In the x86 architecture, the cpuid instruction is a processor supplementary instruction allowing. Intel processor identification and the cpuid instruction. Download pdf using cpuid to detect the presence of sse 4. The sample program on page 77 will call the cpuid instruction and output the result. It was introduced by intel in 1993 when it introduced the pentium and slenhanced 486 processors.
The cpuid opcode is a processor supplementary instruction its name derived from cpu identification for the x86 architecture. Output the number entered mov eax, 4 mov ebx, 1 mov ecx, num mov edx, 5 int 80h. Cpuid is an instruction used to query processor specific information. Also, eax is set to the maximum eax value supported for cpuid calls, as not all queries are supported on all processors. Extended cpuid x86, x64 autoit example scripts autoit forums. Note that different brands of cpus may have given different meanings to these. Be aware of this when reading disassembly listings. The cpuid opcode is 0fa2h and the value in the eax register. User prompt mov eax, 4 mov ebx, 1 mov ecx, usermsg mov edx, lenusermsg int 80h. The cpuid instruction identified by a cpuid opcode is a processor supplementary instruction its name derived from cpu identification for the x86 architecture allowing software to discover details of the processor. Contribute to tychocpuid development by creating an account on github. One of the lessknown antisandbox detection tricks relies on the instruction cpuid that is executed with eax1 as an input parameter.
The code i have written, only works on linux for x86i386i686 etc. If s is specified, the condition flags are updated on the result of the operation. See also x86 assembly language for a quick tutorial for this processor family. The mov instruction copies the value of operand2 into rd.
Learn vocabulary, terms, and more with flashcards, games, and other study tools. When eax is set to 1, the 31st bit in ecx cpuid s returned value is set, it indicates that the program is being run in hypervisor. It was introduced by intel in 1993 when it introduced the pentium and sl enhanced 486 processors. One of the lessknown antisandbox detection tricks relies on the instruction cpuid that is executed with eax 1 as an input parameter. I wanted to learn some x86 assembly code, so i wrote a tiny program which reads the cpuid feature bits found on intel cpus and outputs this to the display. Exit code mov eax, 1 mov ebx, 0 int 80h when the above code is compiled. The length of the message dispmsg db you have entered. In order to determine the highest acceptable value for the eax register input and cpuid operation, the program should set the eax register parameter value to 0 and then execute the cpuid instruction as follows mov eax, 00h cpuid id r pentium and p6 family processors. Issue xgetbv, and verify that the featureenabled mask at bits 1 and 2 are 11b xmm state and ymm state enabled by the operating system. Most if not all of these instructions are available in 32bit mode. Check if being run in hypervisor via cpuid instruction. Assemblers and compilers will choose registers for such purposes where theres no write dependency. In the x86 architecture, the cpuid instruction identified by a cpuid opcode is a processor supplementary instruction its name derived from cpu identification allowing software to discover details of the processor. Main index download documentation examples message board.
Varies according to which level number you ask it for. This can be done by looking at the eflags register. Starting with windows server 2012 and windows 8, if cpuid. The url provides like 30 different chunks of cpuid results, which of these chunks need to be converted into binary and place into cpuid. Eax 80000008h returns linearphysical address size data. Check whether extended function 0x80000001 is available are not. In a 32 bit environment like windows 9x and nt2000 the address is stored in 32 bits i.
We need to store an extra copy of the flags on the stack and edx, 1. For example, it would be silly to use mov eax, eax if the instruction immediately before it were writing. The cpuid opcode is 0fh, a2h as two bytes, or 0fa2h as a single word and the value in the eax register, and in some cases the ecx register, specifies what information to return. You cannot use pc r15 for rd, or in operand2, in 32bit thumb mov instructions. Use a binary calculator to convert hexadecimal to binary, and you get.
Advancing to subleaf 1 by making another call to cpuid with eaxbh and ecx1 could for instance. Identification of x86 cpus and their features with cpuid. Hexacorn blog protecting vmware from cpuid hypervisor detection. Yes or you wouldnt be reading this one by now anyway, but if you still want to verify, you check the ecxs bit 5 after a cpuid with eax 1. Why the eax segment in the packet you had in the other post is marked as cpuid. Getting 64bit cpuid sample code to compile in vs2008. Eax contains a value of 1, windows assumes that the hypervisor imposes no specific limit to the number of vps. When the processor executes the instruction with a 32bit generalpurpose register, it assumes that the 16 leastsignificant bits of the generalpurpose register are the destination or source operand. Nolongmode mov eax, 0x80000000 cpuid cmp eax, 0x80000001. Its basically telling the compiler, use the register indicated by asm param %1, in this case, the param of line mov %%ebx, %1. An other way to detect if the program is being run in hypervisor is using the cpuid instruction in an other way. The cpuid opcode is a processor supplementary instruction its name derived from cpu identification for the x86 architecture allowing software to discover details of the processor. First, click the download button with the green background the button marked in the picture. Extended cpuid x86, x64 autoit example scripts autoit.
Some malware samples analyse the bit 31th of the value returned in the register ecx. Eax is less than or equal to the maximum input value and the leaf is not supported on that processor then 0 is returned in all the registers. It was introduced by intel in 1993 when it introduced the pentium and slenhanced 486 processors by using the cpuid opcode, software can determine processor type and the presence of features like mmxsse. With most assemblers, using the instruction form mov ds, eax will avoid this unneeded 66h prefix.
By using the cpuid opcode, software can determine processor type and the presence of features like mmxsse. Hexacorn blog protecting vmware from cpuid hypervisor. The code below is the same as the sample bar the final output. This is the full 80868088 instruction set of intel. For the most software products the license verification is done with license keys. When executed the values returned by general purpose registers describe the various processor info and feature bits. During my time in the it i have also seen some products, where the license is tied to the underlying hardware of your server. Return cpuid data for requested cpuid leaf, as found in returned. Instead of setting eax the argument to cpuid to be 0x40000000, eax is set to 1.
Eflags to detect cpuid the first step is to check whether the computer actually supports the cpuid instruction. Aug 25, 2014 one of the lessknown antisandbox detection tricks relies on the instruction cpuid that is executed with eax1 as an input parameter. Table 38 shows information returned, depending on the initial value loaded into the eax register. Eax is higher than the maximum input value for basic or extended function for that processor then the data for the. Ecx bit 281 intel avx supported andor bit 251 aes supported andor bit 121 fma supported andor bit 11 pclmulqdq are supported. Getting 64bit cpuid sample code to compile in vs2008 stack. The following shows information returned, depending on the initial value loaded into the eax register.
Ecx bit 28 1 intel avx supported andor bit 25 1 aes supported andor bit 12 1 fma supported andor bit 1 1 pclmulqdq are supported. Assembly system calls system calls are apis for the interface between the user space and the kernel space. It was introduced by intel in 1993 when it introduced the pentium and slenhanced 486 processors a program can use the cpuid to determine processor type and whether features. For example, the following pseudocode loads eax with 00h and causes cpuid to return a maximum return value and the vendor identification string in the appropriate registers. In this case, windows server 2012 guest vms may use more than 64 vps, up to the maximum supported number of processors applicable to the specific windows version being.
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