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Jan-Erik Rediger 2023-09-15 11:18:37 +00:00
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# `xchg rax, rax`
So I got myself a hard copy of [`xchg rax, rax`](https://www.xorpd.net/pages/xchg_rax/snip_00.html).
Now I have to learn enough `x86_64` assembler to read it.
And probably also some `gdb` or `lldb` to inspect the running program.
I'll try to do that.
## Build
Individual chapters are in their respective `0x??.asm` files, probably with added comments.
They can be build using `make`:
```
make 0x00
```
Resulting in a binary file `0x00`
## Debug
Break on main, inspect the registers, run the full thing and inspect it again.
```
gdb 0x00
(gdb) break main
(gdb) run
(gdb) info registers
rax 0x401110 4198672
rbx 0x7fffffffc968 140737488341352
rcx 0x403e00 4210176
rdx 0x7fffffffc978 140737488341368
rsi 0x7fffffffc968 140737488341352
rdi 0x1 1
rbp 0x1 0x1
-- snip --
(gdb) continue
```
| Command | Short | Meaning |
| ------- | ----- | ------- |
| break main | b main | Set a breakpoint on the entry of function `main` |
| run | r | Run the program until a breakpoint or end |
| info registers | i r | Show values of all registers |
| continue | c | Continue running the program |

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global main global main
main: main:
xor eax, eax