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SubjectRe: [PATCH] SPI LPC information kernel module
On Mon, Jun 29, 2020 at 07:59:32PM -0300, Daniel Gutson wrote:
> This kernel module exports configuration attributes for the
> system SPI chip.
> This initial version exports the BIOS Write Enable (bioswe),
> BIOS Lock Enable (ble), and the SMM Bios Write Protect (SMM_BWP)
> fields of the Bios Control register. The idea is to keep adding more
> flags, not only from the BC but also from other registers in following
> versions.
>
> The goal is that the attributes are avilable to fwupd when SecureBoot
> is turned on.
>
> A technical note: I check if *ppos == BUFFER_SIZE in the reading function
> to exit early and avoid an extra access to the HW, for example when using
> the 'cat' command, which causes two read operations.

Why not use the simple_* functions which should prevent that type of
thing?



>
> Signed-off-by: Daniel Gutson <daniel.gutson@eclypsium.com>
> ---
> Documentation/ABI/stable/securityfs-spi-lpc | 23 +

Why is this going in securityfs at all? Why not just sysfs as it is a
CPU attribute, right?


> MAINTAINERS | 6 +
> drivers/misc/Kconfig | 1 +
> drivers/misc/Makefile | 1 +
> drivers/misc/spi_lpc/Kconfig | 20 +
> drivers/misc/spi_lpc/Makefile | 8 +
> drivers/misc/spi_lpc/bios_data_access.c | 559 +++++++++++++++++++
> drivers/misc/spi_lpc/bios_data_access.h | 181 +++++++
> drivers/misc/spi_lpc/low_level_access.c | 59 ++
> drivers/misc/spi_lpc/low_level_access.h | 21 +
> drivers/misc/spi_lpc/spi_lpc_main.c | 176 ++++++
> drivers/misc/spi_lpc/viddid_arch_map.c | 566 ++++++++++++++++++++
> drivers/misc/spi_lpc/viddid_arch_map.h | 17 +
> 13 files changed, 1638 insertions(+)
> create mode 100644 Documentation/ABI/stable/securityfs-spi-lpc
> create mode 100644 drivers/misc/spi_lpc/Kconfig
> create mode 100644 drivers/misc/spi_lpc/Makefile
> create mode 100644 drivers/misc/spi_lpc/bios_data_access.c
> create mode 100644 drivers/misc/spi_lpc/bios_data_access.h
> create mode 100644 drivers/misc/spi_lpc/low_level_access.c
> create mode 100644 drivers/misc/spi_lpc/low_level_access.h
> create mode 100644 drivers/misc/spi_lpc/spi_lpc_main.c
> create mode 100644 drivers/misc/spi_lpc/viddid_arch_map.c
> create mode 100644 drivers/misc/spi_lpc/viddid_arch_map.h
>
> diff --git a/Documentation/ABI/stable/securityfs-spi-lpc b/Documentation/ABI/stable/securityfs-spi-lpc
> new file mode 100644
> index 000000000000..22660a7fd914
> --- /dev/null
> +++ b/Documentation/ABI/stable/securityfs-spi-lpc
> @@ -0,0 +1,23 @@
> +What: /sys/kernel/security/firmware/bioswe
> +Date: June 2020
> +KernelVersion: 5.8.0
> +Contact: daniel.gutson@eclypsium.com
> +Description: If the system firmware set BIOS Write Enable.
> + 0: writes disabled, 1: writes enabled.

THis is very x86-specific, what about ARM/MIPS/anything else? Perhaps a
cpu/arch-specific thing instead?

Again, which makes it seem like securityfs is not the thing for this, as
it describes the hardware, not a security model which is what securityfs
has been for in the past, right?

thanks,

greg k-h

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