ELF file .text section file offset
Posted: Sun Mar 19, 2017 2:00 am
Hey.
I use this https://github.com/alexhoppus/rpios/blo ... r/Makefile Makefile to build this https://github.com/alexhoppus/rpios/blo ... ser/app1.c application with the use of this https://github.com/alexhoppus/rpios/blo ... /linker.ld linker script. After building it turned out that the size of this app is abnormally huge, currently I tested it on Ubuntu 16.04/14.04 and for different versions of arm-none-eabi-* toolchain it gives 70K/35K appropriately. The reason of such a big size of ELF file is that .text section is placed inside ELF file with a big offset:
As you can see in this case .text section is located at offset 0x8000 inside ELF file. The space between ELF header and text section is filled with zeros.
I use this application from inside of my self-written OS and this app is linked as a data blob with the kernel image. The kernel is loaded using UART bootloader that's why the final image size is critical. Also as you have guessed i use ELF loader for apps so preserving ELF format is important for me. The question is - why this text section offset is so huge, what is the reason for this? And how can i control it?
Actually, i have found the similar question on SO, but it is unanswered http://stackoverflow.com/questions/2683 ... in-linking
I use this https://github.com/alexhoppus/rpios/blo ... r/Makefile Makefile to build this https://github.com/alexhoppus/rpios/blo ... ser/app1.c application with the use of this https://github.com/alexhoppus/rpios/blo ... /linker.ld linker script. After building it turned out that the size of this app is abnormally huge, currently I tested it on Ubuntu 16.04/14.04 and for different versions of arm-none-eabi-* toolchain it gives 70K/35K appropriately. The reason of such a big size of ELF file is that .text section is placed inside ELF file with a big offset:
Code: Select all
user (master) $ arm-linux-gnueabi-readelf --sections app1 | grep .text
[ 1] .text PROGBITS 00800000 008000 000078 00 AX 0 0 4Code: Select all
user (master) $ hexdump -C ./app1 | lessCode: Select all
00000000 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 |.ELF............|
00000010 02 00 28 00 01 00 00 00 00 00 80 00 34 00 00 00 |..(.........4...|
00000020 5c 81 00 00 02 02 00 05 34 00 20 00 01 00 28 00 |\.......4. ...(.|
00000030 09 00 06 00 01 00 00 00 00 80 00 00 00 00 80 00 |................|
00000040 00 00 80 00 b8 00 00 00 b8 00 00 00 05 00 00 00 |................|
00000050 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00008000 00 00 a0 e3 00 10 a0 e3 1a 00 00 ea 04 40 2d e5 |.............@-.|
00008010 03 40 a0 e1 02 30 a0 e1 01 20 a0 e1 00 10 a0 e1 |[email protected]... ......|
00008020 01 00 a0 e3 00 00 00 ef 04 40 9d e4 1e ff 2f e1 |.........@..../.|
00008030 04 40 2d e5 03 40 a0 e1 02 30 a0 e1 01 20 a0 e1 |.@[email protected]... ..|Actually, i have found the similar question on SO, but it is unanswered http://stackoverflow.com/questions/2683 ... in-linking