+void main(void)
+{
+    sclp_setup();
+    sclp_print("Network boot starting...\n");
+
+    virtio_setup();
+
+    panic("Failed to load OS from network\n");
+}