CoreDebug->DHCSR

Hi there,

We are using cortex M0 uC. We need to recognize at our code whether or not the debugger is attached.
We have found after a lot of search and effort that we cannot use CoreDebug->DHCSR with cortex M0.

We have found a different approach using the HardFault exception and software breakpoint
that indirect recognize if the debugger is attached.

In this approach using assembly if a hardware exception occurs due to a breakpoint
then no debugger is attach and the HardFault exception return to the program
skipping the breakpoint instruction.

Below is the assembly code we have found and slightly changed:

__asm("MOVS R0, #4");
__asm("MOV R1, __return_address()");
__asm("TST R0, R1");
__asm("BEQ _MSP");
__asm("MRS R0, PSP");
__asm("B _checkFaultInstruction");
__asm("_MSP: ");
__asm("MRS R0, MSP");
__asm("_checkFaultInstruction: ");
__asm("LDR R1, [R0,#24]");
__asm("LDRH R2, [R1]");
__asm("LDR R3,=0xBEAB");
__asm("CMP R2, R3");
__asm("BNE HardFault_HandlerC ");
__asm("ADDS R1, #2");
__asm("STR R1, [R0,#24]");
__asm("BX __return_address()");

The compiler is throwing the follows errors:

1) __asm("LDR R3,=0xBEAB"); -> error #29: expected an expression
We have replaced this instruction with:
__asm("MOV R3, 0xBEAB");
Does this instruction has the same effect?

2) __asm("BX __return_address()"); -> error #1084: This instruction not permitted in inline assembler.
How can we replace this unsupported instruction?

3) __asm("BNE HardFault_HandlerC "); -> error #114:label "HardFault_HandlerC" was reference but not defined
HardFault_HandlerC is a function name
4) __asm("BX __return_address()"); -> error #114:label "..." was reference but not defined

What is wrong with 3 and 4?

Thanks in advance.