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invoke.texi (Instrumentation Options): Clarify -mmpx linking requirements. 

2016-01-20  Sandra Loosemore <sandra@codesourcery.com>

	gcc/
	* doc/invoke.texi (Instrumentation Options): Clarify -mmpx linking
	requirements.

From-SVN: r232648
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Sandra Loosemore 2016-01-20 20:03:42 -05:00 committed by Sandra Loosemore
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commit 42d4fbb0f4
2 changed files with 16 additions and 11 deletions
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@ -1,3 +1,8 @@
2016-01-20 Sandra Loosemore <sandra@codesourcery.com>
* doc/invoke.texi (Instrumentation Options): Clarify -mmpx linking
requirements.
2016-01-20 Sandra Loosemore <sandra@codesourcery.com>
* common.opt (feliminate-dwarf2-dups): Replace references to

22
gcc/doc/invoke.texi
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@ -9923,22 +9923,22 @@ is instrumented with checks of the pointer used for memory access against
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