[PATCH 0/2] boot to a mapped device

[PATCH 0/2] boot to a mapped device

[Helen Koike]

This series is reviving an old patchwork.
Booting from a mapped device requires an initramfs. This series is
allows for device-mapper targets to be configured at boot time for
use early in the boot process (as the root device or otherwise).

Example, the following could be added in the boot parameters.
dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0

Enric Balletbo i Serra (1):
  dm ioctl: add a device mapper ioctl function.

Will Drewry (1):
  init: add support to directly boot to a mapped device

 .../admin-guide/kernel-parameters.rst         |   1 +
 .../admin-guide/kernel-parameters.txt         |   3 +
 Documentation/device-mapper/dm-boot.txt       |  63 +++
 drivers/md/dm-ioctl.c                         |  50 ++
 include/linux/device-mapper.h                 |   6 +
 init/Makefile                                 |   1 +
 init/do_mounts.c                              |   1 +
 init/do_mounts.h                              |  10 +
 init/do_mounts_dm.c                           | 475 ++++++++++++++++++
 9 files changed, 610 insertions(+)
 create mode 100644 Documentation/device-mapper/dm-boot.txt
 create mode 100644 init/do_mounts_dm.c

-- 
2.19.0

[linux-lvm] [PATCH 0/2] boot to a mapped device

[Helen Koike]

This series is reviving an old patchwork.
Booting from a mapped device requires an initramfs. This series is
allows for device-mapper targets to be configured at boot time for
use early in the boot process (as the root device or otherwise).

Example, the following could be added in the boot parameters.
dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0

Enric Balletbo i Serra (1):
  dm ioctl: add a device mapper ioctl function.

Will Drewry (1):
  init: add support to directly boot to a mapped device

 .../admin-guide/kernel-parameters.rst         |   1 +
 .../admin-guide/kernel-parameters.txt         |   3 +
 Documentation/device-mapper/dm-boot.txt       |  63 +++
 drivers/md/dm-ioctl.c                         |  50 ++
 include/linux/device-mapper.h                 |   6 +
 init/Makefile                                 |   1 +
 init/do_mounts.c                              |   1 +
 init/do_mounts.h                              |  10 +
 init/do_mounts_dm.c                           | 475 ++++++++++++++++++
 9 files changed, 610 insertions(+)
 create mode 100644 Documentation/device-mapper/dm-boot.txt
 create mode 100644 init/do_mounts_dm.c

-- 
2.19.0

[PATCH 0/2] boot to a mapped device

[Helen Koike]

This series is reviving an old patchwork.
Booting from a mapped device requires an initramfs. This series is
allows for device-mapper targets to be configured at boot time for
use early in the boot process (as the root device or otherwise).

Example, the following could be added in the boot parameters.
dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0

Enric Balletbo i Serra (1):
  dm ioctl: add a device mapper ioctl function.

Will Drewry (1):
  init: add support to directly boot to a mapped device

 .../admin-guide/kernel-parameters.rst         |   1 +
 .../admin-guide/kernel-parameters.txt         |   3 +
 Documentation/device-mapper/dm-boot.txt       |  63 +++
 drivers/md/dm-ioctl.c                         |  50 ++
 include/linux/device-mapper.h                 |   6 +
 init/Makefile                                 |   1 +
 init/do_mounts.c                              |   1 +
 init/do_mounts.h                              |  10 +
 init/do_mounts_dm.c                           | 475 ++++++++++++++++++
 9 files changed, 610 insertions(+)
 create mode 100644 Documentation/device-mapper/dm-boot.txt
 create mode 100644 init/do_mounts_dm.c

-- 
2.19.0

[PATCH 1/2] dm ioctl: add a device mapper ioctl function.

[Helen Koike]

From: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Add a dm_ioctl_cmd to issue the equivalent of a DM ioctl call in kernel.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
 drivers/md/dm-ioctl.c         | 50 +++++++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  6 +++++
 2 files changed, 56 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index b810ea77e6b1..68ce2557c62b 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -2024,3 +2024,53 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
 
 	return r;
 }
+
+/**
+ * dm_ioctl_cmd - Device mapper ioctl's
+ * @command: ioctl command
+ * @param: Pointer to device mapped ioctl struct
+ */
+int dm_ioctl_cmd(uint command, struct dm_ioctl *param)
+{
+	int r = 0;
+	int ioctl_flags;
+	unsigned int cmd;
+	ioctl_fn fn = NULL;
+	size_t input_param_size;
+	struct file *filp = NULL;
+
+	if (_IOC_TYPE(command) != DM_IOCTL)
+		return -ENOTTY;
+
+	/* DM_DEV_ARM_POLL is not supported */
+	if (command == DM_DEV_ARM_POLL)
+		return -EINVAL;
+
+	cmd = _IOC_NR(command);
+
+	/*
+	 * Nothing more to do for the version command.
+	 */
+	if (cmd == DM_VERSION_CMD)
+		return 0;
+
+	fn = lookup_ioctl(cmd, &ioctl_flags);
+	if (!fn) {
+		DMWARN("dm_ioctl: unknown command 0x%x", command);
+		return -ENOTTY;
+	}
+
+	input_param_size = param->data_size;
+	r = validate_params(cmd, param);
+	if (r)
+		return r;
+
+	param->data_size = sizeof(*param);
+	r = fn(filp, param, input_param_size);
+
+	if (unlikely(param->flags & DM_BUFFER_FULL_FLAG) &&
+	    unlikely(ioctl_flags & IOCTL_FLAGS_NO_PARAMS))
+		DMERR("ioctl %d tried to output some data but has IOCTL_FLAGS_NO_PARAMS set", cmd);
+
+	return r;
+}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 6fb0808e87c8..df5a5a60f9aa 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -12,6 +12,7 @@
 #include <linux/blkdev.h>
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
+#include <linux/dm-ioctl.h>
 
 struct dm_dev;
 struct dm_target;
@@ -424,6 +425,11 @@ void dm_remap_zone_report(struct dm_target *ti, struct bio *bio,
 			  sector_t start);
 union map_info *dm_get_rq_mapinfo(struct request *rq);
 
+/*
+ * Device mapper ioctl function.
+ */
+int dm_ioctl_cmd(unsigned int command, struct dm_ioctl *param);
+
 struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
 
 /*
-- 
2.19.0

[linux-lvm] [PATCH 1/2] dm ioctl: add a device mapper ioctl function.

[Helen Koike]

From: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Add a dm_ioctl_cmd to issue the equivalent of a DM ioctl call in kernel.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
 drivers/md/dm-ioctl.c         | 50 +++++++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  6 +++++
 2 files changed, 56 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index b810ea77e6b1..68ce2557c62b 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -2024,3 +2024,53 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
 
 	return r;
 }
+
+/**
+ * dm_ioctl_cmd - Device mapper ioctl's
+ * @command: ioctl command
+ * @param: Pointer to device mapped ioctl struct
+ */
+int dm_ioctl_cmd(uint command, struct dm_ioctl *param)
+{
+	int r = 0;
+	int ioctl_flags;
+	unsigned int cmd;
+	ioctl_fn fn = NULL;
+	size_t input_param_size;
+	struct file *filp = NULL;
+
+	if (_IOC_TYPE(command) != DM_IOCTL)
+		return -ENOTTY;
+
+	/* DM_DEV_ARM_POLL is not supported */
+	if (command == DM_DEV_ARM_POLL)
+		return -EINVAL;
+
+	cmd = _IOC_NR(command);
+
+	/*
+	 * Nothing more to do for the version command.
+	 */
+	if (cmd == DM_VERSION_CMD)
+		return 0;
+
+	fn = lookup_ioctl(cmd, &ioctl_flags);
+	if (!fn) {
+		DMWARN("dm_ioctl: unknown command 0x%x", command);
+		return -ENOTTY;
+	}
+
+	input_param_size = param->data_size;
+	r = validate_params(cmd, param);
+	if (r)
+		return r;
+
+	param->data_size = sizeof(*param);
+	r = fn(filp, param, input_param_size);
+
+	if (unlikely(param->flags & DM_BUFFER_FULL_FLAG) &&
+	    unlikely(ioctl_flags & IOCTL_FLAGS_NO_PARAMS))
+		DMERR("ioctl %d tried to output some data but has IOCTL_FLAGS_NO_PARAMS set", cmd);
+
+	return r;
+}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 6fb0808e87c8..df5a5a60f9aa 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -12,6 +12,7 @@
 #include <linux/blkdev.h>
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
+#include <linux/dm-ioctl.h>
 
 struct dm_dev;
 struct dm_target;
@@ -424,6 +425,11 @@ void dm_remap_zone_report(struct dm_target *ti, struct bio *bio,
 			  sector_t start);
 union map_info *dm_get_rq_mapinfo(struct request *rq);
 
+/*
+ * Device mapper ioctl function.
+ */
+int dm_ioctl_cmd(unsigned int command, struct dm_ioctl *param);
+
 struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
 
 /*
-- 
2.19.0

[PATCH 1/2] dm ioctl: add a device mapper ioctl function.

[Helen Koike]

From: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Add a dm_ioctl_cmd to issue the equivalent of a DM ioctl call in kernel.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
 drivers/md/dm-ioctl.c         | 50 +++++++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  6 +++++
 2 files changed, 56 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index b810ea77e6b1..68ce2557c62b 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -2024,3 +2024,53 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
 
 	return r;
 }
+
+/**
+ * dm_ioctl_cmd - Device mapper ioctl's
+ * @command: ioctl command
+ * @param: Pointer to device mapped ioctl struct
+ */
+int dm_ioctl_cmd(uint command, struct dm_ioctl *param)
+{
+	int r = 0;
+	int ioctl_flags;
+	unsigned int cmd;
+	ioctl_fn fn = NULL;
+	size_t input_param_size;
+	struct file *filp = NULL;
+
+	if (_IOC_TYPE(command) != DM_IOCTL)
+		return -ENOTTY;
+
+	/* DM_DEV_ARM_POLL is not supported */
+	if (command == DM_DEV_ARM_POLL)
+		return -EINVAL;
+
+	cmd = _IOC_NR(command);
+
+	/*
+	 * Nothing more to do for the version command.
+	 */
+	if (cmd == DM_VERSION_CMD)
+		return 0;
+
+	fn = lookup_ioctl(cmd, &ioctl_flags);
+	if (!fn) {
+		DMWARN("dm_ioctl: unknown command 0x%x", command);
+		return -ENOTTY;
+	}
+
+	input_param_size = param->data_size;
+	r = validate_params(cmd, param);
+	if (r)
+		return r;
+
+	param->data_size = sizeof(*param);
+	r = fn(filp, param, input_param_size);
+
+	if (unlikely(param->flags & DM_BUFFER_FULL_FLAG) &&
+	    unlikely(ioctl_flags & IOCTL_FLAGS_NO_PARAMS))
+		DMERR("ioctl %d tried to output some data but has IOCTL_FLAGS_NO_PARAMS set", cmd);
+
+	return r;
+}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 6fb0808e87c8..df5a5a60f9aa 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -12,6 +12,7 @@
 #include <linux/blkdev.h>
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
+#include <linux/dm-ioctl.h>
 
 struct dm_dev;
 struct dm_target;
@@ -424,6 +425,11 @@ void dm_remap_zone_report(struct dm_target *ti, struct bio *bio,
 			  sector_t start);
 union map_info *dm_get_rq_mapinfo(struct request *rq);
 
+/*
+ * Device mapper ioctl function.
+ */
+int dm_ioctl_cmd(unsigned int command, struct dm_ioctl *param);
+
 struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
 
 /*
-- 
2.19.0

[PATCH 2/2] init: add support to directly boot to a mapped device

[Helen Koike]

From: Will Drewry <wad@chromium.org>

Add a dm= kernel parameter modeled after the md= parameter from
do_mounts_md. It allows for device-mapper targets to be configured at
boot time for use early in the boot process (as the root device or
otherwise).

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
[rework to use dm_ioctl calls]
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
[rework to use concise format | rework for upstream]
Signed-off-by: Helen Koike <helen.koike@collabora.com>
---
 .../admin-guide/kernel-parameters.rst         |   1 +
 .../admin-guide/kernel-parameters.txt         |   3 +
 Documentation/device-mapper/dm-boot.txt       |  63 +++
 init/Makefile                                 |   1 +
 init/do_mounts.c                              |   1 +
 init/do_mounts.h                              |  10 +
 init/do_mounts_dm.c                           | 475 ++++++++++++++++++
 7 files changed, 554 insertions(+)
 create mode 100644 Documentation/device-mapper/dm-boot.txt
 create mode 100644 init/do_mounts_dm.c

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index b8d0bc07ed0a..bd628865f66f 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -91,6 +91,7 @@ parameter is applicable::
 	AX25	Appropriate AX.25 support is enabled.
 	CLK	Common clock infrastructure is enabled.
 	CMA	Contiguous Memory Area support is enabled.
+	DM	Device mapper support is enabled.
 	DRM	Direct Rendering Management support is enabled.
 	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
 	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f42240d..331195d19b32 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -880,6 +880,9 @@
 
 	dis_ucode_ldr	[X86] Disable the microcode loader.
 
+	dm=		[DM] Allows early creation of a device-mapper device.
+			See Documentation/device-mapper/boot.txt.
+
 	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
 			this option disables the debugging code at boot.
 
diff --git a/Documentation/device-mapper/dm-boot.txt b/Documentation/device-mapper/dm-boot.txt
new file mode 100644
index 000000000000..f598f102c980
--- /dev/null
+++ b/Documentation/device-mapper/dm-boot.txt
@@ -0,0 +1,63 @@
+Boot time creation of mapped devices
+====================================
+
+It is possible to configure a device mapper device to act as the root
+device for your system in two ways.
+
+The first is to build an initial ramdisk which boots to a minimal
+userspace which configures the device, then pivot_root(8) in to it.
+
+The second is to possible when the device-mapper and any targets are
+compiled into the kernel (not a module), one or more device-mappers may
+be created and used as the root device at boot time with the parameters
+given with the boot line dm=...
+
+The format is specified as a simple string of data separated by commas and
+optionally semi-colons, where:
+ - a comma is used to separate fields like name, uuid, flags and table (specifies
+   one device)
+ - a semi-colon is used to separate devices.
+
+So the format will look like this:
+
+ dm=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
+
+Where,
+	<dev_name>	::= The device name.
+	<uuid>		::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
+	<minor>		::= The device minor number.
+	<flags>		::= "ro" | "rw"
+	<table>		::= <start> <length> <type> <options>
+	<type>		::= "verity" | "bootcache" | ...
+
+The dm line may be as normal when using the dmsetup tool when using the
+--concise argument.
+
+Examples
+========
+An example of booting to a linear array made up of user-mode linux block
+devices:
+
+  dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
+  root=/dev/dm-0
+
+This will boot to a rw dm-linear target of 8192 sectors split across two
+block devices identified by their major:minor numbers.  After boot, udev
+will rename this target to /dev/mapper/lroot (depending on the rules).
+No uuid was assigned.
+
+An example of multiple device-mappers, with the dm="..." contents shown
+here split on multiple lines for readability:
+
+    vboot,,ro,
+      0 1768000 bootcache
+        aa55b119-2a47-8c45-946a-5ac57765011f+1
+        76e9be054b15884a9fa85973e9cb274c93afadb6
+        1768000 100000 23 20000;
+    vroot,,ro,
+      0 1740800 verity 254:0 254:0 1740800 sha1
+        76e9be054b15884a9fa85973e9cb274c93afadb6
+        5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe;
+    vram,,rw,
+      0 32768 linear 1:0 0,
+      32768 32768 linear 1:1 0
diff --git a/init/Makefile b/init/Makefile
index a3e5ce2bcf08..f814f0ff5974 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -19,6 +19,7 @@ mounts-y			:= do_mounts.o
 mounts-$(CONFIG_BLK_DEV_RAM)	+= do_mounts_rd.o
 mounts-$(CONFIG_BLK_DEV_INITRD)	+= do_mounts_initrd.o
 mounts-$(CONFIG_BLK_DEV_MD)	+= do_mounts_md.o
+mounts-$(CONFIG_BLK_DEV_DM)	+= do_mounts_dm.o
 
 # dependencies on generated files need to be listed explicitly
 $(obj)/version.o: include/generated/compile.h
diff --git a/init/do_mounts.c b/init/do_mounts.c
index e1c9afa9d8c9..d707f12be6e7 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -555,6 +555,7 @@ void __init prepare_namespace(void)
 	wait_for_device_probe();
 
 	md_run_setup();
+	dm_run_setup();
 
 	if (saved_root_name[0]) {
 		root_device_name = saved_root_name;
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 0bb0806de4ce..0f57528ea324 100644
--- a/init/do_mounts.h
+++ b/init/do_mounts.h
@@ -61,3 +61,13 @@ void md_run_setup(void);
 static inline void md_run_setup(void) {}
 
 #endif
+
+#ifdef CONFIG_BLK_DEV_DM
+
+void dm_run_setup(void);
+
+#else
+
+static inline void dm_run_setup(void) {}
+
+#endif
diff --git a/init/do_mounts_dm.c b/init/do_mounts_dm.c
new file mode 100644
index 000000000000..507ae31808ef
--- /dev/null
+++ b/init/do_mounts_dm.c
@@ -0,0 +1,475 @@
+// SPDX-License-Identifier: <SPDX License Expression>
+
+/*
+ * do_mounts_dm.c
+ * Copyright (C) 2017 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Based on do_mounts_md.c
+ *
+ * This file is released under the GPLv2.
+ */
+#include <linux/async.h>
+#include <linux/ctype.h>
+#include <linux/device-mapper.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/delay.h>
+
+#include "do_mounts.h"
+
+#define DM_MAX_DEVICES 256
+#define DM_MAX_NAME 32
+#define DM_MAX_UUID 129
+
+#define DM_MSG_PREFIX "init"
+
+#define is_even(a) (((a) & 1) == 0)
+
+/* See Documentation/device-mapper/dm-boot.txt for dm="..." format details. */
+
+struct target {
+	sector_t start;
+	sector_t length;
+	char *type;
+	char *params;
+	/* simple singly linked list */
+	struct target *next;
+};
+
+struct dm_device {
+	int minor;
+	int ro;
+	char name[DM_MAX_NAME];
+	char uuid[DM_MAX_UUID];
+	struct target *table;
+	int table_count;
+	/* simple singly linked list */
+	struct dm_device *next;
+};
+
+static struct {
+	unsigned long num_devices;
+	char *str;
+} dm_setup_args __initdata;
+
+static int dm_early_setup __initdata;
+
+static void __init *_align(void *ptr, unsigned int a)
+{
+	register unsigned long agn = --a;
+
+	return (void *) (((unsigned long) ptr + agn) & ~agn);
+}
+
+/*
+ * Unescape characters in situ, it replaces all occurrences of "\c"
+ * with 'c'. This is normally used to unescape colons and semi-colons used
+ * in boot format.
+ */
+static char __init *_unescape_char(char *str, const char c)
+{
+	int i = 0, j = 0;
+	int len = strlen(str);
+
+	if (len < 2)
+		return str;
+
+	while (j < len - 1) {
+		if (str[j] == '\\' && str[j + 1] == c) {
+			j = j + 2;
+			str[i++] = c;
+			continue;
+		}
+		str[i++] = str[j++];
+	}
+
+	if (j == len - 1)
+		str[i++] = str[j];
+
+	str[i] = '\0';
+
+	return str;
+}
+
+static void __init dm_setup_cleanup(struct dm_device *devices)
+{
+	struct dm_device *dev = devices;
+
+	while (dev) {
+		struct dm_device *old_dev = dev;
+		struct target *table = dev->table;
+
+		while (table) {
+			struct target *old_table = table;
+
+			kfree(table->type);
+			kfree(table->params);
+			table = table->next;
+			kfree(old_table);
+			dev->table_count--;
+		}
+		WARN_ON(dev->table_count);
+		dev = dev->next;
+		kfree(old_dev);
+	}
+}
+
+/*
+ * Splits a string into tokens ignoring escaped chars
+ *
+ * Updates @s to point after the token, ready for the next call.
+ *
+ * @str: The string to be searched
+ * @c: The character to search for
+ *
+ * Returns:
+ *   The string found or NULL.
+ */
+static char __init *dm_find_unescaped_char(char **str, const char c)
+{
+	char *s = *str;
+	char *p = strchr(*str, c);
+
+	/* loop through all the characters */
+	while (p != NULL) {
+		/* scan backwards through preceding escapes */
+		char *q = p;
+
+		while (q > s && *(q - 1) == '\\')
+			--q;
+		/* even number of escapes so c is a token */
+		if (is_even(p - q)) {
+			*p = '\0';
+			*str = p + 1;
+			return s;
+		}
+		/* else odd escapes so c is escaped, keep going */
+		p = strchr(p + 1, c);
+	}
+
+	if (strlen(*str)) {
+		*str += strlen(*str);
+		return s;
+	}
+
+	return NULL;
+}
+
+static struct target __init *dm_parse_table(struct dm_device *dev, char *str)
+{
+	char type[DM_MAX_TYPE_NAME], *ptr;
+	struct target *table;
+	int n;
+
+	/* trim trailing space */
+	for (ptr = str + strlen(str) - 1; ptr >= str; ptr--)
+		if (!isspace((int) *ptr))
+			break;
+	ptr++;
+	*ptr = '\0';
+
+	/* trim leading space */
+	for (ptr = str; *ptr && isspace((int) *ptr); ptr++)
+		;
+
+	if (!*ptr)
+		return NULL;
+
+	table = kzalloc(sizeof(struct target), GFP_KERNEL);
+	if (!table)
+		return NULL;
+
+	if (sscanf(ptr, "%llu %llu %s %n", &table->start, &table->length,
+		   type, &n) < 3) {
+		DMERR("invalid format of table \"%s\"", str);
+		goto parse_fail;
+	}
+
+	table->type = kstrndup(type, strlen(type), GFP_KERNEL);
+	if (!table->type) {
+		DMERR("invalid type of table");
+		goto parse_fail;
+	}
+
+	ptr += n;
+	table->params = kstrndup(ptr, strlen(ptr), GFP_KERNEL);
+	if (!table->params) {
+		DMERR("invalid params for table");
+		goto parse_fail;
+	}
+
+	dev->table_count++;
+
+	return table;
+
+parse_fail:
+	kfree(table);
+	return NULL;
+}
+
+static int __init dm_parse_device(struct dm_device *dev, char *dev_info)
+{
+	char *aux, *str = dev_info, *ptr = dev_info;
+	struct target **tail = &dev->table;
+	struct target *table;
+	int field = 0;
+
+	while ((str = dm_find_unescaped_char(&ptr, ',')) != NULL) {
+		str = _unescape_char(str, ',');
+		DMDEBUG("Parsing %s", str);
+		switch (field) {
+		case 0: /* set device name */
+			/* ignore path */
+			aux = strrchr(str, '/');
+			str = aux ? &aux[1] : str;
+			DMDEBUG("name %s\n", str);
+			if (strscpy(dev->name, str, sizeof(dev->name)) < 0)
+				return -EINVAL;
+			break;
+		case 1: /* set uuid if any */
+			if (strscpy(dev->uuid, str, sizeof(dev->uuid)) < 0)
+				return -EINVAL;
+			break;
+		case 2: /* set minor if any */
+			if (!strlen(str) || kstrtoint(str, 0, &dev->minor))
+				dev->minor = DM_ANY_MINOR;
+			break;
+		case 3:
+			/* set as read-only if flags = "ro" | "" */
+			if (!strncmp(str, "ro", strlen(str)) || !strlen(str))
+				dev->ro = 1;
+			else if (!strncmp(str, "rw", strlen(str)))
+				dev->ro = 0;
+			else
+				return -EINVAL;
+			break;
+		default:
+			table = dm_parse_table(dev, str);
+			if (!table)
+				goto parse_fail;
+
+			*tail = table;
+			tail = &table->next;
+
+			break;
+		}
+		field++;
+	}
+
+	if (field < 4)
+		goto parse_fail;
+
+	return 0;
+
+parse_fail:
+	return -EINVAL;
+}
+
+static struct dm_device __init *dm_parse_args(void)
+{
+	struct dm_device *devices = NULL;
+	struct dm_device **tail = &devices;
+	struct dm_device *dev;
+	char *dev_info, *str = dm_setup_args.str;
+
+	while ((dev_info = dm_find_unescaped_char(&str, ';')) != NULL) {
+		dev_info = _unescape_char(dev_info, ';');
+		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+		if (!dev)
+			goto error;
+
+		if (dm_parse_device(dev, dev_info))
+			goto error;
+
+		*tail = dev;
+		tail = &dev->next;
+
+		if (++dm_setup_args.num_devices > DM_MAX_DEVICES) {
+			DMERR("too many devices %lu > %d",
+			      dm_setup_args.num_devices, DM_MAX_DEVICES);
+			goto error;
+		}
+	}
+	return devices;
+error:
+	dm_setup_cleanup(devices);
+	return NULL;
+}
+
+/*
+ * Parse the command-line parameters given our kernel, but do not
+ * actually try to invoke the DM device now; that is handled by
+ * dm_setup_drives after the low-level disk drivers have initialised.
+ * dm format is described at the top of the file.
+ *
+ * Because dm minor numbers are assigned in ascending order starting with 0,
+ * You can assume the first device is /dev/dm-0, the next device is /dev/dm-1,
+ * and so forth.
+ */
+static int __init dm_setup(char *str)
+{
+	if (!str) {
+		DMERR("Invalid arguments supplied to dm=.");
+		return 0;
+	}
+
+	DMDEBUG("Want to parse \"%s\"", str);
+
+	dm_setup_args.num_devices = 0;
+	dm_setup_args.str = str;
+
+	dm_early_setup = 1;
+
+	return 1;
+}
+
+static char __init *dm_add_target(struct target *table, char *out, char *end)
+{
+	char *out_sp = out;
+	struct dm_target_spec sp;
+	size_t sp_size = sizeof(struct dm_target_spec);
+	int len;
+	char *pt;
+
+	if (strlen(table->type) >= sizeof(sp.target_type)) {
+		DMERR("target type name %s is too long.", table->type);
+		return NULL;
+	}
+
+	sp.status = 0;
+	sp.sector_start = table->start;
+	sp.length = table->length;
+	strscpy(sp.target_type, table->type, sizeof(sp.target_type));
+	sp.target_type[sizeof(sp.target_type) - 1] = '\0';
+
+	out += sp_size;
+	pt = table->params;
+	len = strlen(table->params);
+
+	if ((out >= end) || (out + len + 1) >= end) {
+		DMERR("ran out of memory building ioctl parameter");
+		return NULL;
+	}
+
+	strcpy(out, table->params);
+	out += len + 1;
+	/* align next block */
+	out = _align(out, 8);
+
+	sp.next = out - out_sp;
+	memcpy(out_sp, &sp, sp_size);
+
+	return out;
+}
+
+static struct dm_ioctl __init *dm_setup_ioctl(struct dm_device *dev, int flags)
+{
+	const size_t min_size = 16 * 1024;
+	size_t len = sizeof(struct dm_ioctl);
+	struct dm_ioctl *dmi;
+	struct target *table = dev->table;
+	char *b, *e;
+
+	if (len < min_size)
+		len = min_size;
+
+	dmi = kzalloc(len, GFP_KERNEL);
+	if (!dmi)
+		return NULL;
+
+	dmi->version[0] = 4;
+	dmi->version[1] = 0;
+	dmi->version[2] = 0;
+	dmi->data_size = len;
+	dmi->data_start = sizeof(struct dm_ioctl);
+	dmi->flags = flags;
+	dmi->target_count = dev->table_count;
+	dmi->event_nr = 1;
+
+	/* Only one between uuid, name and dev should be filled */
+	if (*dev->uuid)
+		strscpy(dmi->uuid, dev->uuid, sizeof(dmi->uuid));
+	else if (*dev->name)
+		strscpy(dmi->name, dev->name, sizeof(dmi->name));
+	else if (dev->minor > 0)
+		dmi->dev = dev->minor;
+	else
+		return NULL;
+
+	b = (char *) (dmi + 1);
+	e = (char *) dmi + len;
+
+	while (table != NULL) {
+		DMDEBUG("device %s adding table '%llu %llu %s %s'",
+			dev->name,
+			(unsigned long long) table->start,
+			(unsigned long long) table->length,
+			table->type, table->params);
+		b = dm_add_target(table, b, e);
+		if (!b) {
+			kfree(dmi);
+			return NULL;
+		}
+		table = table->next;
+	}
+
+	return dmi;
+}
+
+static void __init dm_setup_drives(void)
+{
+	struct dm_device *dev;
+	int flags;
+	struct dm_device *devices;
+	struct dm_ioctl *io = NULL;
+
+	devices = dm_parse_args();
+
+	for (dev = devices; dev; dev = dev->next) {
+		flags = dev->minor < 0 ? 0 : DM_PERSISTENT_DEV_FLAG;
+		io = dm_setup_ioctl(dev, flags);
+		if (!io)
+			return;
+		io->dev = dev->minor;
+		/* create a new device */
+		if (dm_ioctl_cmd(DM_DEV_CREATE, io)) {
+			DMERR("failed to create device %s", dev->name);
+			goto out_free;
+		}
+		kfree(io);
+
+		flags = dev->ro ? DM_READONLY_FLAG : 0;
+		io = dm_setup_ioctl(dev, flags);
+		if (!io)
+			return;
+		/* load a table into the 'inactive' slot for the device. */
+		if (dm_ioctl_cmd(DM_TABLE_LOAD, io)) {
+			DMERR("failed to load device %s tables", dev->name);
+			goto out_free;
+		}
+		kfree(io);
+
+		io = dm_setup_ioctl(dev, 0);
+		if (!io)
+			return;
+		/* resume and the device should be ready. */
+		if (dm_ioctl_cmd(DM_DEV_SUSPEND, io)) {
+			DMERR("failed to resume device %s", dev->name);
+			goto out_free;
+		}
+
+		DMINFO("dm-%d (%s) is ready", dev->minor, dev->name);
+	}
+
+out_free:
+	kfree(io);
+}
+
+__setup("dm=", dm_setup);
+
+void __init dm_run_setup(void)
+{
+	if (!dm_early_setup)
+		return;
+	DMINFO("attempting early device configuration.");
+	dm_setup_drives();
+}
-- 
2.19.0

[linux-lvm] [PATCH 2/2] init: add support to directly boot to a mapped device

[Helen Koike]

From: Will Drewry <wad@chromium.org>

Add a dm= kernel parameter modeled after the md= parameter from
do_mounts_md. It allows for device-mapper targets to be configured at
boot time for use early in the boot process (as the root device or
otherwise).

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
[rework to use dm_ioctl calls]
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
[rework to use concise format | rework for upstream]
Signed-off-by: Helen Koike <helen.koike@collabora.com>
---
 .../admin-guide/kernel-parameters.rst         |   1 +
 .../admin-guide/kernel-parameters.txt         |   3 +
 Documentation/device-mapper/dm-boot.txt       |  63 +++
 init/Makefile                                 |   1 +
 init/do_mounts.c                              |   1 +
 init/do_mounts.h                              |  10 +
 init/do_mounts_dm.c                           | 475 ++++++++++++++++++
 7 files changed, 554 insertions(+)
 create mode 100644 Documentation/device-mapper/dm-boot.txt
 create mode 100644 init/do_mounts_dm.c

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index b8d0bc07ed0a..bd628865f66f 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -91,6 +91,7 @@ parameter is applicable::
 	AX25	Appropriate AX.25 support is enabled.
 	CLK	Common clock infrastructure is enabled.
 	CMA	Contiguous Memory Area support is enabled.
+	DM	Device mapper support is enabled.
 	DRM	Direct Rendering Management support is enabled.
 	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
 	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f42240d..331195d19b32 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -880,6 +880,9 @@
 
 	dis_ucode_ldr	[X86] Disable the microcode loader.
 
+	dm=		[DM] Allows early creation of a device-mapper device.
+			See Documentation/device-mapper/boot.txt.
+
 	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
 			this option disables the debugging code at boot.
 
diff --git a/Documentation/device-mapper/dm-boot.txt b/Documentation/device-mapper/dm-boot.txt
new file mode 100644
index 000000000000..f598f102c980
--- /dev/null
+++ b/Documentation/device-mapper/dm-boot.txt
@@ -0,0 +1,63 @@
+Boot time creation of mapped devices
+====================================
+
+It is possible to configure a device mapper device to act as the root
+device for your system in two ways.
+
+The first is to build an initial ramdisk which boots to a minimal
+userspace which configures the device, then pivot_root(8) in to it.
+
+The second is to possible when the device-mapper and any targets are
+compiled into the kernel (not a module), one or more device-mappers may
+be created and used as the root device at boot time with the parameters
+given with the boot line dm=...
+
+The format is specified as a simple string of data separated by commas and
+optionally semi-colons, where:
+ - a comma is used to separate fields like name, uuid, flags and table (specifies
+   one device)
+ - a semi-colon is used to separate devices.
+
+So the format will look like this:
+
+ dm=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
+
+Where,
+	<dev_name>	::= The device name.
+	<uuid>		::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
+	<minor>		::= The device minor number.
+	<flags>		::= "ro" | "rw"
+	<table>		::= <start> <length> <type> <options>
+	<type>		::= "verity" | "bootcache" | ...
+
+The dm line may be as normal when using the dmsetup tool when using the
+--concise argument.
+
+Examples
+========
+An example of booting to a linear array made up of user-mode linux block
+devices:
+
+  dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
+  root=/dev/dm-0
+
+This will boot to a rw dm-linear target of 8192 sectors split across two
+block devices identified by their major:minor numbers.  After boot, udev
+will rename this target to /dev/mapper/lroot (depending on the rules).
+No uuid was assigned.
+
+An example of multiple device-mappers, with the dm="..." contents shown
+here split on multiple lines for readability:
+
+    vboot,,ro,
+      0 1768000 bootcache
+        aa55b119-2a47-8c45-946a-5ac57765011f+1
+        76e9be054b15884a9fa85973e9cb274c93afadb6
+        1768000 100000 23 20000;
+    vroot,,ro,
+      0 1740800 verity 254:0 254:0 1740800 sha1
+        76e9be054b15884a9fa85973e9cb274c93afadb6
+        5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe;
+    vram,,rw,
+      0 32768 linear 1:0 0,
+      32768 32768 linear 1:1 0
diff --git a/init/Makefile b/init/Makefile
index a3e5ce2bcf08..f814f0ff5974 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -19,6 +19,7 @@ mounts-y			:= do_mounts.o
 mounts-$(CONFIG_BLK_DEV_RAM)	+= do_mounts_rd.o
 mounts-$(CONFIG_BLK_DEV_INITRD)	+= do_mounts_initrd.o
 mounts-$(CONFIG_BLK_DEV_MD)	+= do_mounts_md.o
+mounts-$(CONFIG_BLK_DEV_DM)	+= do_mounts_dm.o
 
 # dependencies on generated files need to be listed explicitly
 $(obj)/version.o: include/generated/compile.h
diff --git a/init/do_mounts.c b/init/do_mounts.c
index e1c9afa9d8c9..d707f12be6e7 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -555,6 +555,7 @@ void __init prepare_namespace(void)
 	wait_for_device_probe();
 
 	md_run_setup();
+	dm_run_setup();
 
 	if (saved_root_name[0]) {
 		root_device_name = saved_root_name;
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 0bb0806de4ce..0f57528ea324 100644
--- a/init/do_mounts.h
+++ b/init/do_mounts.h
@@ -61,3 +61,13 @@ void md_run_setup(void);
 static inline void md_run_setup(void) {}
 
 #endif
+
+#ifdef CONFIG_BLK_DEV_DM
+
+void dm_run_setup(void);
+
+#else
+
+static inline void dm_run_setup(void) {}
+
+#endif
diff --git a/init/do_mounts_dm.c b/init/do_mounts_dm.c
new file mode 100644
index 000000000000..507ae31808ef
--- /dev/null
+++ b/init/do_mounts_dm.c
@@ -0,0 +1,475 @@
+// SPDX-License-Identifier: <SPDX License Expression>
+
+/*
+ * do_mounts_dm.c
+ * Copyright (C) 2017 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Based on do_mounts_md.c
+ *
+ * This file is released under the GPLv2.
+ */
+#include <linux/async.h>
+#include <linux/ctype.h>
+#include <linux/device-mapper.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/delay.h>
+
+#include "do_mounts.h"
+
+#define DM_MAX_DEVICES 256
+#define DM_MAX_NAME 32
+#define DM_MAX_UUID 129
+
+#define DM_MSG_PREFIX "init"
+
+#define is_even(a) (((a) & 1) == 0)
+
+/* See Documentation/device-mapper/dm-boot.txt for dm="..." format details. */
+
+struct target {
+	sector_t start;
+	sector_t length;
+	char *type;
+	char *params;
+	/* simple singly linked list */
+	struct target *next;
+};
+
+struct dm_device {
+	int minor;
+	int ro;
+	char name[DM_MAX_NAME];
+	char uuid[DM_MAX_UUID];
+	struct target *table;
+	int table_count;
+	/* simple singly linked list */
+	struct dm_device *next;
+};
+
+static struct {
+	unsigned long num_devices;
+	char *str;
+} dm_setup_args __initdata;
+
+static int dm_early_setup __initdata;
+
+static void __init *_align(void *ptr, unsigned int a)
+{
+	register unsigned long agn = --a;
+
+	return (void *) (((unsigned long) ptr + agn) & ~agn);
+}
+
+/*
+ * Unescape characters in situ, it replaces all occurrences of "\c"
+ * with 'c'. This is normally used to unescape colons and semi-colons used
+ * in boot format.
+ */
+static char __init *_unescape_char(char *str, const char c)
+{
+	int i = 0, j = 0;
+	int len = strlen(str);
+
+	if (len < 2)
+		return str;
+
+	while (j < len - 1) {
+		if (str[j] == '\\' && str[j + 1] == c) {
+			j = j + 2;
+			str[i++] = c;
+			continue;
+		}
+		str[i++] = str[j++];
+	}
+
+	if (j == len - 1)
+		str[i++] = str[j];
+
+	str[i] = '\0';
+
+	return str;
+}
+
+static void __init dm_setup_cleanup(struct dm_device *devices)
+{
+	struct dm_device *dev = devices;
+
+	while (dev) {
+		struct dm_device *old_dev = dev;
+		struct target *table = dev->table;
+
+		while (table) {
+			struct target *old_table = table;
+
+			kfree(table->type);
+			kfree(table->params);
+			table = table->next;
+			kfree(old_table);
+			dev->table_count--;
+		}
+		WARN_ON(dev->table_count);
+		dev = dev->next;
+		kfree(old_dev);
+	}
+}
+
+/*
+ * Splits a string into tokens ignoring escaped chars
+ *
+ * Updates @s to point after the token, ready for the next call.
+ *
+ * @str: The string to be searched
+ * @c: The character to search for
+ *
+ * Returns:
+ *   The string found or NULL.
+ */
+static char __init *dm_find_unescaped_char(char **str, const char c)
+{
+	char *s = *str;
+	char *p = strchr(*str, c);
+
+	/* loop through all the characters */
+	while (p != NULL) {
+		/* scan backwards through preceding escapes */
+		char *q = p;
+
+		while (q > s && *(q - 1) == '\\')
+			--q;
+		/* even number of escapes so c is a token */
+		if (is_even(p - q)) {
+			*p = '\0';
+			*str = p + 1;
+			return s;
+		}
+		/* else odd escapes so c is escaped, keep going */
+		p = strchr(p + 1, c);
+	}
+
+	if (strlen(*str)) {
+		*str += strlen(*str);
+		return s;
+	}
+
+	return NULL;
+}
+
+static struct target __init *dm_parse_table(struct dm_device *dev, char *str)
+{
+	char type[DM_MAX_TYPE_NAME], *ptr;
+	struct target *table;
+	int n;
+
+	/* trim trailing space */
+	for (ptr = str + strlen(str) - 1; ptr >= str; ptr--)
+		if (!isspace((int) *ptr))
+			break;
+	ptr++;
+	*ptr = '\0';
+
+	/* trim leading space */
+	for (ptr = str; *ptr && isspace((int) *ptr); ptr++)
+		;
+
+	if (!*ptr)
+		return NULL;
+
+	table = kzalloc(sizeof(struct target), GFP_KERNEL);
+	if (!table)
+		return NULL;
+
+	if (sscanf(ptr, "%llu %llu %s %n", &table->start, &table->length,
+		   type, &n) < 3) {
+		DMERR("invalid format of table \"%s\"", str);
+		goto parse_fail;
+	}
+
+	table->type = kstrndup(type, strlen(type), GFP_KERNEL);
+	if (!table->type) {
+		DMERR("invalid type of table");
+		goto parse_fail;
+	}
+
+	ptr += n;
+	table->params = kstrndup(ptr, strlen(ptr), GFP_KERNEL);
+	if (!table->params) {
+		DMERR("invalid params for table");
+		goto parse_fail;
+	}
+
+	dev->table_count++;
+
+	return table;
+
+parse_fail:
+	kfree(table);
+	return NULL;
+}
+
+static int __init dm_parse_device(struct dm_device *dev, char *dev_info)
+{
+	char *aux, *str = dev_info, *ptr = dev_info;
+	struct target **tail = &dev->table;
+	struct target *table;
+	int field = 0;
+
+	while ((str = dm_find_unescaped_char(&ptr, ',')) != NULL) {
+		str = _unescape_char(str, ',');
+		DMDEBUG("Parsing %s", str);
+		switch (field) {
+		case 0: /* set device name */
+			/* ignore path */
+			aux = strrchr(str, '/');
+			str = aux ? &aux[1] : str;
+			DMDEBUG("name %s\n", str);
+			if (strscpy(dev->name, str, sizeof(dev->name)) < 0)
+				return -EINVAL;
+			break;
+		case 1: /* set uuid if any */
+			if (strscpy(dev->uuid, str, sizeof(dev->uuid)) < 0)
+				return -EINVAL;
+			break;
+		case 2: /* set minor if any */
+			if (!strlen(str) || kstrtoint(str, 0, &dev->minor))
+				dev->minor = DM_ANY_MINOR;
+			break;
+		case 3:
+			/* set as read-only if flags = "ro" | "" */
+			if (!strncmp(str, "ro", strlen(str)) || !strlen(str))
+				dev->ro = 1;
+			else if (!strncmp(str, "rw", strlen(str)))
+				dev->ro = 0;
+			else
+				return -EINVAL;
+			break;
+		default:
+			table = dm_parse_table(dev, str);
+			if (!table)
+				goto parse_fail;
+
+			*tail = table;
+			tail = &table->next;
+
+			break;
+		}
+		field++;
+	}
+
+	if (field < 4)
+		goto parse_fail;
+
+	return 0;
+
+parse_fail:
+	return -EINVAL;
+}
+
+static struct dm_device __init *dm_parse_args(void)
+{
+	struct dm_device *devices = NULL;
+	struct dm_device **tail = &devices;
+	struct dm_device *dev;
+	char *dev_info, *str = dm_setup_args.str;
+
+	while ((dev_info = dm_find_unescaped_char(&str, ';')) != NULL) {
+		dev_info = _unescape_char(dev_info, ';');
+		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+		if (!dev)
+			goto error;
+
+		if (dm_parse_device(dev, dev_info))
+			goto error;
+
+		*tail = dev;
+		tail = &dev->next;
+
+		if (++dm_setup_args.num_devices > DM_MAX_DEVICES) {
+			DMERR("too many devices %lu > %d",
+			      dm_setup_args.num_devices, DM_MAX_DEVICES);
+			goto error;
+		}
+	}
+	return devices;
+error:
+	dm_setup_cleanup(devices);
+	return NULL;
+}
+
+/*
+ * Parse the command-line parameters given our kernel, but do not
+ * actually try to invoke the DM device now; that is handled by
+ * dm_setup_drives after the low-level disk drivers have initialised.
+ * dm format is described at the top of the file.
+ *
+ * Because dm minor numbers are assigned in ascending order starting with 0,
+ * You can assume the first device is /dev/dm-0, the next device is /dev/dm-1,
+ * and so forth.
+ */
+static int __init dm_setup(char *str)
+{
+	if (!str) {
+		DMERR("Invalid arguments supplied to dm=.");
+		return 0;
+	}
+
+	DMDEBUG("Want to parse \"%s\"", str);
+
+	dm_setup_args.num_devices = 0;
+	dm_setup_args.str = str;
+
+	dm_early_setup = 1;
+
+	return 1;
+}
+
+static char __init *dm_add_target(struct target *table, char *out, char *end)
+{
+	char *out_sp = out;
+	struct dm_target_spec sp;
+	size_t sp_size = sizeof(struct dm_target_spec);
+	int len;
+	char *pt;
+
+	if (strlen(table->type) >= sizeof(sp.target_type)) {
+		DMERR("target type name %s is too long.", table->type);
+		return NULL;
+	}
+
+	sp.status = 0;
+	sp.sector_start = table->start;
+	sp.length = table->length;
+	strscpy(sp.target_type, table->type, sizeof(sp.target_type));
+	sp.target_type[sizeof(sp.target_type) - 1] = '\0';
+
+	out += sp_size;
+	pt = table->params;
+	len = strlen(table->params);
+
+	if ((out >= end) || (out + len + 1) >= end) {
+		DMERR("ran out of memory building ioctl parameter");
+		return NULL;
+	}
+
+	strcpy(out, table->params);
+	out += len + 1;
+	/* align next block */
+	out = _align(out, 8);
+
+	sp.next = out - out_sp;
+	memcpy(out_sp, &sp, sp_size);
+
+	return out;
+}
+
+static struct dm_ioctl __init *dm_setup_ioctl(struct dm_device *dev, int flags)
+{
+	const size_t min_size = 16 * 1024;
+	size_t len = sizeof(struct dm_ioctl);
+	struct dm_ioctl *dmi;
+	struct target *table = dev->table;
+	char *b, *e;
+
+	if (len < min_size)
+		len = min_size;
+
+	dmi = kzalloc(len, GFP_KERNEL);
+	if (!dmi)
+		return NULL;
+
+	dmi->version[0] = 4;
+	dmi->version[1] = 0;
+	dmi->version[2] = 0;
+	dmi->data_size = len;
+	dmi->data_start = sizeof(struct dm_ioctl);
+	dmi->flags = flags;
+	dmi->target_count = dev->table_count;
+	dmi->event_nr = 1;
+
+	/* Only one between uuid, name and dev should be filled */
+	if (*dev->uuid)
+		strscpy(dmi->uuid, dev->uuid, sizeof(dmi->uuid));
+	else if (*dev->name)
+		strscpy(dmi->name, dev->name, sizeof(dmi->name));
+	else if (dev->minor > 0)
+		dmi->dev = dev->minor;
+	else
+		return NULL;
+
+	b = (char *) (dmi + 1);
+	e = (char *) dmi + len;
+
+	while (table != NULL) {
+		DMDEBUG("device %s adding table '%llu %llu %s %s'",
+			dev->name,
+			(unsigned long long) table->start,
+			(unsigned long long) table->length,
+			table->type, table->params);
+		b = dm_add_target(table, b, e);
+		if (!b) {
+			kfree(dmi);
+			return NULL;
+		}
+		table = table->next;
+	}
+
+	return dmi;
+}
+
+static void __init dm_setup_drives(void)
+{
+	struct dm_device *dev;
+	int flags;
+	struct dm_device *devices;
+	struct dm_ioctl *io = NULL;
+
+	devices = dm_parse_args();
+
+	for (dev = devices; dev; dev = dev->next) {
+		flags = dev->minor < 0 ? 0 : DM_PERSISTENT_DEV_FLAG;
+		io = dm_setup_ioctl(dev, flags);
+		if (!io)
+			return;
+		io->dev = dev->minor;
+		/* create a new device */
+		if (dm_ioctl_cmd(DM_DEV_CREATE, io)) {
+			DMERR("failed to create device %s", dev->name);
+			goto out_free;
+		}
+		kfree(io);
+
+		flags = dev->ro ? DM_READONLY_FLAG : 0;
+		io = dm_setup_ioctl(dev, flags);
+		if (!io)
+			return;
+		/* load a table into the 'inactive' slot for the device. */
+		if (dm_ioctl_cmd(DM_TABLE_LOAD, io)) {
+			DMERR("failed to load device %s tables", dev->name);
+			goto out_free;
+		}
+		kfree(io);
+
+		io = dm_setup_ioctl(dev, 0);
+		if (!io)
+			return;
+		/* resume and the device should be ready. */
+		if (dm_ioctl_cmd(DM_DEV_SUSPEND, io)) {
+			DMERR("failed to resume device %s", dev->name);
+			goto out_free;
+		}
+
+		DMINFO("dm-%d (%s) is ready", dev->minor, dev->name);
+	}
+
+out_free:
+	kfree(io);
+}
+
+__setup("dm=", dm_setup);
+
+void __init dm_run_setup(void)
+{
+	if (!dm_early_setup)
+		return;
+	DMINFO("attempting early device configuration.");
+	dm_setup_drives();
+}
-- 
2.19.0

[PATCH 2/2] init: add support to directly boot to a mapped device

[Helen Koike]

From: Will Drewry <wad@chromium.org>

Add a dm= kernel parameter modeled after the md= parameter from
do_mounts_md. It allows for device-mapper targets to be configured at
boot time for use early in the boot process (as the root device or
otherwise).

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
[rework to use dm_ioctl calls]
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
[rework to use concise format | rework for upstream]
Signed-off-by: Helen Koike <helen.koike@collabora.com>
---
 .../admin-guide/kernel-parameters.rst         |   1 +
 .../admin-guide/kernel-parameters.txt         |   3 +
 Documentation/device-mapper/dm-boot.txt       |  63 +++
 init/Makefile                                 |   1 +
 init/do_mounts.c                              |   1 +
 init/do_mounts.h                              |  10 +
 init/do_mounts_dm.c                           | 475 ++++++++++++++++++
 7 files changed, 554 insertions(+)
 create mode 100644 Documentation/device-mapper/dm-boot.txt
 create mode 100644 init/do_mounts_dm.c

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index b8d0bc07ed0a..bd628865f66f 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -91,6 +91,7 @@ parameter is applicable::
 	AX25	Appropriate AX.25 support is enabled.
 	CLK	Common clock infrastructure is enabled.
 	CMA	Contiguous Memory Area support is enabled.
+	DM	Device mapper support is enabled.
 	DRM	Direct Rendering Management support is enabled.
 	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
 	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f42240d..331195d19b32 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -880,6 +880,9 @@
 
 	dis_ucode_ldr	[X86] Disable the microcode loader.
 
+	dm=		[DM] Allows early creation of a device-mapper device.
+			See Documentation/device-mapper/boot.txt.
+
 	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
 			this option disables the debugging code at boot.
 
diff --git a/Documentation/device-mapper/dm-boot.txt b/Documentation/device-mapper/dm-boot.txt
new file mode 100644
index 000000000000..f598f102c980
--- /dev/null
+++ b/Documentation/device-mapper/dm-boot.txt
@@ -0,0 +1,63 @@
+Boot time creation of mapped devices
+====================================
+
+It is possible to configure a device mapper device to act as the root
+device for your system in two ways.
+
+The first is to build an initial ramdisk which boots to a minimal
+userspace which configures the device, then pivot_root(8) in to it.
+
+The second is to possible when the device-mapper and any targets are
+compiled into the kernel (not a module), one or more device-mappers may
+be created and used as the root device at boot time with the parameters
+given with the boot line dm=...
+
+The format is specified as a simple string of data separated by commas and
+optionally semi-colons, where:
+ - a comma is used to separate fields like name, uuid, flags and table (specifies
+   one device)
+ - a semi-colon is used to separate devices.
+
+So the format will look like this:
+
+ dm=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
+
+Where,
+	<dev_name>	::= The device name.
+	<uuid>		::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
+	<minor>		::= The device minor number.
+	<flags>		::= "ro" | "rw"
+	<table>		::= <start> <length> <type> <options>
+	<type>		::= "verity" | "bootcache" | ...
+
+The dm line may be as normal when using the dmsetup tool when using the
+--concise argument.
+
+Examples
+========
+An example of booting to a linear array made up of user-mode linux block
+devices:
+
+  dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
+  root=/dev/dm-0
+
+This will boot to a rw dm-linear target of 8192 sectors split across two
+block devices identified by their major:minor numbers.  After boot, udev
+will rename this target to /dev/mapper/lroot (depending on the rules).
+No uuid was assigned.
+
+An example of multiple device-mappers, with the dm="..." contents shown
+here split on multiple lines for readability:
+
+    vboot,,ro,
+      0 1768000 bootcache
+        aa55b119-2a47-8c45-946a-5ac57765011f+1
+        76e9be054b15884a9fa85973e9cb274c93afadb6
+        1768000 100000 23 20000;
+    vroot,,ro,
+      0 1740800 verity 254:0 254:0 1740800 sha1
+        76e9be054b15884a9fa85973e9cb274c93afadb6
+        5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe;
+    vram,,rw,
+      0 32768 linear 1:0 0,
+      32768 32768 linear 1:1 0
diff --git a/init/Makefile b/init/Makefile
index a3e5ce2bcf08..f814f0ff5974 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -19,6 +19,7 @@ mounts-y			:= do_mounts.o
 mounts-$(CONFIG_BLK_DEV_RAM)	+= do_mounts_rd.o
 mounts-$(CONFIG_BLK_DEV_INITRD)	+= do_mounts_initrd.o
 mounts-$(CONFIG_BLK_DEV_MD)	+= do_mounts_md.o
+mounts-$(CONFIG_BLK_DEV_DM)	+= do_mounts_dm.o
 
 # dependencies on generated files need to be listed explicitly
 $(obj)/version.o: include/generated/compile.h
diff --git a/init/do_mounts.c b/init/do_mounts.c
index e1c9afa9d8c9..d707f12be6e7 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -555,6 +555,7 @@ void __init prepare_namespace(void)
 	wait_for_device_probe();
 
 	md_run_setup();
+	dm_run_setup();
 
 	if (saved_root_name[0]) {
 		root_device_name = saved_root_name;
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 0bb0806de4ce..0f57528ea324 100644
--- a/init/do_mounts.h
+++ b/init/do_mounts.h
@@ -61,3 +61,13 @@ void md_run_setup(void);
 static inline void md_run_setup(void) {}
 
 #endif
+
+#ifdef CONFIG_BLK_DEV_DM
+
+void dm_run_setup(void);
+
+#else
+
+static inline void dm_run_setup(void) {}
+
+#endif
diff --git a/init/do_mounts_dm.c b/init/do_mounts_dm.c
new file mode 100644
index 000000000000..507ae31808ef
--- /dev/null
+++ b/init/do_mounts_dm.c
@@ -0,0 +1,475 @@
+// SPDX-License-Identifier: <SPDX License Expression>
+
+/*
+ * do_mounts_dm.c
+ * Copyright (C) 2017 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Based on do_mounts_md.c
+ *
+ * This file is released under the GPLv2.
+ */
+#include <linux/async.h>
+#include <linux/ctype.h>
+#include <linux/device-mapper.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/delay.h>
+
+#include "do_mounts.h"
+
+#define DM_MAX_DEVICES 256
+#define DM_MAX_NAME 32
+#define DM_MAX_UUID 129
+
+#define DM_MSG_PREFIX "init"
+
+#define is_even(a) (((a) & 1) == 0)
+
+/* See Documentation/device-mapper/dm-boot.txt for dm="..." format details. */
+
+struct target {
+	sector_t start;
+	sector_t length;
+	char *type;
+	char *params;
+	/* simple singly linked list */
+	struct target *next;
+};
+
+struct dm_device {
+	int minor;
+	int ro;
+	char name[DM_MAX_NAME];
+	char uuid[DM_MAX_UUID];
+	struct target *table;
+	int table_count;
+	/* simple singly linked list */
+	struct dm_device *next;
+};
+
+static struct {
+	unsigned long num_devices;
+	char *str;
+} dm_setup_args __initdata;
+
+static int dm_early_setup __initdata;
+
+static void __init *_align(void *ptr, unsigned int a)
+{
+	register unsigned long agn = --a;
+
+	return (void *) (((unsigned long) ptr + agn) & ~agn);
+}
+
+/*
+ * Unescape characters in situ, it replaces all occurrences of "\c"
+ * with 'c'. This is normally used to unescape colons and semi-colons used
+ * in boot format.
+ */
+static char __init *_unescape_char(char *str, const char c)
+{
+	int i = 0, j = 0;
+	int len = strlen(str);
+
+	if (len < 2)
+		return str;
+
+	while (j < len - 1) {
+		if (str[j] == '\\' && str[j + 1] == c) {
+			j = j + 2;
+			str[i++] = c;
+			continue;
+		}
+		str[i++] = str[j++];
+	}
+
+	if (j == len - 1)
+		str[i++] = str[j];
+
+	str[i] = '\0';
+
+	return str;
+}
+
+static void __init dm_setup_cleanup(struct dm_device *devices)
+{
+	struct dm_device *dev = devices;
+
+	while (dev) {
+		struct dm_device *old_dev = dev;
+		struct target *table = dev->table;
+
+		while (table) {
+			struct target *old_table = table;
+
+			kfree(table->type);
+			kfree(table->params);
+			table = table->next;
+			kfree(old_table);
+			dev->table_count--;
+		}
+		WARN_ON(dev->table_count);
+		dev = dev->next;
+		kfree(old_dev);
+	}
+}
+
+/*
+ * Splits a string into tokens ignoring escaped chars
+ *
+ * Updates @s to point after the token, ready for the next call.
+ *
+ * @str: The string to be searched
+ * @c: The character to search for
+ *
+ * Returns:
+ *   The string found or NULL.
+ */
+static char __init *dm_find_unescaped_char(char **str, const char c)
+{
+	char *s = *str;
+	char *p = strchr(*str, c);
+
+	/* loop through all the characters */
+	while (p != NULL) {
+		/* scan backwards through preceding escapes */
+		char *q = p;
+
+		while (q > s && *(q - 1) == '\\')
+			--q;
+		/* even number of escapes so c is a token */
+		if (is_even(p - q)) {
+			*p = '\0';
+			*str = p + 1;
+			return s;
+		}
+		/* else odd escapes so c is escaped, keep going */
+		p = strchr(p + 1, c);
+	}
+
+	if (strlen(*str)) {
+		*str += strlen(*str);
+		return s;
+	}
+
+	return NULL;
+}
+
+static struct target __init *dm_parse_table(struct dm_device *dev, char *str)
+{
+	char type[DM_MAX_TYPE_NAME], *ptr;
+	struct target *table;
+	int n;
+
+	/* trim trailing space */
+	for (ptr = str + strlen(str) - 1; ptr >= str; ptr--)
+		if (!isspace((int) *ptr))
+			break;
+	ptr++;
+	*ptr = '\0';
+
+	/* trim leading space */
+	for (ptr = str; *ptr && isspace((int) *ptr); ptr++)
+		;
+
+	if (!*ptr)
+		return NULL;
+
+	table = kzalloc(sizeof(struct target), GFP_KERNEL);
+	if (!table)
+		return NULL;
+
+	if (sscanf(ptr, "%llu %llu %s %n", &table->start, &table->length,
+		   type, &n) < 3) {
+		DMERR("invalid format of table \"%s\"", str);
+		goto parse_fail;
+	}
+
+	table->type = kstrndup(type, strlen(type), GFP_KERNEL);
+	if (!table->type) {
+		DMERR("invalid type of table");
+		goto parse_fail;
+	}
+
+	ptr += n;
+	table->params = kstrndup(ptr, strlen(ptr), GFP_KERNEL);
+	if (!table->params) {
+		DMERR("invalid params for table");
+		goto parse_fail;
+	}
+
+	dev->table_count++;
+
+	return table;
+
+parse_fail:
+	kfree(table);
+	return NULL;
+}
+
+static int __init dm_parse_device(struct dm_device *dev, char *dev_info)
+{
+	char *aux, *str = dev_info, *ptr = dev_info;
+	struct target **tail = &dev->table;
+	struct target *table;
+	int field = 0;
+
+	while ((str = dm_find_unescaped_char(&ptr, ',')) != NULL) {
+		str = _unescape_char(str, ',');
+		DMDEBUG("Parsing %s", str);
+		switch (field) {
+		case 0: /* set device name */
+			/* ignore path */
+			aux = strrchr(str, '/');
+			str = aux ? &aux[1] : str;
+			DMDEBUG("name %s\n", str);
+			if (strscpy(dev->name, str, sizeof(dev->name)) < 0)
+				return -EINVAL;
+			break;
+		case 1: /* set uuid if any */
+			if (strscpy(dev->uuid, str, sizeof(dev->uuid)) < 0)
+				return -EINVAL;
+			break;
+		case 2: /* set minor if any */
+			if (!strlen(str) || kstrtoint(str, 0, &dev->minor))
+				dev->minor = DM_ANY_MINOR;
+			break;
+		case 3:
+			/* set as read-only if flags = "ro" | "" */
+			if (!strncmp(str, "ro", strlen(str)) || !strlen(str))
+				dev->ro = 1;
+			else if (!strncmp(str, "rw", strlen(str)))
+				dev->ro = 0;
+			else
+				return -EINVAL;
+			break;
+		default:
+			table = dm_parse_table(dev, str);
+			if (!table)
+				goto parse_fail;
+
+			*tail = table;
+			tail = &table->next;
+
+			break;
+		}
+		field++;
+	}
+
+	if (field < 4)
+		goto parse_fail;
+
+	return 0;
+
+parse_fail:
+	return -EINVAL;
+}
+
+static struct dm_device __init *dm_parse_args(void)
+{
+	struct dm_device *devices = NULL;
+	struct dm_device **tail = &devices;
+	struct dm_device *dev;
+	char *dev_info, *str = dm_setup_args.str;
+
+	while ((dev_info = dm_find_unescaped_char(&str, ';')) != NULL) {
+		dev_info = _unescape_char(dev_info, ';');
+		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+		if (!dev)
+			goto error;
+
+		if (dm_parse_device(dev, dev_info))
+			goto error;
+
+		*tail = dev;
+		tail = &dev->next;
+
+		if (++dm_setup_args.num_devices > DM_MAX_DEVICES) {
+			DMERR("too many devices %lu > %d",
+			      dm_setup_args.num_devices, DM_MAX_DEVICES);
+			goto error;
+		}
+	}
+	return devices;
+error:
+	dm_setup_cleanup(devices);
+	return NULL;
+}
+
+/*
+ * Parse the command-line parameters given our kernel, but do not
+ * actually try to invoke the DM device now; that is handled by
+ * dm_setup_drives after the low-level disk drivers have initialised.
+ * dm format is described at the top of the file.
+ *
+ * Because dm minor numbers are assigned in ascending order starting with 0,
+ * You can assume the first device is /dev/dm-0, the next device is /dev/dm-1,
+ * and so forth.
+ */
+static int __init dm_setup(char *str)
+{
+	if (!str) {
+		DMERR("Invalid arguments supplied to dm=.");
+		return 0;
+	}
+
+	DMDEBUG("Want to parse \"%s\"", str);
+
+	dm_setup_args.num_devices = 0;
+	dm_setup_args.str = str;
+
+	dm_early_setup = 1;
+
+	return 1;
+}
+
+static char __init *dm_add_target(struct target *table, char *out, char *end)
+{
+	char *out_sp = out;
+	struct dm_target_spec sp;
+	size_t sp_size = sizeof(struct dm_target_spec);
+	int len;
+	char *pt;
+
+	if (strlen(table->type) >= sizeof(sp.target_type)) {
+		DMERR("target type name %s is too long.", table->type);
+		return NULL;
+	}
+
+	sp.status = 0;
+	sp.sector_start = table->start;
+	sp.length = table->length;
+	strscpy(sp.target_type, table->type, sizeof(sp.target_type));
+	sp.target_type[sizeof(sp.target_type) - 1] = '\0';
+
+	out += sp_size;
+	pt = table->params;
+	len = strlen(table->params);
+
+	if ((out >= end) || (out + len + 1) >= end) {
+		DMERR("ran out of memory building ioctl parameter");
+		return NULL;
+	}
+
+	strcpy(out, table->params);
+	out += len + 1;
+	/* align next block */
+	out = _align(out, 8);
+
+	sp.next = out - out_sp;
+	memcpy(out_sp, &sp, sp_size);
+
+	return out;
+}
+
+static struct dm_ioctl __init *dm_setup_ioctl(struct dm_device *dev, int flags)
+{
+	const size_t min_size = 16 * 1024;
+	size_t len = sizeof(struct dm_ioctl);
+	struct dm_ioctl *dmi;
+	struct target *table = dev->table;
+	char *b, *e;
+
+	if (len < min_size)
+		len = min_size;
+
+	dmi = kzalloc(len, GFP_KERNEL);
+	if (!dmi)
+		return NULL;
+
+	dmi->version[0] = 4;
+	dmi->version[1] = 0;
+	dmi->version[2] = 0;
+	dmi->data_size = len;
+	dmi->data_start = sizeof(struct dm_ioctl);
+	dmi->flags = flags;
+	dmi->target_count = dev->table_count;
+	dmi->event_nr = 1;
+
+	/* Only one between uuid, name and dev should be filled */
+	if (*dev->uuid)
+		strscpy(dmi->uuid, dev->uuid, sizeof(dmi->uuid));
+	else if (*dev->name)
+		strscpy(dmi->name, dev->name, sizeof(dmi->name));
+	else if (dev->minor > 0)
+		dmi->dev = dev->minor;
+	else
+		return NULL;
+
+	b = (char *) (dmi + 1);
+	e = (char *) dmi + len;
+
+	while (table != NULL) {
+		DMDEBUG("device %s adding table '%llu %llu %s %s'",
+			dev->name,
+			(unsigned long long) table->start,
+			(unsigned long long) table->length,
+			table->type, table->params);
+		b = dm_add_target(table, b, e);
+		if (!b) {
+			kfree(dmi);
+			return NULL;
+		}
+		table = table->next;
+	}
+
+	return dmi;
+}
+
+static void __init dm_setup_drives(void)
+{
+	struct dm_device *dev;
+	int flags;
+	struct dm_device *devices;
+	struct dm_ioctl *io = NULL;
+
+	devices = dm_parse_args();
+
+	for (dev = devices; dev; dev = dev->next) {
+		flags = dev->minor < 0 ? 0 : DM_PERSISTENT_DEV_FLAG;
+		io = dm_setup_ioctl(dev, flags);
+		if (!io)
+			return;
+		io->dev = dev->minor;
+		/* create a new device */
+		if (dm_ioctl_cmd(DM_DEV_CREATE, io)) {
+			DMERR("failed to create device %s", dev->name);
+			goto out_free;
+		}
+		kfree(io);
+
+		flags = dev->ro ? DM_READONLY_FLAG : 0;
+		io = dm_setup_ioctl(dev, flags);
+		if (!io)
+			return;
+		/* load a table into the 'inactive' slot for the device. */
+		if (dm_ioctl_cmd(DM_TABLE_LOAD, io)) {
+			DMERR("failed to load device %s tables", dev->name);
+			goto out_free;
+		}
+		kfree(io);
+
+		io = dm_setup_ioctl(dev, 0);
+		if (!io)
+			return;
+		/* resume and the device should be ready. */
+		if (dm_ioctl_cmd(DM_DEV_SUSPEND, io)) {
+			DMERR("failed to resume device %s", dev->name);
+			goto out_free;
+		}
+
+		DMINFO("dm-%d (%s) is ready", dev->minor, dev->name);
+	}
+
+out_free:
+	kfree(io);
+}
+
+__setup("dm=", dm_setup);
+
+void __init dm_run_setup(void)
+{
+	if (!dm_early_setup)
+		return;
+	DMINFO("attempting early device configuration.");
+	dm_setup_drives();
+}
-- 
2.19.0

Re: [PATCH 2/2] init: add support to directly boot to a mapped device

[Randy Dunlap]

On 9/25/18 10:00 PM, Helen Koike wrote:
> From: Will Drewry <wad@chromium.org>
> 
> Add a dm= kernel parameter modeled after the md= parameter from
> do_mounts_md. It allows for device-mapper targets to be configured at
> boot time for use early in the boot process (as the root device or
> otherwise).
> 
> Signed-off-by: Will Drewry <wad@chromium.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> [rework to use dm_ioctl calls]
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> [rework to use concise format | rework for upstream]
> Signed-off-by: Helen Koike <helen.koike@collabora.com>

Hi,

A few small comments inline...

> ---
>  .../admin-guide/kernel-parameters.rst         |   1 +
>  .../admin-guide/kernel-parameters.txt         |   3 +
>  Documentation/device-mapper/dm-boot.txt       |  63 +++
>  init/Makefile                                 |   1 +
>  init/do_mounts.c                              |   1 +
>  init/do_mounts.h                              |  10 +
>  init/do_mounts_dm.c                           | 475 ++++++++++++++++++
>  7 files changed, 554 insertions(+)
>  create mode 100644 Documentation/device-mapper/dm-boot.txt
>  create mode 100644 init/do_mounts_dm.c

> diff --git a/Documentation/device-mapper/dm-boot.txt b/Documentation/device-mapper/dm-boot.txt
> new file mode 100644
> index 000000000000..f598f102c980
> --- /dev/null
> +++ b/Documentation/device-mapper/dm-boot.txt
> @@ -0,0 +1,63 @@
> +Boot time creation of mapped devices
> +====================================
> +
> +It is possible to configure a device mapper device to act as the root
> +device for your system in two ways.
> +
> +The first is to build an initial ramdisk which boots to a minimal
> +userspace which configures the device, then pivot_root(8) in to it.
> +
> +The second is to possible when the device-mapper and any targets are

parse error:  ^^^^^^^^^^^^^^

> +compiled into the kernel (not a module), one or more device-mappers may
> +be created and used as the root device at boot time with the parameters
> +given with the boot line dm=...
> +
> +The format is specified as a simple string of data separated by commas and

for some definition of "simple".

> +optionally semi-colons, where:
> + - a comma is used to separate fields like name, uuid, flags and table (specifies
> +   one device)
> + - a semi-colon is used to separate devices.
> +
> +So the format will look like this:
> +
> + dm=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
> +
> +Where,
> +	<dev_name>	::= The device name.
> +	<uuid>		::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
> +	<minor>		::= The device minor number.
> +	<flags>		::= "ro" | "rw"
> +	<table>		::= <start> <length> <type> <options>
> +	<type>		::= "verity" | "bootcache" | ...
> +
> +The dm line may be as normal when using the dmsetup tool when using the
> +--concise argument.
> +
> +Examples
> +========
> +An example of booting to a linear array made up of user-mode linux block
> +devices:
> +
> +  dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
> +  root=/dev/dm-0
> +
> +This will boot to a rw dm-linear target of 8192 sectors split across two
> +block devices identified by their major:minor numbers.  After boot, udev
> +will rename this target to /dev/mapper/lroot (depending on the rules).
> +No uuid was assigned.
> +
> +An example of multiple device-mappers, with the dm="..." contents shown
> +here split on multiple lines for readability:
> +
> +    vboot,,ro,
> +      0 1768000 bootcache
> +        aa55b119-2a47-8c45-946a-5ac57765011f+1
> +        76e9be054b15884a9fa85973e9cb274c93afadb6
> +        1768000 100000 23 20000;
> +    vroot,,ro,
> +      0 1740800 verity 254:0 254:0 1740800 sha1
> +        76e9be054b15884a9fa85973e9cb274c93afadb6
> +        5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe;
> +    vram,,rw,
> +      0 32768 linear 1:0 0,
> +      32768 32768 linear 1:1 0

> diff --git a/init/do_mounts_dm.c b/init/do_mounts_dm.c
> new file mode 100644
> index 000000000000..507ae31808ef
> --- /dev/null
> +++ b/init/do_mounts_dm.c
> @@ -0,0 +1,475 @@
> +// SPDX-License-Identifier: <SPDX License Expression>
> +
> +/*
> + * do_mounts_dm.c
> + * Copyright (C) 2017 The Chromium OS Authors <chromium-os-dev@chromium.org>
> + * Based on do_mounts_md.c
> + *
> + * This file is released under the GPLv2.
> + */
> +#include <linux/async.h>
> +#include <linux/ctype.h>
> +#include <linux/device-mapper.h>
> +#include <linux/fs.h>
> +#include <linux/string.h>
> +#include <linux/delay.h>
> +
> +#include "do_mounts.h"
> +
> +#define DM_MAX_DEVICES 256
> +#define DM_MAX_NAME 32
> +#define DM_MAX_UUID 129
> +
> +#define DM_MSG_PREFIX "init"
> +
> +#define is_even(a) (((a) & 1) == 0)
> +
> +/* See Documentation/device-mapper/dm-boot.txt for dm="..." format details. */
> +
> +struct target {
> +	sector_t start;
> +	sector_t length;
> +	char *type;
> +	char *params;
> +	/* simple singly linked list */
> +	struct target *next;
> +};
> +
> +struct dm_device {
> +	int minor;
> +	int ro;
> +	char name[DM_MAX_NAME];
> +	char uuid[DM_MAX_UUID];
> +	struct target *table;
> +	int table_count;
> +	/* simple singly linked list */
> +	struct dm_device *next;
> +};
> +
> +static struct {
> +	unsigned long num_devices;
> +	char *str;
> +} dm_setup_args __initdata;
> +
> +static int dm_early_setup __initdata;
> +

// @a: must be a power of 2

> +static void __init *_align(void *ptr, unsigned int a)
> +{
> +	register unsigned long agn = --a;
> +
> +	return (void *) (((unsigned long) ptr + agn) & ~agn);
> +}


thanks.
-- 
~Randy

Re: [linux-lvm] [PATCH 2/2] init: add support to directly boot to a mapped device

[Randy Dunlap]

On 9/25/18 10:00 PM, Helen Koike wrote:
> From: Will Drewry <wad@chromium.org>
> 
> Add a dm= kernel parameter modeled after the md= parameter from
> do_mounts_md. It allows for device-mapper targets to be configured at
> boot time for use early in the boot process (as the root device or
> otherwise).
> 
> Signed-off-by: Will Drewry <wad@chromium.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> [rework to use dm_ioctl calls]
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> [rework to use concise format | rework for upstream]
> Signed-off-by: Helen Koike <helen.koike@collabora.com>

Hi,

A few small comments inline...

> ---
>  .../admin-guide/kernel-parameters.rst         |   1 +
>  .../admin-guide/kernel-parameters.txt         |   3 +
>  Documentation/device-mapper/dm-boot.txt       |  63 +++
>  init/Makefile                                 |   1 +
>  init/do_mounts.c                              |   1 +
>  init/do_mounts.h                              |  10 +
>  init/do_mounts_dm.c                           | 475 ++++++++++++++++++
>  7 files changed, 554 insertions(+)
>  create mode 100644 Documentation/device-mapper/dm-boot.txt
>  create mode 100644 init/do_mounts_dm.c

> diff --git a/Documentation/device-mapper/dm-boot.txt b/Documentation/device-mapper/dm-boot.txt
> new file mode 100644
> index 000000000000..f598f102c980
> --- /dev/null
> +++ b/Documentation/device-mapper/dm-boot.txt
> @@ -0,0 +1,63 @@
> +Boot time creation of mapped devices
> +====================================
> +
> +It is possible to configure a device mapper device to act as the root
> +device for your system in two ways.
> +
> +The first is to build an initial ramdisk which boots to a minimal
> +userspace which configures the device, then pivot_root(8) in to it.
> +
> +The second is to possible when the device-mapper and any targets are

parse error:  ^^^^^^^^^^^^^^

> +compiled into the kernel (not a module), one or more device-mappers may
> +be created and used as the root device at boot time with the parameters
> +given with the boot line dm=...
> +
> +The format is specified as a simple string of data separated by commas and

for some definition of "simple".

> +optionally semi-colons, where:
> + - a comma is used to separate fields like name, uuid, flags and table (specifies
> +   one device)
> + - a semi-colon is used to separate devices.
> +
> +So the format will look like this:
> +
> + dm=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
> +
> +Where,
> +	<dev_name>	::= The device name.
> +	<uuid>		::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
> +	<minor>		::= The device minor number.
> +	<flags>		::= "ro" | "rw"
> +	<table>		::= <start> <length> <type> <options>
> +	<type>		::= "verity" | "bootcache" | ...
> +
> +The dm line may be as normal when using the dmsetup tool when using the
> +--concise argument.
> +
> +Examples
> +========
> +An example of booting to a linear array made up of user-mode linux block
> +devices:
> +
> +  dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
> +  root=/dev/dm-0
> +
> +This will boot to a rw dm-linear target of 8192 sectors split across two
> +block devices identified by their major:minor numbers.  After boot, udev
> +will rename this target to /dev/mapper/lroot (depending on the rules).
> +No uuid was assigned.
> +
> +An example of multiple device-mappers, with the dm="..." contents shown
> +here split on multiple lines for readability:
> +
> +    vboot,,ro,
> +      0 1768000 bootcache
> +        aa55b119-2a47-8c45-946a-5ac57765011f+1
> +        76e9be054b15884a9fa85973e9cb274c93afadb6
> +        1768000 100000 23 20000;
> +    vroot,,ro,
> +      0 1740800 verity 254:0 254:0 1740800 sha1
> +        76e9be054b15884a9fa85973e9cb274c93afadb6
> +        5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe;
> +    vram,,rw,
> +      0 32768 linear 1:0 0,
> +      32768 32768 linear 1:1 0

> diff --git a/init/do_mounts_dm.c b/init/do_mounts_dm.c
> new file mode 100644
> index 000000000000..507ae31808ef
> --- /dev/null
> +++ b/init/do_mounts_dm.c
> @@ -0,0 +1,475 @@
> +// SPDX-License-Identifier: <SPDX License Expression>
> +
> +/*
> + * do_mounts_dm.c
> + * Copyright (C) 2017 The Chromium OS Authors <chromium-os-dev@chromium.org>
> + * Based on do_mounts_md.c
> + *
> + * This file is released under the GPLv2.
> + */
> +#include <linux/async.h>
> +#include <linux/ctype.h>
> +#include <linux/device-mapper.h>
> +#include <linux/fs.h>
> +#include <linux/string.h>
> +#include <linux/delay.h>
> +
> +#include "do_mounts.h"
> +
> +#define DM_MAX_DEVICES 256
> +#define DM_MAX_NAME 32
> +#define DM_MAX_UUID 129
> +
> +#define DM_MSG_PREFIX "init"
> +
> +#define is_even(a) (((a) & 1) == 0)
> +
> +/* See Documentation/device-mapper/dm-boot.txt for dm="..." format details. */
> +
> +struct target {
> +	sector_t start;
> +	sector_t length;
> +	char *type;
> +	char *params;
> +	/* simple singly linked list */
> +	struct target *next;
> +};
> +
> +struct dm_device {
> +	int minor;
> +	int ro;
> +	char name[DM_MAX_NAME];
> +	char uuid[DM_MAX_UUID];
> +	struct target *table;
> +	int table_count;
> +	/* simple singly linked list */
> +	struct dm_device *next;
> +};
> +
> +static struct {
> +	unsigned long num_devices;
> +	char *str;
> +} dm_setup_args __initdata;
> +
> +static int dm_early_setup __initdata;
> +

// @a: must be a power of 2

> +static void __init *_align(void *ptr, unsigned int a)
> +{
> +	register unsigned long agn = --a;
> +
> +	return (void *) (((unsigned long) ptr + agn) & ~agn);
> +}


thanks.
-- 
~Randy

Re: [PATCH 0/2] boot to a mapped device

[Helen Koike]

On 9/26/18 2:00 AM, Helen Koike wrote:
> This series is reviving an old patchwork.
> Booting from a mapped device requires an initramfs. This series is
> allows for device-mapper targets to be configured at boot time for
> use early in the boot process (as the root device or otherwise).
> 
> Example, the following could be added in the boot parameters.
> dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> 
> Enric Balletbo i Serra (1):
>   dm ioctl: add a device mapper ioctl function.
> 
> Will Drewry (1):
>   init: add support to directly boot to a mapped device
> 
>  .../admin-guide/kernel-parameters.rst         |   1 +
>  .../admin-guide/kernel-parameters.txt         |   3 +
>  Documentation/device-mapper/dm-boot.txt       |  63 +++
>  drivers/md/dm-ioctl.c                         |  50 ++
>  include/linux/device-mapper.h                 |   6 +
>  init/Makefile                                 |   1 +
>  init/do_mounts.c                              |   1 +
>  init/do_mounts.h                              |  10 +
>  init/do_mounts_dm.c                           | 475 ++++++++++++++++++
>  9 files changed, 610 insertions(+)
>  create mode 100644 Documentation/device-mapper/dm-boot.txt
>  create mode 100644 init/do_mounts_dm.c
> 

Sorry about sending this email multiple times, my git send-email wans't
properly configured.

Helen

Re: [linux-lvm] [PATCH 0/2] boot to a mapped device

[Helen Koike]

On 9/26/18 2:00 AM, Helen Koike wrote:
> This series is reviving an old patchwork.
> Booting from a mapped device requires an initramfs. This series is
> allows for device-mapper targets to be configured at boot time for
> use early in the boot process (as the root device or otherwise).
> 
> Example, the following could be added in the boot parameters.
> dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> 
> Enric Balletbo i Serra (1):
>   dm ioctl: add a device mapper ioctl function.
> 
> Will Drewry (1):
>   init: add support to directly boot to a mapped device
> 
>  .../admin-guide/kernel-parameters.rst         |   1 +
>  .../admin-guide/kernel-parameters.txt         |   3 +
>  Documentation/device-mapper/dm-boot.txt       |  63 +++
>  drivers/md/dm-ioctl.c                         |  50 ++
>  include/linux/device-mapper.h                 |   6 +
>  init/Makefile                                 |   1 +
>  init/do_mounts.c                              |   1 +
>  init/do_mounts.h                              |  10 +
>  init/do_mounts_dm.c                           | 475 ++++++++++++++++++
>  9 files changed, 610 insertions(+)
>  create mode 100644 Documentation/device-mapper/dm-boot.txt
>  create mode 100644 init/do_mounts_dm.c
> 

Sorry about sending this email multiple times, my git send-email wans't
properly configured.

Helen

Re: [PATCH 0/2] boot to a mapped device

[Richard Weinberger]

Helen,

On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
>
> This series is reviving an old patchwork.
> Booting from a mapped device requires an initramfs. This series is
> allows for device-mapper targets to be configured at boot time for
> use early in the boot process (as the root device or otherwise).

What is the reason for this patch series?
Setting up non-trivial root filesystems/storage always requires an
initramfs, there is nothing
wrong about this.

> Example, the following could be added in the boot parameters.
> dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0

Hmmm, the new dm= parameter is anything but easy to get right.

-- 
Thanks,
//richard

Re: [linux-lvm] [PATCH 0/2] boot to a mapped device

[Richard Weinberger]

Helen,

On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
>
> This series is reviving an old patchwork.
> Booting from a mapped device requires an initramfs. This series is
> allows for device-mapper targets to be configured at boot time for
> use early in the boot process (as the root device or otherwise).

What is the reason for this patch series?
Setting up non-trivial root filesystems/storage always requires an
initramfs, there is nothing
wrong about this.

> Example, the following could be added in the boot parameters.
> dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0

Hmmm, the new dm= parameter is anything but easy to get right.

-- 
Thanks,
//richard

Re: [PATCH 0/2] boot to a mapped device

[Mike Snitzer]

On Wed, Sep 26 2018 at  3:16am -0400,
Richard Weinberger <richard.weinberger@gmail.com> wrote:

> Helen,
> 
> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
> >
> > This series is reviving an old patchwork.
> > Booting from a mapped device requires an initramfs. This series is
> > allows for device-mapper targets to be configured at boot time for
> > use early in the boot process (as the root device or otherwise).
> 
> What is the reason for this patch series?
> Setting up non-trivial root filesystems/storage always requires an
> initramfs, there is nothing
> wrong about this.

Exactly.  If phones or whatever would benefit from this patchset then
say as much.

I will not accept this patchset at this time.

> > Example, the following could be added in the boot parameters.
> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> 
> Hmmm, the new dm= parameter is anything but easy to get right.

No, it isn't.. exposes way too much potential for users hanging
themselves.

Re: [linux-lvm] [PATCH 0/2] boot to a mapped device

[Mike Snitzer]

On Wed, Sep 26 2018 at  3:16am -0400,
Richard Weinberger <richard.weinberger@gmail.com> wrote:

> Helen,
> 
> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
> >
> > This series is reviving an old patchwork.
> > Booting from a mapped device requires an initramfs. This series is
> > allows for device-mapper targets to be configured at boot time for
> > use early in the boot process (as the root device or otherwise).
> 
> What is the reason for this patch series?
> Setting up non-trivial root filesystems/storage always requires an
> initramfs, there is nothing
> wrong about this.

Exactly.  If phones or whatever would benefit from this patchset then
say as much.

I will not accept this patchset at this time.

> > Example, the following could be added in the boot parameters.
> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> 
> Hmmm, the new dm= parameter is anything but easy to get right.

No, it isn't.. exposes way too much potential for users hanging
themselves.

Re: [PATCH 0/2] boot to a mapped device

[Kees Cook]

On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer <snitzer@redhat.com> wrote:
> On Wed, Sep 26 2018 at  3:16am -0400,
> Richard Weinberger <richard.weinberger@gmail.com> wrote:
>
>> Helen,
>>
>> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
>> >
>> > This series is reviving an old patchwork.
>> > Booting from a mapped device requires an initramfs. This series is
>> > allows for device-mapper targets to be configured at boot time for
>> > use early in the boot process (as the root device or otherwise).
>>
>> What is the reason for this patch series?
>> Setting up non-trivial root filesystems/storage always requires an
>> initramfs, there is nothing
>> wrong about this.
>
> Exactly.  If phones or whatever would benefit from this patchset then
> say as much.

I think some of the context for the series was lost in commit logs,
but yes, both Android and Chrome OS do not use initramfs. The only
thing that was needed to do this was being able to configure dm
devices on the kernel command line, so the overhead of a full
initramfs was seen as a boot time liability, a boot image size
liability (e.g. Chrome OS has a limited amount of storage available
for the boot image that is covered by the static root of trust
signature), and a complexity risk: everything that is needed for boot
could be specified on the kernel command line, so better to avoid the
whole initramfs dance.

So, instead, this plumbs the dm commands directly instead of bringing
up a full userspace and performing ioctls.

> I will not accept this patchset at this time.
>
>> > Example, the following could be added in the boot parameters.
>> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
>>
>> Hmmm, the new dm= parameter is anything but easy to get right.
>
> No, it isn't.. exposes way too much potential for users hanging
> themselves.

IIRC, the changes in syntax were suggested back when I was trying to
drive this series:
https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html

And it matches the "concise" format in dmsetup:
https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534

What do you feel are next steps?

Thanks!

-Kees

-- 
Kees Cook
Pixel Security

Re: [linux-lvm] [PATCH 0/2] boot to a mapped device

[Kees Cook]

On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer <snitzer@redhat.com> wrote:
> On Wed, Sep 26 2018 at  3:16am -0400,
> Richard Weinberger <richard.weinberger@gmail.com> wrote:
>
>> Helen,
>>
>> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
>> >
>> > This series is reviving an old patchwork.
>> > Booting from a mapped device requires an initramfs. This series is
>> > allows for device-mapper targets to be configured at boot time for
>> > use early in the boot process (as the root device or otherwise).
>>
>> What is the reason for this patch series?
>> Setting up non-trivial root filesystems/storage always requires an
>> initramfs, there is nothing
>> wrong about this.
>
> Exactly.  If phones or whatever would benefit from this patchset then
> say as much.

I think some of the context for the series was lost in commit logs,
but yes, both Android and Chrome OS do not use initramfs. The only
thing that was needed to do this was being able to configure dm
devices on the kernel command line, so the overhead of a full
initramfs was seen as a boot time liability, a boot image size
liability (e.g. Chrome OS has a limited amount of storage available
for the boot image that is covered by the static root of trust
signature), and a complexity risk: everything that is needed for boot
could be specified on the kernel command line, so better to avoid the
whole initramfs dance.

So, instead, this plumbs the dm commands directly instead of bringing
up a full userspace and performing ioctls.

> I will not accept this patchset at this time.
>
>> > Example, the following could be added in the boot parameters.
>> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
>>
>> Hmmm, the new dm= parameter is anything but easy to get right.
>
> No, it isn't.. exposes way too much potential for users hanging
> themselves.

IIRC, the changes in syntax were suggested back when I was trying to
drive this series:
https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html

And it matches the "concise" format in dmsetup:
https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534

What do you feel are next steps?

Thanks!

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCH 0/2] boot to a mapped device

[Mike Snitzer]

On Thu, Sep 27 2018 at 12:36pm -0400,
Kees Cook <keescook@chromium.org> wrote:

> On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer <snitzer@redhat.com> wrote:
> > On Wed, Sep 26 2018 at  3:16am -0400,
> > Richard Weinberger <richard.weinberger@gmail.com> wrote:
> >
> >> Helen,
> >>
> >> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
> >> >
> >> > This series is reviving an old patchwork.
> >> > Booting from a mapped device requires an initramfs. This series is
> >> > allows for device-mapper targets to be configured at boot time for
> >> > use early in the boot process (as the root device or otherwise).
> >>
> >> What is the reason for this patch series?
> >> Setting up non-trivial root filesystems/storage always requires an
> >> initramfs, there is nothing
> >> wrong about this.
> >
> > Exactly.  If phones or whatever would benefit from this patchset then
> > say as much.
> 
> I think some of the context for the series was lost in commit logs,
> but yes, both Android and Chrome OS do not use initramfs. The only
> thing that was needed to do this was being able to configure dm
> devices on the kernel command line, so the overhead of a full
> initramfs was seen as a boot time liability, a boot image size
> liability (e.g. Chrome OS has a limited amount of storage available
> for the boot image that is covered by the static root of trust
> signature), and a complexity risk: everything that is needed for boot
> could be specified on the kernel command line, so better to avoid the
> whole initramfs dance.
> 
> So, instead, this plumbs the dm commands directly instead of bringing
> up a full userspace and performing ioctls.
> 
> > I will not accept this patchset at this time.
> >
> >> > Example, the following could be added in the boot parameters.
> >> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> >>
> >> Hmmm, the new dm= parameter is anything but easy to get right.
> >
> > No, it isn't.. exposes way too much potential for users hanging
> > themselves.
> 
> IIRC, the changes in syntax were suggested back when I was trying to
> drive this series:
> https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html
> 
> And it matches the "concise" format in dmsetup:
> https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534
> 
> What do you feel are next steps?

There is quite a lot of init/ code, to handle parsing the concise DM
format, that is being proposed for inclusion.  I question why that
DM-specific code would be located in init/

There also needs to be a careful comparison done between the proposed
init/ code to support consise DM format and the userspace lvm2
equivalent (e.g. lvm2.git commit 827be0175)

That aside, the DM targets that are allowed to be supported by this dm=
commandline boot interface must be constrained (there are serious risks
in allowing activation of certain DM targets without first using
userspace tools to check the validity of associated metadata, as is done
by the DM thin and cache targets).  Also, all targets supported must be
upstream.  "linear", "verity" and "bootcache" DM targets are referenced
in Documentation, "bootcache" must be a Google target.  I'm not aware of
it.

Mike

Re: [linux-lvm] [PATCH 0/2] boot to a mapped device

[Mike Snitzer]

On Thu, Sep 27 2018 at 12:36pm -0400,
Kees Cook <keescook@chromium.org> wrote:

> On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer <snitzer@redhat.com> wrote:
> > On Wed, Sep 26 2018 at  3:16am -0400,
> > Richard Weinberger <richard.weinberger@gmail.com> wrote:
> >
> >> Helen,
> >>
> >> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
> >> >
> >> > This series is reviving an old patchwork.
> >> > Booting from a mapped device requires an initramfs. This series is
> >> > allows for device-mapper targets to be configured at boot time for
> >> > use early in the boot process (as the root device or otherwise).
> >>
> >> What is the reason for this patch series?
> >> Setting up non-trivial root filesystems/storage always requires an
> >> initramfs, there is nothing
> >> wrong about this.
> >
> > Exactly.  If phones or whatever would benefit from this patchset then
> > say as much.
> 
> I think some of the context for the series was lost in commit logs,
> but yes, both Android and Chrome OS do not use initramfs. The only
> thing that was needed to do this was being able to configure dm
> devices on the kernel command line, so the overhead of a full
> initramfs was seen as a boot time liability, a boot image size
> liability (e.g. Chrome OS has a limited amount of storage available
> for the boot image that is covered by the static root of trust
> signature), and a complexity risk: everything that is needed for boot
> could be specified on the kernel command line, so better to avoid the
> whole initramfs dance.
> 
> So, instead, this plumbs the dm commands directly instead of bringing
> up a full userspace and performing ioctls.
> 
> > I will not accept this patchset at this time.
> >
> >> > Example, the following could be added in the boot parameters.
> >> > dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> >>
> >> Hmmm, the new dm= parameter is anything but easy to get right.
> >
> > No, it isn't.. exposes way too much potential for users hanging
> > themselves.
> 
> IIRC, the changes in syntax were suggested back when I was trying to
> drive this series:
> https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html
> 
> And it matches the "concise" format in dmsetup:
> https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534
> 
> What do you feel are next steps?

There is quite a lot of init/ code, to handle parsing the concise DM
format, that is being proposed for inclusion.  I question why that
DM-specific code would be located in init/

There also needs to be a careful comparison done between the proposed
init/ code to support consise DM format and the userspace lvm2
equivalent (e.g. lvm2.git commit 827be0175)

That aside, the DM targets that are allowed to be supported by this dm=
commandline boot interface must be constrained (there are serious risks
in allowing activation of certain DM targets without first using
userspace tools to check the validity of associated metadata, as is done
by the DM thin and cache targets).  Also, all targets supported must be
upstream.  "linear", "verity" and "bootcache" DM targets are referenced
in Documentation, "bootcache" must be a Google target.  I'm not aware of
it.

Mike

Re: [PATCH 0/2] boot to a mapped device

[Helen Koike]

Hi all,

Sorry the delay of my reply.

On 9/27/18 3:31 PM, Mike Snitzer wrote:
> On Thu, Sep 27 2018 at 12:36pm -0400,
> Kees Cook <keescook@chromium.org> wrote:
> 
>> On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer <snitzer@redhat.com> wrote:
>>> On Wed, Sep 26 2018 at  3:16am -0400,
>>> Richard Weinberger <richard.weinberger@gmail.com> wrote:
>>>
>>>> Helen,
>>>>
>>>> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
>>>>>
>>>>> This series is reviving an old patchwork.
>>>>> Booting from a mapped device requires an initramfs. This series is
>>>>> allows for device-mapper targets to be configured at boot time for
>>>>> use early in the boot process (as the root device or otherwise).
>>>>
>>>> What is the reason for this patch series?
>>>> Setting up non-trivial root filesystems/storage always requires an
>>>> initramfs, there is nothing
>>>> wrong about this.
>>>
>>> Exactly.  If phones or whatever would benefit from this patchset then
>>> say as much.
>>
>> I think some of the context for the series was lost in commit logs,
>> but yes, both Android and Chrome OS do not use initramfs. The only
>> thing that was needed to do this was being able to configure dm
>> devices on the kernel command line, so the overhead of a full
>> initramfs was seen as a boot time liability, a boot image size
>> liability (e.g. Chrome OS has a limited amount of storage available
>> for the boot image that is covered by the static root of trust
>> signature), and a complexity risk: everything that is needed for boot
>> could be specified on the kernel command line, so better to avoid the
>> whole initramfs dance.
>>
>> So, instead, this plumbs the dm commands directly instead of bringing
>> up a full userspace and performing ioctls.

Sorry about the missing context, I should've added the change log and
worked a bit more in the cover letter with a more verbose explanation on
the reasons for this patch.

Just for reference (I'll describe better the changes in the next version):

v5: https://www.redhat.com/archives/dm-devel/2016-February/msg00112.html
v6: https://www.redhat.com/archives/dm-devel/2017-April/msg00316.html
v7: http://lkml.iu.edu/hypermail/linux/kernel/1705.2/02657.html
v8: https://www.redhat.com/archives/linux-lvm/2017-May/msg00055.html

>>
>>> I will not accept this patchset at this time.
>>>
>>>>> Example, the following could be added in the boot parameters.
>>>>> dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
>>>>
>>>> Hmmm, the new dm= parameter is anything but easy to get right.
>>>
>>> No, it isn't.. exposes way too much potential for users hanging
>>> themselves.
>>
>> IIRC, the changes in syntax were suggested back when I was trying to
>> drive this series:
>> https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html
>>
>> And it matches the "concise" format in dmsetup:
>> https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534

Exactly, this is the "concise" format from dmsetup, it also makes it
easier for users to copy and paste from "dmsetup --concise", which
doesn't mean this format is ideal, but imho keeping it consistent with
dmsetup is a good thing, please let me know if you have any other ideas.

>>
>> What do you feel are next steps?
> 
> There is quite a lot of init/ code, to handle parsing the concise DM
> format, that is being proposed for inclusion.  I question why that
> DM-specific code would be located in init/

The main reason was that, taking "md=" and "raid=" as a reference, its
command line arguments are parsed in init/do_mounts_md.c, I could move
the parsing logic to drivers/md/* but I was wondering if it wouldn't be
better to be consistent with init/do_mounts_md.c, what do you think?

> 
> There also needs to be a careful comparison done between the proposed
> init/ code to support consise DM format and the userspace lvm2
> equivalent (e.g. lvm2.git commit 827be0175)

Yes, I am taking a deeper look into the lvm2 parsing code, and actually
we can use almost the same logic for parsing, which seems better because
lvm2 is already using it, we already have some validation/review and it
also seems cleaner.
I'll update this in the next version.

> 
> That aside, the DM targets that are allowed to be supported by this dm=
> commandline boot interface must be constrained (there are serious risks
> in allowing activation of certain DM targets without first using
> userspace tools to check the validity of associated metadata, as is done
> by the DM thin and cache targets).  Also, all targets supported must be
> upstream.  "linear", "verity" and "bootcache" DM targets are referenced
> in Documentation, "bootcache" must be a Google target.  I'm not aware of
> it.
> 
> Mike
> 

I see, I can add this constraint and I'll clean up the documentation for
the next version.


Thank you all for your comments and reviews, I am working on the next
version of this patch series taking yours comments into consideration
and cleaning up several parts of the code and documentation.

Please let me know if you have any other concerns.

Thanks
Helen

Re: [linux-lvm] [PATCH 0/2] boot to a mapped device

[Helen Koike]

Hi all,

Sorry the delay of my reply.

On 9/27/18 3:31 PM, Mike Snitzer wrote:
> On Thu, Sep 27 2018 at 12:36pm -0400,
> Kees Cook <keescook@chromium.org> wrote:
> 
>> On Thu, Sep 27, 2018 at 7:23 AM, Mike Snitzer <snitzer@redhat.com> wrote:
>>> On Wed, Sep 26 2018 at  3:16am -0400,
>>> Richard Weinberger <richard.weinberger@gmail.com> wrote:
>>>
>>>> Helen,
>>>>
>>>> On Wed, Sep 26, 2018 at 7:01 AM Helen Koike <helen.koike@collabora.com> wrote:
>>>>>
>>>>> This series is reviving an old patchwork.
>>>>> Booting from a mapped device requires an initramfs. This series is
>>>>> allows for device-mapper targets to be configured at boot time for
>>>>> use early in the boot process (as the root device or otherwise).
>>>>
>>>> What is the reason for this patch series?
>>>> Setting up non-trivial root filesystems/storage always requires an
>>>> initramfs, there is nothing
>>>> wrong about this.
>>>
>>> Exactly.  If phones or whatever would benefit from this patchset then
>>> say as much.
>>
>> I think some of the context for the series was lost in commit logs,
>> but yes, both Android and Chrome OS do not use initramfs. The only
>> thing that was needed to do this was being able to configure dm
>> devices on the kernel command line, so the overhead of a full
>> initramfs was seen as a boot time liability, a boot image size
>> liability (e.g. Chrome OS has a limited amount of storage available
>> for the boot image that is covered by the static root of trust
>> signature), and a complexity risk: everything that is needed for boot
>> could be specified on the kernel command line, so better to avoid the
>> whole initramfs dance.
>>
>> So, instead, this plumbs the dm commands directly instead of bringing
>> up a full userspace and performing ioctls.

Sorry about the missing context, I should've added the change log and
worked a bit more in the cover letter with a more verbose explanation on
the reasons for this patch.

Just for reference (I'll describe better the changes in the next version):

v5: https://www.redhat.com/archives/dm-devel/2016-February/msg00112.html
v6: https://www.redhat.com/archives/dm-devel/2017-April/msg00316.html
v7: http://lkml.iu.edu/hypermail/linux/kernel/1705.2/02657.html
v8: https://www.redhat.com/archives/linux-lvm/2017-May/msg00055.html

>>
>>> I will not accept this patchset at this time.
>>>
>>>>> Example, the following could be added in the boot parameters.
>>>>> dm="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
>>>>
>>>> Hmmm, the new dm= parameter is anything but easy to get right.
>>>
>>> No, it isn't.. exposes way too much potential for users hanging
>>> themselves.
>>
>> IIRC, the changes in syntax were suggested back when I was trying to
>> drive this series:
>> https://www.redhat.com/archives/dm-devel/2016-February/msg00199.html
>>
>> And it matches the "concise" format in dmsetup:
>> https://sourceware.org/git/?p=lvm2.git;a=commit;h=827be01758ec5adb7b9d5ea75b658092adc65534

Exactly, this is the "concise" format from dmsetup, it also makes it
easier for users to copy and paste from "dmsetup --concise", which
doesn't mean this format is ideal, but imho keeping it consistent with
dmsetup is a good thing, please let me know if you have any other ideas.

>>
>> What do you feel are next steps?
> 
> There is quite a lot of init/ code, to handle parsing the concise DM
> format, that is being proposed for inclusion.  I question why that
> DM-specific code would be located in init/

The main reason was that, taking "md=" and "raid=" as a reference, its
command line arguments are parsed in init/do_mounts_md.c, I could move
the parsing logic to drivers/md/* but I was wondering if it wouldn't be
better to be consistent with init/do_mounts_md.c, what do you think?

> 
> There also needs to be a careful comparison done between the proposed
> init/ code to support consise DM format and the userspace lvm2
> equivalent (e.g. lvm2.git commit 827be0175)

Yes, I am taking a deeper look into the lvm2 parsing code, and actually
we can use almost the same logic for parsing, which seems better because
lvm2 is already using it, we already have some validation/review and it
also seems cleaner.
I'll update this in the next version.

> 
> That aside, the DM targets that are allowed to be supported by this dm=
> commandline boot interface must be constrained (there are serious risks
> in allowing activation of certain DM targets without first using
> userspace tools to check the validity of associated metadata, as is done
> by the DM thin and cache targets).  Also, all targets supported must be
> upstream.  "linear", "verity" and "bootcache" DM targets are referenced
> in Documentation, "bootcache" must be a Google target.  I'm not aware of
> it.
> 
> Mike
> 

I see, I can add this constraint and I'll clean up the documentation for
the next version.


Thank you all for your comments and reviews, I am working on the next
version of this patch series taking yours comments into consideration
and cleaning up several parts of the code and documentation.

Please let me know if you have any other concerns.

Thanks
Helen