How to send nmi on same system

I need to send an nmi on the system I am working on. I want to te开发者_如何学Pythonst few things which I have implemented. Is there any windows driver routine which allows us to do that? I think I can write to a port using __outword. Is there any other way to do it?

I have one more question. Are there any specific scenarios which causes an NMI? (However, I dont want system to BSOD or triple fault.)

Thanks

From Intel's Software Development Manual: System Programming Guide:

The nonmaskable interrupt (NMI) can be generated in either of two ways:

• External hardware asserts the NMI pin.
• The processor receives a message on the system bus (Pentium 4, Intel Core Duo, Intel Core 2, Intel Atom, and Intel Xeon processors) or the APIC serial bus (P6 family and Pentium processors) with a delivery mode NMI.

and

It is possible to issue a maskable hardware interrupt (through the INTR pin) to vector 2 to invoke the NMI interrupt handler; however, this interrupt will not truly be an NMI interrupt. A true NMI interrupt that activates the processors NMI-handling hardware can only be delivered through one of the mechanisms listed above.

So, if all you want to do is trigger the NMI handler, you can simply use int $2 (int 02h in Intel syntax). But, if you need to ensure that it is not masked, you will either need external hardware to trigger it, or to use the APIC.

If you choose to use the APIC to send an NMI, the easiest way to do it is to send an inter-processor interrupt. To do this, you will need access to the local APIC's registers, which are mapped into physical memory, by default at the address 0xFEE00000, although that can be changed. You will need to find the physical page containing the APIC's registers and map it into virtual memory so that you can access them.

In order to send an IPI, you need to write into the interrupt configuration register. The ICR's low 32 bits are located at 0x300 within the APIC's page, and the upper 32 bits are at 0x310. To send the NMI, you need to:

1. Get the APIC ID of the processor you want to send the NMI to. If you want to send it to the processor you are running on, this is simple since you can read it from the APIC at 0x20 in bits 24-31.
2. Write the APIC ID into the destination field, bits 24-31 of the high ICR register.
3. Write the value 0x4400 into the low ICR register. Bits 8-10 of this value indicate that you are sending an NMI, and bit 14 indicates that you are using the assert trigger mode.

When writing to an APIC register, you must write a full 32 bit value. Also, bits 13, 16-17, and 20-55 in the ICR are reserved, so you should not change their values. You also must write to the high bits of the ICR before the low bits, since the IPI is triggered by the write to the low bits.

Here is an example of sending an NMI to the current processor in C.

#define APIC_ID_OFFSET 0x20
#define ICR_LOW_OFFSET 0x300
#define ICR_HIGH_OFFSET 0x310
// Convenience macro used to access APIC registers
#define APIC_REG(offset) (*(unsigned int*)(apicAddress + offset))

void *apicAddress; // This should contain the virtual address that the APIC registers are mapped to

// Get the current APIC ID. Leave it in the high 8 bits since that is where it needs to be written anyway
unsigned int apicID = APIC_REG(APIC_ID_OFFSET) & 0xFF000000;
unsigned int high = APIC_REG(ICR_HIGH_OFFSET) & 0x00FFFFFF;
high |= apicID;
unsigned int low = APIC_REG(ICR_LOW_OFFSET) & 0xFFF32000;
low |= 0x4400;
APIC_REG(ICR_HIGH_OFFSET) = high;
APIC_REG(ICR_LOW_OFFSET) = low;