For ELF file, how to tell which section contains execution binary code? - elf

Question

I am studying ELF and having a doubt for a while. I tried to search for the answer but in vain. I'd apprciated if somebody could give me the answer or guide me to the place to find an answer.
Almost all the documents I read about ELF said .text section contains executable binary code (and .data contains data....). However, when I used readelf to see the sections contain in an obj file, I saw no .text section but a section called i.main which contains the executable code (from the code contained in this section I found the machine code). The following shows the sections parsed by readelf
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] i.main PROGBITS 00000000 000034 00000a 00 AX 0 0 2
[ 2] .arm_vfe_header PROGBITS 00000000 000040 000004 00 0 0 4
[ 3] .comment PROGBITS 00000000 000044 0001c6 00 0 0 1
[ 4] .debug_frame PROGBITS 00000000 00020a 00003c 00 0 0 1
[ 5] .debug_info PROGBITS 00000000 000246 000088 00 0 0 1
[ 6] .debug_info PROGBITS 00000000 0002ce 0000dc 00 0 0 1
[ 7] .debug_line PROGBITS 00000000 0003aa 000030 00 0 0 1
[ 8] .debug_line PROGBITS 00000000 0003da 000044 00 0 0 1
[ 9] .debug_loc PROGBITS 00000000 00041e 000014 00 0 0 1
[10] .debug_macinfo PROGBITS 00000000 000432 000308 00 0 0 1
[11] .debug_pubnames PROGBITS 00000000 00073a 00001b 00 0 0 1
[12] __ARM_grp..debug_ GROUP 00000000 000758 000008 04 14 14 4
[13] .debug_abbrev PROGBITS 00000000 000760 0005a4 00 G 0 0 1
[14] .symtab SYMTAB 00000000 000d04 000110 10 21 13 4
[15] .rel.debug_frame REL 00000000 000e14 000010 08 14 4 4
[16] .rel.debug_info REL 00000000 000e24 000018 08 14 5 4
[17] .rel.debug_info REL 00000000 000e3c 000038 08 14 6 4
[18] .rel.debug_line REL 00000000 000e74 000008 08 14 8 4
[19] .rel.debug_pubnam REL 00000000 000e7c 000008 08 14 11 4
[20] .shstrtab STRTAB 00000000 000e84 0000f2 00 0 0 1
[21] .strtab STRTAB 00000000 000f76 0001b3 00 0 0 1
[22] .ARM.attributes ARM_ATTRIBUTES 00000000 001129 000044 00 0 0 1
It seems that the section name can be arbitrarily chosen (am I right?) If so, then my questiones are
how to tell which section contains what? (for example, which section contains code and which section contains read only data....).
How to know the definition of each section, for example how do I know the section "[12] __ARM_grp..debug_" is for what purpose?
Thanks in advance.

Answer 1

As for the first part of your question, when determining what sections contain code and which sections contain read only data, a good thing to look for is the section attribute flags.
With the readelf -S command, an X indicates that the section contains executable instructions, an A indicates that the section occupies memory during process execution, and a W indicates that the section should be writable.
So in your object file, there is one section, i.main that is executable, and it is also read only. The other sections aren't writable, but not read only since they aren't in memory at all.
I'm not very familiar with ARM binaries, so I can't really address the other parts of your question.