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Fixed some of markup.

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Reviewed by:	jhb
This commit is contained in:
Ruslan Ermilov 2011-12-17 06:57:35 +00:00
parent f3fbaba136
commit e9a2004460
1 changed files with 18 additions and 19 deletions
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37
share/man/man9/shm_map.9
View File

@ -30,9 +30,8 @@
.Dt SHM_MAP 9
.Os
.Sh NAME
.Nm shm_map ,
.Nm shm_unmap
.Nd map shared memory objects into the kernel's address space
.Nm shm_map , shm_unmap
.Nd "map shared memory objects into the kernel's address space"
.Sh SYNOPSIS
.In sys/types.h
.In sys/mman.h
@ -42,9 +41,9 @@
.Fn shm_unmap "struct file *fp" "void *mem" "size_t size"
.Sh DESCRIPTION
The
.Nm shm_map
.Fn shm_map
and
.Nm shm_unmap
.Fn shm_unmap
functions provide an API for mapping shared memory objects into the kernel.
Shared memory objects are created by
.Xr shm_open 2 .
@ -57,13 +56,13 @@ Shared memory objects can still be grown while mapped into the kernel.
.Pp
To simplify the accounting needed to enforce the above requirement,
callers of this API are required to unmap the entire region mapped by
.Nm shm_map
.Fn shm_map
when calling
.Nm shm_unmap .
.Fn shm_unmap .
Unmapping only a portion of the region is not permitted.
.Pp
The
.Nm shm_map
.Fn shm_map
function locates the shared memory object associated with the open file
.Fa fp .
It maps the region of that object described by
@ -77,9 +76,9 @@ will be set to the start of the mapping.
All pages for the range will be wired into memory upon successful return.
.Pp
The
.Nm shm_unmap
.Fn shm_unmap
function unmaps a region previously mapped by
.Nm shm_map .
.Fn shm_map .
The
.Fa mem
argument should match the value previously returned in
@ -87,22 +86,22 @@ argument should match the value previously returned in
and the
.Fa size
argument should match the value passed to
.Nm shm_map .
.Fn shm_map .
.Pp
Note that
.Nm shm_map
.Fn shm_map
will not hold an extra reference on the open file
.Fa fp
for the lifetime of the mapping.
Instead,
the calling code is required to do this if it wishes to use
.Nm shm_unmap
.Fn shm_unmap
on the region in the future.
.Sh RETURN VALUES
The
.Nm shm_map
.Fn shm_map
and
.Nm shm_unmap
.Fn shm_unmap
functions return zero on success or an error on failure.
.Sh EXAMPLES
The following function accepts a file descriptor for a shared memory
@ -110,7 +109,7 @@ object.
It maps the first sixteen kilobytes of the object into the kernel,
performs some work on that address,
and then unmaps the address before returning.
.Bd -literal
.Bd -literal -offset indent
int
shm_example(int fd)
{
@ -118,7 +117,7 @@ shm_example(int fd)
void *mem;
int error;
error = fget(curthread, fd, CAP_MMAP, &fp)
error = fget(curthread, fd, CAP_MMAP, &fp);
if (error)
return (error);
error = shm_map(fp, 16384, 0, &mem);
@ -136,7 +135,7 @@ shm_example(int fd)
.Ed
.Sh ERRORS
The
.Nm shm_map
.Fn shm_map
function returns the following errors on failure:
.Bl -tag -width Er
.It Bq Er EINVAL
@ -158,7 +157,7 @@ The shared memory object could not be mapped due to some other VM error.
.El
.Pp
The
.Nm shm_unmap
.Fn shm_unmap
function returns the following errors on failure:
.Bl -tag -width Er
.It Bq Er EINVAL