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1bf8331ffb
Debian 12's initrd by default now consists of an uncompressed cpio archive containing microcode, followed by a zstd-compressed cpio archive. inject_firmware.sh only supported gzip-compressed cpio, so it could not extract /init from this archive. Add zstd-decompress to decompress zstd streams (uncompressed size is about 180 KB). Add unpack_initramfs.sh which is able to decompress uncompressed, gzip, or zstd archives, with multiple segments, much like the Linux kernel itself does. Use unpack_initramfs.sh to extract /init for blob jail. Don't compress the new archive segment containing firmware and the updated /init. Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>
111 lines
4.0 KiB
Bash
Executable File
111 lines
4.0 KiB
Bash
Executable File
#! /bin/bash
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set -e -o pipefail
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. /etc/functions
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# Unpack a Linux initramfs archive.
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#
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# In general, the initramfs archive is one or more cpio archives, optionally
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# compressed, concatenated together. Uncompressed and compressed segments can
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# exist in the same file. Zero bytes between segments are skipped. To properly
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# unpack such an archive, all segments must be unpacked.
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#
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# This script unpacks such an archive, but with a limitation that once a
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# compressed segment is reached, no more segments can be read. This works for
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# common initrds on x86, where the microcode must be stored in an initial
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# uncompressed segment, followed by the "real" initramfs content which is
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# usually in one compressed segment.
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#
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# The limitation comes from gunzip/unzstd, there's no way to prevent them from
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# consuming trailing data or tell us the member/frame length. The script
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# succeeds with whatever was extracted, since this is used to extract particular
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# files and boot can proceed as long as those files were found.
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INITRAMFS_ARCHIVE="$1"
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DEST_DIR="$2"
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shift
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shift
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# rest of args go to cpio, can specify filename patterns
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CPIO_ARGS=("$@")
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# Consume zero bytes, the first nonzero byte read (if any) is repeated on stdout
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consume_zeros() {
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next_byte='00'
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while [ "$next_byte" = "00" ]; do
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# if we reach EOF, next_byte becomes empty (dd does not fail)
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next_byte="$(dd bs=1 count=1 status=none | xxd -p | tr -d ' ')"
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done
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# if we finished due to nonzero byte (not EOF), then carry that byte
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if [ -n "$next_byte" ]; then
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echo -n "$next_byte" | xxd -p -r
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fi
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}
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unpack_cpio() {
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(cd "$dest_dir"; cpio -i "${CPIO_ARGS[@]}" 2>/dev/null)
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}
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# unpack the first segment of an archive, then write the rest to another file
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unpack_first_segment() {
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unpack_archive="$1"
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dest_dir="$2"
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rest_archive="$3"
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mkdir -p "$dest_dir"
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# peek the beginning of the file to determine what type of content is next
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magic="$(dd if="$unpack_archive" bs=6 count=1 status=none | xxd -p)"
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# read this segment of the archive, then write the rest to the next file
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(
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# Magic values correspond to Linux init/initramfs.c (zero, cpio) and
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# lib/decompress.c (gzip)
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case "$magic" in
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00*)
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# Skip zero bytes and copy the first nonzero byte
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consume_zeros
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# Copy the remaining data
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cat
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;;
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303730373031*|303730373032*) # plain cpio
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# Unpack the plain cpio, this stops reading after the trailer
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unpack_cpio
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# Copy the remaining data
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cat
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;;
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1f8b*|1f9e*) # gzip
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# gunzip won't stop when reaching the end of the gzipped member,
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# so we can't read another segment after this. We can't
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# reasonably determine the member length either, this requires
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# walking all the compressed blocks.
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gunzip | unpack_cpio
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;;
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28b5*) # zstd
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# Like gunzip, this will not stop when reaching the end of the
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# frame, and determining the frame length requires walking all
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# of its blocks.
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(zstd-decompress -d || true) | unpack_cpio
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;;
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*) # unknown
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die "Can't decompress initramfs archive, unknown type: $magic"
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;;
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esac
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) <"$unpack_archive" >"$rest_archive"
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orig_size="$(stat -c %s "$unpack_archive")"
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rest_size="$(stat -c %s "$rest_archive")"
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DEBUG "archive segment $magic: $((orig_size - rest_size)) bytes"
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}
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DEBUG "Unpacking $INITRAMFS_ARCHIVE to $DEST_DIR"
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next_archive="$INITRAMFS_ARCHIVE"
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rest_archive="/tmp/unpack_initramfs_rest"
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# Break when there is no remaining data
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while [ -s "$next_archive" ]; do
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unpack_first_segment "$next_archive" "$DEST_DIR" "$rest_archive"
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next_archive="/tmp/unpack_initramfs_next"
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mv "$rest_archive" "$next_archive"
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done
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