Can _start be the thumb function?

Question

Help me please with gnu assembler for arm926ejs cpu.

I try to build a simple program(test.S):

.global _start 
_start:
    mov r0, #2
    bx lr
         


        

Answer 1

here answer.

Thanks for all.

http://stuff.mit.edu/afs/sipb/project/egcs/src/egcs/gcc/config/arm/README-interworking

• Calls via function pointers should use the BX instruction if the call is made in ARM mode:

      .code 32
      mov lr, pc
      bx  rX
  

  This code sequence will not work in Thumb mode however, since the mov instruction will not set the bottom bit of the lr register. Instead a branch-and-link to the _call_via_rX functions should be used instead:

      .code 16
      bl  _call_via_rX
  

  where rX is replaced by the name of the register containing the function address.