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Advancing to subleaf 1 (by making another call to CPUID with EAX=Bh and ECX=1) could for instance return 201h in ECX, meaning that this is a core-type level, and 4 in EBX because there are 4 logical processors in the package; EAX returned could be any value greater than 3, because it so happens that bit number 2 is used to identify the core in ...
Takes as input a CPUID leaf index in EAX and, depending on leaf, a sub-index in ECX. Result is returned in EAX,EBX,ECX,EDX. [e] Instruction is serializing, and causes a mandatory #VMEXIT under virtualization. Support for CPUID can be checked by toggling bit 21 of EFLAGS (EFLAGS.ID) – if this bit can be toggled, CPUID is present. Usually 3 [f]
From x86 mode, the availability of the Alternate Instruction Set can be detected by executing a CPUID with the EAX register set to 0xc0000001 and then examining the EDX register. If EDX bit 0 is set to 1, then AIS is supported. If EDX bit 1 is also set to 1, then AIS is enabled. [9]
Call to VM monitor from guest by causing a VMEXIT. Guest SKINIT EAX: 0F 01 DE: Secure Init and Jump with Attestation. Initializes CPU to known state, designates a 64 Kbyte memory area specified by EAX as an SLB ("Secure Loader Block"), submits a copy of the memory area to the system TPM for validation using a digital signature, then jumps into ...
; The 'enter' instruction can also do something similar); sub esp, 12 : 'enter' instruction could do this for us; mov [ebp-4], 3 : or mov [esp+8], 3; mov [ebp-8], 2 : or mov [esp+4], 2; mov [ebp-12], 1 : or mov [esp], 1 push 3 push 2 push 1 call callee; call subroutine 'callee' add esp, 12; remove call arguments from frame add eax, 5; modify ...
The article says "To obtain extended function information CPUID should be called with the second most significant bit of EAX set. To determine the highest extended function calling parameter, call CPUID with EAX = 80000000h." Isn't 0x80000000 setting the most significant bit, rather than the 2nd msb?
push EAX; pass some register result push dword [EBP + 20]; pass some memory variable (FASM/TASM syntax) push 3; pass some constant call calc; the returned result is now in EAX Typical callee structure: (some or all (except ret) of the instructions below may be optimized away in simple procedures).
The FLAGS register is the status register that contains the current state of an x86 CPU.The size and meanings of the flag bits are architecture dependent. It usually reflects the result of arithmetic operations as well as information about restrictions placed on the CPU operation at the current time.