zipl: add basic support of environment block by zipl(8)

When installing a boot record for "ipl" and "menu" job, always add
an environment block as a boot component located in bootmap file
at offset alinged on file system block size boundary. When adding,
first try to import environment from a file at location specified
by newly introduced "--environment" zipl option, or by default at
"/etc/ziplenv". If nothing was imported, then add a blank environment
block. Optionally print the content of the environment block.

Store environment block size and address (as of boot component) in
stage3_parms.

Change interface of add_ipl_program(): add 2 additional arguments:
a pointer to bootmap file name and a predicate indicating if we
need to add environment block as a boot component.

Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Eduard Shishkin <edward6@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zipl/src/bootmap_header.c

@@ -0,0 +1,64 @@
+/*
+ * zipl - zSeries Initial Program Loader tool
+ *
+ * Functions to manipulate with bootmap header
+ *
+ * Copyright IBM Corp. 2021
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include <errno.h>
+#include <string.h>
+
+#include "bootmap.h"
+#include "error.h"
+#include "misc.h"
+
+int bootmap_header_init(int fd)
+{
+	struct bootmap_header bh = {
+		.header_text =
+		"zSeries bootmap file\n"
+		"created by zIPL\n",
+		.version = BOOTMAP_HEADER_VERSION
+	};
+
+	return misc_write(fd, &bh, sizeof(bh));
+}
+
+static int bootmap_header_access(int fd, struct bootmap_header *bh, int read)
+{
+	off_t cur_off;
+	int ret;
+
+	cur_off = lseek(fd, 0, SEEK_CUR);
+	if (cur_off == -1) {
+		error_reason(strerror(errno));
+		return -1;
+	}
+	if (lseek(fd, 0, SEEK_SET) == -1) {
+		error_reason(strerror(errno));
+		ret = -1;
+		goto out;
+	}
+	if (read)
+		ret = misc_read(fd, bh, sizeof(*bh));
+	else
+		ret = misc_write(fd, bh, sizeof(*bh));
+out:
+	if (lseek(fd, cur_off, SEEK_SET) == -1)
+		return -1;
+	return ret;
+}
+
+int bootmap_header_read(int fd, struct bootmap_header *bh)
+{
+	return bootmap_header_access(fd, bh, 1);
+}
+
+int bootmap_header_write(int fd, struct bootmap_header *bh)
+{
+	return bootmap_header_access(fd, bh, 0);
+}