Kernel live patching

2022-08-06T12:33:43Z

Androw: Created page with "Kernel Live Patching (KLP) enables the capacity to apply patch to the kernel without rebooting the system. To use KLP, you should follow the following steps: * Run a livepatc..."

Kernel Live Patching (KLP) enables the capacity to apply patch to the kernel without rebooting the system.

To use KLP, you should follow the following steps:
* Run a livepatching enabled kernel
* Obtain the source tree of the kernel
* Prepare and build the patch
* Apply the patch

You can use Kernel Live Patching in Alpine Linux by running a modified kernel.

= Building the kernel =

# Obtain the source
# Enable the following flag CONFIG_LIVEPATCH and CONFIG_DEBUG_INFO
# Build the kernel: <code>make</code>
# Install: <code>doas make modules_install && doas make install</code>
# Rebuild initramfs
# Update bootloader
# Reboot: <code>doas reboot</code>

= Patching the kernel =

# Install kpatch: <code>doas apk add kpatch</code>
# Prepare the patch. You can create a file some.patch containing something around the following (it can need update depending on the kernel version):

Index: src/fs/proc/meminfo.c
===================================================================
--- src.orig/fs/proc/meminfo.c
+++ src/fs/proc/meminfo.c
@@ -95,7 +95,7 @@ static int meminfo_proc_show(struct seq_
"Committed_AS: %8lu kB\n"
"VmallocTotal: %8lu kB\n"
"VmallocUsed: %8lu kB\n"
- "VmallocChunk: %8lu kB\n"
+ "VMALLOCCHUNK: %8lu kB\n"
#ifdef CONFIG_MEMORY_FAILURE
"HardwareCorrupted: %5lu kB\n"
#endif

# Build the patch: <code>kpatch-build -s /path/to/kernel/source some.patch</code>

= Enabling the patch =

# Enable the patch: <code>doas insmod kpatch-some.ko</code> or <code>doas kpatch load kpatch-some.ko</code>
# Check that the patch has been loaded: <code>grep -i chunk /proc/meminfo</code>
# Disable the patch: <code>doas kpatch unload kpatch-some.ko</code>

Alpine Linux - User contributions [en]

Kernel live patching