From 86eaa3dc742035636541d3222a6ea58175ba6c2b Mon Sep 17 00:00:00 2001
From: Florian Schmaus <flow@gentoo.org>
Date: Tue, 14 Mar 2023 11:02:59 +0100
Subject: [PATCH] Add 'update' action to kernel module

The 'update' action attempts to update the /usr/src/linux symlink to
point to the sources of the running kernel.

Signed-off-by: Florian Schmaus <flow@gentoo.org>
---
 man/kernel.eselect.5   | 10 ++++++
 modules/kernel.eselect | 70 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/man/kernel.eselect.5 b/man/kernel.eselect.5
index b3c5aa5de606..66014912d14f 100644
--- a/man/kernel.eselect.5
+++ b/man/kernel.eselect.5
@@ -14,6 +14,8 @@ kernel.eselect \- The kernel symlink management module for Gentoo's eselect
 .I target
 .br
 .B eselect kernel show
+.br
+.B eselect kernel update [ifunset]
 .SH DESCRIPTION
 .B eselect
 is Gentoo's configuration and management tool.  It features modules
@@ -45,6 +47,14 @@ output).
 .B eselect kernel show
 .br
 Show the currently selected kernel.
+.SH ACTION: UPDATE
+.B eselect kernel update [ifunset]
+.br
+Updates the /usr/src/linux symlink to point to the sources of the
+running kernel.  If
+.IR ifunset
+is given, then the symlink will only be updated if it is not currently
+pointing to a valid kernel source tree.
 .SH AUTHOR
 Aaron Walker <ka0ttic@gentoo.org>
 .SH SEE ALSO
diff --git a/modules/kernel.eselect b/modules/kernel.eselect
index 64b5e773d68d..e617d61ee767 100644
--- a/modules/kernel.eselect
+++ b/modules/kernel.eselect
@@ -125,3 +125,73 @@ do_set() {
 
 	set_symlink "$1" || die -q "Couldn't set a new symlink"
 }
+
+### update action ###
+
+describe_update() {
+	echo "Update the kernel symlink to running kernel"
+}
+
+describe_update_options() {
+	echo "ifunset: Do not override currently set version"
+}
+
+do_update() {
+	[[ -z $1 || $1 == ifunset ]] || die -q "Usage error"
+	[[ $# -gt 1 ]] && die -q "Too many parameters"
+	test_for_root
+
+	if [[ -e ${EROOT}/usr/src/linux && ! -L ${EROOT}/usr/src/linux ]]; then
+		# we have something strange
+		die -q "${EROOT}/usr/src/linux exists but is not a symlink"
+	fi
+
+	if [[ $1 == ifunset \
+			  && -L ${EROOT}/usr/src/linux \
+			  && -e ${EROOT}/usr/src/linux ]]; then
+		# The /usr/src/linux symlink exists, points to a path that
+		# exists, and 'ifunset' is provided. Nothing to do.
+		return
+	fi
+
+	local targets=( $(find_targets) )
+	local running_kernel_release
+	running_kernel_release=$(uname -r)
+	if (( $? > 0 )); then
+		die -q "Executing uname failed with $?"
+	fi
+	local running_kernel_symlink_target="linux-${running_kernel_release}"
+
+	if [[ -L ${EROOT}/usr/src/linux ]]; then
+		local current_target
+		current_target=$(basename "$(canonicalise "${EROOT}/usr/src/linux")")
+		if [[ ${current_target} == "${running_kernel_symlink_target}" ]]; then
+			# The /usr/src/linux symlink already points to the running
+			# kernel's sources. Nothing to do.
+			return
+		fi
+	fi
+
+	local target
+	local target_list=()
+	for target in "${targets[@]}"; do
+		if [[ ${target} == "${running_kernel_symlink_target}" ]]; then
+			set_symlink "${target}"
+			return
+		fi
+		target_list+=("\n- ${target}")
+	done
+
+	local msg
+	msg="No kernel sources for running kernel ${running_kernel_release} found."
+	msg+=" Available sources:${target_list[*]}"
+	die -q "${msg}"
+}
+
+### helper functions ###
+
+test_for_root() {
+	if [[ ! -w ${EROOT}/usr/src ]]; then
+		die -q "${EROOT}/usr/src not writeable by current user. Are you root?"
+	fi
+}
-- 
2.39.2