/* Author: Steve Fink (http://foxglove.dnsalias.org/~sfink/) */

#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>

int main(int argc, char ** argv) {
  char* pid_arg = argv[1];
  char* offset_arg = argv[2];
  char* size_arg = argv[3];
  pid_t pid = strtol(pid_arg, NULL, 0);
  int fd;
  char fname[200];
  long offset;
  long size = 4096;
  char buffer[4096];

  if ((int)pid <= 0) {
    fprintf(stderr, "Invalid pid arg '%s'\n", pid_arg);
    exit(1);
  }

  fprintf(stderr, "attaching to process %d...\n", pid);
  if (ptrace(PTRACE_ATTACH, pid, NULL, NULL) < 0) {
    fprintf(stderr, "attach failed: %s\n", strerror(errno));
    exit(1);
  }

  wait(NULL);

  sprintf(fname, "/proc/%d/mem", pid);
  fd = open(fname, O_RDONLY);
  if (fd < 0) {
    fprintf(stderr, "open %s: %s\n", fname, strerror(errno));
    goto ERROR;
  }
  
  if (offset_arg != NULL) {
    offset = strtol(offset_arg, NULL, 0);
    if (offset <= 0) {
      fprintf(stderr, "invalid offset '%s'\n", offset_arg);
      goto ERROR;
    }
  }

  if (offset_arg != NULL && size_arg != NULL) {
    size = strtol(size_arg, NULL, 0);
    if (size <= 0) {
      fprintf(stderr, "invalid size '%s'\n", size_arg);
      goto ERROR;
    }
  }

  if (offset != 0) {
    if (lseek(fd, offset, SEEK_SET) == (off_t) -1) {
      fprintf(stderr, "seek failed: %s\n", strerror(errno));
      goto ERROR;
    }
  }

  while (size > 0) {
    int n = (size > 4096) ? 4096 : size;
    int nread = read(fd, buffer, n);
    if (nread < 0) {
      fprintf(stderr, "read failed: %s\n", strerror(errno));
      goto ERROR;
    }
    if (nread == 0) break;
    write(1, buffer, nread);
    size -= nread;
  }

  ptrace(PTRACE_DETACH, pid, NULL, NULL);
  return 0;

ERROR:
    ptrace(PTRACE_DETACH, pid, NULL, NULL);
    return 1;
}