Simple Instruction Level Debugger

This is a homework of the course "Advanced Programming in the UNIX Environment" at NYCU. I implement a simple instruction-level debugger that allows a user to debug a program interactively at the assembly instruction level.

The debugger supports following features:

• Shows disassembly of 5 instructions following the program counter.
• Step one instruction with command si.
• Set breakpoints with command break <address>.
• Continue the program until it it terminates or hits a breakpoint with command cont.
• Time travel: set an anchor point at any time with command anchor and go back to the latest anchor with command timetravel. The program state is restored when going back to an anchor.

Building and Running

You should have Rust programming language environment installed.

cargo build
cargo run <program being debugged>

Example Output

$ cargo run ./guess
* program './guess' loaded. entry point 0x40108b
      40108b: f3 0f 1e fa                     endbr64
      40108f: 55                              push      rbp
      401090: 48 89 e5                        mov       rbp, rsp
      401093: 48 83 ec 10                     sub       rsp, 0x10
      401097: ba 12 00 00 00                  mov       edx, 0x12
(sdb) break 0x4010bf
** set a breakpoint at 0x4010bf
(sdb) break 0x40111e
** set a breakpoint at 0x40111e
(sdb) cont
guess a number > ** hit a breakpoint at 0x4010bf
      4010bf: bf 00 00 00 00                  mov       edi, 0
      4010c4: e8 67 00 00 00                  call      0x401130
      4010c9: 48 89 45 f8                     mov       qword ptr [rbp - 8], rax
      4010cd: 48 8d 05 3e 0f 00 00            lea       rax, [rip + 0xf3e]
      4010d4: 48 89 c6                        mov       rsi, rax
(sdb) anchor
** dropped an anchor
(sdb) cont
haha

no no no
** hit a breakpoint at 0x40111e
      40111e: bf 00 00 00 00                  mov       edi, 0
      401123: e8 10 00 00 00                  call      0x401138
      401128: b8 01 00 00 00                  mov       eax, 1
      40112d: 0f 05                           syscall
      40112f: c3                              ret
(sdb) timetravel
** go back to the anchor point
      4010bf: bf 00 00 00 00                  mov       edi, 0
      4010c4: e8 67 00 00 00                  call      0x401130
      4010c9: 48 89 45 f8                     mov       qword ptr [rbp - 8], rax
      4010cd: 48 8d 05 3e 0f 00 00            lea       rax, [rip + 0xf3e]
      4010d4: 48 89 c6                        mov       rsi, rax
(sdb) cont
42

yes
** hit a breakpoint at 0x40111e
      40111e: bf 00 00 00 00                  mov       edi, 0
      401123: e8 10 00 00 00                  call      0x401138
      401128: b8 01 00 00 00                  mov       eax, 1
      40112d: 0f 05                           syscall
      40112f: c3                              ret
(sdb) cont
** the target program terminated.