Accessing the vm areas of a process - memory

Question

I am trying to write a LKM that have to read the vm areas address from a process. I am using pid_task() to get the pointer to the task_struct, but i getting compiling error when i try to use it to get the start address of the vmarea.
struct task_struct *ts;
ts = pid_task(find_vpid(pid_t)pid,PIDTYPE_PID);
printk(KERN_INFO "%lu",ts->mm->mmap->start);
And i am getting the error "error: dereferencing pointer to incomplete type"
I am a linux noob and a completely noob in LKM.
I'd appreciate any help.
Thank you all

Answer 1

I have a test on my kernel source tree(2.6.35) with following codes, the compilation is okey:
struct task_struct *ts;
pid_t pid;
ts = pid_task(find_vpid(pid),PIDTYPE_PID);
printk(KERN_INFO "%lu",ts->mm->mmap->vm_start);
Could you try with the above codes in your kernel source tree? I think maybe you have to include all header files needed, such as:
#include <asm/uaccess.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/string.h>
#include <linux/namei.h>
#include <linux/mnt_namespace.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>
#include <linux/resource.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/cgroup.h>
#include <linux/cpuset.h>
#include <linux/audit.h>
#include <linux/poll.h>
#include <linux/nsproxy.h>
#include <linux/oom.h>
#include <linux/elf.h>
#include <linux/pid_namespace.h>
#include <linux/fs_struct.h>
Another:
After compilation successfully, you should judge the pointers is NULL or not.