gbootroot/skas-or-tt/skas-or-tt.c

/* 
skas_or_tt Copyright (C) 2003  
Jonathan Rosenbaum <freesource@users.sourceforge.net>

A program to check for the existence of the skas patch in the host
kernel and /proc/mm.  Basically borrowed/simplified from jdike's
process.c.  This is a good way to learn about clone() and ptrace().
 */

#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <wait.h>
#include <sys/mman.h>  /* for mmap */
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sched.h>  /* clone */
#define PTRACE_FAULTINFO 52
#define PAGE_SIZE 1024

int main(void)
{

  int n, pid, ret = 1;
  void *stack;
 
  struct ptrace_faultinfo {
	  int is_write;
	  unsigned long addr;
  };
  

  struct ptrace_faultinfo fi;

  printf("Checking for the skas3 patch in the host...");
  pid = start_ptraced_child(&stack);

  n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
  if(n < 0){
	  if(errno == EIO) 
		  printf("not found\n");
	  else printf("No (unexpected errno - %d)\n", errno);
	  ret = 0;
	}
  else  printf("found\n");
  

  printf("Checking for /proc/mm...");
  if(access("/proc/mm", W_OK)){
	  printf("not found\n");
	  ret = 0;
  }
  else printf("found\n");

  kill(pid, SIGKILL);
  return(ret);

}


int threadFunction( void* argument )
{
         printf( "child thread exiting\n" );
	 exit(0);
}


int os_getpid(void)
{
	return(getpid());
}

void os_stop_process(int pid)
{
	kill(pid, SIGSTOP);
}

void os_kill_process(int pid, int reap_child)
{
	kill(pid, SIGKILL);
	if(reap_child)
		waitpid(pid, NULL, 0);
		
}

static int ptrace_child(void *arg)
{
	int pid = os_getpid(); 

	if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
		perror("ptrace");
		os_kill_process(pid, 0);
	}

	os_stop_process(pid);
	_exit(os_getpid() == pid);

}


int start_ptraced_child(void **stack_out)
{
	void *stack;
	unsigned long sp;
	int pid, n, status;
	
	stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if(stack == MAP_FAILED)
	        printf("check_ptrace : mmap failed, errno = %d", errno);
	sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
	if(pid < 0) {
		printf("check_ptrace : clone failed, errno = %d\n", errno);
		exit(0);
	}
	n = waitpid(pid, &status, WUNTRACED);
	if(n < 0) {
		printf("check_ptrace : wait failed, errno = %d\n", errno);
		exit(0);
	}
	if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
		printf("check_ptrace : expected SIGSTOP, got status = %d\n",
		      status);
		exit(0);
	}
	*stack_out = stack;
	return(pid);
}


/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-file-style: "linux"
 * End:
 */