Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix debug symbols loading in libproc: 0 is a valid file descriptor.

Reported by: Chris Torek <chris.torek@gmail.com>

Teach libproc how to find debugging symbols in /usr/lib/debug.

MFC after: 1 week

Stop iterating and return if the caller-supplied callback function returns
a non-zero value.

MFC after: 1 week

Ensure that we don't try to demangle a symbol name if we failed to look
up the symbol. Add a test to exercise this code path.

Reviewed by: adrian

Fix a memory leak that occured when looking up CTF info for a symbol.

Remove an incorrect and useless debug print.

X-MFC-With: r272488

Hook up support for userland CTF support in DTrace. This required some
modifications to libproc to support fetching the CTF info for a given file.

With this change, dtrace(1) is able to resolve type info for function and
USDT probe arguments, and function return values. In particular, the args[n]
syntax should now work for referencing arguments of userland probes,
provided that the requisite CTF info is available.

The uctf tests pass if the test programs are compiled with CTF info. The
current infrastructure around the DTrace test suite doesn't support this
yet.

Differential Revision: https://reviews.freebsd.org/D891
MFC after: 1 month
Relnotes: yes
Sponsored by: EMC / Isilon Storage Division

Factor out some of the duplicated code in the symbol lookup functions, in
preparation for adding userland CTF support to DTrace.

MFC after: 1 month
Sponsored by: EMC / Isilon Storage Division

Fix a bug in r265255: only return NULL if the requested map wasn't found.

Submitted by: Luke Chang-Hsien Tsai <luke.tw@gmail.com>
MFC after: 1 week

In r268463, I misplaced a return in demangle(), causing the function to
erroneously skip symbols that were not mangled at all. Fix this by
moving the return into the preceding if block.

While here, simplify the code by letting __cxa_demangle() allocate the
needed space for the demangled symbol. This also fixes a memory leak,
which would occur whenever __cxa_demangle() failed.

Reported by: pgj
MFC after: 3 days

In libproc, avoid calling __cxa_demangle(), and thus depending on either
libcxxrt or libsupc++, if WITHOUT_CXX is defined.

Noticed by: sbruno
MFC after: 1 week

Allow "a.out" as an alias for the executable if no other matching entries
are found. This improves compatibility with Solaris' libproc and fixes a
number of failing DTrace tests that rely on this feature.

MFC after: 3 weeks

Fix some off-by-one errors. The kve_end and rdl_eaddr fields contain the
first address after the end of the map entry and should therefore be
excluded.

MFC after: 2 weeks

Consistently add the relocation offset only when the ELF type is not
ET_EXEC. This fixes several problems with the DTrace pid provider not
being able to match probes.

Reviewed by: rpaulo
MFC after: 2 weeks

Fix an off-by-one error when checking whether a given address is within
the extent of a symbol.

Submitted by: Prashanth Kumar <pra_udupi@yahoo.co.in>
Reviewed by: rpaulo
MFC after: 1 week

Remove an incorrect debug printf.

Clean up the debug printing in libproc a bit. In particular:

* Don't print any error messages to stderr unless DEBUG is defined.
* Add a DPRINTFX macro for use when errno isn't set.
* Print the error string from libelf when appropriate.

Fix the return value when we found a symbol in .dynstr. This nasty bug was
preventing a lot of symbol lookups in dtruss -s, for example.

When calling the C++ demangler, make sure to free the returned buffer,
which might have been reallocated.

Pointed out by: stefanf

Add support for demangling C++ symbols. This requires linking libproc with
libc++rt/libsupc++.

Discussed with: theraven

Make sure we visit both symbol sections even if one of them doesn't
exist. This makes it possible to dtrace some C++ programs like devd.

Several fixes for libproc:
o return the correct status in proc_wstatus()
o proc_read takes a void *
o correctly allocate the objs structure array

Sponsored by: The FreeBSD Foundation

New version of libproc. Changes are:
* breakpoint setup support
* register query
* symbol to address mapping and vice-versa
* more misc utility functions based on their Solaris counterpart

Also, I've written some test cases.

Sponsored by: The FreeBSD Foundation

Add a process library with some stubs that the DTrace client needs.
These will be fleshed out as part of the DTrace userland tracing
development.

For now, the kernel tracing part of DTrace requires minimal functionality
for this library.

The API for this library is deliberately different from the libproc in
OpenSolaris due to licensing restrictions.