ARM assembler syntax query

[AussieBruce]

Hi,  I'm wading through a heap of system assembler files to sort out an IRQ problem on an ARM-7 target. Included is the following, they look like memory allocations.  I can't find any reference to the 'b', is it shorthand for 'byte'? In fact, from the module context these should be  exception/interrupt vectors,  more than 8 bits. What do these lines do?

undef_handler:
  b undef_handler
 
swi_handler:
  b swi_handler
 
pabort_handler:
  b pabort_handler
 

[retiredfeline]

Maybe branch unconditionally, i.e. handlers are infinite loops?

[westfw]

“B” is “branch” (unconditional)
You are looking at tiny little default interrupt handlers that are short infinite loops.

[abyrvalg]

To clarify a bit: on ARM7 the vector table doesn’t hold addresses (unlike Cortex-M etc), the CPU jumps right into the table and each entry is a single instruction (so it is typical to use either “B real_handler” or “LDR PC, =real_handler”).

[SiliconWizard]

Maybe branch unconditionally, i.e. handlers are infinite loops?

Yes. This is not maybe, this is for sure.

[rstofer]

Sometimes you will see something like:

b 1b

This is a branch to the label 1 backward

b 1f is a branch to label 1 forward

https://stackoverflow.com/questions/27353096/1b-and-1f-in-gnu-assembly