diff mbox

-z bndplt documentation in GCC manual

Message ID 569ED7FC.2000008@codesourcery.com
State New
Headers show

Commit Message

Sandra Loosemore Jan. 20, 2016, 12:42 a.m. UTC 
On 01/19/2016 03:24 AM, Ilya Enkovich wrote:
> 2016-01-19 5:25 GMT+03:00 Sandra Loosemore <sandra@codesourcery.com>:
>> I think the documentation relating to '-z bndplt' in the GCC manual
>> description of -fcheck-pointer-bounds is incorrect.  It looks like, as of
>> r225862, the GCC driver is supposed to emit an error message if GCC was
>> configured with a linker that doesn't support this option and you pass -mmpx
>> without -static.  Is that right?  I'll fix the documentation once I'm clear
>> on what the actual behavior is.
>
> Compiler just emits a note where user is warned that GCC configuration may
> lead to decreased instrumentation coverage.

OK.  Is the attached patch accurate?  The existing text has several 
markup/grammatical/spelling errors and I'd like to simplify it to make 
it less repetitive and more direct and user-friendly.

(BTW, part of the problem I had parsing the code is that the manual 
doesn't document the %n spec file syntax, or several other % escapes.  I 
opened PR69367 for that since I have too many other things in my pile to 
get to it any time soon.)

-Sandra

Comments

Ilya Enkovich Jan. 20, 2016, 9:48 a.m. UTC | #1 
2016-01-20 3:42 GMT+03:00 Sandra Loosemore <sandra@codesourcery.com>:
> On 01/19/2016 03:24 AM, Ilya Enkovich wrote:
>>
>> 2016-01-19 5:25 GMT+03:00 Sandra Loosemore <sandra@codesourcery.com>:
>>>
>>> I think the documentation relating to '-z bndplt' in the GCC manual
>>> description of -fcheck-pointer-bounds is incorrect.  It looks like, as of
>>> r225862, the GCC driver is supposed to emit an error message if GCC was
>>> configured with a linker that doesn't support this option and you pass
>>> -mmpx
>>> without -static.  Is that right?  I'll fix the documentation once I'm
>>> clear
>>> on what the actual behavior is.
>>
>>
>> Compiler just emits a note where user is warned that GCC configuration may
>> lead to decreased instrumentation coverage.
>
>
> OK.  Is the attached patch accurate?  The existing text has several
> markup/grammatical/spelling errors and I'd like to simplify it to make it
> less repetitive and more direct and user-friendly.

I think your text accurately describes the situation. Thanks!

Ilya

>
> (BTW, part of the problem I had parsing the code is that the manual doesn't
> document the %n spec file syntax, or several other % escapes.  I opened
> PR69367 for that since I have too many other things in my pile to get to it
> any time soon.)
>
> -Sandra
diff mbox

Patch

Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi	(revision 232583)
+++ gcc/doc/invoke.texi	(working copy)
@@ -9919,22 +9919,22 @@  is instrumented with checks of the point
 bounds associated with that pointer.  
 
 Currently there
-is only an implementation for Intel MPX available, thus x86 target
+is only an implementation for Intel MPX available, thus x86 GNU/Linux target
 and @option{-mmpx} are required to enable this feature.  
 MPX-based instrumentation requires
 a runtime library to enable MPX in hardware and handle bounds
 violation signals.  By default when @option{-fcheck-pointer-bounds}
 and @option{-mmpx} options are used to link a program, the GCC driver
-links against the @file{libmpx} runtime library and @file{libmpxwrappers}
-library.  It also passes '-z bndplt' to a linker in case it supports this
-option (which is checked on libmpx configuration).  Note that old versions
-of linker may ignore option.  Gold linker doesn't support '-z bndplt'
-option.  With no '-z bndplt' support in linker all calls to dynamic libraries
-lose passed bounds reducing overall protection level.  It's highly
-recommended to use linker with '-z bndplt' support.  In case such linker
-is not available it is adviced to always use @option{-static-libmpxwrappers}
-for better protection level or use @option{-static} to completely avoid
-external calls to dynamic libraries.  MPX-based instrumentation
+links against the @file{libmpx} and @file{libmpxwrappers} libraries.
+Bounds checking on calls to dynamic libraries requires a linker
+with @option{-z bndplt} support; if GCC was configured with a linker
+without support for this option (including the Gold linker and older
+versions of ld), a warning is given if you link with @option{-mmpx}
+without also specifying @option{-static}, since the overall effectiveness
+of the bounds checking protection is reduced.
+See also @option{-static-libmpxwrappers}.
+
+MPX-based instrumentation
 may be used for debugging and also may be included in production code
 to increase program security.  Depending on usage, you may
 have different requirements for the runtime library.  The current version