segger embedded studio data breakpoints expressions nRF52833

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Mon, 23 Jan 2023 14:53:38 GMT

Hi Mohamed,

It is good to hear that you were able to find out what triggered the fault in the end.

[quote user="Learner"]I would have thought the tools would have reported a BUFFER OVERFLOW error instead.[/quote]

I am not sure how a fault handler could be made to detect buffer overruns. There are not any mechanisms to catch buffer overruns before memory corruption occurs either. The first step which I normally take in these situations is to have a look at the stack trace to see if I can determine where the exception was raised. The "Faulting instruction address" indicated that you may have had a corrupt function pointer.

[quote user="Learner"]I would appreciate it if you could answer it or point me to a document that describes this.[/quote]

I am not aware of any documentation that covers this, but I showed you where you could find the stack areas in the .map file.

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Wed, 18 Jan 2023 10:23:18 GMT

Good Morning Vidar,

The root cause of the MPU FAULT I was getting is an index that went astray and caused a buffer overflow. I would have thought the tools would have reported a BUFFER OVERFLOW error instead.

So, although I managed to find the bug in my firmware I am still interested in your answer to my previous question,

[quote userid="92434" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404410"]please help me find where the stack starts and whether it builds up or down.[/quote]

I would appreciate it if you could answer it or point me to a document that describes this.

Thank you for your support over the last 10 days or so.

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Fri, 13 Jan 2023 09:45:45 GMT

Hi Mohamed,

The system workqueue stack is here:

.noinit."WEST_TOPDIR/zephyr/kernel/system_work_q.c".0
0x2000d760 0x820 zephyr/kernel/libkernel.a(system_work_q.c.obj)

[quote userid="92434" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404744"]Did you have a look at the stack analyzer log file stack_analyzer_logs.txt I attached as a link in my previous message? there is nothing in the logs that suggest the stack is overflowing. Please have a[/quote]

I did, and I am not saying a believe it is a stack overflow. My suggestion was in response to your comment here:

[quote userid="92434" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404503"]There is no mention of stack overflow violation but I am suspecting there is.[/quote]

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Fri, 13 Jan 2023 09:12:16 GMT

Good Morning Vidar,

[quote userid="4240" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404734"]The map file did not get uploaded. [/quote]

Here it is again.

/cfs-file/__key/communityserver-discussions-components-files/4/1106.zephyr.map

[quote userid="4240" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404734"]Anyway, the easiest way to try to rule out a stack overflow is often to try increasing the stack size, or have you tried that already?[/quote]

Did you have a look at the stack analyzer log file stack_analyzer_logs.txt I attached as a link in my previous message? there is nothing in the logs that suggest the stack is overflowing. Please have a look.

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Fri, 13 Jan 2023 08:46:39 GMT

Hi Mohamed,

The map file did not get uploaded. Anyway, the easiest way to try to rule out a stack overflow is often to try increasing the stack size, or have you tried that already? The sysworkq stack can be adjusted through the CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE symbol.

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Thu, 12 Jan 2023 09:35:58 GMT

Good Morning Vidar,

[quote userid="4240" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404457"]The stack area allocated to each thread can be found in the map file.[/quote]

I am attaching my map file please let me know where the stack area is.

/cfs-file/__key/communityserver-discussions-components-files/4/2437.zephyr.map

[quote userid="4240" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404457"]If you are unsure if it is enabled, you can check if CONFIG_MPU_STACK_GUARD=y[/quote]

It is already enabled in my .config file and this is the error I am getting. There is no mention of stack overflow violation but I am suspecting there is. So, what else could be causing this fault ?

[00:19:08.163,787] \033[1;31m<err> os: ***** MPU FAULT *****\033[0m
[00:19:08.163,787] \033[1;31m<err> os: Instruction Access Violation\033[0m
[00:19:08.163,787] \033[1;31m<err> os: r0/a1: 0x00000000 r1/a2: 0x2000cfc0 r2/a3: 0x2000cfc0\033[0m
[00:19:08.163,787] \033[1;31m<err> os: r3/a4: 0x200042ff r12/ip: 0x000000e2 r14/lr: 0x00010cff\033[0m
[00:19:08.163,818] \033[1;31m<err> os: xpsr: 0x60000000\033[0m
[00:19:08.163,818] \033[1;31m<err> os: Faulting instruction address (r15/pc): 0xeb699002\033[0m
[00:19:08.163,818] \033[1;31m<err> os: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0\033[0m
[00:19:08.163,818] \033[1;31m<err> os: Current thread: 0x20001f40 (sysworkq)\033[0m
[00:19:09.107,147] \033[1;31m<err> os: Halting system\033[0m

I have enabled the STACK_ANALYZER and I am attaching the stack analyzer logs from boot up to the "MPU FAULT" crash. Note, where you see the three dots (...) is where I removed my application logs (LOG_DBG/INF/WRN/ERR) for readability.

devzone.nordicsemi.com/.../stack_5F00_analyzer_5F00_logs.txt

Thank you

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Thu, 12 Jan 2023 07:49:49 GMT

Hi Mohamed,

The 'data sampling' feature is used for monitoring a variable over time. The only reason it may not be as good as a data breakpoint in this case is that it will not halt the CPU if an invalid value is written.

There are multiple stacks (main stack for interrupt handling + 1 stack for each thread - stack pointers). The stack area allocated to each thread can be found in the map file.

There is already a built-in stack guard to catch stack overruns and it should be enabled by default in the board files (MPU-assisted stack overflow detection). If you are unsure if it is enabled, you can check if CONFIG_MPU_STACK_GUARD=y is included in your <build folder>/zephyr/.config file.

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Wed, 11 Jan 2023 18:32:32 GMT

Hi Vidar,

Thank you.

As you said, this is not as good as a breakpoint because I need to monitor it.

In order to check if I am running out of stack I would like to fill the stack memory section with say 0xAA and run the program until it crashes. I then check if all the AA in the stack locations have disappeared i.e. overwritten. However, I am not sure where to find where the stack starts and whether it builds up or down. I looked in the .map file but it is not clear. All I know is I am setting the stack size to 8192 bytes in prj.conf.

CONFIG_MAIN_STACK_SIZE=8192
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

I have only one main thread from which I am submitting a work queue. The code looks something like this,

static struct k_work WorkQ1;

void main( void )
{

...[snip]...

k_work_init( &WorkQ1, WorkQ1_tasks );

...

k_work_submit( &WorkQ1 );

...[snip]

}

So, please help me find where the stack starts and whether it builds up or down.

Thank you.

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Wed, 11 Jan 2023 12:32:41 GMT

Hi Mohamed,

I am not sure what you have tried so far, but it seems like you have to do is to open the 'Data sampling' view and then input your expression. It is the first time I have used this myself.

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Wed, 11 Jan 2023 10:37:07 GMT

Good Morning Vidar,

[quote userid="4240" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404123"]An alternative (not as good as a breakpoint) may be to use trace in Ozone and sample the register value periodically. This way you can monitor whether the array element is overwritten or not.[/quote]

I am not sure how to do this. Could you please give me an idiot step by step guide ?

Thank you.

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Tue, 10 Jan 2023 14:11:44 GMT

I am glad to hear that it worked!

[quote userid="92434" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404088"]I am chasing an intermittent bug which could be caused by a possible stack overflow. How do I set a data breakpoint that is triggered when ble_[6] != 0x19?[/quote]

I do not think the HW comparators on Cortex M4 support these kinds of expressions. It does not appear to be supported in Ozone, at least.

An alternative (not as good as a breakpoint) may be to use trace in Ozone and sample the register value periodically. This way you can monitor whether the array element is overwritten or not.

[quote userid="92434" url="~/f/nordic-q-a/95469/segger-embedded-studio-data-breakpoints-expressions-nrf52833/404088"]One more question. how do I capture the debugging logs appearing in the Terminal window in a text file automatically?[/quote]

The documentation explains how you can do it in Ozone, but it is not something I have tried myself. For SES you can do it like this:

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Tue, 10 Jan 2023 12:35:41 GMT

Great! it works now Thank you. The moral is "Read the user manual" 🙂

I am chasing an intermittent bug which could be caused by a possible stack overflow. How do I set a data breakpoint that is triggered when ble_[6] != 0x19?

One more question. how do I capture the debugging logs appearing in the Terminal window in a text file automatically?

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Tue, 10 Jan 2023 12:24:08 GMT

Hi Mohammed,

In Ozone, the value condition is specified at the end and not as a part of the expression. Please try to do it like this:

Also, notice that the value mask is set to '0'. '1's in the mask are used to mark bits to ignore.

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Tue, 10 Jan 2023 11:51:39 GMT

Hi Vidar,

I downloaded Ozone and got it running but I still cannot set a data breakpoint with a C-like expression. See screen capture below. The OK field remains always greyed out and the only option available is 'Cancel'. What am I doing wrong?

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Mon, 09 Jan 2023 19:41:02 GMT

Hi Mohamed,

Ozone must be downloaded and installed separately. You should be able to open it via SES once installed.

Download link: https://www.segger.com/downloads/jlink/#Ozone

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Mon, 09 Jan 2023 17:25:59 GMT

Hi Vidar,

Do I need to download the Segger Ozone debugger app or is it already included in nRF Connect tools?

Where can I download it from and any getting started guide would be appreciated?

It looks like Segger Ozone is built into SES NE. I have found in SES NE under

Debug -> Debug With Ozone

But when I selected it nothing happened.

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Mon, 09 Jan 2023 16:03:51 GMT

Hi Mohamed,

I was testing with SES version 5.68 (Not the nordic edition).

Ozone is a standalone debugger application from Segger. All you need to do to debug with Ozone is to load the *.elf file from your SES build.

I realize it is not as convenient to have to debug with a separate application. But maybe it is OK as a workaround to use the Ozone debugger when you need to use data breakpoints?

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Mon, 09 Jan 2023 15:56:05 GMT

Hi Vidar,

Not good news. So, does this mean I will not be able to set data breakpoint expressions in SES NE?

Which version of SES NE are you using?

I am using v5.60,

SEGGER Embedded Studio for ARM
Release 5.60 Build 2021081102.47262
Nordic Edition
Windows x64

I have never used Segger Ozone, is it newer or older that SES?

Will my SES NE project build and run on Segger Ozone?

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Mon, 09 Jan 2023 14:01:20 GMT

Hi Mohamed,

I see the same as you now when I try to configure the breakpoint to trigger on a specific value. I do not get the question mark next to it, but it does not break either. I wonder if this may be an issue with Segger embedded studio because it does break when I try to configure the same breakpoint in Segger Ozone.

Kind regards,

Vidar

RE: segger embedded studio data breakpoints expressions nRF52833

Learner — Mon, 09 Jan 2023 12:33:53 GMT

Hi Vidar,

Thank you for the quick response.

What you did worked for me too. I ran into problems when I tried to use a data breakpoint expression applied to that variable. I suggest you edit your data breakpoint and try to use the expression I am using ble_ad[4] != 0 or any other C-like expression.

After restarting SES IDE I can now set the data breakpoint expression without getting the '?' next to it. Very odd!

However, the program is not breaking as expected. I checked this by setting a breakpoint at the line where ble_ad[6] is assigned the value 0x19 and it does execute this line an breaks.

ble_ad[6] = LINK_LINE_TYPE_HOMEBEACON;

Note, is an enum, defined ia header file as

typedef enum eLinkLineType
{
LINK_LINE_TYPE_AGENCY = 0x00, /**< ? */
LINK_LINE_TYPE_BUILDING_OWN = 0x01, /**< ? */

...
LINK_LINE_TYPE_HOMEBEACON = 0x19U,

...

} link_PacketType_t;

Thank you.

Kind regards

Mohamed

RE: segger embedded studio data breakpoints expressions nRF52833

Vidar Berg — Mon, 09 Jan 2023 08:54:42 GMT

Hello Mohamed,

I created a global array named 'ble_ad' to try and reproduce this here, but it seemed to work for me. In your case, when you start typing your expression, does the variable get displayed up in the suggestion list as shown here:

Kind regards,

Vidar