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Diffstat (limited to 'manual')
| -rw-r--r-- | manual/llio.texi | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/manual/llio.texi b/manual/llio.texi index 41c3e068d1..8b2f599c79 100644 --- a/manual/llio.texi +++ b/manual/llio.texi @@ -1801,6 +1801,69 @@ the given @var{name} previously created by @code{shm_open}. On failure @code{errno} is set. @end deftypefn +@deftypefun int memfd_create (const char *@var{name}, unsigned int @var{flags}) +@standards{Linux, sys/mman.h} +@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{@acsfd{}}} +The @code{memfd_create} function returns a file descriptor which can be +used to create memory mappings using the @code{mmap} function. It is +similar to the @code{shm_open} function in the sense that these mappings +are not backed by actual files. However, the descriptor returned by +@code{memfd_create} does not correspond to a named object; the +@var{name} argument is used for debugging purposes only (e.g., will +appear in @file{/proc}), and separate invocations of @code{memfd_create} +with the same @var{name} will not return descriptors for the same region +of memory. The descriptor can also be used to create alias mappings +within the same process. + +The descriptor initially refers to a zero-length file. Before mappings +can be created which are backed by memory, the file size needs to be +increased with the @code{ftruncate} function. @xref{File Size}. + +The @var{flags} argument can be a combination of the following flags: + +@vtable @code +@item MFD_CLOEXEC +@standards{Linux, sys/mman.h} +The descriptor is created with the @code{O_CLOEXEC} flag. + +@item MFD_ALLOW_SEALING +@standards{Linux, sys/mman.h} +The descriptor supports the addition of seals using the @code{fcntl} +function. + +@item MFD_HUGETLB +@standards{Linux, sys/mman.h} +This requests that mappings created using the returned file descriptor +use a larger page size. See @code{MAP_HUGETLB} above for details. + +This flag is incompatible with @code{MFD_ALLOW_SEALING}. +@end vtable + +@code{memfd_create} returns a file descriptor on success, and @math{-1} +on failure. + +The following @code{errno} error conditions are defined for this +function: + +@table @code +@item EINVAL +An invalid combination is specified in @var{flags}, or @var{name} is +too long. + +@item EFAULT +The @var{name} argument does not point to a string. + +@item EMFILE +The operation would exceed the file descriptor limit for this process. + +@item ENFILE +The operation would exceed the system-wide file descriptor limit. + +@item ENOMEM +There is not enough memory for the operation. +@end table +@end deftypefun + @node Waiting for I/O @section Waiting for Input or Output @cindex waiting for input or output |