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IPE is designed to provide system level trust guarantees, this usually implies that trust starts from bootup with a hardware root of trust, which validates the bootloader. After this, the bootloader verifies the kernel and the initramfs. As there's no currently supported integrity method for initramfs, and it's typically already verified by the bootloader. This patch introduces a new IPE property `boot_verified` which allows author of IPE policy to indicate trust for files from initramfs. The implementation of this feature utilizes the newly added `initramfs_populated` hook. This hook marks the superblock of the rootfs after the initramfs has been unpacked into it. Before mounting the real rootfs on top of the initramfs, initramfs script will recursively remove all files and directories on the initramfs. This is typically implemented by using switch_root(8) (https://man7.org/linux/man-pages/man8/switch_root.8.html). Therefore the initramfs will be empty and not accessible after the real rootfs takes over. It is advised to switch to a different policy that doesn't rely on the `boot_verified` property after this point. This ensures that the trust policies remain relevant and effective throughout the system's operation. Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com> Signed-off-by: Fan Wu <wufan@linux.microsoft.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.