#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

#include <sys/mman.h>
#include <asm/prctl.h>
#include <sys/prctl.h>

extern int TLS_SIZE;
extern unsigned long tls_position(void);

extern int __real_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
				 void *(*start_routine) (void *), void *arg);

extern int arch_prctl(int code, unsigned long addr);

// This data structure is used to pass the function+args that the user
// called during the thread creation.
typedef struct _target {
	void *(*the_start_routine)(void*);
	void * the_arg;
} target;

void* tls_setup(void*);


// wrapper for pthread_create()
int __wrap_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg){

  target *trg;
  int ret;

  trg = (target*)malloc(sizeof(target));
  trg->the_start_routine = start_routine; 
  trg->the_arg = arg;

  // real pthread_create call
  ret = __real_pthread_create(thread, attr, tls_setup, (void*)trg);	

  return ret;
}

void * tls_setup(void * args){

  unsigned long addr;
  void *(*the_start_routine)(void*);
  void * the_arg;

  // Creation of TLS zone
  addr = (unsigned long)mmap(NULL,
			     TLS_SIZE,
			     PROT_READ|PROT_WRITE,
			     MAP_ANONYMOUS|MAP_PRIVATE,
			     0,0);

  // set addr of TLS inside the TLS zone
  *(unsigned long*)addr = addr;

  // Set base of segment GS to newly created TLS zone  
  arch_prctl(ARCH_SET_GS,addr);

  // execute init function for thread
  the_start_routine = ((target*)args)->the_start_routine;
  the_arg = ((target*)args)->the_arg;

  return the_start_routine(the_arg);
}