[OE-core][PATCH v4 1/4] kernel.bbclass: re-sign kernel modules after package stripping process

[Anis Bougrine <anis.bougrine10@gmail.com>]

Fixes [YOCTO #12927]

Currently, signed kernel modules are not stripped in order to preserve
their valid signatures. See commit 4c47e5f.

Therefore, this commit makes kernel modules stripped and correctly
signed. Two options are possible:

    - Strip the kernel modules after installation and before signing.
    - Re-sign the kernel modules after stripping and before package splitting.

The first option was rejected because debug symbols would be dropped early
in the build workflow, which may impact the SPDX process.

The second option is adopted because it does not impact the build flow.

Reported-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Anis Bougrine <anis.bougrine10@gmail.com>
---
    changes in v4:
    
    - Re-sign kernel modules after package stripping process
    - Remove package-stripping skip in package.py
    - Add MOD_INSTALL_PREFIX variable
    
    changes in v3:
    
    - Fixing rebase issue.
    
    changes in v2:
    
    - Use the conditional INSTALL_MOD_STRIP environment variable to avoid
      duplicating the oe_runmake call.
    - Use `scripts/config` script instead of grepping .config file.
---
 .../kernel-module-split.bbclass               | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/meta/classes-recipe/kernel-module-split.bbclass b/meta/classes-recipe/kernel-module-split.bbclass
index ab2f0d1c37..253a723b95 100644
--- a/meta/classes-recipe/kernel-module-split.bbclass
+++ b/meta/classes-recipe/kernel-module-split.bbclass
@@ -35,6 +35,11 @@ modprobedir ??= "${@bb.utils.contains('DISTRO_FEATURES', 'systemd', '${nonarch_b
 
 KERNEL_SPLIT_MODULES ?= "1"
 PACKAGESPLITFUNCS =+ "split_kernel_module_packages"
+# Order matters:
+# 1. Strip the modules
+# 2. Re-sign the modules (if enabled)
+# 3. Split the packages
+PACKAGESPLITFUNCS =+ "post_strip_kernel_modules_signing"
 
 KERNEL_MODULES_META_PACKAGE ?= "${@ d.getVar("KERNEL_PACKAGE_NAME") or "kernel" }-modules"
 
@@ -42,6 +47,22 @@ KERNEL_MODULE_PACKAGE_PREFIX ?= ""
 KERNEL_MODULE_PACKAGE_SUFFIX ?= "-${KERNEL_VERSION}"
 KERNEL_MODULE_PROVIDE_VIRTUAL ?= "1"
 
+# Sign kernel modules if auto-signing is enabled in the kernel config
+post_strip_kernel_modules_signing(){
+    # Read .config values
+    is_modules="$(${S}/scripts/config --file ${B}/.config --state MODULES)"
+    is_module_sig="$(${S}/scripts/config --file ${B}/.config --state MODULE_SIG)"
+    is_module_sig_all="$(${S}/scripts/config --file ${B}/.config --state MODULE_SIG_ALL)"
+
+    if [ "$is_modules" = "y" ] && [ "$is_module_sig" = "y" ] && [ "$is_module_sig_all" = "y" ]; then
+        # Sign modules under ${PKGD}
+        oe_runmake \
+            -C ${B} \
+            MODLIB=${PKGD}${nonarch_base_libdir}/modules/${KERNEL_VERSION} \
+            modules_sign
+    fi
+}
+
 python split_kernel_module_packages () {
     import re
 
-- 
2.50.1 (Apple Git-155)