[PATCH 5/8] mtd: Allow passing a custom cmdline to cmdline line parser

Richard Weinberger
2021-01-24T23:22:04Z

The cmdline parser uses usually the mtdparts string from the kernel cmdline.
For special purpose MTDs like MUSE it is useful to pass a custom
mtdparts string to the parser. This allows the MTD simulator in
userspace directly passing a mtdparts string and the new MTD
partitioned.

To achieve this, struct mtd_part_parser_data now has a mtdparts pointer
where a custom mtdparts string can be provided, it overrules the kernel
cmdline.
Since the cmdline parser stays for ever in the kernel, the memory lifecycle
had to be changed a little such that custom mtdparts string don't result
in memory leaks.

Signed-off-by: Richard Weinberger <richard@nod.at>
---
drivers/mtd/parsers/cmdlinepart.c | 73 ++++++++++++++++++++++++-------
include/linux/mtd/partitions.h | 2 +
2 files changed, 58 insertions(+), 17 deletions(-)

diff --git a/drivers/mtd/parsers/cmdlinepart.c b/drivers/mtd/parsers/cmdlinepart.c
index 0ddff1a4b51f..f0fe87267380 100644
--- a/drivers/mtd/parsers/cmdlinepart.c
+++ b/drivers/mtd/parsers/cmdlinepart.c
@@ -64,7 +64,7 @@ struct cmdline_mtd_partition {
};

/* mtdpart_setup() parses into here */
-static struct cmdline_mtd_partition *partitions;
+static struct cmdline_mtd_partition *cmdline_partitions;

/* the command line passed to mtdpart_setup() */
static char *mtdparts;
@@ -138,9 +138,6 @@ static struct mtd_partition * newpart(char *s,
name_len = 13; /* Partition_000 */
}

- /* record name length for memory allocation later */
- extra_mem_size += name_len + 1;
-
/* test for options */
if (strncmp(s, "ro", 2) == 0) {
mask_flags |= MTD_WRITEABLE;
@@ -192,12 +189,17 @@ static struct mtd_partition * newpart(char *s,
parts[this_part].offset = offset;
parts[this_part].mask_flags = mask_flags;
parts[this_part].add_flags = add_flags;
+
+ /*
+ * Will get free()'ed in ->cleanup()
+ */
if (name)
- strlcpy(extra_mem, name, name_len + 1);
+ parts[this_part].name = kmemdup_nul(name, name_len, GFP_KERNEL);
else
- sprintf(extra_mem, "Partition_%03d", this_part);
- parts[this_part].name = extra_mem;
- extra_mem += name_len + 1;
+ parts[this_part].name = kasprintf(GFP_KERNEL, "Partition_%03d", this_part);
+
+ if (!parts[this_part].name)
+ return ERR_PTR(-ENOMEM);

dbg(("partition %d: name <%s>, offset %llx, size %llx, mask flags %x\n",
this_part, parts[this_part].name, parts[this_part].offset,
@@ -217,7 +219,7 @@ static struct mtd_partition * newpart(char *s,
/*
* Parse the command line.
*/
-static int mtdpart_setup_real(char *s)
+static int mtdpart_setup_real(char *s, struct cmdline_mtd_partition **partitions)
{
cmdline_parsed = 1;

@@ -301,8 +303,8 @@ static int mtdpart_setup_real(char *s)
strlcpy(this_mtd->mtd_id, mtd_id, mtd_id_len + 1);

/* link into chain */
- this_mtd->next = partitions;
- partitions = this_mtd;
+ this_mtd->next = *partitions;
+ *partitions = this_mtd;

dbg(("mtdid=<%s> num_parts=<%d>\n",
this_mtd->mtd_id, this_mtd->num_parts));
@@ -335,13 +337,23 @@ static int parse_cmdline_partitions(struct mtd_info *master,
struct mtd_part_parser_data *data)
{
unsigned long long offset;
- int i, err;
+ int i, err, num_parts;
struct cmdline_mtd_partition *part;
const char *mtd_id = master->name;
+ struct cmdline_mtd_partition *parsed_parts = cmdline_partitions;
+ bool free_parts = false;
+
+ if (data && data->mtdparts) {
+ parsed_parts = NULL;

- /* parse command line */
- if (!cmdline_parsed) {
- err = mtdpart_setup_real(cmdline);
+ err = mtdpart_setup_real(data->mtdparts, &parsed_parts);
+ if (err)
+ return err;
+
+ free_parts = true;
+ } else if (!cmdline_parsed) {
+ /* parse command line */
+ err = mtdpart_setup_real(cmdline, &cmdline_partitions);
if (err)
return err;
}
@@ -350,7 +362,7 @@ static int parse_cmdline_partitions(struct mtd_info *master,
* Search for the partition definition matching master->name.
* If master->name is not set, stop at first partition definition.
*/
- for (part = partitions; part; part = part->next) {
+ for (part = parsed_parts; part; part = part->next) {
if ((!mtd_id) || (!strcmp(part->mtd_id, mtd_id)))
break;
}
@@ -384,12 +396,38 @@ static int parse_cmdline_partitions(struct mtd_info *master,
}
}

+ /*
+ * Will get free()'ed in ->cleanup()
+ */
*pparts = kmemdup(part->parts, sizeof(*part->parts) * part->num_parts,
GFP_KERNEL);
if (!*pparts)
return -ENOMEM;

- return part->num_parts;
+ num_parts = part->num_parts;
+
+ if (free_parts == true) {
+ part = parsed_parts;
+ while (part) {
+ struct cmdline_mtd_partition *next = part->next;
+
+ kfree(part->parts);
+ part = next;
+ }
+ }
+
+ return num_parts;
+}
+
+static void cmdline_partitions_cleanup(const struct mtd_partition *pparts,
+ int nr_parts)
+{
+ int i;
+
+ for (i = 0; i < nr_parts; i++)
+ kfree(pparts[i].name);
+
+ kfree(pparts);
}

@@ -410,6 +448,7 @@ __setup("mtdparts=", mtdpart_setup);

static struct mtd_part_parser cmdline_parser = {
.parse_fn = parse_cmdline_partitions,
+ .cleanup = cmdline_partitions_cleanup,
.name = "cmdlinepart",
};

diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
index b74a539ec581..6c8b3399143d 100644
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -65,9 +65,11 @@ struct device_node;
/**
* struct mtd_part_parser_data - used to pass data to MTD partition parsers.
* @origin: for RedBoot, start address of MTD device
+ * @mtdparts: for cmdline parser, use this string instead of mtdparts= from cmdline
*/
struct mtd_part_parser_data {
unsigned long origin;
+ char *mtdparts;
};

--
2.26.2