arm breakpoint detection, standard mode

/*

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@ Arm / Thumb Anti debugging 101  @
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.section .text
.global scan

@ scan(void* code, unsigned int depth);
scan:
    .code 32
    ldr r3, =0xE7F00000 @ load breakpoint constant
    ldr r4, =0xFFFF0000 @ mask
loop:
    ldr r2, [r0]    @ load byte code into r2
    and r2, r4  @ clear out extra data in bytecode with mask
    cmp r2, r3  @ is it a breakpoint?
    beq fuck    @ if so FUCK
    cmp r1, #0  @ are we at the end?
    beq safe    @ if so we are safe
    sub r1, #1  @ decrement the counter
    add r0, #1  @ increment our pointer
    bne loop    @ if we are still looping, loop
safe:
    mov r0, #0  @ return false
    mov r1, r0
    bx lr
fuck:
    mov r0, #0x1    @ return true
    mov r1, #0
    bx lr



*/

bool scan(void (*fun), unsigned int depth)  /// scans a section of a function for break points
{
    int i;
    unsigned int inst;
    for(i=0;i<=depth;i+=sizeof(inst))   /// count from offset start to depth
    {
        inst = (*(volatile unsigned int *)((unsigned int)fun + i) & 0xffff0000)>>16;
        if (inst == 0xE7F0) /// if this is a break point
            return true;    /// return true
    }
    return false;
}