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== Article purpose == | == Article purpose == | ||
This article provides the basic information needed to start using the Linux kernel tool: '''kmemleak'''<ref name=procodedotorg/>. | This article provides the basic information needed to start using the Linux kernel tool: '''kmemleak'''<ref name=procodedotorg/>. | ||
| Line 16: | Line 7: | ||
| [[Kmemleak|kmemleak]] | | [[Kmemleak|kmemleak]] | ||
| [[:Category:Monitoring tools|Monitoring tools]] | | [[:Category:Monitoring tools|Monitoring tools]] | ||
| style="text-align:left;" | '''kmemleak'''<ref name=procodedotorg>http://www.procode.org/kmemleak/</ref> provides a means to detect possible kernel memory leaks in a similar way to a tracing garbage collector, with the difference that the orphan objects are not freed, but only reported via /sys/kernel/debug/kmemleak | | style="text-align:left;" | '''kmemleak'''<ref name=procodedotorg>http://www.procode.org/kmemleak/</ref> provides a means to detect possible kernel memory leaks in a similar way to a tracing garbage collector, with the difference that the orphan objects are not freed, but only reported via /sys/kernel/debug/kmemleak. | ||
| {{N}} || {{Y}} || {{Y}} | | {{N}} || {{Y}} || {{Y}} | ||
| | | {{N}} || {{N}} || {{Y}} | ||
|- | |- | ||
</onlyinclude> | </onlyinclude> | ||
| Line 31: | Line 21: | ||
Memory Debugging --> | Memory Debugging --> | ||
{{highlight|[*] Kernel memory leak detector}} | {{highlight|[*] Kernel memory leak detector}} | ||
'''For {{EcosystemRelease | revision=2.0.0 | range=and after}}''': | |||
In this ecosystem release, this is possible to enable/disable automatic kmemleak scan at boot up.<br> | |||
This configuration is activated by default when DEBUG_KMEMLEAK configuration is set. | |||
Symbol: '''DEBUG_KMEMLEAK_AUTO_SCAN''' | |||
Location: | |||
Kernel Hacking ---> | |||
Memory Debugging --> | |||
[*] Kernel memory leak detector | |||
{{highlight|Enable kmemleak auto scan thread on boot up}} | |||
<div class="mw-collapsible mw-collapsed"> | |||
'''For {{EcosystemRelease | revision=1.1.0 | range=and before}}''': | |||
<div class="mw-collapsible-content"> | |||
Since memory may be allocated or freed before kmemleak is initialised, an early log buffer is used to store these actions.<br> | Since memory may be allocated or freed before kmemleak is initialised, an early log buffer is used to store these actions.<br> | ||
In this ecosystem release, the default buffer size is limited, and this is recommended to increase it. | |||
{{Warning|If kmemleak reports "''early log buffer exceeded''" and debugfs entry is not present, you can increase the log buffer size by changing the configuration value, for example to 5000 | {{Warning|If kmemleak reports "''early log buffer exceeded''" and debugfs entry is not present, you can increase the log buffer size by changing the configuration value, for example to 5000 | ||
Symbol: '''DEBUG_KMEMLEAK_EARLY_LOG_SIZE''' [=400] | Symbol: '''DEBUG_KMEMLEAK_EARLY_LOG_SIZE''' [=400] | ||
| Line 42: | Line 48: | ||
{{highlight|(400) Maximum kmemleak early log entries}} | {{highlight|(400) Maximum kmemleak early log entries}} | ||
}} | }} | ||
</div></div> | |||
=== Using STM32MPU Embedded Software Distribution === | === Using STM32MPU Embedded Software Distribution === | ||
==== Developer Package ==== | ==== Developer Package ==== | ||
To enable '''CONFIG_DEBUG_KMEMLEAK''' in the Linux kernel configuration, please refer to the [[Menuconfig or how to configure kernel]] article to find instructions for modification of the configuration and recompiling Linux kernel image in | To enable '''CONFIG_DEBUG_KMEMLEAK''' in the Linux kernel configuration, please refer to the [[Menuconfig or how to configure kernel]] article to find instructions for modification of the configuration and recompiling Linux kernel image in Developer Package context. | ||
==== Distribution Package | ==== Distribution Package ==== | ||
To enable '''CONFIG_DEBUG_KMEMLEAK''' in the Linux kernel configuration, please refer to the [[Menuconfig or how to configure kernel]] article to find instructions for modifying the configuration and recompiling the Linux kernel image in the | To enable '''CONFIG_DEBUG_KMEMLEAK''' in the Linux kernel configuration, please refer to the [[Menuconfig or how to configure kernel]] article to find instructions for modifying the configuration and recompiling the Linux kernel image in the Distribution Package context. | ||
=== Using STM32MPU Embedded Software Distribution for Android™ === | === Using STM32MPU Embedded Software Distribution for Android™ === | ||
==== Distribution Package ==== | |||
To enable '''CONFIG_DEBUG_KMEMLEAK''' in the Linux kernel configuration, please refer to the [[How to customize kernel for Android]] article to find instructions for modification of the configuration and recompiling Linux kernel image in Distribution Package context. | |||
== Getting started == | == Getting started == | ||
{{Android | Need to enable root access rights | |||
*Using ADB shell is ADB link available: | |||
{{PC$}} adb root | |||
{{PC$}} adb shell | |||
{{Board$}} ... | |||
*Using uart console shell: | |||
{{Board$}} su | |||
{{Board$}} ... | |||
}} | |||
=== Reading kmemleak report === | === Reading kmemleak report === | ||
A kernel thread scans the memory every 10 minutes (by default) and prints the number of new unreferenced objects found. To display the details of all the possible memory leaks: | A kernel thread scans the memory every 10 minutes (by default) and prints the number of new unreferenced objects found. To display the details of all the possible memory leaks: | ||
| Line 93: | Line 108: | ||
=== All kmemleak commands === | === All kmemleak commands === | ||
Memory scanning parameters can be modified at run-time by writing to the /sys/kernel/debug/kmemleak file. The following parameters are supported: | Memory scanning parameters can be modified at run-time by writing to the <code>/sys/kernel/debug/kmemleak</code> file. The following parameters are supported: | ||
'''off''' - disable kmemleak (irreversible) | '''off''' - disable kmemleak (irreversible) | ||
'''stack=on''' - enable the task stacks scanning (default) | '''stack=on''' - enable the task stacks scanning (default) | ||
| Line 127: | Line 142: | ||
! scope=col | Description | ! scope=col | Description | ||
|- | |- | ||
| | | {{DocSource | domain=Linux kernel | path=dev-tools/kmemleak.html | text=Kernel Memory Leak Detector}} | ||
| Standard | | Standard | ||
| Documentation from kernel.org | | Documentation from kernel.org | ||
|} | |} | ||
{{ArticleBasedOnModel | Trace and debug tools article model }} | |||
{{PublicationRequestId | 9880 | 07Dec'18 }} | |||
[[Category:Linux monitoring tools]] | |||
Latest revision as of 14:24, 19 October 2020
1. Article purpose[edit source]
This article provides the basic information needed to start using the Linux kernel tool: kmemleak[1].
2. Introduction[edit source]
The following table provides a brief description of the tool, as well as its availability depending on the software packages:
Template:Y: this tool is either present (ready to use or to be activated), or can be integrated and activated on the software package.
Template:N: this tool is not present and cannot be integrated, or it is present but cannot be activated on the software package.
| Tool | STM32MPU Embedded Software distribution | STM32MPU Embedded Software distribution for Android™ | ||||||
|---|---|---|---|---|---|---|---|---|
| Name | Category | Purpose | Starter Package | Developer Package | Distribution Package | Starter Package | Developer Package | Distribution Package |
| kmemleak | Monitoring tools | kmemleak[1] provides a means to detect possible kernel memory leaks in a similar way to a tracing garbage collector, with the difference that the orphan objects are not freed, but only reported via /sys/kernel/debug/kmemleak. | Template:N | Template:Y | Template:Y | Template:N | Template:N | Template:Y |
3. Installing the trace and debug tool on your target board[edit source]
In order to use kmemleak, the Linux kernel configuration must activate CONFIG_DEBUG_KMEMLEAK:
Symbol: DEBUG_KMEMLEAK Location: Kernel Hacking ---> Memory Debugging --> Template:Highlight
For ecosystem release ≥ v2.0.0 
:
In this ecosystem release, this is possible to enable/disable automatic kmemleak scan at boot up.
This configuration is activated by default when DEBUG_KMEMLEAK configuration is set.
Symbol: DEBUG_KMEMLEAK_AUTO_SCAN Location: Kernel Hacking ---> Memory Debugging --> [*] Kernel memory leak detector Template:Highlight
Expand
For ecosystem release ≤ v1.1.0 :
3.1. Using STM32MPU Embedded Software Distribution[edit source]
3.1.1. Developer Package[edit source]
To enable CONFIG_DEBUG_KMEMLEAK in the Linux kernel configuration, please refer to the Menuconfig or how to configure kernel article to find instructions for modification of the configuration and recompiling Linux kernel image in Developer Package context.
3.1.2. Distribution Package[edit source]
To enable CONFIG_DEBUG_KMEMLEAK in the Linux kernel configuration, please refer to the Menuconfig or how to configure kernel article to find instructions for modifying the configuration and recompiling the Linux kernel image in the Distribution Package context.
3.2. Using STM32MPU Embedded Software Distribution for Android™[edit source]
3.2.1. Distribution Package[edit source]
To enable CONFIG_DEBUG_KMEMLEAK in the Linux kernel configuration, please refer to the How to customize kernel for Android article to find instructions for modification of the configuration and recompiling Linux kernel image in Distribution Package context.
4. Getting started[edit source]
|
Below information is related to the Android™ distribution Need to enable root access rights
adb root adb shell Template:Board$ ...
Template:Board$ su Template:Board$ ... |
4.1. Reading kmemleak report[edit source]
A kernel thread scans the memory every 10 minutes (by default) and prints the number of new unreferenced objects found. To display the details of all the possible memory leaks:
Template:Board$ cat /sys/kernel/debug/kmemleak
Note: debugfs is mounted by default, otherwise you can mount it using the following command. Please refer to the Debugfs article.
Kmemleak result example: contains an extract of the memory content, and backtrace of function calls, to help you when debugging.
unreferenced object 0xed638800 (size 64):
comm "swapper/0", pid 1, jiffies 4294937542 (age 197.490s)
hex dump (first 32 bytes):
01 00 00 00 77 f9 ff 7a cf 37 dd e3 01 00 00 00 ....w..z.7......
00 92 63 ed 40 00 00 00 00 00 00 00 01 00 00 00 ..c.@...........
backtrace:
[<c048d130>] pinconf_generic_parse_dt_config+0x10c/0x13c
[<c0490f88>] stm32_pctrl_dt_node_to_map+0x90/0x3f4
[<c048ca58>] pinctrl_dt_to_map+0x130/0x35c
[<c04895a0>] create_pinctrl+0x60/0x3b0
[<c0489a08>] devm_pinctrl_get+0x38/0x68
[<c0582a24>] pinctrl_bind_pins+0x48/0x280
[<c055f7f8>] driver_probe_device+0xc0/0x470
[<c055fca8>] __driver_attach+0x100/0x11c
[<c055db08>] bus_for_each_dev+0x4c/0x9c
[<c055ecc4>] bus_add_driver+0x1c0/0x264
[<c0560910>] driver_register+0x78/0xf4
[<c0101c48>] do_one_initcall+0x44/0x168
[<c0f00e74>] kernel_init_freeable+0x1c0/0x24c
[<c0a65ac4>] kernel_init+0x8/0x110
[<c0108b50>] ret_from_fork+0x14/0x24
[<ffffffff>] 0xffffffff
4.2. Trigerring an intermediate memory scan[edit source]
Template:Board$ echo scan > /sys/kernel/debug/kmemleak
4.3. Clearing the list of all current possible memory leaks[edit source]
Template:Board$ echo clear > /sys/kernel/debug/kmemleak
4.4. All kmemleak commands[edit source]
Memory scanning parameters can be modified at run-time by writing to the /sys/kernel/debug/kmemleak file. The following parameters are supported:
off - disable kmemleak (irreversible)
stack=on - enable the task stacks scanning (default)
stack=off - disable the tasks stacks scanning
scan=on - start the automatic memory scanning thread (default)
scan=off - stop the automatic memory scanning thread
scan=<secs> - set the automatic memory scanning period in seconds (default 600, 0 to stop the automatic scanning)
scan - trigger a memory scan
clear - clear list of current memory leak suspects, done by marking all current reported unreferenced objects in grey, or freeing all kmemleak objects if kmemleak is disabled.
dump=<addr> - dump information about the object found at <addr>
5. To go further[edit source]
If enabled in the Linux kernel configuration, Kmemleak can also be disabled at boot time by passing Template:Highlight on the kernel command line.
Conversely, if CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF is enabled in the Linux kernel configuration, kmemleak is disabled by default.
Symbol: DEBUG_KMEMLEAK_DEFAULT_OFF Location: Kernel Hacking ---> Memory Debugging --> [*] Kernel memory leak detector Template:Highlight
Passing Template:Highlight on the kernel command line enables the function.
6. References[edit source]
- Useful external links
| Document link | Document Type | Description |
|---|---|---|
| Kernel Memory Leak Detector | Standard | Documentation from kernel.org |