NOP machine instruction

| Cracking | (gdb) disass Dump of assembler code for function main: 0x0000000000400494 : push %rbp 0x0000000000400495 : mov %rsp,%rbp 0x0000000000400498 : nop => 0x0000000000400499 : jmp 0x400498 End of assembler dump. (gdb) #include<stdio.h> main () { while (1) asm(“nop”); } NOPs are often involved when cracking software that checks for serial numbers, specific hardware …

modify all segment registers except ..(CS)

software | Windows | In computing, a code segment, also known as a text segment or simply as text, is a phrase used to refer to a portion of memory or of an object file that contains executable instructions. source : http://en.wikipedia.org/wiki/Code_segment Note that code may always modify all segment registers except CS (the code …

The Intel IA32 processors have a base pointer..

software | Windows | The Intel IA32 processors have a base pointer register called EBP . The EBP register is typically set to the value of the ESP register at the beginning of a procedure, and used to address the procedure arguments and locally allocated variables throughout the procedure. Thus, the arguments are located at …

Register EDI holds the bit offset …

software | Windows | EDI: The Destination Index Every loop that generates data must store the result in memory, and doing so requires a moving pointer. The destination index, EDI, is that pointer. The destination index holds the implied write address of all string operations. The most useful string instruction, remarkably enough, is the seldom-used …

inferior's auxiliary vector…

(gdb) info auxv 33 AT_SYSINFO_EHDR System-supplied DSO’s ELF header 0x7fff7a9ff000 16 AT_HWCAP Machine-dependent CPU capability hints 0x78bfbff 6 AT_PAGESZ System page size 4096 17 AT_CLKTCK Frequency of times() 100 3 AT_PHDR Program headers for program 0x400040 4 AT_PHENT Size of program header entry 56 5 AT_PHNUM Number of program headers 8 7 AT_BASE Base address …

inferior’s auxiliary vector…

(gdb) info auxv 33 AT_SYSINFO_EHDR System-supplied DSO’s ELF header 0x7fff7a9ff000 16 AT_HWCAP Machine-dependent CPU capability hints 0x78bfbff 6 AT_PAGESZ System page size 4096 17 AT_CLKTCK Frequency of times() 100 3 AT_PHDR Program headers for program 0x400040 4 AT_PHENT Size of program header entry 56 5 AT_PHNUM Number of program headers 8 7 AT_BASE Base address …