What's the meaning of Windbg idt command?

Question

The Windbg !idt command has new parameters:

!idt [-a [-p][-s][-d][-t][-r] | vector]

After use -t option, there might have a huge number under ISR such like:


70:	fffff8004d800000 foobardriver!foofunc (KINTERRUPT ffff88000007b140)

	                	          20 39954561969536            0            0

Answer 1

Hello gqsu,

I believe that the number is the cumulative interrupt service routine execution time in units of CPU cycles.

Gary

Answer 2

Hello

The !idt command in WinDbg is used to display the interrupt service routines (ISRs) for a specified interrupt dispatch table (IDT).

Here’s a breakdown of the command and its options:

!idt: This command without any options will display the IDTs of all processors on the target computer in an abbreviated format.

-a: When used with !idt, it displays the ISRs for each IDT.

As for the -t option you mentioned, it’s not directly specified in the Microsoft documentation. However, based on your output, it seems to be showing detailed information about a specific interrupt vector, including the ISR address, the driver and function handling the interrupt, and some additional numbers which could be related to the state or performance of the interrupt.

In your example, 70:  fffff8004d800000 foobardriver!foofunc (KINTERRUPT ffff88000007b140) indicates that interrupt vector 70 is handled by the function foofunc in the foobardriver driver, and the ISR is located at the memory address fffff8004d800000. The KINTERRUPT structure, which contains information about the interrupt, is at the memory address ffff88000007b140.

The numbers below (20 39954561969536 0 0) could be statistics related to the interrupt, such as the number of times the interrupt has been invoked, but without more context or documentation, it’s hard to say for certain.

I would recommend referring to the official WinDbg documentation or reaching out to the WinDbg community for more specific information.

Reference documentation:

[!idt (WinDbg) - Windows drivers | Microsoft Learn](https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flearn.microsoft.com%2Fen-us%2Fwindows-hardware%2Fdrivers%2Fdebuggercmds%2F-idt&data=05%7C02%7Cwesleyl%40wicresoft.com%7Cb4d67f1d0c2045c0bcbc08dc5ad4a716%7Cb2ae8dd9097749768706861b488b1512%7C0%7C0%7C638485116609263726%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=hPHHe2GttvbwikMAus4xtP00Jbg7Rv8i8UF08i6EFq8%3D&reserved=0"原始 URL: https://learn.microsoft.com/en-us/windows-hardware/drivers/debuggercmds/-idt。如果你信任此链接, 请单击或点击。")

[windows - Which interrupt number in the IDT represents the RTC interrupt - Stack Overflow](https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstackoverflow.com%2Fquestions%2F70131426%2Fwhich-interrupt-number-in-the-idt-represents-the-rtc-interrupt&data=05%7C02%7Cwesleyl%40wicresoft.com%7Cb4d67f1d0c2045c0bcbc08dc5ad4a716%7Cb2ae8dd9097749768706861b488b1512%7C0%7C0%7C638485116609275277%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=ho7SFESrGQlyn8eUOb4SkO6Az492EuRO7YADhPp4sLY%3D&reserved=0"原始 URL: https://stackoverflow.com/questions/70131426/which-interrupt-number-in-the-idt-represents-the-rtc-interrupt。如果你信任此链接, 请单击或点击。")