展讯的s9863a以及s9832e vbmeta和boot等镜像修改签名的方法是一样的。

vbmeta自己修改生成的命令：

python2 avbtool make_vbmeta_image –key rsa4096_vbmeta.pem –algorithm SHA256_RSA4096 –flag 0 –padding_size 16384 \
–chain_partition boot:1:keys/x_key.bin \
–chain_partition dtbo:10:keys/key_dtbo.bin \
–chain_partition recovery:2:keys/key_recovery.bin \
–chain_partition socko:11:keys/key_socko.bin \
–chain_partition odmko:12:keys/key_odmko.bin \
–chain_partition vbmeta_system:3:keys/key_vbmeta_system.bin \
–chain_partition vbmeta_vendor:4:keys/key_vbmeta_vendor.bin \
–chain_partition l_modem:6:keys/key_l_modem.bin \
–chain_partition l_ldsp:7:keys/key_l_ldsp.bin \
–chain_partition l_gdsp:8:keys/key_l_gdsp.bin \
–chain_partition pm_sys:9:keys/key_pm_sys.bin \
–output vbmeta_my.img

其中你要修改的boot.img最后签名跟里面的x_key.bin是对应的

boot，或者recovery的签名命令：

avbtool add_hash_footer –image boot.img –partition_name boot –partition_size 36700160 –key x_private_key.pem –algorithm SHA256_RSA4096

avbtool add_hash_footer –image recovery.img –partition_name recovery –partition_size 41943040 –key x_private_key.pem –algorithm SHA256_RSA4096

x_private_key.pem是你的自己的私有签名，x_key.bin可以由x_private_key.pem生成的