sos-code-article10/sos/process.c

/* Copyright (C) 2005 David Decotigny

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
   USA. 
*/

#include <sos/assert.h>
#include <sos/list.h>
#include <sos/kmem_slab.h>
#include <hwcore/irq.h>
#include <drivers/bochs.h>
#include <hwcore/bitmap.h>
#include <sos/physmem.h> /* for SOS_PAGE_SIZE */

#include <sos/umem_vmm.h>

#include "process.h"

#define SOS_PROCESS_MAX_OPENED_FILES  64
#define SOS_PROCESS_MAX_NAMELEN       32


/**
 * Definition of a process in SOS. A process is basically the
 * collection of all the resources requested by a user program. The
 * threads are one of these resources, the mm_context is one other
 * example of such resources.
 */
struct sos_process
{
  char name[SOS_PROCESS_MAX_NAMELEN];

  /** Process identifier */
  sos_pid_t pid;

  /** First important resource: the address space */
  struct sos_umem_vmm_as *address_space;

  /** Second important resource: the CPU execution contexts, aka the
      threads executing in the context of this process. */
  struct sos_thread      *thread_list;
  sos_count_t            nb_threads;

  /** Reference counter, including threads */
  sos_count_t            ref_cnt;

  /** The array of opened file descriptors */
  struct sos_fs_opened_file * fds[SOS_PROCESS_MAX_OPENED_FILES];

  /** Where the root of the process is (for chroot support). May be NULL */
  struct sos_fs_opened_file * root;

  /** Where the current working dir of the process is */
  struct sos_fs_opened_file * cwd;

  /** To chain the processes in the global list of active processes
      and PIDs */
  struct sos_hash_linkage hlink_pidtable;
};


/** The list of processes in the system */
static struct sos_hash_table * process_hash;


/** The bitmap for PID allocation */
static void * bitmap_pid;


/** Number of bits in the PID bitmap */
#define SOS_PROCESS_PID_BITMAP_NBITS \
  (8 * SOS_PROCESS_PID_BITMAP_NPAGES * SOS_PAGE_SIZE)


/** The PID where we start looking for a free slot */
static sos_pid_t next_base_pid;


/** The cache for the sos_process structures */
struct sos_kslab_cache *cache_struct_process;


/**
 * Helper function for debugging purposes
 */
void sos_process_dumplist(void)
{
  struct sos_thread * cur_thr = sos_thread_get_current();
  int nb_procs = 0;

  /* Internal function used to dump infos about a single process */
  sos_bool_t process_iterator(void* custom_data,
			      struct sos_process * proc)
    {
      struct sos_thread * thr;
      int    nb_thrs;

      nb_procs ++;
      sos_bochs_printf("  proc %d @%p: '%s', %d threads, %d refs\n",
		       proc->pid, proc, proc->name?proc->name:"(none)",
		       proc->nb_threads, proc->ref_cnt);

      list_foreach_forward_named(proc->thread_list, thr, nb_thrs,
				 prev_in_process, next_in_process)
	{
	  if (thr == cur_thr)
	    sos_bochs_printf("    thr@%p: [CURRENT]\n", thr);
	  else
	    sos_bochs_printf("    thr@%p: %cstate=%d eip=%p\n",
			     thr,
			     sos_cpu_context_is_in_user_mode(thr->cpu_state)?'u':'k',
			     thr->state,
			     (void*)sos_cpu_context_get_PC(thr->cpu_state));
	}

      return TRUE;
    }

  sos_bochs_printf("<ps>\n");
  sos_hash_walk(process_hash, (sos_hash_map_func_t*)process_iterator, NULL);
  sos_bochs_printf("  ======= %d processes =======\n", nb_procs);
  sos_bochs_printf("</ps>\n");
}


sos_ret_t sos_process_subsystem_setup()
{

  /* Create the cache for the process structures */
  cache_struct_process = sos_kmem_cache_create("struct_process",
					       sizeof(struct sos_process),
					       3,
					       0,
					       SOS_KSLAB_CREATE_MAP
					       | SOS_KSLAB_CREATE_ZERO);
  if (NULL == cache_struct_process)
    return -SOS_ENOMEM;

  /* Allocate pages for the PID bitmap */
  bitmap_pid = (void*) sos_kmem_vmm_alloc(SOS_PROCESS_PID_BITMAP_NPAGES,
					  SOS_KMEM_VMM_MAP);
  if (NULL == bitmap_pid)
    {
      sos_kmem_cache_destroy(cache_struct_process);
      return -SOS_ENOMEM;
    }

  /* The next process might (and actually will !) have PID 1 */
  next_base_pid = 1;

  /* Create the hash for the process list */
  process_hash = sos_hash_create("pidtable", struct sos_process,
				 NULL, NULL, 37,
				 pid, hlink_pidtable);
  if (NULL == process_hash)
    {
      sos_kmem_cache_destroy(cache_struct_process);
      sos_kmem_vmm_free((sos_vaddr_t)bitmap_pid);
      return -SOS_ENOMEM;
    }

  return SOS_OK;
}


/** Helper function to allocate a PID entry and bind it to the given process */
static sos_ret_t register_process(struct sos_process * proc)
{
  sos_ret_t retval;
  sos_pid_t pid;

  /* First of all: look for a free PID */
  while (TRUE)
    {
      pid = sos_bitmap_ffc(bitmap_pid,
			   SOS_PROCESS_PID_BITMAP_NBITS,
			   next_base_pid);
      if (pid <= 0)
	{
	  if (next_base_pid > 1)
	    {
	      /* try again from the beginning */
	      next_base_pid = 1;
	      continue;
	    }
	  else
	    /* Bad news: no PID left at all ! */
	    return -SOS_EAGAIN;
	}

      if (! sos_bitmap_test_and_set(bitmap_pid, pid))
	/* Could allocate it ! */
	break;
    }

  /* Set the base PID for next process */
  if (pid < SOS_PROCESS_PID_BITMAP_NBITS)
    next_base_pid = pid + 1;
  else
    next_base_pid = 1;
  
  /* Now bind the process into the process hash */
  proc->pid = pid;
  
  retval = sos_hash_insert(process_hash, proc);
  if (SOS_OK != retval)
    {
      /* Bad news: cannot register in hash */
      SOS_ASSERT_FATAL(sos_bitmap_test_and_clear(bitmap_pid, pid));
      return retval;
    }

  return SOS_OK;
}


/** Helper function to deallocate a PID entry and unbind it to the given process */
static sos_ret_t unregister_process(struct sos_process * proc)
{
  SOS_ASSERT_FATAL(SOS_OK == sos_hash_remove(process_hash, proc));
  SOS_ASSERT_FATAL(sos_bitmap_test_and_clear(bitmap_pid, proc->pid));
  proc->pid = 0;
  return SOS_OK;
}


struct sos_process *sos_process_create(const char *name,
				       sos_bool_t do_copy_current_process)
{
  sos_ret_t retval = SOS_OK;
  sos_ui32_t flags;
  struct sos_process *proc;

  proc = (struct sos_process*) sos_kmem_cache_alloc(cache_struct_process, 0);
  if (! proc)
    return NULL;

  /* proc is already filled with 0 (cache has SOS_KSLAB_CREATE_ZERO
     flag) */

  /* Copy the file descriptors when needed */
  if (do_copy_current_process)
    {
      struct sos_process * myself = sos_thread_get_current()->process;
      int fd;

      for (fd = 0 ; fd < SOS_PROCESS_MAX_OPENED_FILES ; fd++)
	if (NULL != myself->fds[fd])
	  {
	    retval = sos_fs_duplicate_opened_file(myself->fds[fd],
						  proc,
						  & proc->fds[fd]);
	    if (SOS_OK != retval)
	      goto end_create_proc;
	  }

      retval = sos_fs_duplicate_opened_file(myself->root,
					    proc,
					    & proc->root);
      if (SOS_OK != retval)
	goto end_create_proc;

      retval = sos_fs_duplicate_opened_file(myself->cwd,
					    proc,
					    & proc->cwd);
      if (SOS_OK != retval)
	goto end_create_proc;
    }

  if (do_copy_current_process)
    {
      struct sos_process * myself = sos_thread_get_current()->process;
      proc->address_space
	= sos_umem_vmm_duplicate_as(sos_process_get_address_space(myself),
				    proc);
    }
  else
    proc->address_space = sos_umem_vmm_create_empty_as(proc);

  if (NULL == proc->address_space)
    {
      /* Error */
      retval = -SOS_ENOMEM;
      goto end_create_proc;
    }

  if (!name)
    {
      struct sos_thread * cur_thr = sos_thread_get_current();
      if (do_copy_current_process)
	name = cur_thr->process->name;
      else
	name = "[UNNAMED]";
    }

  strzcpy(proc->name, name, SOS_PROCESS_MAX_NAMELEN);

  /* Add it to the global list of processes */
  sos_disable_IRQs(flags);
  retval = register_process(proc);
  if (SOS_OK == retval)
    proc->ref_cnt = 1;  /* Mark the process as referenced */
  sos_restore_IRQs(flags);

 end_create_proc:
  if (SOS_OK != retval)
    {
      int fd;

      /* Close the file descriptors */
      for (fd = 0 ; fd < SOS_PROCESS_MAX_OPENED_FILES ; fd++)
	if (NULL != proc->fds[fd])
	  {
	    sos_fs_close(proc->fds[fd]);
	    proc->fds[fd] = NULL;
	  }

      if (proc->root)
	sos_fs_close(proc->root);
      if (proc->cwd)
	sos_fs_close(proc->cwd);
      proc->root = proc->cwd = NULL;

      sos_kmem_cache_free((sos_vaddr_t) proc);
      proc = NULL;
    }

  return proc;
}


inline
sos_ret_t sos_process_ref(struct sos_process *proc)
{
  sos_ui32_t flags;
  sos_disable_IRQs(flags);
  proc->ref_cnt ++;
  sos_restore_IRQs(flags);
  return SOS_OK;
}


sos_pid_t sos_process_get_pid(const struct sos_process *proc)
{
  return proc->pid;
}


sos_count_t sos_process_get_nb_threads(const struct sos_process *proc)
{
  sos_count_t retval;
  sos_ui32_t flags;
  sos_disable_IRQs(flags);
  retval = proc->nb_threads;
  sos_restore_IRQs(flags);
  return retval;
}


struct sos_mm_context *
sos_process_get_mm_context(const struct sos_process *proc)
{
  return sos_umem_vmm_get_mm_context(proc->address_space);
}


struct sos_umem_vmm_as *
sos_process_get_address_space(const struct sos_process *proc)
{
  return proc->address_space;
}


sos_ret_t sos_process_set_address_space(struct sos_process *proc,
					struct sos_umem_vmm_as *new_as)
{
  int fd;

  /* Close the FD that are not allowed to be duplicated */
  for (fd = 0 ; fd < SOS_PROCESS_MAX_OPENED_FILES ; fd++)
    if ( (NULL != proc->fds[fd])
	 && (proc->fds[fd]->open_flags & SOS_FS_OPEN_CLOSEONEXEC) )
      {
	sos_fs_close(proc->fds[fd]);
	proc->fds[fd] = NULL;
      }

  if (proc->address_space)
    {
      sos_ret_t retval = sos_umem_vmm_delete_as(proc->address_space);
      if (SOS_OK != retval)
	return retval;
    }

  proc->address_space = new_as;
  return SOS_OK;
}


struct sos_fs_opened_file *
sos_process_get_root(const struct sos_process *proc)
{
  return proc->root;
}


struct sos_fs_opened_file *
sos_process_get_cwd(const struct sos_process *proc)
{
  return proc->cwd;
}


struct sos_fs_opened_file *
sos_process_get_opened_file(const struct sos_process *proc,
			    int fd)
{
  if ((fd < 0) || (fd >= SOS_PROCESS_MAX_OPENED_FILES))
    return NULL;
  return proc->fds[fd];
}


sos_ret_t
sos_process_chroot(struct sos_process *proc,
		   struct sos_fs_opened_file * new_root,
		   struct sos_fs_opened_file ** old_root)
{
  *old_root = proc->root;
  proc->root = new_root;

  return SOS_OK;
}


sos_ret_t
sos_process_chdir(struct sos_process *proc,
		  struct sos_fs_opened_file * new_cwd,
		  struct sos_fs_opened_file ** old_cwd)
{
  *old_cwd = proc->cwd;
  proc->cwd = new_cwd;

  return SOS_OK;
}


sos_ret_t
sos_process_register_opened_file(struct sos_process *proc,
				 struct sos_fs_opened_file * of,
				 int start_search_at_fd)
{
  int i;
  for (i = start_search_at_fd ;
       i < SOS_PROCESS_MAX_OPENED_FILES ;
       i++)
    if (NULL == proc->fds[i])
      {
	proc->fds[i] = of;
	return i;
      }

  return -SOS_EMFILE;
}


sos_ret_t
sos_process_unregister_opened_file(struct sos_process *proc,
				   int fd)
{  
  if ((fd < 0) || (fd >= SOS_PROCESS_MAX_OPENED_FILES))
    return -SOS_EBADF;

  proc->fds[fd] = NULL;
  return SOS_OK;
}



/* ***************************************************
 * Restricted functions
 */


sos_ret_t sos_process_register_thread(struct sos_process *in_proc,
				      struct sos_thread *thr)
{
  sos_ui32_t flags;

  /* The process is assumed to be referenced by somebody */
  SOS_ASSERT_FATAL(in_proc->ref_cnt > 0);

  /* Only threads that are being created are allowed to be attached to
     a process */
  SOS_ASSERT_FATAL(thr->state == SOS_THR_CREATED);

  /* Update the list of the threads in the process */
  thr->process = in_proc;

  /* Increment the reference count for the process */
  sos_process_ref(in_proc);

  /* Add the thread to the process thread's list */
  sos_disable_IRQs(flags);
  list_add_tail_named(in_proc->thread_list, thr,
		      prev_in_process, next_in_process);
  in_proc->nb_threads ++;
  sos_restore_IRQs(flags);

  return SOS_OK;
}


/** The function responsible for releasing the resources held by the
    process. */
sos_ret_t sos_process_unref(struct sos_process *proc)
{
  sos_ui32_t flags;
  sos_ret_t retval;
  int fd;

  SOS_ASSERT_FATAL(proc->ref_cnt > 0);

  sos_disable_IRQs(flags);
  proc->ref_cnt --;
  if (proc->ref_cnt > 0)
    {
      sos_restore_IRQs(flags);
      return -SOS_EBUSY;
    }
  unregister_process(proc);
  sos_restore_IRQs(flags);

  /* Close the file descriptors */
  for (fd = 0 ; fd < SOS_PROCESS_MAX_OPENED_FILES ; fd++)
    if (NULL != proc->fds[fd])
      {
	sos_fs_close(proc->fds[fd]);
	proc->fds[fd] = NULL;
      }
  
  sos_fs_close(proc->root);
  sos_fs_close(proc->cwd);
  proc->root = proc->cwd = NULL;

  /* First: free the user address space */
  retval = sos_umem_vmm_delete_as(proc->address_space);
  SOS_ASSERT_FATAL(SOS_OK == retval);

  /* Free the process structure */
  sos_kmem_cache_free((sos_vaddr_t)proc);

  return SOS_OK;
}


sos_ret_t sos_process_unregister_thread(struct sos_thread *thr)
{
  sos_ui32_t flags;
  struct sos_process * in_proc = thr->process;

  SOS_ASSERT_FATAL(thr->state == SOS_THR_ZOMBIE);
  
  /* Update the list of the threads in the process */
  thr->process = NULL;
  sos_disable_IRQs(flags);
  list_delete_named(in_proc->thread_list, thr,
		    prev_in_process, next_in_process);
  SOS_ASSERT_FATAL(in_proc->nb_threads > 0);
  in_proc->nb_threads --;
  sos_restore_IRQs(flags);
 
  /* Unreference the process */
  sos_process_unref(in_proc);

  return SOS_OK;
}


sos_ret_t sos_process_set_name(struct sos_process * proc,
			       const char * new_name)
{
  strzcpy(proc->name, new_name, SOS_PROCESS_MAX_NAMELEN);
  return SOS_OK;
}