[platform][vax] add a tool to generate a MOP header

This is used by the legacy mop protocol that many vaxes speak.

The image header is extremely minimal, but good enough to satisfy the
mopd daemon, source at https://github.com/qu1j0t3/mopd

platform/vax/mkmopheader.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2019 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+// Copy input file to output, prepending a MOP header enough to satisfy
+// the mopd daemon used to netboot an image on a VAX.
+//
+// Developed against mopd daemon at https://github.com/qu1j0t3/mopd
+
+int main(int argc, char **argv) {
+    if (argc < 3) {
+        printf("not enough args");
+usage:
+        printf("usage %s <infile> <outfile>\n", argv[0]);
+        return 1;
+    }
+
+    FILE *infp = fopen(argv[1], "rb");
+    if (!infp) {
+        printf("error opening file %s\n", argv[1]);
+        goto usage;
+    }
+
+    FILE *outfp = fopen(argv[2], "wb");
+    if (!infp) {
+        printf("error opening file %s\n", argv[2]);
+        goto usage;
+    }
+
+    // get length of the input file
+    fseek(infp, 0, SEEK_END);
+    long int len = ftell(infp);
+    //printf("input file length %#lx\n", len);
+    rewind(infp);
+
+    // round up to next 512 byte boundary
+    len = (len + 511) / 512 * 512;
+    //printf("rounded %#lx\n", len);
+
+    // generate the header
+    char buffer[512];
+    memset(buffer, 0, sizeof(buffer));
+
+    // main header
+    uint16_t isd = 0xd4;
+    uint16_t iha = 0x30;
+    uint8_t hbcnt = 1;
+    uint16_t image_type = 0xffff;
+    memcpy(buffer + 0, &isd, sizeof(isd));
+    memcpy(buffer + 2, &iha, sizeof(iha));
+    memcpy(buffer + 16, &hbcnt, sizeof(hbcnt));
+    memcpy(buffer + 510, &image_type, sizeof(image_type));
+
+    // image header (at offset isd)
+    uint16_t isize = len / 512;
+    uint16_t load_addr = 0 / 512;
+
+    memcpy(buffer + isd + 2, &isize, sizeof(isize));
+    memcpy(buffer + isd + 4, &load_addr, sizeof(load_addr));
+
+    // something else at iha
+    uint32_t xfer_addr = 0;
+    memcpy(buffer + iha, &xfer_addr, sizeof(xfer_addr));
+
+    // write the header out
+    fseek(outfp, 0, SEEK_SET);
+    fwrite(buffer, sizeof(buffer), 1, outfp);
+
+    // copy the input file to the output file
+    int written = 0;
+    while (!feof(infp)) {
+        char buf[512];
+        int count = fread(buf, 1, sizeof(buf), infp);
+        if (count == 0) {
+            break;
+        }
+        fwrite(buf, 1, count, outfp);
+        written += count;
+    }
+
+    // pad it out with zeros
+    while (written < len) {
+        char zero = 0;
+        fwrite(&zero, 1, 1, outfp);
+        written++;
+    }
+
+    fclose(infp);
+    fclose(outfp);
+
+    return 0;
+}

platform/vax/rules.mk

@@ -37,17 +37,21 @@ KERNEL_LOAD_OFFSET := 0x00100000 # loaded 1MB into physical space
 #KERNEL_BASE = 0x80000000
 KERNEL_BASE = 0
 
-#LINKER_SCRIPT += \
-#	$(BUILDDIR)/system-onesegment.ld
+# tool to add a mop header to the output binary to be net bootable
+MKMOPHEADER := $(call TOBUILDDIR,$(LOCAL_DIR)/mkmopheader)
+$(MKMOPHEADER): $(LOCAL_DIR)/mkmopheader.c
+	@$(MKDIR)
+	$(NOECHO)echo compiling host tool $@; \
+	cc -O -Wall $< -o $@
 
-# python script to generate the zynq's bootrom bootheader
-#MKBOOTHEADER := $(LOCAL_DIR)/mkbootheader.py
-#EXTRA_BUILDDEPS += $(BOOTHEADERBIN)
-#GENERATED += $(BOOTHEADERBIN)
+GENERATED += $(MKMOPHEADER)
 
-#$(BOOTHEADERBIN): $(OUTBIN) $(MKBOOTHEADER)
-#	@$(MKDIR)
-#	$(NOECHO)echo generating $@; \
-#	$(MKBOOTHEADER) $(OUTBIN) $@
+$(OUTBIN).mop: $(MKMOPHEADER) $(OUTBIN)
+	@$(MKDIR)
+	$(NOECHO)echo generating $@; \
+	$(MKMOPHEADER) $(OUTBIN) $@
+
+EXTRA_BUILDDEPS += $(OUTBIN).mop
+GENERATED += $(OUTBIN).mop
 
 include make/module.mk