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authorDave Hansen <dave.hansen@intel.com>2016-10-04 09:38:57 -0700
committerThomas Gleixner <tglx@linutronix.de>2016-10-05 10:34:55 +0200
commit6679dac513fd612f34d3a3d99d7b84ed6d5eb5cc (patch)
tree86d7b892cbf634bc83bf2a9ab3619d7d5709de97 /Documentation/x86
parentba6d018e3d2f6a0fad58a668cadf66b2d1f80f59 (diff)
downloadlinux-6679dac513fd612f34d3a3d99d7b84ed6d5eb5cc.tar.bz2
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>
Diffstat (limited to 'Documentation/x86')
-rw-r--r--Documentation/x86/protection-keys.txt14
1 files changed, 5 insertions, 9 deletions
diff --git a/Documentation/x86/protection-keys.txt b/Documentation/x86/protection-keys.txt
index 6da7689601d1..b64304540821 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.