bsd/sys/dtrace_ptss.h

   1 /*
   2  * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 #ifndef _DTRACE_PTSS_H_
  30 #define _DTRACE_PTSS_H_
  31
  32 #ifdef  __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 /*
  37  * The pid provider needs a small per thread scratch space,
  38  * in the address space of the user task. This code is used to
  39  * manage that space.
  40  *
  41  * High level design:
  42  *
  43  * To avoid serialization, this is a (mostly) lockless allocator. If
  44  * a new page has to be allocated, the process's sprlock will be acquired.
  45  *
  46  * NOTE: The dtrace copyin/copyout code is still the shared code that
  47  * can handle unmapped pages, so the scratch space isn't wired for now.
  48  * * Each page in user space is wired. It cannot be paged out, because
  49  * * dtrace's copyin/copyout is only guaranteed to handle pages already
  50  * * in memory.
  51  *
  52  * Each page in user space is represented by a dt_ptss_page. Page entries
  53  * are chained. Once allocated, a page is not freed until dtrace "cleans up"
  54  * that process.
  55  *
  56  * Clean up works like this:
  57  *
  58  * At process exit, free all kernel allocated memory, but ignore user pages.
  59  * At process exec, free all kernel allocated memory, but ignore user pages.
  60  * At process fork, free user pages copied from parent, and do not allocate kernel memory.
  61  *
  62  * This is making the assumption that it is faster to let the bulk vm_map
  63  * operations in exec/exit do their work, instead of explicit page free(s)
  64  * via mach_vm_deallocate.
  65  *
  66  * As each page is allocated, its entries are chained and added to the
  67  * free_list. To claim an entry, cas it off the list. When a thread exits,
  68  * cas its entry onto the list. We could potentially optimize this by
  69  * keeping a head/tail, and cas'ing the frees to the tail instead of the
  70  * head. Without evidence to support such a need, it seems better to keep
  71  * things simple for now.
  72  */
  73
  74 #define DTRACE_PTSS_SCRATCH_SPACE_PER_THREAD 64
  75 #define DTRACE_PTSS_ENTRIES_PER_PAGE (PAGE_SIZE / DTRACE_PTSS_SCRATCH_SPACE_PER_THREAD)
  76
  77 struct dtrace_ptss_page_entry {
  78         struct dtrace_ptss_page_entry*  next;
  79         user_addr_t                     addr;
  80 };
  81
  82 struct dtrace_ptss_page {
  83         struct dtrace_ptss_page*       next;
  84         struct dtrace_ptss_page_entry  entries[DTRACE_PTSS_ENTRIES_PER_PAGE];
  85 };
  86
  87 struct dtrace_ptss_page_entry*  dtrace_ptss_claim_entry(struct proc* p); /* sprlock not held */
  88 struct dtrace_ptss_page_entry*  dtrace_ptss_claim_entry_locked(struct proc* p); /* sprlock held */
  89 void                            dtrace_ptss_release_entry(struct proc* p, struct dtrace_ptss_page_entry* e);
  90
  91 struct dtrace_ptss_page*        dtrace_ptss_allocate_page(struct proc* p);
  92 void                            dtrace_ptss_free_page(struct proc* p, struct dtrace_ptss_page* ptss_page);
  93
  94 void                            dtrace_ptss_enable(struct proc* p);
  95 void                            dtrace_ptss_exec_exit(struct proc* p);
  96 void                            dtrace_ptss_fork(struct proc* parent, struct proc* child);
  97
  98 #ifdef  __cplusplus
  99 }
 100 #endif
 101
 102 #endif  /* _DTRACE_PTSS_H_ */
 103