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SubjectRe: [PATCH v8 00/15] Introduce support for Dell SMBIOS over WMI
I like how this series turned out and I think it puts us in a
exceedingly better position than the dcdbas path. This series is,

Reviewed-by: Edward O'Callaghan <quasisec@google.com>

On Sat, Oct 14, 2017 at 4:32 PM, Mario Limonciello
<mario.limonciello@dell.com> wrote:
> The existing way that the dell-smbios helper module and associated
> other drivers (dell-laptop, dell-wmi) communicate with the platform
> really isn't secure. It requires creating a buffer in physical
> DMA32 memory space and passing that to the platform via SMM.
>
> Since the platform got a physical memory pointer, you've just got
> to trust that the platform has only modified (and accessed) memory
> within that buffer.
>
> Dell Platform designers recognize this security risk and offer a
> safer way to communicate with the platform over ACPI. This is
> in turn exposed via a WMI interface to the OS.
>
> When communicating over WMI-ACPI the communication doesn't occur
> with physical memory pointers. When the ASL is invoked, the fixed
> length ACPI buffer is copied to a small operating region. The ASL
> will invoke the SMI, and SMM will only have access to this operating
> region. When the ASL returns the buffer is copied back for the OS
> to process.
>
> This method of communication should also deprecate the usage of the
> dcdbas kernel module and software dependent upon it's interface.
> Instead offer a character device interface for communicating with this
> ASL method to allow userspace to use instead.
>
> To faciliate that this patch series introduces a generic way for WMI
> drivers to be able to create discoverable character devices with
> a predictable IOCTL interface through the WMI bus when desired.
> Requiring WMI drivers to explicitly ask for this functionality will
> act as an effective vendor whitelist to character device creation.
>
> Some of this work is the basis for what will be a proper interpreter
> of MOF in the kernel and controls for what drivers will be able to
> do with that MOF.
>
> NOTE: This patch series is intended to go on top of platform-drivers-x86
> linux-next.
>
> For convenience the entire series including those is also available here:
> https://github.com/superm1/linux/tree/wmi-smbios
> changes bweteen v7 and v8:
> * fix typo s/desc_buffer/buffer/ in 32k split commit
> * Add missing include for <linux/types.h> in uapi
> * dell-smbios: initialize correct attribute files
> * Output class/select in debug messages in base 10.
> * Don't send the u64 length argument to ACPI call length
> * Only filter calls that originate from userspace
> * Filter kernel calls from userspace
> * Add more blacklisting/whitelisting logic per Alan Cox's
> recommendations
> * Adjust tokens attributes to only be accessible to CAP_SYS_ADMIN
> * Set default permissions on character device.
> * Move token, class, select definitions for items used in drivers
> to dells-smios.h.
> changes between v6 and v7:
> * Use deferred probing in any function results needed from
> dell-wmi-descriptor
> * Protect against a list entry disappearing when running an ioctl from
> WMI bus
> * Move ioctl uapi declaration into a common header file for all WMI
> drivers.
> * New patch: create required_buffer_size for method type WMI objects
> in WMI core rather than vendor driver.
> * WSMT patch: Add comment explaining WSMT
> * Filtering patch: Add comments explaining what I can about blacklists.
> * WMI, dell-smbios-wmi: Add back in compat ioctl, it is needed.
> My previous test was erroneous in forgetting to copy an updated header
> into the chroot.
> * dell-laptop, dell-wmi: allocate less memory for buffer, page no longer
> needed
> * dell-laptop make the changes (hopefully) more amenable to pali style
> wise.
> * read SMM cmd address in dell-smbios-smm rather than dell-smbios
> * shuffle structure definitions for this
> changes between v5 and v6:
> * Adjust Kconfig for dell-smbios to not depend on anything.
> - SMM and WMI drivers will both select dell-smbios
> - Technically the module can run on it's own (it's just not useful)
> * Add a new tokens sysfs interface
> * Rework blacklisting into easily expandable structures
> * Lock modules during ioctl call from WMI bus
> * drop references to compat ioctl in both WMI and dell-smbios-wmi
> drivers. (Made sure ioctl worked in both 32 and 64 userspace though)
> * dell-smbios-wmi
> - s/buffer_size/req_buf_size/ to make it clearer that userspace
> doesn't get to set this, it's set internally.
> - read just buffer length before reading whole structure from
> userspace
> - if buffer length is too big, show a warning
> - I tried to rename argument for unlocked_ioctl, but this caused
> problems in matching initialization lists, so still casting.
> - Add comments clarifying everything happening in ioctl
> changes between v4 and v5:
> * Remove Andy's S suggested by in sysfs tokens patch
> * Make some output in dell-wmi-descriptor debug only
> * Adjust various Kconfig dependencies as recommended by Darren
> * Drop patch to set dell-smbios to default on ACPI_WMI,
> it's not needed after the Kconfig dependencies rework
> * Move WSMT check patch to after WMI driver is introduced.
> * Make common smbios call return value int as there could be
> errors now with drivers not being loaded.
> * Make SMBIOS call methods for all drivers return status
> * Reorder patches 2 and 4.
> * Don't export symbols for calling functions on dispatchers
> * wmi patch:
> - use sprintf instead of strcpy
> - remove needless bool for tracking found
> - adjust logic to look for instance_count - 1, it's zero
> based not 1 based.
> - Pass a callback to unlocked_ioctl instead of full file
> operations object
> - ioctl: Don't fail on no bound WMI driver
> - Add missing header for uapi
> - Make helper macros include data types
> - add compat ioctl
> * dell-smbios:
> - Add filtering functionality for SMBIOS calling interface
> - Use dev_dbg rather than pr_debug where possible
> * dell-smbios-wmi:
> - test for handle on b1 table
> - correct misc flags comment
> - drop access checks
> - use dev_dbg instead of pr_* calls
> - use filtering functionality
> - add mutexes around list add/remove
> - switch from get_first_device to get_first_priv and inline
> - add mutex locking to prevent unloading mid-call.
> - update to new ioctl passing
> - fix userspace uapi to use __u32 instead of u32
> - Don't use a header file for internal only use
> - make sure it works with compat ioctl
> * dell-laptop: make dell_smbios_send_request local function
> for boilerplate calls.
> * ioctl patch
> - Change API to have a simpler structure to pass back and
> forth
> - Rename header file
> - Export to sysfs properly
> - Add the size of the length variable into the requested
> buffersize to sysfs, do math in the driver when copying
> data around.
> changes between v3 and v4:
> * Make Dell WMI notifications driver fail notifications fail
> when WMI descriptor driver is unavailable.
> * Add a patch to check for Dell OEM string to stop dell-smbios
> module from being loaded in unsupported systems manually.
> * Split Dell WMI descriptor into it's own driver for others to
> query.
> * Test the misc BIOS flags table to decide whether to run in WMI
> or SMI mode.
> * s/dell-wmi-smbios/dell-smbios/ in a few patch titles
> * Add missing Suggested-by to a patch from v2 (Sorry Andy S!)
> * Adjust cleanup order of wmi character device.
> * Fix a remaining reference to /dev/wmi-$driver
> * Use get_order to get size for pages
> * Split up dell-smbios into 3 drivers:
> dell-smbios
> -> dell-smbios-smm
> -> dell-smbios-wmi
> If either of the two dispatcher drivers is unloaded but
> the other still works, gracefully fall back to that driver
> * Remove unneded open and release on file operations in WMI
> driver
> * Switch to misc character device in WMI bus.
> * Query the size of the calling interface buffer from WMI
> descriptor driver.
> * Require userspace to use this information to build an
> appropriately sized buffer.
> * Verify the size of buffer passed from userspace matches
> expectation of buffer processed in kernel.
> * Add more documentation about the IOCTL API.
> * Add in a recommendation from Andy S about outputing tokens
> * Add a patch to test for non-functional SMM due to WSMT
> * Define macros for IOCTL's through the WMI bus.
> * Pass all IOCTL calls for WMI drivers through WMI bus
> WMI bus will guarantee instance count matches and prevent
> creating too many more IOCTLs.
> changes between v2 and v3:
> * Drop patches 1-7, they're in Darren's review tree now
> * Add missing newline on new Documentation
> * Add Reviewed by from Edward O'Callaghan
> * Adjust path of character device from /dev/wmi-$driver to
> /dev/wmi/$driver
> * Store wmi_device pointer rather than using a boolean has_wmi
> to indicate driver is running in WMI mode
> * Don't guard free_page from freeing NULL (this is OK)
> * New patch: add wmidev_evaluate_method to wmi bus as recommended
> by Andy L
> * Adjust ACPI-WMI interface for this patch change ^
> * Add back in sysfs token patch, drop 2nd and 3rd ioctls per discussion
> on mailing list.
> * On sysfs interface: adjust the delimiter to be tabs
> * Drop the rename dell-smbios -> dell-wmi-smbios patch
> * Remove/move some unnecessary tests for CONFIG_DCDBAS
> * Reword s/platform/SMM/ in the WMI-ACPI patch.
> * Update Kconfig to recommend using CONFIG_DCDBAS on old machines.
> * Allocate buffer to the same pointer regardless of the struct
> assigned to it. Keep track of the buffer size for cleaning up.
> * Explain policy around character device creation in commit message
> changes between v1 and v2:
> * Introduce another patch to sort the includes in wmi.c
> * Introduce another patch to cleanup dell_wmi_check_descriptor_buffer
> checks.
> * Add a commit message to the pr_fmt commit
> * Introduce includes to wmi.c in proper location
> * Add Reviewed-by to relevant patches from Pali
> * Make the WMI introduction patch fallback to legacy SMI
> if compiled with CONFIG_DCDBAS
> * Separate format of WMI and SMI buffers. WMI buffer supports more
> arguments and data.
> * Adjust the rename patch for changes to fallback
> * Drop sysfs token creation patch
> * Adjust WMI descriptor check patch for changes to fallback
> * introduce another patch to remove needless includes in dell-smbios.c
> * Add token ioctl interface to character device.
> - Can query number of tokens
> - Can query values in all tokens
> * Expose format of all buffers and IOCTL commands to uapi header
> * Drop the read interface from character device. It doesn't make
> sense with multiple different ioctl methods.
> * Default WMI interface to 32k (This would normally be queried via
> MOF, but that's not possible yet)
> * Create separate buffers for WMI and SMI. If WMI is available,
> free the SMI buffer.
> * Reorder patches so all fixups come first in the series.
>
> Mario Limonciello (15):
> platform/x86: wmi: Add new method wmidev_evaluate_method
> platform/x86: dell-wmi: increase severity of some failures
> platform/x86: dell-wmi: clean up wmi descriptor check
> platform/x86: dell-wmi: allow 32k return size in the descriptor
> platform/x86: dell-wmi-descriptor: split WMI descriptor into it's own
> driver
> platform/x86: wmi: Don't allow drivers to get each other's GUIDs
> platform/x86: dell-smbios: only run if proper oem string is detected
> platform/x86: dell-smbios: Add a sysfs interface for SMBIOS tokens
> platform/x86: dell-smbios: Introduce dispatcher for SMM calls
> platform/x86: dell-smbios-wmi: Add new WMI dispatcher driver
> platform/x86: dell-smbios-smm: test for WSMT
> platform/x86: dell-smbios: Add filtering support
> platform/x86: wmi: Add sysfs attribute for required_buffer_size
> platform/x86: wmi: create userspace interface for drivers
> platform/x86: dell-smbios-wmi: introduce userspace interface
>
> Documentation/ABI/testing/dell-smbios-wmi | 41 ++
> .../ABI/testing/sysfs-platform-dell-smbios | 21 +
> MAINTAINERS | 25 +
> drivers/platform/x86/Kconfig | 34 +-
> drivers/platform/x86/Makefile | 3 +
> drivers/platform/x86/dell-laptop.c | 283 +++++-------
> drivers/platform/x86/dell-smbios-smm.c | 195 ++++++++
> drivers/platform/x86/dell-smbios-wmi.c | 292 ++++++++++++
> drivers/platform/x86/dell-smbios.c | 510 +++++++++++++++++++--
> drivers/platform/x86/dell-smbios.h | 68 ++-
> drivers/platform/x86/dell-wmi-descriptor.c | 162 +++++++
> drivers/platform/x86/dell-wmi-descriptor.h | 18 +
> drivers/platform/x86/dell-wmi.c | 91 +---
> drivers/platform/x86/wmi.c | 192 +++++++-
> include/linux/wmi.h | 17 +-
> include/uapi/linux/wmi.h | 52 +++
> 16 files changed, 1655 insertions(+), 349 deletions(-)
> create mode 100644 Documentation/ABI/testing/dell-smbios-wmi
> create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-smbios
> create mode 100644 drivers/platform/x86/dell-smbios-smm.c
> create mode 100644 drivers/platform/x86/dell-smbios-wmi.c
> create mode 100644 drivers/platform/x86/dell-wmi-descriptor.c
> create mode 100644 drivers/platform/x86/dell-wmi-descriptor.h
> create mode 100644 include/uapi/linux/wmi.h
>
> --
> 2.14.1
>

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