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ptrace ex 5
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <sys/user.h>
#include <sys/reg.h>
int waitchild(pid_t pid) {
int status;
waitpid(pid, &status, 0);
if(WIFSTOPPED(status)) {
return 0;
}
else if (WIFEXITED(status)) {
return 1;
}
else {
printf("%d raised an unexpected status %d", pid, status);
return 1;
}
}
unsigned long to_ulong(char * s) {
return strtol(s, NULL, 16);
}
unsigned long readMemoryAt(pid_t tracee, unsigned long address) {
return ptrace(PTRACE_PEEKTEXT, tracee, address, NULL);
}
void writeMemoryAt(pid_t tracee, unsigned long address, unsigned long instruction) {
ptrace(PTRACE_POKETEXT, tracee, address, instruction);
}
unsigned long readRegister(pid_t tracee, int reg) {
return ptrace(PTRACE_PEEKUSER, tracee, 8 * reg, NULL);
}
void writeRegister(pid_t tracee, int reg, unsigned long value) {
ptrace(PTRACE_POKEUSER, tracee, 8 * reg, value);
}
unsigned long setbp(pid_t tracee, unsigned long address) {
unsigned long original = readMemoryAt(tracee, address);
unsigned long sigtrap = (original & 0xFFFFFFFFFFFFFF00) | 0x00000000000000CC;
writeMemoryAt(tracee, address, sigtrap);
printf("Set breakpoint at %lx, new instruction is %lx instead of %lx\n",
address, readMemoryAt(tracee, address), original);
return original;
}
void removebp(pid_t tracee, unsigned long address, unsigned long original) {
unsigned long previously = readMemoryAt(tracee, address);
writeMemoryAt(tracee, address, original);
printf("Unset breakpoint at %lx, new instruction is %lx, instead of %lx\n",
address, readMemoryAt(tracee, address), previously);
}
void showregisters(pid_t tracee) {
printf("RIP = %lx\nRAX = %lx\n",
readRegister(tracee, RIP), readRegister(tracee, ORIG_RAX));
}
void setIp(pid_t tracee, unsigned long address) {
writeRegister(tracee, RIP, address);
}
void presskey() {
getchar();
}
int main(int argc, char ** argv) {
setbuf(stdout, NULL);
unsigned long bpAddress = to_ulong(argv[1]);
pid_t child = fork();
if(child == 0) {
ptrace(PTRACE_TRACEME, 0, NULL, NULL);
execve(argv[2], argv + 2, NULL);
}
else {
// wait for the child to stop
waitchild(child);
unsigned long originalInstruction = setbp(child, bpAddress);
ptrace(PTRACE_CONT, child, NULL, NULL);
while(waitchild(child) < 1) {
printf("Breakpoint hit !\n");
showregisters(child);
presskey();
removebp(child, bpAddress, originalInstruction);
setIp(child, bpAddress);
ptrace(PTRACE_SINGLESTEP, child, NULL, NULL);
waitchild(child);
setbp(child, bpAddress);
ptrace(PTRACE_CONT, child, NULL, NULL);
}
}
return 0;
}
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