gems-kernel/source/THIRDPARTY/xnu/bsd/sys/dtrace_ptss.h
2024-06-03 11:29:39 -05:00

105 lines
4.2 KiB
C

/*
* Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*/
#ifndef _DTRACE_PTSS_H_
#define _DTRACE_PTSS_H_
#ifdef __cplusplus
extern "C" {
#endif
/*
* The pid provider needs a small per thread scratch space,
* in the address space of the user task. This code is used to
* manage that space.
*
* High level design:
*
* To avoid serialization, this is a (mostly) lockless allocator. If
* a new page has to be allocated, the process's sprlock will be acquired.
*
* NOTE: The dtrace copyin/copyout code is still the shared code that
* can handle unmapped pages, so the scratch space isn't wired for now.
* * Each page in user space is wired. It cannot be paged out, because
* * dtrace's copyin/copyout is only guaranteed to handle pages already
* * in memory.
*
* Each page in user space is represented by a dt_ptss_page. Page entries
* are chained. Once allocated, a page is not freed until dtrace "cleans up"
* that process.
*
* Clean up works like this:
*
* At process exit, free all kernel allocated memory, but ignore user pages.
* At process exec, free all kernel allocated memory, but ignore user pages.
* At process fork, free user pages copied from parent, and do not allocate kernel memory.
*
* This is making the assumption that it is faster to let the bulk vm_map
* operations in exec/exit do their work, instead of explicit page free(s)
* via mach_vm_deallocate.
*
* As each page is allocated, its entries are chained and added to the
* free_list. To claim an entry, cas it off the list. When a thread exits,
* cas its entry onto the list. We could potentially optimize this by
* keeping a head/tail, and cas'ing the frees to the tail instead of the
* head. Without evidence to support such a need, it seems better to keep
* things simple for now.
*/
#define DTRACE_PTSS_SCRATCH_SPACE_PER_THREAD (64)
#define DTRACE_PTSS_ENTRIES_PER_PAGE (PAGE_MAX_SIZE / DTRACE_PTSS_SCRATCH_SPACE_PER_THREAD)
struct dtrace_ptss_page_entry {
struct dtrace_ptss_page_entry* next;
user_addr_t addr;
user_addr_t write_addr;
};
struct dtrace_ptss_page {
struct dtrace_ptss_page* next;
struct dtrace_ptss_page_entry entries[DTRACE_PTSS_ENTRIES_PER_PAGE];
};
struct dtrace_ptss_page_entry* dtrace_ptss_claim_entry(struct proc* p); /* sprlock not held */
struct dtrace_ptss_page_entry* dtrace_ptss_claim_entry_locked(struct proc* p); /* sprlock held */
void dtrace_ptss_release_entry(struct proc* p, struct dtrace_ptss_page_entry* e);
struct dtrace_ptss_page* dtrace_ptss_allocate_page(struct proc* p);
void dtrace_ptss_free_page(struct proc* p, struct dtrace_ptss_page* ptss_page);
void dtrace_ptss_enable(struct proc* p);
void dtrace_ptss_exec_exit(struct proc* p);
void dtrace_ptss_fork(struct proc* parent, struct proc* child);
#ifdef __cplusplus
}
#endif
#endif /* _DTRACE_PTSS_H_ */