diff options
| -rw-r--r-- | man2/pkey_alloc.2 | 42 |
1 files changed, 23 insertions, 19 deletions
diff --git a/man2/pkey_alloc.2 b/man2/pkey_alloc.2 index 222136fd13..863332ced4 100644 --- a/man2/pkey_alloc.2 +++ b/man2/pkey_alloc.2 @@ -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) |