a5f843f0f2
Provide a -n flag to 'shim debug' so that the setting persists across reboots. Co-developed-by: Claude <noreply@anthropic.com> Signed-off-by: Simon Glass <sjg@chromium.org>
110 lines
2.8 KiB
ReStructuredText
110 lines
2.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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shim command
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============
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Synopsis
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--------
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::
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shim debug [[-n] <0/1>]
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Description
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-----------
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The ``shim`` command provides utilities for controlling and configuring the
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UEFI Shim bootloader when U-Boot is running as an EFI application. Shim is a
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UEFI bootloader that is used to verify and boot signed operating system
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loaders, commonly used in secure boot environments.
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The ``shim debug`` subcommand manages the Shim verbose debugging mode through
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the ``SHIM_VERBOSE`` EFI variable.
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Subcommands
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~~~~~~~~~~~
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shim debug
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^^^^^^^^^^
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Controls the Shim verbose debugging mode.
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**Usage:**
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::
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shim debug # Display current debug state (0 or 1)
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shim debug 0 # Disable verbose debugging
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shim debug 1 # Enable verbose debugging
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shim debug -n 1 # Enable verbose debugging (non-volatile)
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The command reads from or writes to the ``SHIM_VERBOSE`` EFI variable in the
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Shim Lock GUID namespace. When verbose mode is enabled (value = 1), Shim will
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output additional debugging information during the boot process. When disabled
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(value = 0 or variable doesn't exist), Shim operates silently.
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**Parameters:**
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* ``-n`` - Makes the variable non-volatile (persistent across reboots)
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* ``<0/1>`` - Optional parameter to set debug mode:
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* ``0`` - Disable verbose debugging
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* ``1`` - Enable verbose debugging
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* If omitted, displays current debug state
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**Return value:**
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The command returns 0 on success, 1 on failure.
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**Examples:**
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Check current debug state::
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=> shim debug
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0
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Enable verbose debugging::
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=> shim debug 1
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Disable verbose debugging::
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=> shim debug 0
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Enable verbose debugging with persistence across reboots::
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=> shim debug -n 1
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Configuration
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~~~~~~~~~~~~~
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The shim command is available when:
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* ``CONFIG_CMD_SHIM`` is enabled
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* U-Boot is running as an EFI application
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* EFI-variable support is available
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Implementation Details
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~~~~~~~~~~~~~~~~~~~~~~
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The command uses the EFI variable services to read and write the
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``SHIM_VERBOSE`` variable with the following characteristics:
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* **Variable Name:** ``SHIM_VERBOSE`` (Unicode string)
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* **GUID:** EFI Shim Lock GUID (``605dab50-e046-4300-abb6-3dd810dd8b23``)
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* **Attributes:** ``EFI_VARIABLE_BOOTSERVICE_ACCESS`` (default) or
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``EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_NON_VOLATILE`` (with ``-n`` flag)
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* **Data Type:** 32-bit unsigned integer (4 bytes)
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* **Values:** 0 (disabled) or 1 (enabled)
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By default, the variable is volatile and will be reset on reboot. When the
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``-n`` flag is used, the variable becomes non-volatile and persists across
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reboots until explicitly changed or the variable store is cleared.
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See Also
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~~~~~~~~
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* :doc:`efidebug` - EFI debugging utilities
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* :doc:`bootefi` - Boot EFI applications
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* :doc:`/develop/uefi/u-boot_on_efi`
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