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| author | Jack Rosenthal <jrosenth@chromium.org> | 2022-11-04 17:15:28 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-11-10 18:51:56 +0100 |
| commit | 19d54020883c210a0cc78e5c735900ee9e9f64b3 (patch) | |
| tree | e63fdba785288ce5e634bf5392308376c4e32fc1 /drivers/firmware/google/Kconfig | |
| parent | test_firmware: Fix spelling mistake "EMTPY" -> "EMPTY" (diff) | |
| download | linux-19d54020883c210a0cc78e5c735900ee9e9f64b3.tar.xz linux-19d54020883c210a0cc78e5c735900ee9e9f64b3.zip | |
firmware: google: Implement cbmem in sysfs driver
The CBMEM area is a downward-growing memory region used by coreboot to
dynamically allocate tagged data structures ("CBMEM entries") that
remain resident during boot.
This implements a driver which exports access to the CBMEM entries
via sysfs under /sys/bus/coreboot/devices/cbmem-<id>.
This implementation is quite versatile. Examples of how it could be
used are given below:
* Tools like util/cbmem from the coreboot tree could use this driver
instead of finding CBMEM in /dev/mem directly. Alternatively,
firmware developers debugging an issue may find the sysfs interface
more ergonomic than the cbmem tool and choose to use it directly.
* The crossystem tool, which exposes verified boot variables, can use
this driver to read the vboot work buffer.
* Tools which read the BIOS SPI flash (e.g., flashrom) can find the
flash layout in CBMEM directly, which is significantly faster than
searching the flash directly.
Write access is provided to all CBMEM regions via
/sys/bus/coreboot/devices/cbmem-<id>/mem, as the existing cbmem
tooling updates this memory region, and envisioned use cases with
crossystem can benefit from updating memory regions.
Link: https://issuetracker.google.com/239604743
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Signed-off-by: Jack Rosenthal <jrosenth@chromium.org>
Link: https://lore.kernel.org/r/20221104161528.531248-1-jrosenth@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/firmware/google/Kconfig')
| -rw-r--r-- | drivers/firmware/google/Kconfig | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/drivers/firmware/google/Kconfig b/drivers/firmware/google/Kconfig index 983e07dc022e..9f190eab43ed 100644 --- a/drivers/firmware/google/Kconfig +++ b/drivers/firmware/google/Kconfig @@ -19,6 +19,21 @@ config GOOGLE_SMI driver provides an interface for reading and writing NVRAM variables. +config GOOGLE_CBMEM + tristate "CBMEM entries in sysfs" + depends on GOOGLE_COREBOOT_TABLE + help + CBMEM is a downwards-growing memory region created by the + Coreboot BIOS containing tagged data structures from the + BIOS. These data structures expose things like the verified + boot firmware variables, flash layout, firmware event log, + and more. + + This option enables the cbmem module, which causes the + kernel to search for Coreboot CBMEM entries, and expose the + memory for each entry in sysfs under + /sys/bus/coreboot/devices/cbmem-<id>. + config GOOGLE_COREBOOT_TABLE tristate "Coreboot Table Access" depends on HAS_IOMEM && (ACPI || OF) |