diff options
Diffstat (limited to '')
| -rw-r--r-- | man2/mmap.2 | 62 |
1 files changed, 32 insertions, 30 deletions
diff --git a/man2/mmap.2 b/man2/mmap.2 index 3d9a887..300eb2b 100644 --- a/man2/mmap.2 +++ b/man2/mmap.2 @@ -18,7 +18,7 @@ .\" 2007-07-10, mtk, Added an example program. .\" 2008-11-18, mtk, document MAP_STACK .\" -.TH mmap 2 2023-07-20 "Linux man-pages 6.05.01" +.TH mmap 2 2023-10-31 "Linux man-pages 6.7" .SH NAME mmap, munmap \- map or unmap files or devices into memory .SH LIBRARY @@ -27,13 +27,13 @@ Standard C library .SH SYNOPSIS .nf .B #include <sys/mman.h> -.PP +.P .BI "void *mmap(void " addr [. length "], size_t " length \ ", int " prot ", int " flags , .BI " int " fd ", off_t " offset ); .BI "int munmap(void " addr [. length "], size_t " length ); .fi -.PP +.P See NOTES for information on feature test macro requirements. .SH DESCRIPTION .BR mmap () @@ -44,7 +44,7 @@ The starting address for the new mapping is specified in The .I length argument specifies the length of the mapping (which must be greater than 0). -.PP +.P If .I addr is NULL, @@ -64,7 +64,7 @@ may or may not depend on the hint. .\" Before Linux 2.6.24, the address was rounded up to the next page .\" boundary; since Linux 2.6.24, it is rounded down! The address of the new mapping is returned as the result of the call. -.PP +.P The contents of a file mapping (as opposed to an anonymous mapping; see .B MAP_ANONYMOUS below), are initialized using @@ -76,13 +76,13 @@ in the file (or other object) referred to by the file descriptor .I offset must be a multiple of the page size as returned by .IR sysconf(_SC_PAGE_SIZE) . -.PP +.P After the .BR mmap () call has returned, the file descriptor, .IR fd , can be closed immediately without invalidating the mapping. -.PP +.P The .I prot argument describes the desired memory protection of the mapping @@ -147,7 +147,7 @@ the underlying file. It is unspecified whether changes made to the file after the .BR mmap () call are visible in the mapped region. -.PP +.P Both .B MAP_SHARED and @@ -155,7 +155,7 @@ and are described in POSIX.1-2001 and POSIX.1-2008. .B MAP_SHARED_VALIDATE is a Linux extension. -.PP +.P In addition, zero or more of the following values can be ORed in .IR flags : .TP @@ -299,7 +299,9 @@ See the Linux kernel source file .I Documentation/admin\-guide/mm/hugetlbpage.rst for further information, as well as NOTES, below. .TP -.BR MAP_HUGE_2MB ", " MAP_HUGE_1GB " (since Linux 3.8)" +.B MAP_HUGE_2MB +.TQ +.BR MAP_HUGE_1GB " (since Linux 3.8)" .\" See https://lwn.net/Articles/533499/ Used in conjunction with .B MAP_HUGETLB @@ -443,7 +445,7 @@ option. Because of the security implications, that option is normally enabled only on embedded devices (i.e., devices where one has complete control of the contents of user memory). -.PP +.P Of the above flags, only .B MAP_FIXED is specified in POSIX.1-2001 and POSIX.1-2008. @@ -465,7 +467,7 @@ The region is also automatically unmapped when the process is terminated. On the other hand, closing the file descriptor does not unmap the region. -.PP +.P The address .I addr must be a multiple of the page size (but @@ -488,7 +490,7 @@ On error, the value is returned, and .I errno is set to indicate the error. -.PP +.P On success, .BR munmap () returns 0. @@ -629,13 +631,14 @@ and is not a member of the group; see the description of .I /proc/sys/vm/sysctl_hugetlb_shm_group in +.BR proc_sys (5). .TP .B ETXTBSY .B MAP_DENYWRITE was set but the object specified by .I fd is open for writing. -.PP +.P Use of a mapped region can result in these signals: .TP .B SIGSEGV @@ -662,7 +665,6 @@ T{ .BR munmap () T} Thread safety MT-Safe .TE -.sp 1 .SH VERSIONS On some hardware architectures (e.g., i386), .B PROT_WRITE @@ -676,7 +678,7 @@ or not. Portable programs should always set .B PROT_EXEC if they intend to execute code in the new mapping. -.PP +.P The portable way to create a mapping is to specify .I addr as 0 (NULL), and omit @@ -691,7 +693,7 @@ If the flag is specified, and .I addr is 0 (NULL), then the mapped address will be 0 (NULL). -.PP +.P Certain .I flags constants are defined only if suitable feature test macros are defined @@ -745,7 +747,7 @@ POSIX.1-2008. POSIX.1-2001, SVr4, 4.4BSD. .\" SVr4 documents additional error codes ENXIO and ENODEV. .\" SUSv2 documents additional error codes EMFILE and EOVERFLOW. -.PP +.P On POSIX systems on which .BR mmap (), .BR msync (2), @@ -765,7 +767,7 @@ Memory mapped by is preserved across .BR fork (2), with the same attributes. -.PP +.P A file is mapped in multiples of the page size. For a file that is not a multiple of the page size, @@ -775,7 +777,7 @@ and modifications to that region are not written out to the file. The effect of changing the size of the underlying file of a mapping on the pages that correspond to added or removed regions of the file is unspecified. -.PP +.P An application can determine which pages of a mapping are currently resident in the buffer/page cache using .BR mincore (2). @@ -792,7 +794,7 @@ otherwise, the use of .B MAP_FIXED is hazardous because it forcibly removes preexisting mappings, making it easy for a multithreaded process to corrupt its own address space. -.PP +.P For example, suppose that thread A looks through .IR /proc/ pid /maps in order to locate an unused address range that it can map using @@ -820,7 +822,7 @@ Examples include and the PAM libraries .UR http://www.linux-pam.org .UE . -.PP +.P Since Linux 4.17, a multithreaded program can use the .B MAP_FIXED_NOREPLACE flag to avoid the hazard described above @@ -834,7 +836,7 @@ field for the mapped file may be updated at any time between the .BR mmap () and the corresponding unmapping; the first reference to a mapped page will update the field if it has not been already. -.PP +.P The .I st_ctime and @@ -859,7 +861,7 @@ and .BR munmap () differ somewhat from the requirements for mappings that use the native system page size. -.PP +.P For .BR mmap (), .I offset @@ -867,7 +869,7 @@ must be a multiple of the underlying huge page size. The system automatically aligns .I length to be a multiple of the underlying huge page size. -.PP +.P For .BR munmap (), .IR addr , @@ -880,14 +882,14 @@ On Linux, there are no guarantees like those suggested above under .BR MAP_NORESERVE . By default, any process can be killed at any moment when the system runs out of memory. -.PP +.P Before Linux 2.6.7, the .B MAP_POPULATE flag has effect only if .I prot is specified as .BR PROT_NONE . -.PP +.P SUSv3 specifies that .BR mmap () should fail if @@ -902,7 +904,7 @@ Since Linux 2.6.12, fails with the error .B EINVAL for this case. -.PP +.P POSIX specifies that the system shall always zero fill any partial page at the end of the object and that system will never write any modification of the @@ -1021,14 +1023,14 @@ main(int argc, char *argv[]) .BR userfaultfd (2), .BR shm_open (3), .BR shm_overview (7) -.PP +.P The descriptions of the following files in .BR proc (5): .IR /proc/ pid /maps , .IR /proc/ pid /map_files , and .IR /proc/ pid /smaps . -.PP +.P B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128\[en]129 and 389\[en]391. .\" .\" Repeat after me: private read-only mappings are 100% equivalent to |