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pkey_alloc.2: Various tweaks to the text 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2016-10-13 12:25:46 +02:00
parent 79a2a43713
commit b638d22097
1 changed files with 23 additions and 19 deletions
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42
man2/pkey_alloc.2
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@ -34,14 +34,17 @@ pkey_alloc, pkey_free \- allocate or free a protection key
.fi
.SH DESCRIPTION
.BR pkey_alloc ()
allocates a protection key and allows it to be passed to
.BR pkey_mprotect (2) .
allocates a protection key (pkey) and allows it to be passed to
.BR pkey_mprotect (2).
.BR pkey_alloc ()
is always safe to call whether or not the operating system
is always safe to call regardless of whether or not the operating system
supports protection keys.
It can be used in lieu of any other enumeration of the feature
and will simply return ENOSPC in the case that the operating
system has no protection keys support.
It can be used in lieu of any other mechanism for detecting pkey support
and will simply fail with the error
.B ENOSPC
if the operating system has no pkey support.
The kernel guarantees that the contents of the hardware rights
register (PKRU) will be preserved only for allocated protection
keys.
@ -49,8 +52,8 @@ Any time a key is unallocated (either before the first call
returning that key from
.BR pkey_alloc ()
or after it is freed via
.BR pkey_free ()
), the kernel may make arbitrary changes to the parts of the
.BR pkey_free ()),
the kernel may make arbitrary changes to the parts of the
rights register affecting access to that key.
.PP
.BR pkey_free ()
@ -63,12 +66,13 @@ An application should not call
on any protection key which has been assigned to an address
range by
.BR pkey_mprotect (2)
and which is still in use. The behavior in this case is
undefined and may result in an error.
and which is still in use.
The behavior in this case is undefined and may result in an error.
.PP
.RB ( pkey_alloc ())
The
.BR pkey_alloc ()
.I flags
may contain zero or more disable operations:
argument may contain zero or more disable operations:
.TP
.B PKEY_DISABLE_ACCESS
Disable all data access to memory covered by the returned protection key.
@ -94,31 +98,31 @@ or
is invalid.
.TP
.B ENOSPC
.(RB pkey_alloc ())
.RB ( pkey_alloc ())
All protection keys available for the current process have
been allocated.
The number of keys available is architecture-specific and
implementation-specfic and may be reduced by kernel-internal use
implementation-specific and may be reduced by kernel-internal use
of certain keys.
There are currently 15 keys available to user programs on x86.
This will also be returned if the processor or operating system
This error will also be returned if the processor or operating system
does not support protection keys.
Applications should always be prepared to handle this error since
Applications should always be prepared to handle this error, since
factors outside of the application's control can reduce the number
of available pkeys.
.SH VERSIONS
.BR pkey_alloc ()
and
.BR pkey_free ()
were added to Linux in kernel <FIXME>;
library support was added to glibc in version <FIXME>.
were added to Linux in kernel 4.9.
Glibc support is not yet available.
.SH CONFORMING TO
The
.BR pkey_alloc ()
and
.BR pkey_free ()
system calls are Linux-specific.
.SH
.SH SEE ALSO
.BR pkey_mprotect (2),
.BR pkey (7)