linux-kernel - Re: [PATCH 12/27] Documentation: x86: convert protection-keys.txt to reST

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Message-ID: <20190427145300.29254985@coco.lan>
Date:   Sat, 27 Apr 2019 14:53:00 -0300
From:   Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Jonathan Corbet <corbet@....net>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/27] Documentation: x86: convert protection-keys.txt
 to reST

Em Fri, 26 Apr 2019 23:31:35 +0800
Changbin Du <changbin.du@...il.com> escreveu:

> This converts the plain text documentation to reStructuredText format and
> add it to Sphinx TOC tree. No essential content change.
> 
> Signed-off-by: Changbin Du <changbin.du@...il.com>

Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>

> ---
>  Documentation/x86/index.rst                   |  1 +
>  ...rotection-keys.txt => protection-keys.rst} | 33 ++++++++++++-------
>  2 files changed, 22 insertions(+), 12 deletions(-)
>  rename Documentation/x86/{protection-keys.txt => protection-keys.rst} (83%)
> 
> diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
> index e06b5c0ea883..576628b121cc 100644
> --- a/Documentation/x86/index.rst
> +++ b/Documentation/x86/index.rst
> @@ -18,3 +18,4 @@ Linux x86 Support
>     tlb
>     mtrr
>     pat
> +   protection-keys
> diff --git a/Documentation/x86/protection-keys.txt b/Documentation/x86/protection-keys.rst
> similarity index 83%
> rename from Documentation/x86/protection-keys.txt
> rename to Documentation/x86/protection-keys.rst
> index ecb0d2dadfb7..49d9833af871 100644
> --- a/Documentation/x86/protection-keys.txt
> +++ b/Documentation/x86/protection-keys.rst
> @@ -1,3 +1,9 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +======================
> +Memory Protection Keys
> +======================
> +
>  Memory Protection Keys for Userspace (PKU aka PKEYs) is a feature
>  which is found on Intel's Skylake "Scalable Processor" Server CPUs.
>  It will be avalable in future non-server parts.
> @@ -23,9 +29,10 @@ even though there is theoretically space in the PAE PTEs.  These
>  permissions are enforced on data access only and have no effect on
>  instruction fetches.
>  
> -=========================== Syscalls ===========================
> +Syscalls
> +========
>  
> -There are 3 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);
> @@ -37,6 +44,7 @@ pkey_alloc().  An application calls the WRPKRU instruction
>  directly in order to change access permissions to memory covered
>  with a key.  In this example WRPKRU is wrapped by a C function
>  called pkey_set().
> +::
>  
>  	int real_prot = PROT_READ|PROT_WRITE;
>  	pkey = pkey_alloc(0, PKEY_DISABLE_WRITE);
> @@ -45,43 +53,44 @@ called pkey_set().
>  	... application runs here
>  
>  Now, if the application needs to update the data at 'ptr', it can
> -gain access, do the update, then remove its write access:
> +gain access, do the update, then remove its write access::
>  
>  	pkey_set(pkey, 0); // clear PKEY_DISABLE_WRITE
>  	*ptr = foo; // assign something
>  	pkey_set(pkey, PKEY_DISABLE_WRITE); // set PKEY_DISABLE_WRITE again
>  
>  Now when it frees the memory, it will also free the pkey since it
> -is no longer in use:
> +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)
> +.. 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 ===========================
> +Behavior
> +========
>  
>  The kernel attempts to make protection keys consistent with the
> -behavior of a plain mprotect().  For instance if you do this:
> +behavior of a plain mprotect().  For instance if you do this::
>  
>  	mprotect(ptr, size, PROT_NONE);
>  	something(ptr);
>  
> -you can expect the same effects with protection keys when doing this:
> +you can expect the same effects with protection keys when doing this::
>  
>  	pkey = pkey_alloc(0, PKEY_DISABLE_WRITE | PKEY_DISABLE_READ);
>  	pkey_mprotect(ptr, size, PROT_READ|PROT_WRITE, pkey);
>  	something(ptr);
>  
>  That should be true whether something() is a direct access to 'ptr'
> -like:
> +like::
>  
>  	*ptr = foo;
>  
>  or when the kernel does the access on the application's behalf like
> -with a read():
> +with a read()::
>  
>  	read(fd, ptr, 1);
>  



Thanks,
Mauro