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105 lines
4.1 KiB
Bash
Executable File
105 lines
4.1 KiB
Bash
Executable File
#!/bin/bash
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# If blob jail is enabled, copy initrd and inject firmware.
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# Prints new initrd path (in memory) if firmware was injected.
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#
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# This does not alter the initrd on disk:
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# * Signatures are not invalidated
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# * If the injection fails for any reason, we just proceed with the original
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# initrd (lacking firmware, but still booting).
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# * If, somehow, this injection malfunctions (without failing outright) and
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# prevents a boot, the user can work around it just by disabling blob jail.
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# We do not risk ruining the real initrd.
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#
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# The injection has some requirements on the initrd that are all true for
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# Debian:
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# * initrd must be a gzipped cpio (Linux supports other compression methods)
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# * /init must be a shell script (so we can inject a command to copy firmware)
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# * There must be an 'exec run-init ... ${rootmnt} ...' line that moves the
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# real root to / and invokes init
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#
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# If the injection can't be performed, boot will continue with no firmware.
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set -e -o pipefail
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. /tmp/config
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. /etc/functions
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if [ "$(load_config_value CONFIG_USE_BLOB_JAIL)" != "y" ]; then
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# Blob jail not active, nothing to do
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exit 0
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fi
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ORIG_INITRD="$1"
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# Extract the init script from the initrd
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INITRD_ROOT="/tmp/inject_firmware_initrd_root"
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rm -rf "$INITRD_ROOT" || true
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mkdir "$INITRD_ROOT"
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# Unpack just 'init' from the original initrd
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unpack_initramfs.sh "$ORIG_INITRD" "$INITRD_ROOT" init
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# Copy the firmware into the initrd
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for f in $(cbfs -l | grep firmware); do
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mkdir -p "$INITRD_ROOT/$(dirname "$f")"
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cbfs -r "$f" > "$INITRD_ROOT/$f"
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if [[ "$f" == *.lzma ]]; then
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lzma -d "$INITRD_ROOT/$f"
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fi
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done
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# awk will happily pass through a binary file, so look for the match we want
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# before modifying init to ensure it's a shell script and not an ELF, etc.
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if ! grep -E -q '^exec run-init .*\$\{rootmnt\}' "$INITRD_ROOT/init"; then
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warn "Can't apply firmware blob jail, unknown init script"
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exit 0
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fi
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# In general, firmware files must be available _both_ during the initrd _and_
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# once root is moved to /. Firmware loading may happen in either phase (e.g.
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# i915 GUC firmware is usually loaded in the initrd because i915 is used there,
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# but Wi-Fi/BT modules typically are not in the initrd, they're loaded later).
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#
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# We want to place the firmware after boot in /run, since this is a tmpfs mount
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# - it works even if the root filesystem is read-only and does not persist
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# anything. But we cannot place it there for the initrd, since the initrd also
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# mounts a tmpfs on /run. We can only specify one custom firmware path, but we
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# can change it at runtime.
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#
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# So during the initrd, the firmware is in /firmware, and we provide that path
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# on the kernel command line. Just before invoking the real init (after root is
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# mounted), we copy it to /run/firmware and also change the firmware path.
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#
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# Debian's init script ends with an "exec run-init ..." (followed by a few lines
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# to print a message in case it fails). At that point, root is mounted, and
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# run-init will move it to / and then exec init. We can insert the firmware
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# actions just before that, so we don't have to know anything about how root was
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# mounted.
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#
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# The root path is in ${rootmnt}, which should appear in the run-init command.
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# If it doesn't, then we don't understand the init script.
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AWK_INSERT_CP='
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BEGIN{inserted=0}
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/^exec run-init .*\$\{rootmnt\}/ && inserted==0 {
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print "cp -r /firmware ${rootmnt}/run/firmware"
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print "echo -n /run/firmware >${rootmnt}/sys/module/firmware_class/parameters/path"
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inserted=1
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}
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{print $0}'
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awk -e "$AWK_INSERT_CP" "$INITRD_ROOT/init" >"$INITRD_ROOT/init_fw"
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mv "$INITRD_ROOT/init_fw" "$INITRD_ROOT/init"
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chmod a+x "$INITRD_ROOT/init"
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# Pad the original initrd to 512 byte blocks. Uncompressed cpio contents must
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# be 4-byte aligned, and anecdotally gzip frames might not be padded by dracut.
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# Linux ignores zeros between archive segments, so any extra padding is not
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# harmful.
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FW_INITRD="/tmp/inject_firmware_initrd.cpio.gz"
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dd if="$ORIG_INITRD" of="$FW_INITRD" bs=512 conv=sync status=none
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# Pack up the new contents and append to the initrd. Don't spend time
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# compressing this.
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(cd "$INITRD_ROOT"; find . | cpio -o -H newc) >>"$FW_INITRD"
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# Use this initrd
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echo "$FW_INITRD"
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