assemblyarmgnu-assemblerinstruction-set

What does `b .` mean in this ASSEMBLY code?

So I'm looking into the source code for Redox OS (An operating system made with Rust) just to see if I can learn something.

I'm reading the assembly file start.s in the bootloader folder. In the interrupt_vector_table label we have:

interrupt_vector_table:
    b . @ Reset
    b . 
    b . @ SWI instruction
    b . 
    b .
    b .
    b .
    b .

What exactly is b .?

I'm not a complete beginner in assembly, I just never came across this before.

Solution

  • The b instruction for the ARM CPU is nearly the same as the jmp instruction for the x86 CPU: A jump instruction

    Using the GNU tool chain . means: Address of the instruction itself.

    So b . is equal to:

    temporaryLabel:
    b temporaryLabel

    or (for x86 CPUs):

    temporaryLabel:
    jmp temporaryLabel