elf parser seems not working properly

[Katzenberger.Michael]

After loading the elf file variables are detected incorrect (wrong address an/or size)

Two examples with output of readelf

1) used in *.c file:

uint8_t counter_error_handler __attribute__((section(".internal_ram")));

> readelf Bluepill_USB_CDC.elf -s |grep error
  1374: 20002e28     1 OBJECT  GLOBAL DEFAULT    9 counter_error_handler

2) used in *.cpp file:

static uint16_t blink_period;

> readelf Bluepill_USB_CDC.elf -a |grep blink
   389: 2000052c     2 OBJECT  LOCAL  DEFAULT    8 _ZL12blink_period

in STM32CubeMonitor these variables are listed with incorrect address and size (blink_period) and incorrect address (counter_error_handler)

 

Is this an issue of using a c/cpp project ?

[stephane.legargeant · Accepted solution]

Hello Michael

This is quite strange. I am surprised by the result shown.

• For the _ZL12blink_period, in the readelf, it is shown LOCAL, so it may be not visible, but we see another similar one. Can you tell me how is declared this symbol? The "blink_period" listed 0x20000124 seems to be different. Can you check if there is global declaration for this symbol ?
• For the counter_error_handler, there is an offset of 2 bytes, which is very strange. Are you sure that file used for readelf and in STM32CubeMonitor are exactly the same ? (This offset happen most of the time when a variable is added and elf file is not updated)

Best regards

Stephane

[Tesla DeLorean]

A contemporary .MAP file might be definitive.

G​enerally I'd have more confidence in the Linker than the average ELF parser.

[Katzenberger.Michael]

Hi Stephane,

thanks for your feedback.

According to your notes I've tried to reproduce the issue with a clean build. But I can't ;-)

The addresses and sizes are now correct. Don't know whats going wrong the first time - therefore sorry for any confusion ...

> readelf Bluepill_USB_CDC.elf -s | grep blink
   343: 200002bc     2 OBJECT  LOCAL  DEFAULT    7 _ZL12blink_period

> readelf Bluepill_USB_CDC.elf -s | grep error
  1208: 20002b60     1 OBJECT  GLOBAL DEFAULT    8 counter_error_handler

Best regards,

Michel