[PATCH v2 06/10] add helper functions to get kernel path by kernel release and the path of current running kernel

[Coiby Xu]

grubby --info=kernel-path or --add-kernel=kernel-path accepts a kernel
path (e.g. /boot/vmlinuz-5.14.14-200.fc34.x86_64) instead of kernel release
(e.g 5.14.14-200.fc34.x86_64). So we need to know the kernel path given
a kernel release. Although for Fedora/RHEL, the kernel path is
"/boot/vmlinuz-<KERNEL_RELEASE>", a path kernel could also be
/boot/<machine-id>/<KERNEL_RELEASE>/vmlinuz. So the most reliable way to
find the kernel path given a kernel release is to use "grubby --info".

Note these helper functions doesn't support CoreOS/Atomic/Silverblue
since grubby isn't used by them.

Signed-off-by: Coiby Xu <coxu(a)redhat.com&gt;
---
 kdumpctl | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/kdumpctl b/kdumpctl
index f42a8c6..0b8dc0f 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -1351,6 +1351,36 @@ get_dump_mode_by_kernel()
 	fi
 }
 
+_filter_grubby_kernel_str()
+{
+    local _grubby_kernel_str=$1 _kernel_path
+    _kernel_path=${_grubby_kernel_str#kernel=}
+    _kernel_path=${_kernel_path#\"}
+    _kernel_path=${_kernel_path%\"}
+    echo -n "$_kernel_path"
+}
+
+_find_kernel_path_by_release()
+{
+    local _release="$1" _grubby_kernel_str _kernel_path
+    _grubby_kernel_str=$(grubby --info ALL | grep "^kernel=.*$_release")
+    _kernel_path=$(_filter_grubby_kernel_str "$_grubby_kernel_str")
+    [[ -e "$_kernel_path" ]] || derror "kernel $_release doesn't
exist" && return 1
+    echo -n "$_kernel_path"
+}
+
+_get_current_running_kernel_path()
+{
+    local _release _path
+
+    _release=$(uname -r)
+    if _path=$(_find_kernel_path_by_release "$_release"); then
+        echo -n "$_path"
+    else
+        return 1
+    fi
+}
+
 reset_crashkernel()
 {
 	local kernel=$1 entry crashkernel_default
-- 
2.31.1