zdump: Implement DFI interface for NGDump

The NGDump DFI interface enables zgetdump to read and mount dumps created
with NGDump stand-alone dump.

Under the hood, the NGDump DFI delegates the task of reading and
parsing of ELF dump files to the ELF DFI interface dfi_elf.

Usage example 1:
----------------

$ zgetdump -i /dev/nvme0n1p1
General dump info:
  Dump format........: elf
  Version............: 1
  UTS node name......: t83lp49.lnxne.boe
  UTS kernel release.: 5.14.0-20210819.rc6.git0.efb8a921eec7.300.fc34.s390x
  UTS kernel version.: #1 SMP Thu Aug 19 00:22:04 CEST 2021
  System arch........: s390x (64 bit)
  CPU count (online).: 32
  Dump memory range..: 16384 MB

Memory map:
  0000000000000000 - 00000003ffffffff (16384 MB)

Usage example 2:
----------------

$ zgetdump /dev/nvme0n1p1 > dump.elf

Usage example 3:
----------------

$ zgetdump -m /dev/nvme0n1p1 /mnt
$ ls -l /mnt/dump.elf
$ zgetdump -u /mnt

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Tested-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdump/Makefile

@@ -54,7 +54,7 @@ OBJECTS = zgetdump.o opts.o zg.o zg_error.o zg_print.o \
 	  dt.o dt_s390sv.o dt_s390sv_ext.o \
 	  dt_s390mv.o dt_s390mv_ext.o \
 	  dt_scsi.o output.o \
-	  ngdump.o dt_ngdump.o
+	  ngdump.o dt_ngdump.o dfi_ngdump.o
 
 ifeq ("$(HAVE_FUSE)","0")
 FUSE_CFLAGS = -DHAVE_FUSE=0 -D_FILE_OFFSET_BITS=64

zdump/dfi.c

@@ -36,6 +36,7 @@ static struct dfi *dfi_vec[] = {
 	&dfi_elf,
 	&dfi_kdump,
 	&dfi_kdump_flat,
+	&dfi_ngdump,
 	NULL,
 };
 

zdump/dfi.h

@@ -242,5 +242,6 @@ extern struct dfi dfi_elf;
 extern struct dfi dfi_kdump;
 extern struct dfi dfi_kdump_flat;
 extern struct dfi dfi_devmem;
+extern struct dfi dfi_ngdump;
 
 #endif /* DFI_H */

zdump/dfi_ngdump.c

@@ -0,0 +1,143 @@
+/*
+ * zgetdump - Tool for copying and converting System z dumps
+ *
+ * NGDump dump input format
+ *
+ * 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 <err.h>
+#include <sys/mount.h>
+
+#include "lib/util_libc.h"
+
+#include "zgetdump.h"
+#include "zg.h"
+#include "dfi.h"
+#include "ngdump.h"
+
+/*
+ * File local static data
+ */
+static struct {
+	char *device;
+	char *mount_point;
+	struct ngdump_meta meta;
+} l;
+
+static int open_dump_file(void)
+{
+	char *mount_point = NULL;
+	char *filename = NULL;
+
+	mount_point = util_strdup("/tmp/zdump-ngdump-XXXXXX");
+
+	/* Create a mount point directory */
+	if (mkdtemp(mount_point) == NULL)
+		goto fail_free;
+
+	if (mount(l.device, mount_point, NGDUMP_FSTYPE, MS_RDONLY, NULL)) {
+		warnx("Could not mount \"%s\" (%s)", l.device, strerror(errno));
+		goto fail_rmdir;
+	}
+
+	util_asprintf(&filename, "%s/%s", mount_point, l.meta.file);
+
+	g.fh = zg_open(filename, O_RDONLY, ZG_CHECK);
+	free(filename);
+	if (!g.fh)
+		goto fail_umount;
+
+	l.mount_point = mount_point;
+
+	return 0;
+
+fail_umount:
+	umount(mount_point);
+fail_rmdir:
+	rmdir(mount_point);
+fail_free:
+	free(mount_point);
+	return -1;
+}
+
+static void cleanup(void)
+{
+	if (l.mount_point) {
+		zg_close(g.fh);
+		g.fh = NULL;
+		umount(l.mount_point);
+		rmdir(l.mount_point);
+		free(l.mount_point);
+		l.mount_point = NULL;
+	}
+	if (l.device) {
+		g.fh = zg_open(l.device, O_RDONLY, ZG_CHECK);
+		free(l.device);
+		l.device = NULL;
+	}
+}
+
+static int dfi_ngdump_init(void)
+{
+	/*
+	 * Copy path to the dump partition and close its file descriptor
+	 * because we don't read raw partitions with NGDump but use a
+	 * file system instead.
+	 */
+	l.device = util_strdup(g.fh->path);
+	zg_close(g.fh);
+	g.fh = NULL;
+
+	/*
+	 * First, we need to read information contained in the meta-data
+	 * file because it will tell us where a dump file on the file system
+	 * is located.
+	 */
+	if (ngdump_read_meta_from_device(l.device, &l.meta)) {
+		cleanup();
+		return -1;
+	}
+
+	/* No dump made yet but partition is a valid NGDump partition. */
+	if (!l.meta.file) {
+		cleanup();
+		return -1;
+	}
+
+	/*
+	 * Now we open the dump file and initialize the ELF DFI.
+	 * After that, the control is passed to the ELF DFI.
+	 */
+	if (open_dump_file()) {
+		cleanup();
+		return -1;
+	}
+
+	if (dfi_elf.init()) {
+		cleanup();
+		return -1;
+	}
+
+	return 0;
+}
+
+static void dfi_ngdump_exit(void)
+{
+	if (dfi_elf.exit)
+		dfi_elf.exit();
+	cleanup();
+}
+
+/*
+ * NGDump DFI operations
+ */
+struct dfi dfi_ngdump = {
+	.name		= "elf",
+	.init		= dfi_ngdump_init,
+	.exit		= dfi_ngdump_exit,
+	.feat_bits	= DFI_FEAT_COPY | DFI_FEAT_SEEK,
+};