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Tyler Durden
Tyler Durden

Reputation: 11532

To what extent are interrupts supported in Win32?

To what extent are interrupts supported in Win32 beyond processor definitions? For example, x86 machines define at least 18 interrupts, including traps such as the breakpoint trap (INT 3). The other 19-255 interrupts are left open by Intel as software defined interrupts. Are any of these used by Windows/WinAPI or are they just open and free for applications to use as they please? If Windows uses them, where can I find the relevant documentation? I looked on MSDN and could not find anything.

(BTW I am doing compiler, debugger and other system-level programming, so please don't lecture me on your opinions about the advisability of using interrupts in the first place.)

Upvotes: 4

Views: 2406

Answers (1)

Alexey Frunze
Alexey Frunze

Reputation: 62048

In Win32 apps, there's probably just one interrupt used commonly, int 2Eh. It's used as the system call entry point. It's analogous to int 21h in DOS. The rest of the interrupts aren't used by apps.

Apps, however, can handle some CPU exceptions (and debug breaks) via Structured Exception Handling (SEH)/Vectored Exception Handling (VEH). Windows catches CPU exceptions originating in apps and reflects them back into the apps, if and however possible (Windows is not perfect in imitating the CPU exception model).

Windows uses device interrupts internally and does not let apps mess with them. The x86 CPU handles interrupts in the most privileged mode, where the kernel runs.

Nowadays many device interrupts aren't associated with fixed interrupt vectors and are configurable and you need to work with the various things like PCI to query or change the settings.

If you want to work with devices and interrupts directly, you need to write a kernel-mode driver for Windows. There's the Device Driver Kit (DDK) and books like Windows Internals that can get you started.

Still, if you're looking for specifics of device XYZ and its interrupt programming, you aren't going to find everything or much on MSDN or in the DDK because you'll need hardware-specific information, something that's outside of Microsoft's control. The kernel provides the functionality necessary to do I/O and handle interrupts, but it's ultimately up to device drivers to use them one way or the other.

Upvotes: 4

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