编译 kernel 给出错误 No rule to make target 'debian/certs/debian-uefi-certs.pem'

Question

Compiling kernel gives error No rule to make target 'debian/certs/debian-uefi-certs.pem I am following this tutorial https://www.cyberciti.biz/tips/compiling-linux-kernel-26.html

CC      kernel/jump_label.o
CC      kernel/iomem.o
CC      kernel/rseq.o
AR      kernel/built-in.a
CC      certs/system_keyring.o
make[1]: *** No rule to make target 'debian/certs/debian-uefi-certs.pem', needed by 'certs/x509_certificate_list'.  Stop.
make: *** [Makefile:1851: certs] Error 2

Answer 1

This seems to be the way to go with the current version:

https://unix.stackexchange.com/a/649484/301245

There are many, many config flags now, and the signing system must stay operational for the build to work. Easiest is to copy debian/ and debian.master/ into the source tree of the kernel to be built, then it works without additional changes. Well, almost: It can happen that references to key files still exist. The keys section in the.conf file should look like this:

#
# Certificates for signature checking
#
CONFIG_MODULE_SIG_KEY="certs/signing_key.pem"
CONFIG_SYSTEM_TRUSTED_KEYRING=y
CONFIG_SYSTEM_TRUSTED_KEYS=""
CONFIG_SYSTEM_EXTRA_CERTIFICATE=y
CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE=4096
CONFIG_SECONDARY_TRUSTED_KEYRING=y
CONFIG_SYSTEM_BLACKLIST_KEYRING=y
CONFIG_SYSTEM_BLACKLIST_HASH_LIST=""
CONFIG_SYSTEM_REVOCATION_LIST=y
CONFIG_SYSTEM_REVOCATION_KEYS=""
# end of Certificates for signature checking

Answer 2

Instead of removing the kernel signature checking, I've just configured it correctly:

#
# Certificates for signature checking
#
CONFIG_MODULE_SIG_KEY="certs/signing_key.pem"
CONFIG_MODULE_SIG_KEY_TYPE_RSA=y
CONFIG_MODULE_SIG_KEY_TYPE_ECDSA=y
CONFIG_SYSTEM_TRUSTED_KEYRING=y
CONFIG_SYSTEM_TRUSTED_KEYS="/usr/local/src/debian/canonical-certs.pem"
CONFIG_SYSTEM_EXTRA_CERTIFICATE=y
CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE=4096
CONFIG_SECONDARY_TRUSTED_KEYRING=y
CONFIG_SYSTEM_BLACKLIST_KEYRING=y
CONFIG_SYSTEM_BLACKLIST_HASH_LIST=""
CONFIG_SYSTEM_REVOCATION_LIST=y
CONFIG_SYSTEM_REVOCATION_KEYS="/usr/local/src/debian/canonical-revoked-certs.pem"
# end of Certificates for signature checking

To get there, I've just followed these steps:

sudo mkdir -p /usr/local/src/debian
sudo apt install linux-source
sudo cp -v /usr/src/linux-source-*/debian/canonical-*.pem /usr/local/src/debian/
sudo apt purge linux-source*

...which:

1. installs the Ubuntu Linux kernel sources
2. copies the certificates into a dedicated non-package-managed directory
3. removes any kernel sources package again

This process can be repeated whenever an update is required (eg new certificates).