Unix/Linux系統調用
accept()函數 Unix/Linux
access()函數 Unix/Linux
acct()函數 Unix/Linux
add_key()函數 Unix/Linux
adjtimex()函數 Unix/Linux
afs_syscall()函數 Unix/Linux
alarm()函數 Unix/Linux
alloc_hugepages()函數 Unix/Linux
arch_prctl()函數 Unix/Linux
bdflush()函數 Unix/Linux
bind()函數 Unix/Linux
break未實現 Unix/Linux
brk()函數 Unix/Linux
cacheflush()函數 Unix/Linux
chdir()函數 Unix/Linux
chmod()函數 Unix/Linux
chown()函數 Unix/Linux
chroot()函數 Unix/Linux
clone()函數 Unix/Linux
close()函數 Unix/Linux
connect()函數 Unix/Linux
create_module()函數 Unix/Linux
open()函數 Unix/Linux
dup2()函數 Unix/Linux
dup()函數 Unix/Linux
epoll_create()函數 Unix/Linux
epoll_ctl()函數 Unix/Linux
epoll_wait()函數 Unix/Linux
execve()函數 Unix/Linux
exit_group函數 Unix/Linux
_exit()函數 Unix/Linux
exit()函數 Unix/Linux
faccessat()函數 Unix/Linux
fattach()函數 Unix/Linux
fchdir()函數 Unix/Linux
fchmodat()函數 Unix/Linux
fchmod()函數 Unix/Linux
fchownat()函數 Unix/Linux
fchown()函數 Unix/Linux
fcntl()函數 Unix/Linux
fdatasync()函數 Unix/Linux
fdetach()函數 Unix/Linux
flock()函數 Unix/Linux
fork()函數 Unix/Linux
alloc_hugepages()函數 Unix/Linux
fstatat()函數 Unix/Linux
statfs()函數 Unix/Linux
stat()函數 Unix/Linux
statvfs()函數 Unix/Linux
fsync()函數 Unix/Linux
truncate()函數 Unix/Linux
futex()函數 Unix/Linux
futimesat()函數 Unix/Linux
getcontext()函數 Unix/Linux
getcwd()函數 Unix/Linux
getdents()函數 Unix/Linux
getdomainname()函數 Unix/Linux
getdtablesize()函數 Unix/Linux
getgid()函數 Unix/Linux
getuid()函數 Unix/Linux
getgroups()函數 Unix/Linux
getgroups()函數 Unix/Linux
gethostname()函數 Unix/Linux
getitimer()函數 Unix/Linux
get_kernel_syms()函數 Unix/Linux
unimplemented()函數 Unix/Linux
getpagesize()函數 Unix/Linux
getpeername()函數 Unix/Linux
setpgid()函數 Unix/Linux
getpgrp()函數 Unix/Linux
getpid()函數 Unix/Linux
getpmsg()函數 Unix/Linux
getppid()函數 Unix/Linux
getpriority()函數 Unix/Linux
getresuid()函數 Unix/Linux
getrlimit()函數 Unix/Linux
get_robust_list()函數 Unix/Linux
getrusage()函數 Unix/Linux
getsid()函數 Unix/Linux
getsockname()函數 Unix/Linux
getsockopt()函數 Unix/Linux
get_thread_area()函數 Unix/Linux
gettid()函數 Unix/Linux
gettimeofday()函數 Unix/Linux
getuid()函數 Unix/Linux
getunwind()函數 Unix/Linux
gtty()函數 Unix/Linux
idle()函數 Unix/Linux
outb()函數 Unix/Linux
inb_p()函數 Unix/Linux
inl()函數 Unix/Linux
inl_p()函數 Unix/Linux
inotify_add_watch()函數 Unix/Linux
inotify_init()函數 Unix/Linux
inotify_rm_watch()函數 Unix/Linux
outb()函數 Unix/Linux
insl()函數 Unix/Linux
insw()函數 Unix/Linux
intro()函數 Unix/Linux
inw()函數 Unix/Linux
inw_p()函數 Unix/Linux
io_cancel()函數 Unix/Linux
ioctl()函數 Unix/Linux
ioctl_list()函數 Unix/Linux
io_destroy()函數 Unix/Linux
io_getevents()函數 Unix/Linux
ioperm()函數 Unix/Linux
iopl()函數 Unix/Linux
ioprio_set()函數 Unix/Linux
io_setup()函數 Unix/Linux
io_submit()函數 Unix/Linux
ipc()函數 Unix/Linux
isastream()函數 Unix/Linux
kexec_load()函數 Unix/Linux
keyctl()函數 Unix/Linux
kill()函數 Unix/Linux
killpg()函數 Unix/Linux
lchown()函數 Unix/Linux
linkat()函數 Unix/Linux
link()函數 Unix/Linux
listen()函數 Unix/Linux
_llseek()函數 Unix/Linux
llseek()函數 Unix/Linux
lock()函數 Unix/Linux
lookup_dcookie()函數 Unix/Linux
lseek()函數 Unix/Linux
lstat()函數 Unix/Linux
madvise()函數 Unix/Linux
mincore()函數 Unix/Linux
mkdirat()函數 Unix/Linux
mkdir()函數 Unix/Linux
mknod()函數 Unix/Linux
mlockall()函數 Unix/Linux
mlock()函數 Unix/Linux
mmap2()函數 Unix/Linux
mmap()函數 Unix/Linux
modify_ldt()函數 Unix/Linux
mount()函數 Unix/Linux
move_pages()函數 Unix/Linux
mprotect()函數 Unix/Linux
mpx()函數 Unix/Linux
mq_getsetattr()函數 Unix/Linux
mremap()函數 Unix/Linux
msgctl()函數 Unix/Linux
msgget()函數 Unix/Linux
msgop()函數 Unix/Linux
msgsnd()函數 Unix/Linux
msync()函數 Unix/Linux
multiplexer()函數 Unix/Linux
munlockall()函數 Unix/Linux
munlock()函數 Unix/Linux
munmap()函數 Unix/Linux
nanosleep()函數 Unix/Linux
_newselect()函數 Unix/Linux
nfsservctl()函數 Unix/Linux
nice()函數 Unix/Linux
obsolete()函數 Unix/Linux
oldfstat()函數 Unix/Linux
oldlstat()函數 Unix/Linux
oldolduname()函數 Unix/Linux
oldstat()函數 Unix/Linux
olduname()函數 Unix/Linux
openat()函數 Unix/Linux
open()函數 Unix/Linux
outb()函數 Unix/Linux
outb_p()函數 Unix/Linux
outsb()函數 Unix/Linux
outsl()函數 Unix/Linux
outsw()函數 Unix/Linux
outw()函數 Unix/Linux
outw_p()函數 Unix/Linux
path_resolution()函數 Unix/Linux
pause()函數 Unix/Linux
perfmonctl()函數 Unix/Linux
personality()函數 Unix/Linux
pipe()函數 Unix/Linux
pivot_root()函數 Unix/Linux
poll()函數 Unix/Linux
posix_fadvise()函數 Unix/Linux
ppoll()函數 Unix/Linux
prctl()函數 Unix/Linux
pread()函數 Unix/Linux
prof()函數 Unix/Linux
pselect()函數 Unix/Linux
ptrace()函數 Unix/Linux
putmsg()函數 Unix/Linux
putpmsg()函數 Unix/Linux
pwrite()函數 Unix/Linux
query_module()函數 Unix/Linux
quotactl()函數 Unix/Linux
readahead()函數 Unix/Linux
readdir()函數 Unix/Linux
read()函數 Unix/Linux
readlinkat()函數 Unix/Linux
readlink()函數 Unix/Linux
readv()函數 Unix/Linux
reboot()函數 Unix/Linux
recvfrom()函數 Unix/Linux
recv()函數 Unix/Linux
recvmsg()函數 Unix/Linux
remap_file_pages()函數 Unix/Linux
renameat()函數 Unix/Linux
rename()函數 Unix/Linux
request_key()函數 Unix/Linux
rmdir()函數 Unix/Linux
sbrk()函數 Unix/Linux
sched_setaffinity()函數 Unix/Linux
sched_getparam()函數 Unix/Linux
sched_get_priority_max()函數 Unix/Linux
sched_get_priority_min()函數 Unix/Linux
sched_setscheduler()函數 Unix/Linux
sched_rr_get_interval()函數 Unix/Linux
sched_setparam()函數 Unix/Linux
sched_yield()函數 Unix/Linux
security()函數 Unix/Linux
select()函數 Unix/Linux
select_tut()函數 Unix/Linux
semctl()函數 Unix/Linux

mlockall()函數 Unix/Linux

mlock, munlock, mlockall, munlockall - 鎖定和解鎖內存

內容簡介

#include <sys/mman.h>

int mlock(const void **addr*, size_t len**);**

int munlock(const void **addr*, size_t len**);**

int mlockall(int flags**);**

int munlockall(void);

描述

mlock () and  mlockall () respectively lock part or all of the calling process’s virtual address space into RAM, preventing that memory from being paged to the swap area. munlock () and  munlockall () perform the converse operation, respectively unlocking part or all of the calling process’s virtual address space, so that pages in the specified virtual address range may once more to be swapped out if required by the kernel memory manager. Memory locking and unlocking are performed in units of whole pages.

mlock() and munlock()

mlock () locks pages in the address range starting at  addr  and continuing for  len  bytes. All pages that contain a part of the specified address range are guaranteed to be resident in RAM when the call returns successfully; the pages are guaranteed to stay in RAM until later unlocked.

munlock() unlocks pages in the address range starting at addr and continuing for lenbytes. After this call, all pages that contain a part of the specified memory range can be moved to external swap space again by the kernel.

mlockall() and munlockall()

mlockall () locks all pages mapped into the address space of the calling process. This includes the pages of the code, data and stack segment, as well as shared libraries, user space kernel data, shared memory, and memory-mapped files. All mapped pages are guaranteed to be resident in RAM when the call returns successfully; the pages are guaranteed to stay in RAM until later unlocked.

The flags argument is constructed as the bitwise OR of one or more of the following constants:

標籤

描述

MCL_CURRENT

Lock all pages which are currently mapped into the address space of the process.

MCL_FUTURE

Lock all pages which will become mapped into the address space of the process in the future. These could be for instance new pages required by a growing heap and stack as well as new memory mapped files or shared memory regions.

If  MCL_FUTURE  has been specified, then a later system call (e.g.,  mmap (2),  sbrk (2), malloc (3)), may fail if it would cause the number of locked bytes to exceed the permitted maximum (see below). In the same circumstances, stack growth may likewise fail: the kernel will deny stack expansion and deliver a  SIGSEGV  signal to the process.

munlockall() unlocks all pages mapped into the address space of the calling process.

注意

Memory locking has two main applications: real-time algorithms and high-security data processing. Real-time applications require deterministic timing, and, like scheduling, paging is one major cause of unexpected program execution delays. Real-time applications will usually also switch to a real-time scheduler with sched_setscheduler (2). Cryptographic security software often handles critical bytes like passwords or secret keys as data structures. As a result of paging, these secrets could be transferred onto a persistent swap store medium, where they might be accessible to the enemy long after the security software has erased the secrets in RAM and terminated. (But be aware that the suspend mode on laptops and some desktop computers will save a copy of the system’s RAM to disk, regardless of memory locks.)

Real-time processes that are using mlockall() to prevent delays on page faults should reserve enough locked stack pages before entering the time-critical section, so that no page fault can be caused by function calls. This can be achieved by calling a function that allocates a sufficiently large automatic variable (an array) and writes to the memory occupied by this array in order to touch these stack pages. This way, enough pages will be mapped for the stack and can be locked into RAM. The dummy writes ensure that not even copy-on-write page faults can occur in the critical section.

Memory locks are not inherited by a child created via fork(2) and are automatically removed (unlocked) during an execve(2) or when the process terminates.

The memory lock on an address range is automatically removed if the address range is unmapped via munmap(2).

Memory locks do not stack, i.e., pages which have been locked several times by calls tomlock() or mlockall() will be unlocked by a single call to munlock() for the corresponding range or by munlockall(). Pages which are mapped to several locations or by several processes stay locked into RAM as long as they are locked at least at one location or by at least one process.

LINUX 注意事項

Under Linux,  mlock () and  munlock () automatically round  addr  down to the nearest page boundary. However, POSIX.1-2001 allows an implementation to require that  addr  is page aligned, so portable applications should ensure this.

限額和權限

In Linux 2.6.8 and earlier, a process must be privileged ( CAP_IPC_LOCK ) in order to lock memory and the  RLIMIT_MEMLOCK  soft resource limit defines a limit on how much memory the process may lock.

Since Linux 2.6.9, no limits are placed on the amount of memory that a privileged process can lock and the RLIMIT_MEMLOCK soft resource limit instead defines a limit on how much memory an unprivileged process may lock.

返回值

On success these system calls return 0. On error, -1 is returned,  errno  is set appropriately, and no changes are made to any locks in the address space of the process.

錯誤

標籤

描述

ENOMEM

(Linux 2.6.9 and later) the caller had a non-zeroRLIMIT_MEMLOCK soft resource limit, but tried to lock more memory than the limit permitted. This limit is not enforced if the process is privileged (CAP_IPC_LOCK).

ENOMEM

(Linux 2.4 and earlier) the calling process tried to lock more than half of RAM.

EPERM

(Linux 2.6.9 and later) the caller was not privileged (CAP_IPC_LOCK) and its RLIMIT_MEMLOCK soft resource limit was 0.

EPERM

(Linux 2.6.8 and earlier) The calling process has insufficient privilege to call munlockall(). Under Linux the CAP_IPC_LOCKcapability is required.

For mlock() and munlock():

EINVAL

len was negative.

EINVAL

(Not on Linux) addr was not a multiple of the page size.

ENOMEM

Some of the specified address range does not correspond to mapped pages in the address space of the process.

For mlockall():

EINVAL

Unknown flags were specified.

For munlockall():

EPERM

(Linux 2.6.8 and earlier) The caller was not privileged (CAP_IPC_LOCK).

BUGS

In the 2.4 series Linux kernels up to and including 2.4.17, a bug caused the  mlockall () MCL_FUTURE  flag to be inherited across a  fork (2). This was rectified in kernel 2.4.18.

Since kernel 2.6.9, if a privileged process calls mlockall(MCL_FUTURE) and later drops privileges (loses the CAP_IPC_LOCK capability by, for example, setting its effective UID to a non-zero value), then subsequent memory allocations (e.g., mmap(2), brk(2)) will fail if the RLIMIT_MEMLOCK resource limit is encountered.

可用性

On POSIX systems on which  mlock () and  munlock () are available, _POSIX_MEMLOCK_RANGE  is defined in <unistd.h> and the number of bytes in a page can be determined from the constant  PAGESIZE  (if defined) in <limits.h> or by calling  sysconf(_SC_PAGESIZE) .

On POSIX systems on which mlockall() and munlockall() are available,_POSIX_MEMLOCK is defined in <unistd.h> to a value greater than 0. (See alsosysconf(3).)

遵循於

POSIX.1-2001, SVr4

另請參閱

  • mmap (2)

  • shmctl (2)

  • setrlimit (2)