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1=======2LoadPin3=======4 5LoadPin is a Linux Security Module that ensures all kernel-loaded files6(modules, firmware, etc) all originate from the same filesystem, with7the expectation that such a filesystem is backed by a read-only device8such as dm-verity or CDROM. This allows systems that have a verified9and/or unchangeable filesystem to enforce module and firmware loading10restrictions without needing to sign the files individually.11 12The LSM is selectable at build-time with ``CONFIG_SECURITY_LOADPIN``, and13can be controlled at boot-time with the kernel command line option14"``loadpin.enforce``". By default, it is enabled, but can be disabled at15boot ("``loadpin.enforce=0``").16 17LoadPin starts pinning when it sees the first file loaded. If the18block device backing the filesystem is not read-only, a sysctl is19created to toggle pinning: ``/proc/sys/kernel/loadpin/enabled``. (Having20a mutable filesystem means pinning is mutable too, but having the21sysctl allows for easy testing on systems with a mutable filesystem.)22 23It's also possible to exclude specific file types from LoadPin using kernel24command line option "``loadpin.exclude``". By default, all files are25included, but they can be excluded using kernel command line option such26as "``loadpin.exclude=kernel-module,kexec-image``". This allows to use27different mechanisms such as ``CONFIG_MODULE_SIG`` and28``CONFIG_KEXEC_VERIFY_SIG`` to verify kernel module and kernel image while29still use LoadPin to protect the integrity of other files kernel loads. The30full list of valid file types can be found in ``kernel_read_file_str``31defined in ``include/linux/kernel_read_file.h``.32