I have the following y86-64 program from CMU's Architecture lab that's supposed to sum up the values of a linked list.
# Adam Cooper ac251190
init:
.pos 0x0
irmovq Stack, %rsp # set up stack pointer
irmovq Stack, %rbp # set up base pointer
call Main
halt
# Sample linked list
.align 8
ele1:
.quad 0x00a
.quad ele2
ele2:
.quad 0x0b0
.quad ele3
ele3:
.quad 0xc00
.quad 0
Main:
irmovq ele1, %rax
pushq %rax # Pointer to list pushed to stack
call Sum
ret
Sum:
pushq %rbp # Push %rbp onto the stack
rrmovq %rsp, %rbp
mrmovq 8(%rbp), %rdx # Move ele1 into %rdx
irmovq $0, %rax # Set up a base to add eles to
andq %rdx, %rdx # Is this the end of the list?
je End # If it is, jump to the end
irmovq $8, %rcx # Turn %rcx into a index mover
Loop:
mrmovq (%rdx), %rbx # Move ls into %rbx
addq %rbx, %rax # val += ele
addq %rcx, %rdx # Move to next value in the list
mrmovq (%rdx), %rdx
andq %rdx, %rdx # Are we at the last ele?
jne Loop # If not, go again
End:
popq %rbp # TEAR! DOWN! THE STACK!
ret # Return the original call to Main
.pos 0x400
Stack:
The program halts with status "ADR" at line 0x093 which is the line
Loop:
mrmovq (%rdx), %rbx
Now, I was led to believe by the documentation that an "ADR" error meant the program was trying to access an address higher that 0xFFF, but it's not. The stack also appears to have been initialized and set up correctly. I used the same method as several other programs I've written that worked fine. Not really sure what's going wrong here.
Never mind. Fixed it. Changed mrmovq 8(%rbp), %rdx to mrmovq 16(%rbp), %rdx. Thanks to anybody who considered helping