lkml.org 
[lkml]   [2016]   [Oct]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:mm/pkeys] x86/pkeys: Update documentation
Commit-ID:  6679dac513fd612f34d3a3d99d7b84ed6d5eb5cc
Gitweb: http://git.kernel.org/tip/6679dac513fd612f34d3a3d99d7b84ed6d5eb5cc
Author: Dave Hansen <dave.hansen@intel.com>
AuthorDate: Tue, 4 Oct 2016 09:38:57 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 5 Oct 2016 10:34:55 +0200

x86/pkeys: Update documentation

There are a few items that have gotten stale in the protection
keys documentation. The config option description only applied
to the execute-only support and is not accurate for the current
code. There was also a typo with the number of system calls. I
also wanted to call out that pkey_set() is not a kernel-provided
facility, and where to find an implementation.

Signed-off-by: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: linux-doc@vger.kernel.org
Cc: corbet@lwn.net
Link: http://lkml.kernel.org/r/20161004163857.71E0D6F6@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
Documentation/x86/protection-keys.txt | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/Documentation/x86/protection-keys.txt b/Documentation/x86/protection-keys.txt
index 6da7689..b643045 100644
--- a/Documentation/x86/protection-keys.txt
+++ b/Documentation/x86/protection-keys.txt
@@ -20,7 +20,7 @@ instruction fetches.

=========================== Syscalls ===========================

-There are 2 system calls which directly interact with pkeys:
+There are 3 system calls which directly interact with pkeys:

int pkey_alloc(unsigned long flags, unsigned long init_access_rights)
int pkey_free(int pkey);
@@ -52,6 +52,10 @@ is no longer in use:
munmap(ptr, PAGE_SIZE);
pkey_free(pkey);

+(Note: pkey_set() is a wrapper for the RDPKRU and WRPKRU instructions.
+ An example implementation can be found in
+ tools/testing/selftests/x86/protection_keys.c)
+
=========================== Behavior ===========================

The kernel attempts to make protection keys consistent with the
@@ -79,11 +83,3 @@ with a read():
The kernel will send a SIGSEGV in both cases, but si_code will be set
to SEGV_PKERR when violating protection keys versus SEGV_ACCERR when
the plain mprotect() permissions are violated.
-
-=========================== Config Option ===========================
-
-This config option adds approximately 1.5kb of text. and 50 bytes of
-data to the executable. A workload which does large O_DIRECT reads
-of holes in XFS files was run to exercise get_user_pages_fast(). No
-performance delta was observed with the config option
-enabled or disabled.
\
 
 \ /
  Last update: 2016-10-05 10:40    [W:0.034 / U:0.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site