From b573cc7f4129bc3216f5953978be0a7bd29bfe69 Mon Sep 17 00:00:00 2001
From: Fabian Keil <fk@fabiankeil.de>
Date: Thu, 4 Nov 2021 16:27:31 +0100
Subject: [PATCH 288/310] sbin/geom/misc: Add g_metadata_search()

... which is needed to implement a "search" subcommand for geli.

Obtained from: ElectroBSD
---
 sbin/geom/misc/subr.c | 75 +++++++++++++++++++++++++++++++++++++++++++
 sbin/geom/misc/subr.h |  3 ++
 2 files changed, 78 insertions(+)

diff --git a/sbin/geom/misc/subr.c b/sbin/geom/misc/subr.c
index 3985ae56edc6..5141ce256c67 100644
--- a/sbin/geom/misc/subr.c
+++ b/sbin/geom/misc/subr.c
@@ -273,6 +273,81 @@ g_metadata_read(const char *name, unsigned char *md, size_t size,
 	return (error);
 }
 
+int
+g_metadata_search(const char *name, unsigned char *md, size_t size,
+   const char *magic, off_t *metadata_offset)
+{
+	struct std_metadata stdmd;
+	unsigned char *sector;
+	ssize_t sectorsize;
+	off_t mediasize;
+	int error, fd;
+	off_t offset;
+
+	*metadata_offset = 0;
+	sector = NULL;
+	error = 0;
+
+	fd = g_open(name, 0);
+	if (fd == -1)
+		return (errno);
+	mediasize = g_mediasize(fd);
+	if (mediasize == -1) {
+		error = errno;
+		goto out;
+	}
+	sectorsize = g_sectorsize(fd);
+	if (sectorsize == -1) {
+		error = errno;
+		goto out;
+	}
+	assert(sectorsize >= (ssize_t)size);
+	sector = malloc(sectorsize);
+	if (sector == NULL) {
+		error = ENOMEM;
+		goto out;
+	}
+
+	fprintf(stderr, "Searching for %s metadata on %s.\n", magic, name);
+
+	offset = mediasize - sectorsize;
+	while (offset > 0) {
+		if (offset % 1073741824 == 0) {
+		       /* Should be reworded */
+		       fprintf(stderr,
+			    "Next search offset is %ju.\n", (uintmax_t)offset);
+		}
+		if (pread(fd, sector, sectorsize, offset) !=
+		    sectorsize) {
+			error = errno;
+			fprintf(stderr, "Failed to read at offset %ju.\n",
+			    (uintmax_t)offset);
+			goto out;
+		}
+		if (magic != NULL) {
+			std_metadata_decode(sector, &stdmd);
+			if (strcmp(stdmd.md_magic, magic) != 0) {
+				offset -= sectorsize;
+				continue;
+			} else {
+				fprintf(stderr,
+				    "Found %s meta data at offset %ju.\n",
+				    magic, (uintmax_t)offset);
+				*metadata_offset = offset;
+				break;
+			}
+		}
+		offset -= sectorsize;
+	}
+
+	bcopy(sector, md, size);
+out:
+	if (sector != NULL)
+		free(sector);
+	g_close(fd);
+	return (error);
+}
+
 /* 
  * Actually write the GEOM label to the provider
  *
diff --git a/sbin/geom/misc/subr.h b/sbin/geom/misc/subr.h
index 579c94c21491..9a05d47f2c6f 100644
--- a/sbin/geom/misc/subr.h
+++ b/sbin/geom/misc/subr.h
@@ -41,6 +41,9 @@ unsigned int g_get_sectorsize(const char *name);
 
 int g_metadata_read(const char *name, unsigned char *md, size_t size,
     const char *magic);
+int
+g_metadata_search(const char *name, unsigned char *md, size_t size,
+    const char *magic, off_t *metadata_offset);
 int g_metadata_store(const char *name, const unsigned char *md, size_t size);
 int g_metadata_clear(const char *name, const char *magic);
 
-- 
2.37.1