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Blob jail: Make device firmware available during initrd

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Some device firmware, such as the graphics microcontroller, is needed
during the initrd - i915 is often loaded in the initrd, and this is the
only chance to load GuC firmware.

Device firmware must still be available after the real root is mounted
too, so update the custom firmware path in the kernel when the firmware
is moved to /run.

Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>
This commit is contained in:
Jonathon Hall 2023-09-19 10:36:37 -04:00
parent 439aba5f05
commit af5eb2edf9
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GPG Key ID: 1E9C3CA91AE25114
2 changed files with 22 additions and 12 deletions
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32
initrd/bin/inject_firmware.sh
View File

@ -55,26 +55,36 @@ if ! grep -E -q '^exec run-init .*\$\{rootmnt\}' "$INITRD_ROOT/init"; then
exit 0
fi
# The initrd's /init has to copy the firmware to /run/firmware, so it will be
# present when the real root is moved to /.
# * Wi-Fi/BT firmware loading doesn't happen during the initrd - these modules
# aren't in the initrd anyway, typically.
# * /run is a tmpfs mount, so this works even if the root filesystem is
# read-only, and it doesn't persist anything.
# In general, firmware files must be available _both_ during the initrd _and_
# once root is moved to /. Firmware loading may happen in either phase (e.g.
# i915 GUC firmware is usually loaded in the initrd because i915 is used there,
# but Wi-Fi/BT modules typically are not in the initrd, they're loaded later).
#
# kexec-boot will add a kernel parameter for the kernel to look for firmware in
# /run/firmware.
# We want to place the firmware after boot in /run, since this is a tmpfs mount
# - it works even if the root filesystem is read-only and does not persist
# anything. But we cannot place it there for the initrd, since the initrd also
# mounts a tmpfs on /run. We can only specify one custom firmware path, but we
# can change it at runtime.
#
# So during the initrd, the firmware is in /firmware, and we provide that path
# on the kernel command line. Just before invoking the real init (after root is
# mounted), we copy it to /run/firmware and also change the firmware path.
#
# Debian's init script ends with an "exec run-init ..." (followed by a few lines
# to print a message in case it fails). At that point, root is mounted, and
# run-init will move it to / and then exec init. We can copy the firmware just
# before that, so we don't have to know anything about how root was mounted.
# run-init will move it to / and then exec init. We can insert the firmware
# actions just before that, so we don't have to know anything about how root was
# mounted.
#
# The root path is in ${rootmnt}, which should appear in the run-init command.
# If it doesn't, then we don't understand the init script.
AWK_INSERT_CP='
BEGIN{inserted=0}
/^exec run-init .*\$\{rootmnt\}/ && inserted==0 {print "cp -r /firmware ${rootmnt}/run/firmware"; inserted=1}
/^exec run-init .*\$\{rootmnt\}/ && inserted==0 {
print "cp -r /firmware ${rootmnt}/run/firmware"
print "echo -n /run/firmware >${rootmnt}/sys/module/firmware_class/parameters/path"
inserted=1
}
{print $0}'
awk -e "$AWK_INSERT_CP" "$INITRD_ROOT/init" >"$INITRD_ROOT/init_fw"

2
initrd/bin/kexec-boot
View File

@ -35,7 +35,7 @@ cmdadd="$CONFIG_BOOT_KERNEL_ADD $cmdadd"
cmdremove="$CONFIG_BOOT_KERNEL_REMOVE $cmdremove"
if [ "$(load_config_value CONFIG_USE_BLOB_JAIL)" = "y" ]; then
cmdadd="$cmdadd firmware_class.path=/run/firmware/"
cmdadd="$cmdadd firmware_class.path=/firmware/"
fi
fix_file_path() {