diff options
| -rwxr-xr-x | scripts/image_signing/sign_gsc_firmware.sh | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/scripts/image_signing/sign_gsc_firmware.sh b/scripts/image_signing/sign_gsc_firmware.sh index 768844ad..a464b9b1 100755 --- a/scripts/image_signing/sign_gsc_firmware.sh +++ b/scripts/image_signing/sign_gsc_firmware.sh @@ -36,6 +36,92 @@ to_int32() { print (struct.unpack('i', d)[0])" } +# Functions allowing to determine the base address of a binary blob in ihex +# format. Invoked in a subprocess through () to be able to use stdout as the +# return values. + +# In ihex format binary data is represented as a set of records. Each record +# is a text string of hex values in ASCII. All records start with a header +# which determines the record contents. +# +# The most common record type is the data record, its header includes the 16 +# bit address of where the record data will have to be placed in the physical +# address space. Naturally 16 bits is not enough as of last thirty years, some +# special types of record are used to specify the segment base of there the +# 16 bit address is used as the offset. +# +# The segment base is still represented as a 16 bit value, depending on the +# record type the base is shifted right ether 4 (record type 02) or 16 (record +# type 04) bits. +# +# The first two records of the ihex binary blob are a segment record and a +# data record. Combining the segment value from the first record and the +# address value from the second record one can determine the base address +# where the blob is supposed to be placed. +# +# See https://en.wikipedia.org/wiki/Intel_HEX for further details. +parse_segment() { + local string="$1" + + if [[ "${string}" =~ ^:020000 && "${#string}" -eq 15 ]]; then + local type="${string:7:2}" + local value="0x${string:9:4}" + local segment + + case "${type}" in + (02) + segment=$(( value << 4 )) + ;; + (04) + segment=$(( value << 16 )) + ;; + (*) + error "unknown segment record type ${type}" + ;; + esac + printf "0x%x" "${segment}" + else + error "unexpected segment record: ${string}" + fi +} + +# The second record in the ihex binary blob is mapped to the lowest 16 bit +# address in the segment. +parse_data() { + local string="$1" + + if [[ "${string}" =~ ^:10 && "${#string}" -eq 43 ]]; then + echo "0x${string:3:4}" + else + error "unexpected data record: ${string}" + fi +} + +# Given an ihex binary blob determine its base address as a sum of the segment +# address and the offset of the first record into the segment. +get_hex_base() { + local hexf="$1" + local strings + local segment + local base_offset + + # Some ihex blobs include <cr><lf>, drop <cr> to allow for fixed size check. + mapfile -t strings < <(head -2 "${hexf}" | sed 's/\x0d//') + + if [[ ${#strings[@]} != 2 ]]; then + error "input file ${hexf} too short" + return + fi + segment="$(parse_segment "${strings[0]}")" + base_offset="$(parse_data "${strings[1]}")" + + if [[ -n "${segment}" && -n "${base_offset}" ]]; then + printf "%d\n" $(( segment + base_offset )) + else + error "${hexf} does not seem to be a valid ihex module." + fi +} + # This function accepts one argument, the name of the GSC manifest file which # needs to be verified and in certain cases altered. # |