test pyelf instead of nm for getting all symbol names+sizes

[paulwuertz]

By using pyelf we are more independet of having any compiler.

For some projects the call to nm -Sl was also very slow. Analyzing the prusa mini firmware for example before was 1470 seconds with 1440 of that the call to nm (see comment #101 (comment)) and with pyelf it only takes 32 seconds.

But some file path and line numbers seem changed, so needs some more investigation...

[W-Mai]

Great work, hope it works properly, it will help a lot. 🚀

[ToddyTsui]

Great. the origin get_size_lines method does not support ELF file built from clang family. because llvm-nm does not support "-l" argument, Hope your commit can fix this.

[paulwuertz]

In the binutils it also states at the nm source, that the --line-numbers option will be slow:

/* We need to get the canonical symbols in order to call
bfd_find_nearest_line. This is inefficient, but, then, you
don't have to use --line-numbers. */

As far as I understand it, after the symbols are extracted it searches all the debug symbols for each symbol. Wrapping my head around the macros there seems not so straight forward. Building a map and looking it up may speed nm itself up.

Also the line numbers in the same function further down can be approximate - using either bfd_find_line or bfd_find_nearest_line:

if ((bfd_find_line (abfd, lc->syms, sym, &filename, &lineno)
	       || bfd_find_nearest_line (abfd, bfd_asymbol_section (sym),

so I am unsure - how far the line differences in this change are reasonable.
I think adding some example firmware as a regression suit to puncover and add some tests with the line-number in particular to make sure that things are improved and not worseend.

I was thinking about ELF's of releases of these projects:

• [cannectivity](https://github.com/CANnectivity/cannectivity - using zephyr
• [Prusa-Firmware-Buddy](https://github.com/prusa3d/Prusa-Firmware-Buddy - using FreeRTOS
• [IronOS](https://github.com/Ralim/IronOS - using FreeRTOS
• [PX4-Autopilot](https://github.com/PX4/PX4-Autopilot - using Nuttx

If someone has more ideas happy to add more :)