[PATCH v3 0/2] Driver for Open Profile for DICE

[PATCH v3 0/2] Driver for Open Profile for DICE

[David Brazdil]

Open Profile for DICE is an open protocol for measured boot compatible
with the Trusted Computing Group's Device Identifier Composition
Engine (DICE) specification. The generated Compound Device Identifier
(CDI) certificates represent the measured hardware/software combination
and can be used by userspace for remote attestation and sealing.

This patchset adds DeviceTree bindings for the DICE device referencing
a reserved memory region containing the CDIs, and a driver that exposes
the memory region to userspace via a misc device.

See https://pigweed.googlesource.com/open-dice for more details.

The patches are based on top of v5.16-rc5 and can also be found here:
  https://android-kvm.googlesource.com/linux topic/dice_v3

Changes since v2:
  * renamed from 'dice' to 'open-dice'
  * replaced ioctls with read/write
  * replaced memzero_explicit with memset
  * allowed multiple instances
  * expanded Kconfig description

Changes since v1:
  * converted to miscdevice
  * all mappings now write-combine to simplify semantics
  * removed atomic state, any attempt at exclusive access
  * simplified wipe, applied on ioctl, not on release
  * fixed ioctl return value

David Brazdil (2):
  dt-bindings: firmware: Add Open Profile for DICE
  misc: open-dice: Add driver to expose DICE data to userspace

 .../bindings/firmware/google,open-dice.yaml   |  51 +++++
 drivers/misc/Kconfig                          |  12 ++
 drivers/misc/Makefile                         |   1 +
 drivers/misc/open-dice.c                      | 197 ++++++++++++++++++
 4 files changed, 261 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/firmware/google,open-dice.yaml
 create mode 100644 drivers/misc/open-dice.c

--
2.34.1.173.g76aa8bc2d0-goog

[PATCH v3 1/2] dt-bindings: firmware: Add Open Profile for DICE

[David Brazdil]

Add DeviceTree bindings for Open Profile for DICE, an open protocol for
measured boot. Firmware uses DICE to measure the hardware/software
combination and generates Compound Device Identifier (CDI) certificates.
These are stored in memory and the buffer is described in the DT as
a reserved memory region referenced by a compatible device node.

Signed-off-by: David Brazdil <dbrazdil@google.com>
---
 .../bindings/firmware/google,open-dice.yaml   | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/firmware/google,open-dice.yaml

diff --git a/Documentation/devicetree/bindings/firmware/google,open-dice.yaml b/Documentation/devicetree/bindings/firmware/google,open-dice.yaml
new file mode 100644
index 000000000000..1aa69f381b8c
--- /dev/null
+++ b/Documentation/devicetree/bindings/firmware/google,open-dice.yaml
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/firmware/google,open-dice.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Open Profile for DICE Device Tree Bindings
+
+description: |
+  This binding represents a reserved memory region containing data
+  generated by the Open Profile for DICE protocol.
+
+  See https://pigweed.googlesource.com/open-dice/
+
+maintainers:
+  - David Brazdil <dbrazdil@google.com>
+
+properties:
+  compatible:
+    enum:
+      - google,open-dice
+
+  memory-region:
+    maxItems: 1
+    description: |
+      phandle to the reserved memory node to be associated with the device
+      The reserved memory node should be defined as per the bindings,
+      Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml
+
+required:
+  - compatible
+  - memory-region
+
+additionalProperties: false
+
+examples:
+  - |
+    reserved-memory {
+        #address-cells = <2>;
+        #size-cells = <1>;
+
+        dice_reserved: dice@12340000 {
+            reg = <0x00 0x12340000 0x2000>;
+            no-map;
+        };
+    };
+
+    dice {
+        compatible = "google,open-dice";
+        memory-region = <&dice_reserved>;
+    };
-- 
2.34.1.173.g76aa8bc2d0-goog

[PATCH v3 2/2] misc: open-dice: Add driver to expose DICE data to userspace

[David Brazdil]

Open Profile for DICE is an open protocol for measured boot compatible
with the Trusted Computing Group's Device Identifier Composition
Engine (DICE) specification. The generated Compound Device Identifier
(CDI) certificates represent the hardware/software combination measured
by DICE, and can be used for remote attestation and sealing.

Add a driver that exposes reserved memory regions populated by firmware
with DICE CDIs and exposes them to userspace via a character device.

Userspace obtains the memory region's size from read() and calls mmap()
to create a mapping of the memory region in its address space. The
mapping is not allowed to be write+shared, giving userspace a guarantee
that the data were not overwritten by another process.

Userspace can also call write(), which triggers a wipe of the DICE data
by the driver. Because both the kernel and userspace mappings use
write-combine semantics, all clients observe the memory as zeroed after
the syscall has returned.

Cc: Andrew Scull <ascull@google.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: David Brazdil <dbrazdil@google.com>
---
 drivers/misc/Kconfig     |  12 +++
 drivers/misc/Makefile    |   1 +
 drivers/misc/open-dice.c | 197 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 210 insertions(+)
 create mode 100644 drivers/misc/open-dice.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 0f5a49fc7c9e..4d996485f5a7 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -470,6 +470,18 @@ config HISI_HIKEY_USB
 	  switching between the dual-role USB-C port and the USB-A host ports
 	  using only one USB controller.
 
+config OPEN_DICE
+	tristate "Open Profile for DICE driver"
+	depends on OF_RESERVED_MEM
+	help
+	  This driver exposes a DICE reserved memory region to userspace via
+	  a character device. The memory region contains Compound Device
+	  Identifiers (CDIs) generated by firmware as an output of DICE
+	  measured boot flow. Userspace can uses CDIs for remote attestation
+	  and sealing.
+
+	  If unsure, say N.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index a086197af544..70e800e9127f 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -59,3 +59,4 @@ obj-$(CONFIG_UACCE)		+= uacce/
 obj-$(CONFIG_XILINX_SDFEC)	+= xilinx_sdfec.o
 obj-$(CONFIG_HISI_HIKEY_USB)	+= hisi_hikey_usb.o
 obj-$(CONFIG_HI6421V600_IRQ)	+= hi6421v600-irq.o
+obj-$(CONFIG_OPEN_DICE)		+= open-dice.o
diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c
new file mode 100644
index 000000000000..ea7b1a8d49ac
--- /dev/null
+++ b/drivers/misc/open-dice.c
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 - Google LLC
+ * Author: David Brazdil <dbrazdil@google.com>
+ *
+ * Driver for Open Profile for DICE.
+ *
+ * This driver takes ownership of a reserved memory region containing secrets
+ * derived following the Open Profile for DICE. The contents of the memory
+ * region are not interpreted by the kernel but can be mapped into a userspace
+ * process via a misc device. The memory region can also be wiped, removing
+ * the secrets from memory.
+ *
+ * Userspace can access the data by (w/o error handling):
+ *
+ *     fd = open("/dev/open-dice0", O_RDWR);
+ *     size = read(fd, NULL, 0);
+ *     data = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+ *     write(fd, NULL, 0); // wipe
+ *     close(fd);
+ */
+
+#include <linux/io.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+
+#define DRIVER_NAME "open-dice"
+
+struct open_dice_drvdata {
+	spinlock_t lock;
+	char name[16];
+	struct reserved_mem *rmem;
+	struct miscdevice misc;
+};
+
+static inline struct open_dice_drvdata *to_open_dice_drvdata(struct file *filp)
+{
+	return container_of(filp->private_data, struct open_dice_drvdata, misc);
+}
+
+static int open_dice_size(struct open_dice_drvdata *drvdata)
+{
+	/* '0 < size <= INT_MAX' is checked in the probe function. */
+	return drvdata->rmem->size;
+}
+
+static int open_dice_wipe(struct open_dice_drvdata *drvdata)
+{
+	void *kaddr;
+
+	spin_lock(&drvdata->lock);
+	kaddr = devm_memremap(drvdata->misc.this_device, drvdata->rmem->base,
+			      drvdata->rmem->size, MEMREMAP_WC);
+	if (IS_ERR(kaddr)) {
+		spin_unlock(&drvdata->lock);
+		return PTR_ERR(kaddr);
+	}
+
+	memset(kaddr, 0, drvdata->rmem->size);
+	devm_memunmap(drvdata->misc.this_device, kaddr);
+	spin_unlock(&drvdata->lock);
+	return 0;
+}
+
+/**
+ * Returns the size of the reserved memory region. The user-provided pointer is
+ * never dereferenced.
+ */
+static ssize_t open_dice_read(struct file *filp, char __user *ptr, size_t len,
+			      loff_t *off)
+{
+	return open_dice_size(to_open_dice_drvdata(filp));
+}
+
+/**
+ * Triggers a wipe of the reserved memory region. The user-provided pointer is
+ * never dereferenced.
+ */
+static ssize_t open_dice_write(struct file *filp, const char __user *ptr,
+			       size_t len, loff_t *off)
+{
+	return open_dice_wipe(to_open_dice_drvdata(filp));
+}
+
+/**
+ * Creates a mapping of the reserved memory region in a user address space.
+ */
+static int open_dice_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct open_dice_drvdata *drvdata = to_open_dice_drvdata(filp);
+
+	/* Do not allow userspace to modify the underlying data. */
+	if ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED))
+		return -EPERM;
+
+	/* Create write-combine mapping so all clients observe a wipe. */
+	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+	vma->vm_flags |= VM_DONTCOPY | VM_DONTDUMP;
+	return vm_iomap_memory(vma, drvdata->rmem->base, drvdata->rmem->size);
+}
+
+static const struct file_operations open_dice_fops = {
+	.read = open_dice_read,
+	.write = open_dice_write,
+	.mmap = open_dice_mmap,
+};
+
+static int __init open_dice_probe(struct platform_device *pdev)
+{
+	static size_t dev_idx;
+	struct device *dev = &pdev->dev;
+	struct device_node *rmem_np;
+	struct reserved_mem *rmem;
+	struct open_dice_drvdata *drvdata;
+	int ret;
+
+	rmem_np = of_parse_phandle(dev->of_node, "memory-region", 0);
+	if (!rmem_np) {
+		dev_err(dev, "missing 'memory-region' property\n");
+		return -EINVAL;
+	}
+
+	rmem = of_reserved_mem_lookup(rmem_np);
+	of_node_put(rmem_np);
+	if (!rmem) {
+		dev_err(dev, "failed to lookup reserved memory\n");
+		return -EINVAL;
+	}
+
+	if (!rmem->size || (rmem->size > INT_MAX)) {
+		dev_err(dev, "invalid memory region size\n");
+		return -EINVAL;
+	}
+
+	if (!PAGE_ALIGNED(rmem->base) || !PAGE_ALIGNED(rmem->size)) {
+		dev_err(dev, "memory region must be page-aligned\n");
+		return -EINVAL;
+	}
+
+	drvdata = devm_kmalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	*drvdata = (struct open_dice_drvdata){
+		.lock = __SPIN_LOCK_UNLOCKED(drvdata->lock),
+		.rmem = rmem,
+		.misc = (struct miscdevice){
+			.parent	= dev,
+			.name	= drvdata->name,
+			.minor	= MISC_DYNAMIC_MINOR,
+			.fops	= &open_dice_fops,
+			.mode	= 0600,
+		},
+	};
+
+	/* Index overflow check not needed. misc_register() will fail. */
+	snprintf(drvdata->name, sizeof(drvdata->name), DRIVER_NAME"%d", dev_idx++);
+
+	ret = misc_register(&drvdata->misc);
+	if (ret) {
+		dev_err(dev, "failed to register misc device '%s': %d\n",
+			drvdata->name, ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, drvdata);
+	return 0;
+}
+
+static int open_dice_remove(struct platform_device *pdev)
+{
+	struct open_dice_drvdata *drvdata = platform_get_drvdata(pdev);
+
+	misc_deregister(&drvdata->misc);
+	return 0;
+}
+
+static const struct of_device_id open_dice_of_match[] = {
+	{ .compatible = "google,open-dice" },
+	{},
+};
+
+static struct platform_driver open_dice_driver = {
+	.remove = open_dice_remove,
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = open_dice_of_match,
+	},
+};
+
+module_platform_driver_probe(open_dice_driver, open_dice_probe);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("David Brazdil <dbrazdil@google.com>");
-- 
2.34.1.173.g76aa8bc2d0-goog

Re: [PATCH v3 2/2] misc: open-dice: Add driver to expose DICE data to userspace

[kernel test robot]

Hi David,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on robh/for-next]
[also build test WARNING on char-misc/char-misc-testing soc/for-next v5.16-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/David-Brazdil/Driver-for-Open-Profile-for-DICE/20211214-040051
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
config: sh-allmodconfig (https://download.01.org/0day-ci/archive/20211214/202112141128.lBBmmIuE-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/6fb8e9472d98abcc2dfabd43e95fc4ec5819ecd0
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review David-Brazdil/Driver-for-Open-Profile-for-DICE/20211214-040051
        git checkout 6fb8e9472d98abcc2dfabd43e95fc4ec5819ecd0
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=sh SHELL=/bin/bash drivers/misc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   drivers/misc/open-dice.c:74: warning: Function parameter or member 'filp' not described in 'open_dice_read'
   drivers/misc/open-dice.c:74: warning: Function parameter or member 'ptr' not described in 'open_dice_read'
   drivers/misc/open-dice.c:74: warning: Function parameter or member 'len' not described in 'open_dice_read'
   drivers/misc/open-dice.c:74: warning: Function parameter or member 'off' not described in 'open_dice_read'
>> drivers/misc/open-dice.c:74: warning: expecting prototype for Returns the size of the reserved memory region. The user(). Prototype was for open_dice_read() instead
   drivers/misc/open-dice.c:84: warning: Function parameter or member 'filp' not described in 'open_dice_write'
   drivers/misc/open-dice.c:84: warning: Function parameter or member 'ptr' not described in 'open_dice_write'
   drivers/misc/open-dice.c:84: warning: Function parameter or member 'len' not described in 'open_dice_write'
   drivers/misc/open-dice.c:84: warning: Function parameter or member 'off' not described in 'open_dice_write'
>> drivers/misc/open-dice.c:84: warning: expecting prototype for Triggers a wipe of the reserved memory region. The user(). Prototype was for open_dice_write() instead
>> drivers/misc/open-dice.c:89: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Creates a mapping of the reserved memory region in a user address space.


vim +74 drivers/misc/open-dice.c

    67	
    68	/**
    69	 * Returns the size of the reserved memory region. The user-provided pointer is
    70	 * never dereferenced.
    71	 */
    72	static ssize_t open_dice_read(struct file *filp, char __user *ptr, size_t len,
    73				      loff_t *off)
  > 74	{
    75		return open_dice_size(to_open_dice_drvdata(filp));
    76	}
    77	
    78	/**
    79	 * Triggers a wipe of the reserved memory region. The user-provided pointer is
    80	 * never dereferenced.
    81	 */
    82	static ssize_t open_dice_write(struct file *filp, const char __user *ptr,
    83				       size_t len, loff_t *off)
  > 84	{
    85		return open_dice_wipe(to_open_dice_drvdata(filp));
    86	}
    87	
    88	/**
  > 89	 * Creates a mapping of the reserved memory region in a user address space.
    90	 */
    91	static int open_dice_mmap(struct file *filp, struct vm_area_struct *vma)
    92	{
    93		struct open_dice_drvdata *drvdata = to_open_dice_drvdata(filp);
    94	
    95		/* Do not allow userspace to modify the underlying data. */
    96		if ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED))
    97			return -EPERM;
    98	
    99		/* Create write-combine mapping so all clients observe a wipe. */
   100		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
   101		vma->vm_flags |= VM_DONTCOPY | VM_DONTDUMP;
   102		return vm_iomap_memory(vma, drvdata->rmem->base, drvdata->rmem->size);
   103	}
   104	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH v3 2/2] misc: open-dice: Add driver to expose DICE data to userspace

[kernel test robot]

Hi David,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on robh/for-next]
[also build test WARNING on char-misc/char-misc-testing soc/for-next v5.16-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/David-Brazdil/Driver-for-Open-Profile-for-DICE/20211214-040051
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20211214/202112141150.Hh48OleF-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/6fb8e9472d98abcc2dfabd43e95fc4ec5819ecd0
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review David-Brazdil/Driver-for-Open-Profile-for-DICE/20211214-040051
        git checkout 6fb8e9472d98abcc2dfabd43e95fc4ec5819ecd0
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/misc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   drivers/misc/open-dice.c: In function 'open_dice_probe':
>> drivers/misc/open-dice.c:30:21: warning: format '%d' expects argument of type 'int', but argument 4 has type 'size_t' {aka 'long unsigned int'} [-Wformat=]
      30 | #define DRIVER_NAME "open-dice"
         |                     ^~~~~~~~~~~
   drivers/misc/open-dice.c:160:49: note: in expansion of macro 'DRIVER_NAME'
     160 |  snprintf(drvdata->name, sizeof(drvdata->name), DRIVER_NAME"%d", dev_idx++);
         |                                                 ^~~~~~~~~~~
   drivers/misc/open-dice.c:160:62: note: format string is defined here
     160 |  snprintf(drvdata->name, sizeof(drvdata->name), DRIVER_NAME"%d", dev_idx++);
         |                                                             ~^
         |                                                              |
         |                                                              int
         |                                                             %ld


vim +30 drivers/misc/open-dice.c

    29	
  > 30	#define DRIVER_NAME "open-dice"
    31	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH v3 2/2] misc: open-dice: Add driver to expose DICE data to userspace

[Greg Kroah-Hartman]

On Mon, Dec 13, 2021 at 07:58:33PM +0000, David Brazdil wrote:
> Open Profile for DICE is an open protocol for measured boot compatible
> with the Trusted Computing Group's Device Identifier Composition
> Engine (DICE) specification. The generated Compound Device Identifier
> (CDI) certificates represent the hardware/software combination measured
> by DICE, and can be used for remote attestation and sealing.
> 
> Add a driver that exposes reserved memory regions populated by firmware
> with DICE CDIs and exposes them to userspace via a character device.
> 
> Userspace obtains the memory region's size from read() and calls mmap()
> to create a mapping of the memory region in its address space. The
> mapping is not allowed to be write+shared, giving userspace a guarantee
> that the data were not overwritten by another process.
> 
> Userspace can also call write(), which triggers a wipe of the DICE data
> by the driver. Because both the kernel and userspace mappings use
> write-combine semantics, all clients observe the memory as zeroed after
> the syscall has returned.
> 
> Cc: Andrew Scull <ascull@google.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
>  drivers/misc/Kconfig     |  12 +++
>  drivers/misc/Makefile    |   1 +
>  drivers/misc/open-dice.c | 197 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 210 insertions(+)
>  create mode 100644 drivers/misc/open-dice.c
> 
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 0f5a49fc7c9e..4d996485f5a7 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -470,6 +470,18 @@ config HISI_HIKEY_USB
>  	  switching between the dual-role USB-C port and the USB-A host ports
>  	  using only one USB controller.
>  
> +config OPEN_DICE
> +	tristate "Open Profile for DICE driver"
> +	depends on OF_RESERVED_MEM
> +	help
> +	  This driver exposes a DICE reserved memory region to userspace via
> +	  a character device. The memory region contains Compound Device
> +	  Identifiers (CDIs) generated by firmware as an output of DICE
> +	  measured boot flow. Userspace can uses CDIs for remote attestation
> +	  and sealing.
> +
> +	  If unsure, say N.
> +
>  source "drivers/misc/c2port/Kconfig"
>  source "drivers/misc/eeprom/Kconfig"
>  source "drivers/misc/cb710/Kconfig"
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index a086197af544..70e800e9127f 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -59,3 +59,4 @@ obj-$(CONFIG_UACCE)		+= uacce/
>  obj-$(CONFIG_XILINX_SDFEC)	+= xilinx_sdfec.o
>  obj-$(CONFIG_HISI_HIKEY_USB)	+= hisi_hikey_usb.o
>  obj-$(CONFIG_HI6421V600_IRQ)	+= hi6421v600-irq.o
> +obj-$(CONFIG_OPEN_DICE)		+= open-dice.o
> diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c
> new file mode 100644
> index 000000000000..ea7b1a8d49ac
> --- /dev/null
> +++ b/drivers/misc/open-dice.c
> @@ -0,0 +1,197 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2021 - Google LLC
> + * Author: David Brazdil <dbrazdil@google.com>
> + *
> + * Driver for Open Profile for DICE.
> + *
> + * This driver takes ownership of a reserved memory region containing secrets
> + * derived following the Open Profile for DICE. The contents of the memory
> + * region are not interpreted by the kernel but can be mapped into a userspace
> + * process via a misc device. The memory region can also be wiped, removing
> + * the secrets from memory.
> + *
> + * Userspace can access the data by (w/o error handling):
> + *
> + *     fd = open("/dev/open-dice0", O_RDWR);
> + *     size = read(fd, NULL, 0);

I was thinking you would return the value as a string in the buffer
provided to the read call, not as the return value itself.  That is odd
and probably breaks something.  What would happen if you ran 'cat' on
the device node?

thanks,

greg k-h

Re: [PATCH v3 2/2] misc: open-dice: Add driver to expose DICE data to userspace

[David Brazdil]

On Tue, Dec 14, 2021 at 08:18:38AM +0100, Greg Kroah-Hartman wrote:
> On Mon, Dec 13, 2021 at 07:58:33PM +0000, David Brazdil wrote:
> > Open Profile for DICE is an open protocol for measured boot compatible
> > with the Trusted Computing Group's Device Identifier Composition
> > Engine (DICE) specification. The generated Compound Device Identifier
> > (CDI) certificates represent the hardware/software combination measured
> > by DICE, and can be used for remote attestation and sealing.
> > 
> > Add a driver that exposes reserved memory regions populated by firmware
> > with DICE CDIs and exposes them to userspace via a character device.
> > 
> > Userspace obtains the memory region's size from read() and calls mmap()
> > to create a mapping of the memory region in its address space. The
> > mapping is not allowed to be write+shared, giving userspace a guarantee
> > that the data were not overwritten by another process.
> > 
> > Userspace can also call write(), which triggers a wipe of the DICE data
> > by the driver. Because both the kernel and userspace mappings use
> > write-combine semantics, all clients observe the memory as zeroed after
> > the syscall has returned.
> > 
> > Cc: Andrew Scull <ascull@google.com>
> > Cc: Will Deacon <will@kernel.org>
> > Signed-off-by: David Brazdil <dbrazdil@google.com>
> > ---
> >  drivers/misc/Kconfig     |  12 +++
> >  drivers/misc/Makefile    |   1 +
> >  drivers/misc/open-dice.c | 197 +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 210 insertions(+)
> >  create mode 100644 drivers/misc/open-dice.c
> > 
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 0f5a49fc7c9e..4d996485f5a7 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -470,6 +470,18 @@ config HISI_HIKEY_USB
> >  	  switching between the dual-role USB-C port and the USB-A host ports
> >  	  using only one USB controller.
> >  
> > +config OPEN_DICE
> > +	tristate "Open Profile for DICE driver"
> > +	depends on OF_RESERVED_MEM
> > +	help
> > +	  This driver exposes a DICE reserved memory region to userspace via
> > +	  a character device. The memory region contains Compound Device
> > +	  Identifiers (CDIs) generated by firmware as an output of DICE
> > +	  measured boot flow. Userspace can uses CDIs for remote attestation
> > +	  and sealing.
> > +
> > +	  If unsure, say N.
> > +
> >  source "drivers/misc/c2port/Kconfig"
> >  source "drivers/misc/eeprom/Kconfig"
> >  source "drivers/misc/cb710/Kconfig"
> > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> > index a086197af544..70e800e9127f 100644
> > --- a/drivers/misc/Makefile
> > +++ b/drivers/misc/Makefile
> > @@ -59,3 +59,4 @@ obj-$(CONFIG_UACCE)		+= uacce/
> >  obj-$(CONFIG_XILINX_SDFEC)	+= xilinx_sdfec.o
> >  obj-$(CONFIG_HISI_HIKEY_USB)	+= hisi_hikey_usb.o
> >  obj-$(CONFIG_HI6421V600_IRQ)	+= hi6421v600-irq.o
> > +obj-$(CONFIG_OPEN_DICE)		+= open-dice.o
> > diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c
> > new file mode 100644
> > index 000000000000..ea7b1a8d49ac
> > --- /dev/null
> > +++ b/drivers/misc/open-dice.c
> > @@ -0,0 +1,197 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2021 - Google LLC
> > + * Author: David Brazdil <dbrazdil@google.com>
> > + *
> > + * Driver for Open Profile for DICE.
> > + *
> > + * This driver takes ownership of a reserved memory region containing secrets
> > + * derived following the Open Profile for DICE. The contents of the memory
> > + * region are not interpreted by the kernel but can be mapped into a userspace
> > + * process via a misc device. The memory region can also be wiped, removing
> > + * the secrets from memory.
> > + *
> > + * Userspace can access the data by (w/o error handling):
> > + *
> > + *     fd = open("/dev/open-dice0", O_RDWR);
> > + *     size = read(fd, NULL, 0);
> 
> I was thinking you would return the value as a string in the buffer
> provided to the read call, not as the return value itself.  That is odd
> and probably breaks something.  What would happen if you ran 'cat' on
> the device node?

Ah, I misunderstood. Yeah, running `cat` will endlessly print garbage.
I'll do a quick respin and also change write() to appear to consume the
buffer because 'echo 1 > /dev/open-dice0' currently blocks.

David

Re: [PATCH v3 1/2] dt-bindings: firmware: Add Open Profile for DICE

[Rob Herring]

On Mon, Dec 13, 2021 at 07:58:32PM +0000, David Brazdil wrote:
> Add DeviceTree bindings for Open Profile for DICE, an open protocol for
> measured boot. Firmware uses DICE to measure the hardware/software
> combination and generates Compound Device Identifier (CDI) certificates.
> These are stored in memory and the buffer is described in the DT as
> a reserved memory region referenced by a compatible device node.
> 
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
>  .../bindings/firmware/google,open-dice.yaml   | 51 +++++++++++++++++++
>  1 file changed, 51 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/firmware/google,open-dice.yaml
> 
> diff --git a/Documentation/devicetree/bindings/firmware/google,open-dice.yaml b/Documentation/devicetree/bindings/firmware/google,open-dice.yaml
> new file mode 100644
> index 000000000000..1aa69f381b8c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/google,open-dice.yaml
> @@ -0,0 +1,51 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/firmware/google,open-dice.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Open Profile for DICE Device Tree Bindings
> +
> +description: |
> +  This binding represents a reserved memory region containing data
> +  generated by the Open Profile for DICE protocol.
> +
> +  See https://pigweed.googlesource.com/open-dice/
> +
> +maintainers:
> +  - David Brazdil <dbrazdil@google.com>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - google,open-dice
> +
> +  memory-region:
> +    maxItems: 1
> +    description: |
> +      phandle to the reserved memory node to be associated with the device
> +      The reserved memory node should be defined as per the bindings,
> +      Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml
> +
> +required:
> +  - compatible
> +  - memory-region
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    reserved-memory {
> +        #address-cells = <2>;
> +        #size-cells = <1>;
> +
> +        dice_reserved: dice@12340000 {
> +            reg = <0x00 0x12340000 0x2000>;
> +            no-map;
> +        };
> +    };
> +
> +    dice {
> +        compatible = "google,open-dice";
> +        memory-region = <&dice_reserved>;

There's no need for this indirection. Just add the compatible to the 
dice@12340000 node. You can bind drivers to /reserved-memory nodes.

Rob

Re: [PATCH v3 1/2] dt-bindings: firmware: Add Open Profile for DICE

[David Brazdil]

Hi Rob,

> > +        dice_reserved: dice@12340000 {
> > +            reg = <0x00 0x12340000 0x2000>;
> > +            no-map;
> > +        };
> > +    };
> > +
> > +    dice {
> > +        compatible = "google,open-dice";
> > +        memory-region = <&dice_reserved>;
> 
> There's no need for this indirection. Just add the compatible to the 
> dice@12340000 node. You can bind drivers to /reserved-memory nodes.

I have not found a way to make that work for kernel modules. Built-in
drivers can bind with RESERVEDMEM_OF_DECLARE, which puts an entry in
__reservedmem_of_table and __reserved_mem_init_node() iterates find it
there. A good case study might be CONFIG_TEGRA210_EMC, where the driver
itself can be a module but the rmem parsing is always built-in under
CONFIG_TEGRA210_EMC_TABLE. I don't think that's worth the trouble with
this driver.

David

Re: [PATCH v3 1/2] dt-bindings: firmware: Add Open Profile for DICE

[Rob Herring]

On Wed, Dec 15, 2021 at 3:08 PM David Brazdil <dbrazdil@google.com> wrote:
>
> Hi Rob,
>
> > > +        dice_reserved: dice@12340000 {
> > > +            reg = <0x00 0x12340000 0x2000>;
> > > +            no-map;
> > > +        };
> > > +    };
> > > +
> > > +    dice {
> > > +        compatible = "google,open-dice";
> > > +        memory-region = <&dice_reserved>;
> >
> > There's no need for this indirection. Just add the compatible to the
> > dice@12340000 node. You can bind drivers to /reserved-memory nodes.
>
> I have not found a way to make that work for kernel modules. Built-in
> drivers can bind with RESERVEDMEM_OF_DECLARE, which puts an entry in
> __reservedmem_of_table and __reserved_mem_init_node() iterates find it
> there. A good case study might be CONFIG_TEGRA210_EMC, where the driver
> itself can be a module but the rmem parsing is always built-in under
> CONFIG_TEGRA210_EMC_TABLE. I don't think that's worth the trouble with
> this driver.

I forgot you have to add the compatible to reserved_mem_matches in
drivers/of/platform.c.

Rob

Re: [PATCH v3 1/2] dt-bindings: firmware: Add Open Profile for DICE

[David Brazdil]

On Thu, Dec 16, 2021 at 09:21:00AM -0600, Rob Herring wrote:
> On Wed, Dec 15, 2021 at 3:08 PM David Brazdil <dbrazdil@google.com> wrote:
> >
> > Hi Rob,
> >
> > > > +        dice_reserved: dice@12340000 {
> > > > +            reg = <0x00 0x12340000 0x2000>;
> > > > +            no-map;
> > > > +        };
> > > > +    };
> > > > +
> > > > +    dice {
> > > > +        compatible = "google,open-dice";
> > > > +        memory-region = <&dice_reserved>;
> > >
> > > There's no need for this indirection. Just add the compatible to the
> > > dice@12340000 node. You can bind drivers to /reserved-memory nodes.
> >
> > I have not found a way to make that work for kernel modules. Built-in
> > drivers can bind with RESERVEDMEM_OF_DECLARE, which puts an entry in
> > __reservedmem_of_table and __reserved_mem_init_node() iterates find it
> > there. A good case study might be CONFIG_TEGRA210_EMC, where the driver
> > itself can be a module but the rmem parsing is always built-in under
> > CONFIG_TEGRA210_EMC_TABLE. I don't think that's worth the trouble with
> > this driver.
> 
> I forgot you have to add the compatible to reserved_mem_matches in
> drivers/of/platform.c.

Oh nice! Exactly what I was looking for, thanks. I'll respin shortly.

David