src/svm/ssvm.c - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2015-2019 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 #include <svm/ssvm.h>
 #include <svm/svm_common.h>

 typedef int (*init_fn) (ssvm_private_t *);
 typedef void (*delete_fn) (ssvm_private_t *);

 static init_fn master_init_fns[SSVM_N_SEGMENT_TYPES] =
   { ssvm_master_init_shm, ssvm_master_init_memfd, ssvm_master_init_private };
 static init_fn slave_init_fns[SSVM_N_SEGMENT_TYPES] =
   { ssvm_slave_init_shm, ssvm_slave_init_memfd, ssvm_slave_init_private };
 static delete_fn delete_fns[SSVM_N_SEGMENT_TYPES] =
   { ssvm_delete_shm, ssvm_delete_memfd, ssvm_delete_private };

 int
 ssvm_master_init_shm (ssvm_private_t * ssvm)
 {
   int ssvm_fd;
 #if USE_DLMALLOC == 0
   int mh_flags = MHEAP_FLAG_DISABLE_VM | MHEAP_FLAG_THREAD_SAFE;
 #endif
   clib_mem_vm_map_t mapa = { 0 };
   u8 junk = 0, *ssvm_filename;
   ssvm_shared_header_t *sh;
   uword page_size, requested_va = 0;
   void *oldheap;

   if (ssvm->ssvm_size == 0)
     return SSVM_API_ERROR_NO_SIZE;

   if (CLIB_DEBUG > 1)
     clib_warning ("[%d] creating segment '%s'", getpid (), ssvm->name);

   ASSERT (vec_c_string_is_terminated (ssvm->name));
   ssvm_filename = format (0, "/dev/shm/%s%c", ssvm->name, 0);
   unlink ((char *) ssvm_filename);
   vec_free (ssvm_filename);

   ssvm_fd = shm_open ((char *) ssvm->name, O_RDWR | O_CREAT | O_EXCL, 0777);
   if (ssvm_fd < 0)
     {
       clib_unix_warning ("create segment '%s'", ssvm->name);
       return SSVM_API_ERROR_CREATE_FAILURE;
     }

   if (fchmod (ssvm_fd, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP) < 0)
     clib_unix_warning ("ssvm segment chmod");
   if (svm_get_root_rp ())
     {
       /* TODO: is this really needed? */
       svm_main_region_t *smr = svm_get_root_rp ()->data_base;
       if (fchown (ssvm_fd, smr->uid, smr->gid) < 0)
 	clib_unix_warning ("ssvm segment chown");
     }

   if (lseek (ssvm_fd, ssvm->ssvm_size, SEEK_SET) < 0)
     {
       clib_unix_warning ("lseek");
       close (ssvm_fd);
       return SSVM_API_ERROR_SET_SIZE;
     }

   if (write (ssvm_fd, &junk, 1) != 1)
     {
       clib_unix_warning ("set ssvm size");
       close (ssvm_fd);
       return SSVM_API_ERROR_SET_SIZE;
     }

   page_size = clib_mem_get_fd_page_size (ssvm_fd);
   if (ssvm->requested_va)
     {
       requested_va = ssvm->requested_va;
       clib_mem_vm_randomize_va (&requested_va, min_log2 (page_size));
     }

   mapa.requested_va = requested_va;
   mapa.size = ssvm->ssvm_size;
   mapa.fd = ssvm_fd;
   if (clib_mem_vm_ext_map (&mapa))
     {
       clib_unix_warning ("mmap");
       close (ssvm_fd);
       return SSVM_API_ERROR_MMAP;
     }
   close (ssvm_fd);

   sh = mapa.addr;
   sh->master_pid = ssvm->my_pid;
   sh->ssvm_size = ssvm->ssvm_size;
   sh->ssvm_va = pointer_to_uword (sh);
   sh->type = SSVM_SEGMENT_SHM;
 #if USE_DLMALLOC == 0
   sh->heap = mheap_alloc_with_flags (((u8 *) sh) + page_size,
 				     ssvm->ssvm_size - page_size, mh_flags);
 #else
   sh->heap = create_mspace_with_base (((u8 *) sh) + page_size,
 				      ssvm->ssvm_size - page_size,
 				      1 /* locked */ );
   mspace_disable_expand (sh->heap);
 #endif

   oldheap = ssvm_push_heap (sh);
   sh->name = format (0, "%s", ssvm->name, 0);
   ssvm_pop_heap (oldheap);

   ssvm->sh = sh;
   ssvm->my_pid = getpid ();
   ssvm->i_am_master = 1;

   /* The application has to set set sh->ready... */
   return 0;
 }

 int
 ssvm_slave_init_shm (ssvm_private_t * ssvm)
 {
   struct stat stat;
   int ssvm_fd = -1;
   ssvm_shared_header_t *sh;

   ASSERT (vec_c_string_is_terminated (ssvm->name));
   ssvm->i_am_master = 0;

   while (ssvm->attach_timeout-- > 0)
     {
       if (ssvm_fd < 0)
 	ssvm_fd = shm_open ((char *) ssvm->name, O_RDWR, 0777);
       if (ssvm_fd < 0)
 	{
 	  sleep (1);
 	  continue;
 	}
       if (fstat (ssvm_fd, &stat) < 0)
 	{
 	  sleep (1);
 	  continue;
 	}

       if (stat.st_size > 0)
 	goto map_it;
     }
   clib_warning ("slave timeout");
   return SSVM_API_ERROR_SLAVE_TIMEOUT;

 map_it:
   sh = (void *) mmap (0, MMAP_PAGESIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
 		      ssvm_fd, 0);
   if (sh == MAP_FAILED)
     {
       clib_unix_warning ("slave research mmap");
       close (ssvm_fd);
       return SSVM_API_ERROR_MMAP;
     }

   while (ssvm->attach_timeout-- > 0)
     {
       if (sh->ready)
 	goto re_map_it;
     }
   close (ssvm_fd);
   munmap (sh, MMAP_PAGESIZE);
   clib_warning ("slave timeout 2");
   return SSVM_API_ERROR_SLAVE_TIMEOUT;

 re_map_it:
   ssvm->requested_va = sh->ssvm_va;
   ssvm->ssvm_size = sh->ssvm_size;
   munmap (sh, MMAP_PAGESIZE);

   sh = ssvm->sh = (void *) mmap ((void *) ssvm->requested_va, ssvm->ssvm_size,
 				 PROT_READ | PROT_WRITE,
 				 MAP_SHARED | MAP_FIXED, ssvm_fd, 0);

   if (sh == MAP_FAILED)
     {
       clib_unix_warning ("slave final mmap");
       close (ssvm_fd);
       return SSVM_API_ERROR_MMAP;
     }
   sh->slave_pid = getpid ();
   return 0;
 }

 void
 ssvm_delete_shm (ssvm_private_t * ssvm)
 {
   u8 *fn;

   fn = format (0, "/dev/shm/%s%c", ssvm->name, 0);

   if (CLIB_DEBUG > 1)
     clib_warning ("[%d] unlinking ssvm (%s) backing file '%s'", getpid (),
 		  ssvm->name, fn);

   /* Throw away the backing file */
   if (unlink ((char *) fn) < 0)
     clib_unix_warning ("unlink segment '%s'", ssvm->name);

   vec_free (fn);
   vec_free (ssvm->name);

   munmap ((void *) ssvm->requested_va, ssvm->ssvm_size);
 }

 /**
  * Initialize memfd segment master
  */
 int
 ssvm_master_init_memfd (ssvm_private_t * memfd)
 {
   uword page_size;
   ssvm_shared_header_t *sh;
   void *oldheap;
   clib_mem_vm_alloc_t alloc = { 0 };
   clib_error_t *err;

   if (memfd->ssvm_size == 0)
     return SSVM_API_ERROR_NO_SIZE;

   ASSERT (vec_c_string_is_terminated (memfd->name));

   alloc.name = (char *) memfd->name;
   alloc.size = memfd->ssvm_size;
   alloc.flags = CLIB_MEM_VM_F_SHARED;
   alloc.requested_va = memfd->requested_va;
   if ((err = clib_mem_vm_ext_alloc (&alloc)))
     {
       clib_error_report (err);
       return SSVM_API_ERROR_CREATE_FAILURE;
     }

   memfd->fd = alloc.fd;
   memfd->sh = (ssvm_shared_header_t *) alloc.addr;
   memfd->my_pid = getpid ();
   memfd->i_am_master = 1;

   page_size = 1ull << alloc.log2_page_size;
   sh = memfd->sh;
   sh->master_pid = memfd->my_pid;
   sh->ssvm_size = memfd->ssvm_size;
   sh->ssvm_va = pointer_to_uword (sh);
   sh->type = SSVM_SEGMENT_MEMFD;

 #if USE_DLMALLOC == 0
   uword flags = MHEAP_FLAG_DISABLE_VM | MHEAP_FLAG_THREAD_SAFE;

   sh->heap = mheap_alloc_with_flags (((u8 *) sh) + page_size,
 				     memfd->ssvm_size - page_size, flags);
 #else
   sh->heap = create_mspace_with_base (((u8 *) sh) + page_size,
 				      memfd->ssvm_size - page_size,
 				      1 /* locked */ );
   mspace_disable_expand (sh->heap);
 #endif
   oldheap = ssvm_push_heap (sh);
   sh->name = format (0, "%s", memfd->name, 0);
   ssvm_pop_heap (oldheap);

   /* The application has to set set sh->ready... */
   return 0;
 }

 /**
  * Initialize memfd segment slave
  *
  * Subtly different than svm_slave_init. The caller needs to acquire
  * a usable file descriptor for the memfd segment e.g. via
  * vppinfra/socket.c:default_socket_recvmsg
  */
 int
 ssvm_slave_init_memfd (ssvm_private_t * memfd)
 {
   clib_mem_vm_map_t mapa = { 0 };
   ssvm_shared_header_t *sh;
   uword page_size;

   memfd->i_am_master = 0;

   page_size = clib_mem_get_fd_page_size (memfd->fd);
   if (!page_size)
     {
       clib_unix_warning ("page size unknown");
       return SSVM_API_ERROR_MMAP;
     }

   /*
    * Map the segment once, to look at the shared header
    */
   mapa.fd = memfd->fd;
   mapa.size = page_size;

   if (clib_mem_vm_ext_map (&mapa))
     {
       clib_unix_warning ("slave research mmap (fd %d)", mapa.fd);
       close (memfd->fd);
       return SSVM_API_ERROR_MMAP;
     }

   sh = mapa.addr;
   memfd->requested_va = sh->ssvm_va;
   memfd->ssvm_size = sh->ssvm_size;
   clib_mem_vm_free (sh, page_size);

   /*
    * Remap the segment at the 'right' address
    */
   mapa.requested_va = memfd->requested_va;
   mapa.size = memfd->ssvm_size;
   if (clib_mem_vm_ext_map (&mapa))
     {
       clib_unix_warning ("slave final mmap");
       close (memfd->fd);
       return SSVM_API_ERROR_MMAP;
     }

   sh = mapa.addr;
   sh->slave_pid = getpid ();
   memfd->sh = sh;
   return 0;
 }

 void
 ssvm_delete_memfd (ssvm_private_t * memfd)
 {
   vec_free (memfd->name);
   clib_mem_vm_free (memfd->sh, memfd->ssvm_size);
   close (memfd->fd);
 }

 /**
  * Initialize segment in a private heap
  */
 int
 ssvm_master_init_private (ssvm_private_t * ssvm)
 {
   ssvm_shared_header_t *sh;
   u32 pagesize = clib_mem_get_page_size ();
   u32 rnd_size = 0;
   u8 *heap;

   rnd_size = (ssvm->ssvm_size + (pagesize - 1)) & ~(pagesize - 1);
   rnd_size = clib_min (rnd_size, ((u64) 1 << 32) - pagesize);

 #if USE_DLMALLOC == 0
   {
     mheap_t *heap_header;

     heap = mheap_alloc (0, rnd_size);
     if (heap == 0)
       {
 	clib_unix_warning ("mheap alloc");
 	return -1;
       }
     heap_header = mheap_header (heap);
     heap_header->flags |= MHEAP_FLAG_THREAD_SAFE;
   }
 #else
   heap = create_mspace (rnd_size, 1 /* locked */ );
 #endif

   ssvm->ssvm_size = rnd_size;
   ssvm->i_am_master = 1;
   ssvm->my_pid = getpid ();
   ssvm->requested_va = ~0;

   /* Allocate a [sic] shared memory header, in process memory... */
   sh = clib_mem_alloc_aligned (sizeof (*sh), CLIB_CACHE_LINE_BYTES);
   ssvm->sh = sh;

   clib_memset (sh, 0, sizeof (*sh));
   sh->heap = heap;
   sh->ssvm_va = pointer_to_uword (heap);
   sh->type = SSVM_SEGMENT_PRIVATE;

   return 0;
 }

 int
 ssvm_slave_init_private (ssvm_private_t * ssvm)
 {
   clib_warning ("BUG: this should not be called!");
   return -1;
 }

 void
 ssvm_delete_private (ssvm_private_t * ssvm)
 {
   vec_free (ssvm->name);
 #if USE_DLMALLOC == 0
   mheap_free (ssvm->sh->heap);
 #else
   destroy_mspace (ssvm->sh->heap);
 #endif
   clib_mem_free (ssvm->sh);
 }

 int
 ssvm_master_init (ssvm_private_t * ssvm, ssvm_segment_type_t type)
 {
   return (master_init_fns[type]) (ssvm);
 }

 int
 ssvm_slave_init (ssvm_private_t * ssvm, ssvm_segment_type_t type)
 {
   return (slave_init_fns[type]) (ssvm);
 }

 void
 ssvm_delete (ssvm_private_t * ssvm)
 {
   delete_fns[ssvm->sh->type] (ssvm);
 }

 ssvm_segment_type_t
 ssvm_type (const ssvm_private_t * ssvm)
 {
   return ssvm->sh->type;
 }

 u8 *
 ssvm_name (const ssvm_private_t * ssvm)
 {
   return ssvm->sh->name;
 }

 /*
  * fd.io coding-style-patch-verification: ON
  *
  * Local Variables:
  * eval: (c-set-style "gnu")
  * End:
  */
	/*
	* Copyright (c) 2015-2019 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at:
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	#include <svm/ssvm.h>
	#include <svm/svm_common.h>

	typedef int (init_fn) (ssvm_private_t );
	typedef void (delete_fn) (ssvm_private_t );

	static init_fn master_init_fns[SSVM_N_SEGMENT_TYPES] =
	{ ssvm_master_init_shm, ssvm_master_init_memfd, ssvm_master_init_private };
	static init_fn slave_init_fns[SSVM_N_SEGMENT_TYPES] =
	{ ssvm_slave_init_shm, ssvm_slave_init_memfd, ssvm_slave_init_private };
	static delete_fn delete_fns[SSVM_N_SEGMENT_TYPES] =
	{ ssvm_delete_shm, ssvm_delete_memfd, ssvm_delete_private };

	int
	ssvm_master_init_shm (ssvm_private_t * ssvm)
	{
	int ssvm_fd;
	#if USE_DLMALLOC == 0
	int mh_flags = MHEAP_FLAG_DISABLE_VM \| MHEAP_FLAG_THREAD_SAFE;
	#endif
	clib_mem_vm_map_t mapa = { 0 };
	u8 junk = 0, *ssvm_filename;
	ssvm_shared_header_t *sh;
	uword page_size, requested_va = 0;
	void *oldheap;

	if (ssvm->ssvm_size == 0)
	return SSVM_API_ERROR_NO_SIZE;

	if (CLIB_DEBUG > 1)
	clib_warning ("[%d] creating segment '%s'", getpid (), ssvm->name);

	ASSERT (vec_c_string_is_terminated (ssvm->name));
	ssvm_filename = format (0, "/dev/shm/%s%c", ssvm->name, 0);
	unlink ((char *) ssvm_filename);
	vec_free (ssvm_filename);

	ssvm_fd = shm_open ((char *) ssvm->name, O_RDWR \| O_CREAT \| O_EXCL, 0777);
	if (ssvm_fd < 0)
	{
	clib_unix_warning ("create segment '%s'", ssvm->name);
	return SSVM_API_ERROR_CREATE_FAILURE;
	}

	if (fchmod (ssvm_fd, S_IRUSR \| S_IWUSR \| S_IRGRP \| S_IWGRP) < 0)
	clib_unix_warning ("ssvm segment chmod");
	if (svm_get_root_rp ())
	{
	/* TODO: is this really needed? */
	svm_main_region_t *smr = svm_get_root_rp ()->data_base;
	if (fchown (ssvm_fd, smr->uid, smr->gid) < 0)
	clib_unix_warning ("ssvm segment chown");
	}

	if (lseek (ssvm_fd, ssvm->ssvm_size, SEEK_SET) < 0)
	{
	clib_unix_warning ("lseek");
	close (ssvm_fd);
	return SSVM_API_ERROR_SET_SIZE;
	}

	if (write (ssvm_fd, &junk, 1) != 1)
	{
	clib_unix_warning ("set ssvm size");
	close (ssvm_fd);
	return SSVM_API_ERROR_SET_SIZE;
	}

	page_size = clib_mem_get_fd_page_size (ssvm_fd);
	if (ssvm->requested_va)
	{
	requested_va = ssvm->requested_va;
	clib_mem_vm_randomize_va (&requested_va, min_log2 (page_size));
	}

	mapa.requested_va = requested_va;
	mapa.size = ssvm->ssvm_size;
	mapa.fd = ssvm_fd;
	if (clib_mem_vm_ext_map (&mapa))
	{
	clib_unix_warning ("mmap");
	close (ssvm_fd);
	return SSVM_API_ERROR_MMAP;
	}
	close (ssvm_fd);

	sh = mapa.addr;
	sh->master_pid = ssvm->my_pid;
	sh->ssvm_size = ssvm->ssvm_size;
	sh->ssvm_va = pointer_to_uword (sh);
	sh->type = SSVM_SEGMENT_SHM;
	#if USE_DLMALLOC == 0
	sh->heap = mheap_alloc_with_flags (((u8 *) sh) + page_size,
	ssvm->ssvm_size - page_size, mh_flags);
	#else
	sh->heap = create_mspace_with_base (((u8 *) sh) + page_size,
	ssvm->ssvm_size - page_size,
	1 /* locked */ );
	mspace_disable_expand (sh->heap);
	#endif

	oldheap = ssvm_push_heap (sh);
	sh->name = format (0, "%s", ssvm->name, 0);
	ssvm_pop_heap (oldheap);

	ssvm->sh = sh;
	ssvm->my_pid = getpid ();
	ssvm->i_am_master = 1;

	/* The application has to set set sh->ready... */
	return 0;
	}

	int
	ssvm_slave_init_shm (ssvm_private_t * ssvm)
	{
	struct stat stat;
	int ssvm_fd = -1;
	ssvm_shared_header_t *sh;

	ASSERT (vec_c_string_is_terminated (ssvm->name));
	ssvm->i_am_master = 0;

	while (ssvm->attach_timeout-- > 0)
	{
	if (ssvm_fd < 0)
	ssvm_fd = shm_open ((char *) ssvm->name, O_RDWR, 0777);
	if (ssvm_fd < 0)
	{
	sleep (1);
	continue;
	}
	if (fstat (ssvm_fd, &stat) < 0)
	{
	sleep (1);
	continue;
	}

	if (stat.st_size > 0)
	goto map_it;
	}
	clib_warning ("slave timeout");
	return SSVM_API_ERROR_SLAVE_TIMEOUT;

	map_it:
	sh = (void *) mmap (0, MMAP_PAGESIZE, PROT_READ \| PROT_WRITE, MAP_SHARED,
	ssvm_fd, 0);
	if (sh == MAP_FAILED)
	{
	clib_unix_warning ("slave research mmap");
	close (ssvm_fd);
	return SSVM_API_ERROR_MMAP;
	}

	while (ssvm->attach_timeout-- > 0)
	{
	if (sh->ready)
	goto re_map_it;
	}
	close (ssvm_fd);
	munmap (sh, MMAP_PAGESIZE);
	clib_warning ("slave timeout 2");
	return SSVM_API_ERROR_SLAVE_TIMEOUT;

	re_map_it:
	ssvm->requested_va = sh->ssvm_va;
	ssvm->ssvm_size = sh->ssvm_size;
	munmap (sh, MMAP_PAGESIZE);

	sh = ssvm->sh = (void ) mmap ((void ) ssvm->requested_va, ssvm->ssvm_size,
	PROT_READ \| PROT_WRITE,
	MAP_SHARED \| MAP_FIXED, ssvm_fd, 0);

	if (sh == MAP_FAILED)
	{
	clib_unix_warning ("slave final mmap");
	close (ssvm_fd);
	return SSVM_API_ERROR_MMAP;
	}
	sh->slave_pid = getpid ();
	return 0;
	}

	void
	ssvm_delete_shm (ssvm_private_t * ssvm)
	{
	u8 *fn;

	fn = format (0, "/dev/shm/%s%c", ssvm->name, 0);

	if (CLIB_DEBUG > 1)
	clib_warning ("[%d] unlinking ssvm (%s) backing file '%s'", getpid (),
	ssvm->name, fn);

	/* Throw away the backing file */
	if (unlink ((char *) fn) < 0)
	clib_unix_warning ("unlink segment '%s'", ssvm->name);

	vec_free (fn);
	vec_free (ssvm->name);

	munmap ((void *) ssvm->requested_va, ssvm->ssvm_size);
	}

	/**
	* Initialize memfd segment master
	*/
	int
	ssvm_master_init_memfd (ssvm_private_t * memfd)
	{
	uword page_size;
	ssvm_shared_header_t *sh;
	void *oldheap;
	clib_mem_vm_alloc_t alloc = { 0 };
	clib_error_t *err;

	if (memfd->ssvm_size == 0)
	return SSVM_API_ERROR_NO_SIZE;

	ASSERT (vec_c_string_is_terminated (memfd->name));

	alloc.name = (char *) memfd->name;
	alloc.size = memfd->ssvm_size;
	alloc.flags = CLIB_MEM_VM_F_SHARED;
	alloc.requested_va = memfd->requested_va;
	if ((err = clib_mem_vm_ext_alloc (&alloc)))
	{
	clib_error_report (err);
	return SSVM_API_ERROR_CREATE_FAILURE;
	}

	memfd->fd = alloc.fd;
	memfd->sh = (ssvm_shared_header_t *) alloc.addr;
	memfd->my_pid = getpid ();
	memfd->i_am_master = 1;

	page_size = 1ull << alloc.log2_page_size;
	sh = memfd->sh;
	sh->master_pid = memfd->my_pid;
	sh->ssvm_size = memfd->ssvm_size;
	sh->ssvm_va = pointer_to_uword (sh);
	sh->type = SSVM_SEGMENT_MEMFD;

	#if USE_DLMALLOC == 0
	uword flags = MHEAP_FLAG_DISABLE_VM \| MHEAP_FLAG_THREAD_SAFE;

	sh->heap = mheap_alloc_with_flags (((u8 *) sh) + page_size,
	memfd->ssvm_size - page_size, flags);
	#else
	sh->heap = create_mspace_with_base (((u8 *) sh) + page_size,
	memfd->ssvm_size - page_size,
	1 /* locked */ );
	mspace_disable_expand (sh->heap);
	#endif
	oldheap = ssvm_push_heap (sh);
	sh->name = format (0, "%s", memfd->name, 0);
	ssvm_pop_heap (oldheap);

	/* The application has to set set sh->ready... */
	return 0;
	}

	/**
	* Initialize memfd segment slave
	*
	* Subtly different than svm_slave_init. The caller needs to acquire
	* a usable file descriptor for the memfd segment e.g. via
	* vppinfra/socket.c:default_socket_recvmsg
	*/
	int
	ssvm_slave_init_memfd (ssvm_private_t * memfd)
	{
	clib_mem_vm_map_t mapa = { 0 };
	ssvm_shared_header_t *sh;
	uword page_size;

	memfd->i_am_master = 0;

	page_size = clib_mem_get_fd_page_size (memfd->fd);
	if (!page_size)
	{
	clib_unix_warning ("page size unknown");
	return SSVM_API_ERROR_MMAP;
	}

	/*
	* Map the segment once, to look at the shared header
	*/
	mapa.fd = memfd->fd;
	mapa.size = page_size;

	if (clib_mem_vm_ext_map (&mapa))
	{
	clib_unix_warning ("slave research mmap (fd %d)", mapa.fd);
	close (memfd->fd);
	return SSVM_API_ERROR_MMAP;
	}

	sh = mapa.addr;
	memfd->requested_va = sh->ssvm_va;
	memfd->ssvm_size = sh->ssvm_size;
	clib_mem_vm_free (sh, page_size);

	/*
	* Remap the segment at the 'right' address
	*/
	mapa.requested_va = memfd->requested_va;
	mapa.size = memfd->ssvm_size;
	if (clib_mem_vm_ext_map (&mapa))
	{
	clib_unix_warning ("slave final mmap");
	close (memfd->fd);
	return SSVM_API_ERROR_MMAP;
	}

	sh = mapa.addr;
	sh->slave_pid = getpid ();
	memfd->sh = sh;
	return 0;
	}

	void
	ssvm_delete_memfd (ssvm_private_t * memfd)
	{
	vec_free (memfd->name);
	clib_mem_vm_free (memfd->sh, memfd->ssvm_size);
	close (memfd->fd);
	}

	/**
	* Initialize segment in a private heap
	*/
	int
	ssvm_master_init_private (ssvm_private_t * ssvm)
	{
	ssvm_shared_header_t *sh;
	u32 pagesize = clib_mem_get_page_size ();
	u32 rnd_size = 0;
	u8 *heap;

	rnd_size = (ssvm->ssvm_size + (pagesize - 1)) & ~(pagesize - 1);
	rnd_size = clib_min (rnd_size, ((u64) 1 << 32) - pagesize);

	#if USE_DLMALLOC == 0
	{
	mheap_t *heap_header;

	heap = mheap_alloc (0, rnd_size);
	if (heap == 0)
	{
	clib_unix_warning ("mheap alloc");
	return -1;
	}
	heap_header = mheap_header (heap);
	heap_header->flags \|= MHEAP_FLAG_THREAD_SAFE;
	}
	#else
	heap = create_mspace (rnd_size, 1 /* locked */ );
	#endif

	ssvm->ssvm_size = rnd_size;
	ssvm->i_am_master = 1;
	ssvm->my_pid = getpid ();
	ssvm->requested_va = ~0;

	/* Allocate a [sic] shared memory header, in process memory... */
	sh = clib_mem_alloc_aligned (sizeof (*sh), CLIB_CACHE_LINE_BYTES);
	ssvm->sh = sh;

	clib_memset (sh, 0, sizeof (*sh));
	sh->heap = heap;
	sh->ssvm_va = pointer_to_uword (heap);
	sh->type = SSVM_SEGMENT_PRIVATE;

	return 0;
	}

	int
	ssvm_slave_init_private (ssvm_private_t * ssvm)
	{
	clib_warning ("BUG: this should not be called!");
	return -1;
	}

	void
	ssvm_delete_private (ssvm_private_t * ssvm)
	{
	vec_free (ssvm->name);
	#if USE_DLMALLOC == 0
	mheap_free (ssvm->sh->heap);
	#else
	destroy_mspace (ssvm->sh->heap);
	#endif
	clib_mem_free (ssvm->sh);
	}

	int
	ssvm_master_init (ssvm_private_t * ssvm, ssvm_segment_type_t type)
	{
	return (master_init_fns[type]) (ssvm);
	}

	int
	ssvm_slave_init (ssvm_private_t * ssvm, ssvm_segment_type_t type)
	{
	return (slave_init_fns[type]) (ssvm);
	}

	void
	ssvm_delete (ssvm_private_t * ssvm)
	{
	delete_fns[ssvm->sh->type] (ssvm);
	}

	ssvm_segment_type_t
	ssvm_type (const ssvm_private_t * ssvm)
	{
	return ssvm->sh->type;
	}

	u8 *
	ssvm_name (const ssvm_private_t * ssvm)
	{
	return ssvm->sh->name;
	}

	/*
	* fd.io coding-style-patch-verification: ON
	*
	* Local Variables:
	* eval: (c-set-style "gnu")
	* End:
	*/