DOS ain't dead - User exception handler in C

User exception handler in C (Developers)

posted by Japheth , Germany (South), 23.08.2020, 20:36

> Your "mov eax,0" confused me. Apparently you're clearing the top bits of
> the return value in advance, right?

I assume yes. It's not necessary, however, because you can use the 0x66 prefix:

db 66h ;makes smsw copy all 32 bits to EAX smsw ax

with LMSW, this trick won't work.

On newer cpus, the UMIP flag in CR4 can be set, which will make SMSW a privileged instruction as well.

---
MS-DOS forever!

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Complete thread:

User exception handler in C - RayeR, 24.07.2020, 13:15
- User exception handler in C - Japheth, 24.07.2020, 18:07
- User exception handler in C - Rugxulo, 24.07.2020, 18:39
- User exception handler in C - tkchia, 24.07.2020, 20:47
  - User exception handler in C - RayeR, 30.07.2020, 13:18
    - User exception handler in C - tom, 30.07.2020, 23:54
      - User exception handler in C - RayeR, 01.08.2020, 02:13
        User exception handler in C - Laaca, 16.08.2020, 21:27
        User exception handler in C - Laaca, 16.08.2020, 22:38
        User exception handler in C - Rugxulo, 17.08.2020, 22:35
        User exception handler in C - marcov, 18.08.2020, 12:23
        User exception handler in C - Laaca, 18.08.2020, 20:15
        User exception handler in C - Rugxulo, 19.08.2020, 19:44
        User exception handler in C - Laaca, 19.08.2020, 21:50
        User exception handler in C - Rugxulo, 23.08.2020, 17:32
        User exception handler in C - Japheth, 23.08.2020, 20:36
        User exception handler in C - Rugxulo, 17.08.2020, 22:26
        User exception handler in C - tkchia, 19.08.2020, 18:52
        User exception handler in C - marcov, 20.08.2020, 00:00
        User exception handler in C - Laaca, 20.08.2020, 15:31
    - User exception handler in C - tkchia, 31.07.2020, 19:36
      - User exception handler in C - RayeR, 01.08.2020, 02:16
- User exception handler in C - Guti, 27.07.2020, 08:22