Starting GDB with your program
● Install gdb-multiarch package:
○ sudo apt-get install gdb-multiarch
● Assemble using –g flag and then link
○ aarch64-linux-gnu-as demo.s -g -o demo.o
○ aarch64-linux-gnu-ld demo.o
● Run your program and wait for GDB to connect using the `–g 1234` flag ○ qemu-aarch64 -g 1234 a.out
● On another terminal window, run gdb and connect to the program
○ gdb-multiarch --nh -q a.out -ex 'set disassemble-next-line on'
-ex 'target remote :1234'
-ex 'set solib-search-path /usr/aarch64-linux-gnu-lib/' -ex 'layout regs'
Note: You can find these steps in section B.3.2 of the textbook, backslashes in the final command simply denote new lines.
Interacting with GDB
● Please read section B.3.3 in the textbook (p.184)
● Breakpoints
○ Use b <label> to pause the program when it reaches the label
○ Ex: b _start to pause at the start of the program
● Moving through the program
○ Resume execution using continue or c
○ Step through the program using step or s
● Panel focus
○ Use focus regs to view the values of the registers
○ Use focus asm to go back to the assembly code panel
Printing Memory
● Read section B.3.4 in the textbook
● To print data stored in memory we use the following command:
○ x/<length><format><unit> address
● If we wanted to print 5 bytes in character from the label hello: ○ x/5cb &hello
● To print 2 bytes in decimal from the address stored in x10:
○ x/2db $x10
Starter Code
Task Time
● Come up for attendance before leaving
● Task 1: Calculating Dot Product
○ Use the data in "vec1" and "vec2" to calculate the dot product and store it in "dot"
○ Must be able to assemble, link, and execute without error
○ You are allowed to use the MUL instruction as needed
○ Comment every line
● Task 2: Debugging using GDB
○ Look at appendix B.3
○ Write a report about your program from Task 1
