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Introduction

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i) Kmemleak is a Linux kernel feature designed to detect and report memory leaks in the kernel code. Memory leaks occur when a program allocates memory dynamically but fails to release it when it is no longer needed. This can result in a gradual loss of memory over time, eventually leading to system instability or even crashes.

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iii) Kmemleak is a useful tool for kernel developers and system administrators who want to ensure that their systems are stable and free of memory leaks. It can be enabled in the kernel configuration, and once enabled, it will run automatically in the background, periodically scanning the kernel memory for leaks.

Required kernel configs need to enable

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CONFIG_HAVE_DEBUG_KMEMLEAK=y CONFIG_DEBUG_KMEMLEAK=y CONFIG_DEBUG_KMEMLEAK_TEST=m

Integrating Kmemleak tool  for

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RPI-3

i) Create kmemleak.cfg file under meta-cmf-raspberrypi/recipes-kernel/linux/files with below kernel configs.
Note: Need to add this change in corresponding Platform platform OEM layer.

CONFIG_HAVE_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_TEST=m

ii) Add kmemleak.cfg file  in meta-cmf-raspberrypi/recipes-kernel/linux/linux-raspberrypi_5.10.52.bbbb  
Note: Need to add this change in corresponding Platform platform OEM layer.

Please find below diff file.
Ex:

diff --git a/recipes-kernel/linux/linux-raspberrypi_5.10.52.bb b/recipes-kernel/linux/linux-raspberrypi_5.10.52.bb
index 2c7f19a..224a64a 100644
--- a/recipes-kernel/linux/linux-raspberrypi_5.10.52.bb
+++ b/recipes-kernel/linux/linux-raspberrypi_5.10.52.bb
@@ -11,6 +11,7 @@ FILESEXTRAPATHS_prepend := "${THISDIR}/files:"

 SRC_URI += " file://powersave.cfg \
              file://android-drivers.cfg \
+             file://kmemleak.cfg \
 "

iii) Once build done with above changes, verify the  kernel configs are enabled in final kernel boot config file.
Path of kernel boot config file:  build build-raspberrypi-rdk-mc/tmp/work/raspberrypi_rdk_mc-rdk-linux-gnueabi/linux-raspberrypi/1_5.10.52+gitAUTOINC+dbe03fa900_2697f74031-r0/image/boot/config-5.10.52-v7
Note: Need to verify in corresponding platform specific final kernel boot config file

Ex:

csures569@dvm-yocto3-docker-csures569:~/

rpi-

stack/build-raspberrypi-rdk-mc/tmp/work/raspberrypi_rdk_mc-rdk-linux-gnueabi/linux-raspberrypi/1_5.10.52+gitAUTOINC+dbe03fa900_2697f74031-r0/image/boot$ cat config-5.10.52-v7  | grep "KMEMLEAK"
CONFIG_HAVE_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE=16000
CONFIG_DEBUG_KMEMLEAK_TEST=m
# CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF is not set
CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=y

iv) Once flash On flashing the image with above changes , verify the kmemleak enabled in the device, it will create a kmemleak folder under /sys/modules/ and kmemleak file under /sys/kernel/debug/
Ex:

root@raspberrypi-rdk-mc:/sys/module# ls -l | grep "kmemleak"
drwxr-xr-x    3 root     root             0 Mar  5 09:49 kmemleak

root@raspberrypi-rdk-mc:~# ls /sys/kernel/debug/kmemleak
/sys/kernel/debug/kmemleak

v) Once enabled kmemleak we will get kernel memory leaks in /sys/kernel/debug/kmemleak file if leaks are reported.

Testing kmemleak tool with kmemleak-test module in

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RPI-3

Note: kmemleak-test .ko  test module for memory leaks ,by default in rpi3 this module not compiled , is a test module available as part of kmemleak. By default, this module is not compiled in RPI3 and so there is no kmemleak-test.ko module , so . If needed, we need to enable to build as a module and generated module fileby following the above mentioned kernel configurations.
path Path of kmemleak-test module source : feature-securestorage-rpi-2Mar/ build-raspberrypi-rdk-mc/tmp/work-shared/raspberrypi-rdk-mc/kernel-source/samples/kmemleak/kmemleak-test.c
kmemleak-test.ko

Note: Need to generate kmemleak-test.ko module file from corresponding platform specific kernel source code.

Step 1 : Copy kmemleak-test.ko module to this path /lib/modules/5.10.52-v7/  in box .
Step 2 : load the module to kernel space with insmod command.
Ex:

root@raspberrypi-rdk-mc:~# insmod /lib/modules/5.10.52-v7/kmemleak-test.ko
root@raspberrypi-rdk-mc:~#

Step3 : verify whether module is loaded or not
Ex: lsmod

root@raspberrypi-rdk-mc:~# lsmod

Module                Size      Used by

kmemleak_test    16384        0 //

 kmemleak test module loaded.
ip6t_REJECT         16384       2
nf_reject_ipv6      16384        1 ip6t_REJECT
ip6table_nat        16384        1
br_netfilter           32768       0
xt_state                16384       0

Step4: Perform a scan
Ex: echo scan > /sys/kernel/debug/kmemleak

root@raspberrypi-rdk-mc:~# echo scan > /sys/kernel/debug/kmemleak
root@raspberrypi-rdk-mc:~#

Step5: Collect memory leak data

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Testing memory leaks from your kernel code

TBD

Limitations and Drawbacks

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