Now we can see all the static symbols too along with their addresses. All the explanations will be based on this simple project. A screen-shot of the application is shown below. Rows in the symbol view can be filtered just as the module view. What this means is that the initial values of all the data that a program uses must itself be stored in the program executable file, otherwise there is no way that the RAM can be initialized by the crt0.
I wanted to filter and sort the data generated in an interactive way so I wrote a C WinForms application that reads the data from the map and presents it in a list view using the awesome ObjectListView control. Getting the module wise breakdown of memory is a simple matter of reading the lines corresponding to the.
To reset the symbol view to show all symbols, click the reset syms button. Usually this data is stored after all the code in the program. How did it come to be that when the program was running the global data that the program access happen to have the right values and the memory map looks nice and orderly as above?
The data used by a program can be split into statically allocated global data regions - the initialized DATA segment and the zero-initialised BSS segment and the runtime allocated memory - the Stack and the Heap. Filtering a group of files automatically filters the symbols in the group.
In fact if we had not used the --ffunction-sections option static functions would also have been missing from the map.
Thus the BSS was born and claims all those globals left uninitialized by lazy programmers along with those specifically initialized to zero. The first module in the. The --ffunction-sections option has ensured that each function is compiled in a separate section, which allows the linker via -Wl,--gc-sections to later remove any functions that are not called from the final executable.
Simply adding up the sizes of all the symbols will not normally equal the size of the modules or the actual size of the various sections. In addition to containing all the segments of a program as defined in the linker scriptthe ELF image also contains a Symbol Table which lists all the global static and non-static symbols in the executable.
Note that to generate the maximum debug information, you should use the -g3 LD option.
Subsequent elements related to main. On C based systems this boot code is called the ctr0 the C runtime zero. Thus given that we have the symbol list from NM, we just have to find the compilation unit corresponding to each of the symbols at a particular address.
Next we need to find the segment to section mapping, i. This mapping is configured in the tool Settings, and the information should be available in the target linker script. The symbols shown in the symbol view will be filtered according to the files selected in the module view.
For our intents we can note that the sections named. We can see that the. Fortunately there are some ways around this limitation.
However there was a time in space before the big bang when the program was living entirely on the flash and the RAM was just a jumble of random bits.Introduction.
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Sorry for the late reply, I don't seem to have got any notifications for your comments. This is a good question and I'm afraid I don't know if the GNU-LD linker supports automatically re-locating data into different regions. Texas Instruments (TI) is a well-known US-based semiconductor manufacturer.
TI is perhaps best known to many as the manufacturer of some of the fanciest scientific calculators in the market. Of the long list of electronic devices produced by TI, microcontrollers are on the top.
TI manufactures some of the coolest and advanced .Download