[RFC PATCH 7/7] mtd: partitions: add Google's FMAP partition parser
Brian Norris
computersforpeace at gmail.com
Fri Dec 4 21:19:23 PST 2015
Cc: David Hendricks <dhendrix at chromium.org>
Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
drivers/mtd/partitions/Kconfig | 7 ++
drivers/mtd/partitions/Makefile | 1 +
drivers/mtd/partitions/google_fmap.c | 226 +++++++++++++++++++++++++++++++++++
3 files changed, 234 insertions(+)
create mode 100644 drivers/mtd/partitions/google_fmap.c
diff --git a/drivers/mtd/partitions/Kconfig b/drivers/mtd/partitions/Kconfig
index 0827d7a8be4e..98783f1d3a36 100644
--- a/drivers/mtd/partitions/Kconfig
+++ b/drivers/mtd/partitions/Kconfig
@@ -129,3 +129,10 @@ config MTD_BCM47XX_PARTS
help
This provides partitions parser for devices based on BCM47xx
boards.
+
+config MTD_GOOGLE_FMAP_PARTS
+ tristate "Google's Flash Map (FMAP) partition support"
+ help
+ This provides partition parsing for Google's flash map layout, used
+ primarily on the boot flash of Chrome OS hardware (e.g., Chromebooks
+ and Chromeboxes).
diff --git a/drivers/mtd/partitions/Makefile b/drivers/mtd/partitions/Makefile
index 89822f2bfa59..ab398c7f4d01 100644
--- a/drivers/mtd/partitions/Makefile
+++ b/drivers/mtd/partitions/Makefile
@@ -5,3 +5,4 @@ obj-$(CONFIG_MTD_AFS_PARTS) += afs.o
obj-$(CONFIG_MTD_AR7_PARTS) += ar7part.o
obj-$(CONFIG_MTD_BCM63XX_PARTS) += bcm63xxpart.o
obj-$(CONFIG_MTD_BCM47XX_PARTS) += bcm47xxpart.o
+obj-$(CONFIG_MTD_GOOGLE_FMAP_PARTS) += google_fmap.o
diff --git a/drivers/mtd/partitions/google_fmap.c b/drivers/mtd/partitions/google_fmap.c
new file mode 100644
index 000000000000..abd10eb65c84
--- /dev/null
+++ b/drivers/mtd/partitions/google_fmap.c
@@ -0,0 +1,226 @@
+/*
+ * Parse Google FMAP partitions
+ *
+ * Author: Brian Norris <briannorris at chromium.org>
+ *
+ * Copyright © 2015 Google, Inc.
+ *
+ * This program 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * See:
+ * https://github.com/dhendrix/flashmap/blob/wiki/FmapSpec.md
+ *
+ * Notes:
+ * - scans only at block boundaries; this is not guaranteed for FMAP (the
+ * Chrome OS tools do a kind of stride search, of decreasing size), but
+ * seems like a decent start
+ * - at worst, scans (beginning of) every block on an unformatted flash
+ * - only validates the "__FMAP__" signature, just like the Chrome OS tools;
+ * however, this seems (theoretically) easy to produce false matches
+ * - major/minor version numbers are currently unused
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/compiler.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+
+static const char fmap_signature[] = "__FMAP__";
+
+struct fmap_layout {
+ uint8_t signature[8]; /* "__FMAP__" (0x5F5F50414D465F5F) */
+ uint8_t ver_major; /* major version number of this structure */
+ uint8_t ver_minor; /* minor version of this structure */
+ __le64 base; /* physical memory-mapped address of the flash chip */
+ __le32 size; /* size of the flash chip in bytes */
+ uint8_t name[32]; /* descriptive name of this flash device, 0 terminated */
+ __le16 nareas; /* number of areas described by areas[] below */
+ struct fmap_area {
+ __le32 offset; /* offset of this area in the flash device */
+ __le32 size; /* size of this area in bytes */
+ uint8_t name[32]; /* descriptive name of this area, 0 terminated */
+ __le16 flags; /* flags for this area */
+ } __packed areas[0];
+} __packed;
+
+/* mtd_read() helper */
+static int fmap_mtd_read(struct mtd_info *mtd, loff_t offset, size_t len,
+ void *buf)
+{
+ size_t retlen;
+ int ret;
+
+ ret = mtd_read(mtd, offset, len, &retlen, buf);
+ if (ret)
+ return ret;
+ if (retlen != len)
+ return -EIO;
+ return 0;
+}
+
+/* Return 0 on no match, non-zero on match */
+static inline int fmap_check_signature(struct fmap_layout *fmap)
+{
+ return !strncmp(fmap->signature, fmap_signature,
+ sizeof(fmap->signature));
+}
+
+static int fmap_parse_block(struct mtd_info *master,
+ const struct mtd_partition **pparts,
+ struct fmap_layout *fmap, size_t maxlen)
+{
+ struct mtd_partition *parts;
+ char *names;
+ int nparts;
+ int ret, i, namelen = 0;
+
+ if (!fmap_check_signature(fmap))
+ return 0;
+
+ nparts = le16_to_cpu(fmap->nareas);
+
+ if (!nparts) {
+ pr_err("found FMAP, but no FMAP areas; skipping\n");
+ return -EINVAL;
+ }
+
+ /* pre-process names */
+ for (i = 0; i < nparts; i++) {
+ struct fmap_area *area = &fmap->areas[i];
+
+ /* Terminate */
+ area->name[sizeof(area->name) - 1] = '\0';
+
+ namelen += strlen(area->name);
+ }
+
+ /* partitions + name strings + string terminators */
+ parts = kzalloc(sizeof(*parts) * nparts + namelen + nparts, GFP_KERNEL);
+ if (!parts) {
+ ret = -ENOMEM;
+ goto err;
+ }
+ names = (char *)(parts + nparts);
+
+ for (i = 0; i < nparts; i++) {
+ struct mtd_partition *part = &parts[i];
+ struct fmap_area *area = &fmap->areas[i];
+
+ strcpy(names, area->name);
+ part->name = names;
+ names += strlen(names) + 1;
+
+ part->offset = le32_to_cpu(area->offset);
+ part->size = le32_to_cpu(area->size);
+ }
+
+ *pparts = parts;
+ return nparts;
+
+err:
+ kfree(parts);
+ return ret;
+}
+
+static int fmap_peek_header(struct mtd_info *master, loff_t offs, void *buf)
+{
+ struct fmap_layout *fmap;
+ int ret;
+
+ fmap = buf;
+
+ ret = fmap_mtd_read(master, offs, sizeof(*fmap), fmap);
+ if (ret)
+ return ret;
+
+ return fmap_check_signature(fmap);
+}
+
+static int fmap_parse_partitions(struct mtd_info *master,
+ const struct mtd_partition **pparts,
+ struct mtd_part_parser_data *data)
+{
+ void *buf;
+ struct fmap_layout *fmap;
+ int ret = 0;
+ size_t len;
+ loff_t offset = 0;
+
+ buf = vmalloc(master->erasesize);
+ if (!buf)
+ return -ENOMEM;
+
+ for (offset = 0; offset < master->size; offset += master->erasesize) {
+ if (mtd_block_isbad(master, offset))
+ continue;
+
+ ret = fmap_peek_header(master, offset, buf);
+ if (ret < 0)
+ break;
+ if (!ret)
+ /* No match; don't read the rest */
+ continue;
+
+ len = master->erasesize;
+ ret = fmap_mtd_read(master, offset, len, buf);
+ if (ret)
+ break;
+
+ fmap = buf;
+
+ ret = fmap_parse_block(master, pparts, fmap, len);
+ if (ret < 0)
+ break;
+ if (ret) /* success */
+ break;
+ }
+
+ vfree(buf);
+
+ if (ret < 0) {
+ pr_err("error %d while searching for fmap\n", ret);
+ return ret;
+ } else if (ret) {
+ pr_info("found fmap @ offset %#llx\n", (u64)offset);
+ return ret;
+ } else {
+ pr_debug("no fmap found\n");
+ return 0;
+ }
+}
+
+static const struct of_device_id fmap_match[] = {
+ { .compatible = "google,fmap" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, fmap_match);
+
+static struct mtd_part_parser fmap_parser = {
+ .parse_fn = fmap_parse_partitions,
+ .name = "fmap",
+ .of_match_table = fmap_match,
+};
+module_mtd_part_parser(fmap_parser);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Brian Norris");
+MODULE_DESCRIPTION("Parsing code for Chrome OS FMAP tables");
+/* MTD parsers request the module by parser name */
+MODULE_ALIAS("fmap");
--
2.6.0.rc2.230.g3dd15c0
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