39 lines
1009 B
C
39 lines
1009 B
C
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/*
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* outputs a cpuid key for use in context keyed payload encoding.
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*
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* Author: Dimitris Glynos <dimitris at census-labs.com>
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*/
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#include <stdio.h>
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int main()
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{
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unsigned long eax;
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asm (
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"xorl %%esi, %%esi;" /* esi is key store, zero it out */
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"xorl %%edi, %%edi;" /* edi is loop iterator, ditto */
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"cpuid_loop: movl %%edi, %%eax;" /* iterator is first arg
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to cpuid */
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"xorl %%ecx, %%ecx;" /* ecx is also used as arg to cpuid but
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we'll use it always as zero */
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"cpuid;"
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"xorl %%eax, %%esi;"
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"cmpl %%esi, %%eax;" /* first time round esi = eax */
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/* not very safe heh? */
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"jne not_first_time;"
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"leal 0x1(%%eax, 1), %%edi;" /* first time round ... */
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"not_first_time: xorl %%ebx, %%esi;"
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"xorl %%ecx, %%esi;"
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"xorl %%edx, %%esi;"
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"subl $1, %%edi;"
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"jne cpuid_loop;"
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"movl %%esi, %%eax;"
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: "=a" (eax)
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);
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printf("%#.8lx\n", eax);
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return 0;
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}
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