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 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.
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 (8):
platform/x86: wmi: Add new method wmidev_evaluate_method
platform/x86: dell-smbios: Introduce a WMI-ACPI interface
platform/x86: dell-wmi-smbios: Use Dell WMI descriptor check
platform/x86: wmi: create character devices when requested by drivers
platform/x86: dell-wmi-smbios: introduce character device for
userspace
platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens
platform/x86: Kconfig: Change the default settings for dell-wmi-smbios
platform/x86: dell-wmi-smbios: clean up wmi descriptor check
Documentation/ABI/testing/dell-wmi-smbios | 11 +
.../ABI/testing/sysfs-platform-dell-wmi-smbios | 16 ++
MAINTAINERS | 6 +
drivers/platform/x86/Kconfig | 15 +-
drivers/platform/x86/dell-smbios.c | 315 +++++++++++++++++++--
drivers/platform/x86/dell-smbios.h | 15 +-
drivers/platform/x86/dell-wmi.c | 75 +----
drivers/platform/x86/wmi.c | 126 ++++++++-
include/linux/wmi.h | 7 +
include/uapi/linux/dell-wmi-smbios.h | 30 ++
10 files changed, 498 insertions(+), 118 deletions(-)
create mode 100644 Documentation/ABI/testing/dell-wmi-smbios
create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios
create mode 100644 include/uapi/linux/dell-wmi-smbios.h
--
2.14.1
