Question

I have an embedded hardware system which contains a bootloader based on ARMboot (which is very similar to Uboot and PPCboot).

This bootloader normally serves to load uClinux image from the flash. However, now I am trying to use this bootloader to run a standalone helloworld application, which does not require any linked library. Actually, it contains only while(1){} code in the main function.

My problem is that I cannot find out what GCC settings should I use in order to build a standalone properly formatted binary.

I do use following build command:

cr16-elf-gcc -o helloworld helloworld.c -nostdlib

which produces warning message:
warning: cannot find entry symbol _start; defaulting to 00000004

Thereafter, within the bootloader, I upload a produced application and start it at some address:

tftpboot 0xa00000 helloworld
go 0xa00004

But it doesn’t work 🙁
The system reboots.

Normally it should just hang (because of while(1)).

Answer 1

I don’t know that loader, but I think you should use objcopy like this to dump your executable data to a raw binary file. Don’t jump to ELF headers, people 🙂

objcopy -O binary ./a.out o.bin

Also try to compile position independent code and to read ld and gcc manuals.