How to map machine instctions in memory and execute them? (Aka, how to create a loader)

[Johan]

On Monday, 6 June 2022 at 15:13:45 UTC, rempas wrote:
> ```
>   // mov rdx, <wordLen>
>   *cast(char*)(code + 14) = 0x48;
>   *cast(char*)(code + 15) = 0xC7;
>   *cast(char*)(code + 16) = 0xC2;
>   *cast(char*)(code + 17) = 12;
>   *cast(char*)(code + 18) = 0x00;
>   *cast(char*)(code + 19) = 0x00;
>   *cast(char*)(code + 20) = 0x00;
>
>   // mov rdx, <location where data are allocated>
>   *cast(char*)(code + 21) = 0x48;
>   *cast(char*)(code + 22) = 0xC7;
>   *cast(char*)(code + 23) = 0xC1;
>   *cast(long*)(code + 24) = cast(long)data;
>   *cast(char*)(code + 32) = 0x00;
>   ```

This instruction is wrong. Note that you are writing twice to 
RDX, but also that you are using `mov sign_extend imm32, reg64` 
instead of `mov imm64, reg64` (`0x48 0xBA`?). Third, why append 
an extra zero (`*cast(char*)(code + 32) = 0x00;`)? That must be a 
bug too.

cheers,
   Johan