1 #include <stdio.h> 2 #include <stdlib.h> 3 typedef unsigned long long int ULong; 4 5 ULong data; 6 ULong result; 7 8 9 extern void shrl32_with_0x10 ( void ); 10 asm("\n" 11 "shrl32_with_0x10:\n" 12 "\tpushq %rdx\n" 13 "\tmovq data, %rdx\n" 14 "\tshr $0x10, %edx\n" 15 "\tjne shrl32_with_0x10_jump\n" 16 "\tshrl32_with_0x10_cont:\n" 17 "\tmovq %rdx, result\n" 18 "\tpopq %rdx\n" 19 "\tret\n" 20 "\tshrl32_with_0x10_jump:\n" 21 "\tmov $0xdeaddead, %edx\n" 22 "\tjmp shrl32_with_0x10_cont\n" 23 ); 24 25 26 int main ( void ) 27 { 28 char *p; 29 30 printf("\nshrl 0x10 with unitialised bits\n"); 31 ULong *notinitialised = malloc(sizeof(ULong)); // Not initialised data. 32 data = *notinitialised; 33 p = (char*) &data; 34 p[0] = 0x11; 35 // p[1] = 0x22; 36 p[2] = 0x33; 37 p[3] = 0x44; 38 39 shrl32_with_0x10(); 40 41 printf("non zero jump on p[2..3] 0x%016llx\n", result); 42 43 data = *notinitialised; 44 p = (char*) &data; 45 p[0] = 0x00; 46 // p[1] = 0x00; 47 p[2] = 0x00; 48 p[3] = 0x00; 49 50 shrl32_with_0x10(); 51 52 printf("zero jump on p[2..3] 0x%016llx\n", result); 53 return 0; 54 } 55
