Basically, disable everything except the eh_frame unwind plan, as that's
the only one which supports this right now. The other plans are working
with now trying the interpret everything in between the function parts
as a part of the function, which is more likely to produce wrong results
than correct ones.
I changed the interface for object file plans, to give the
implementations a chance to implement this correctly, but I haven't
actually converted PECallFrameInfo (its only implementation) to handle
that. (from the looks of things, it should be relatively easy to do, if
it becomes necessary)
I'm also deleting UnwindPlan::GetFirstNonPrologueInsn, as it's not used,
and it doesn't work for discontinuous functions.
The macos and sysv ABIs return functionally equivalent unwind plans, so
they can be implemented in the base AArch64 class. The only difference
between them was that the macos plan provided a "pc=lr" rule whereas the
sysv plan called SetReturnAddressRegister (which causes the unwind
machinery to act as if that rule was present). This difference was
enough to cause `CompareUnwindPlansForIdenticalInitialPCLocation` to
return a different value and break the (temporarily reverted)
TestUnwindFramelessFaulted test.
While merging the two functions, I couldn't stop myself from simplifying
them to use the generic register number schemes -- which exposed another
bug in CompareUnwindPlansForIdenticalInitialPCLocation, namely that it
was expecting all unwind plans to use the LLDB numbering scheme. This
patch fixes that as well.
This patch uses the previously build infrastructure to parse multiple
FDE entries into a single unwind plan. There is one catch though: we
parse only one FDE entry per unwind range. This is not fully correct
because lldb coalesces adjecant address ranges, which means that
something that originally looked like two separate address ranges (and
two FDE entries) may get merged into one because if the linker decides
to put the two ranges next to each other. In this case, we will ignore
the second FDE entry.
It would be more correct to try to parse another entry when the one we
found turns out to be short, but I'm not doing this (yet), because:
- this is how we've done things so far (although, monolithic functions
are unlikely to have more than one FDE entry)
- in cases where we don't have debug info or (full) symbol tables, we
can end up with "symbols" which appear to span many megabytes
(potentially, the whole module). If we tried to fill short FDE entries,
we could end up parsing the entire eh_frame section in a single go. In a
way, this would be more correct, but it would also probably be very
slow.
I haven't quite decided what to do about this case yet, though it's not
particularly likely to happen in the "production" cases as typically the
functions are split into two parts (hot/cold) instead of one part per
basic block.
`GetLSDAAddress` and `GetPersonalityRoutinePtrAddress` are unused and
they create a bit of a problem for discontinuous functions, because the
unwind plan for these consists of multiple eh_frame descriptors and (at
least in theory) each of them could have a different value for these
entities.
We could say we only support functions for which these are always the
same, or create some sort of a Address2LSDA lookup map, but I think it's
better to leave this question to someone who actually needs this.
This reverts commit 094904303d50e0ab14bc5f2586a602f79af95953, reapplying
d7afafdbc464e65c56a0a1d77bad426aa7538306 (#133247).
The failure ought to be fixed by
0509932bb6a291ba11253f30c465ab3ad164ae08.
The main change here is that we're now able to correctly look up plans
for these functions. Previously, due to caching, we could end up with
one entry covering most of the address space (because part of the
function was at the beginning and one at the end). Now, we can correctly
recognise that the part in between does not belong to that function, and
we can create a different FuncUnwinders instance for it. It doesn't help
the discontinuous function much (its plan will still be garbled), but
we can at least properly unwind out of the simple functions in between.
Fixing the unwind plans for discontinuous functions requires handling
each unwind source specially, and this setup allows us to make the
transition incrementally.
The whole unwind plan is already stored in a shared pointer, and there's
no need to persist Rows individually. If there's ever a need to do that,
there are at least two options:
- copy the row (they're not that big, and they're being copied left and
right during construction already)
- use the shared_ptr subobject constructor to create a shared_ptr which
points to a Row but holds the entire unwind plan alive
This also changes all of the getter functions to return const Row
pointers, which is important for safety because all of these objects are
cached and potentially accessed from multiple threads. (Technically one
could hand out `shared_ptr<const Row>`s, but we don't have a habit of
doing that.)
As a next step, I'd like to remove the internal UnwindPlan usages of the
shared pointer, but I'm doing this separately to gauge feedback, and
also because the patch got rather big.
lldb has two RegisterLocation classes that do slightly different things.
UnwindPlan::Row::RegisterLocation (new: AbstractRegisterLocation) has a
description of how to find a register's value or location, not specific
to a particular stopping point. It may say that at a given offset into a
function, the caller's register has been spilled to stack memory at CFA
minus an offset. Or it may say that the caller's register is at a DWARF
exprssion.
UnwindLLDB::RegisterLocation (new: ConcreteRegisterLocation) is a
specific address where the register is currently stored, or the register
it has been copied into, or its value at this point in the current
function execution.
When lldb stops in a function, it interprets the
AbstractRegisterLocation's instructions using the register context and
stack memory, to create the ConcreteRegisterLocation at this point in
time for this stack frame.
I'm not thrilled with AbstractRegisterLocation and
ConcreteRegisterLocation, but it's better than the same name and it will
be easier to update them if someone suggests a better pair.
For supported architectures, lldb will do a static scan of the assembly
instructions of a function to detect stack/frame pointer changes,
register stores and loads, so we can retrieve register values for the
caller stack frames. We trust that the function address range reflects
the actual function range, but in a stripped binary or other unusual
environment, we can end up scanning all of the text as a single
"function" which is (1) incorrect and useless, but more importantly (2)
slow.
Cap the max size we will profile to 10MB of instructions. There will
surely be functions longer than this with no unwind info, and we will
miss the final epilogue or mid-function epilogues past the first 10MB,
but I think this will be unusual, and the failure more to missing the
epilogue is that the user will need to step out an extra time or two as
the StackID is not correctly calculated mid-epilogue. I think this is a
good tradeoff of behaviors.
rdar://134391577
These were found by Clang's new -Wsuggest-override.
This patch doesn't touch any code in unittests/, since much of it intentionally doesn't use override to avoid massive warning spam from -Winconsistent-missing-override due to the use of MOCK_*** macros.
Differential Revision: https://reviews.llvm.org/D83847
Summary:
A *.cpp file header in LLDB (and in LLDB) should like this:
```
//===-- TestUtilities.cpp -------------------------------------------------===//
```
However in LLDB most of our source files have arbitrary changes to this format and
these changes are spreading through LLDB as folks usually just use the existing
source files as templates for their new files (most notably the unnecessary
editor language indicator `-*- C++ -*-` is spreading and in every review
someone is pointing out that this is wrong, resulting in people pointing out that this
is done in the same way in other files).
This patch removes most of these inconsistencies including the editor language indicators,
all the different missing/additional '-' characters, files that center the file name, missing
trailing `===//` (mostly caused by clang-format breaking the line).
Reviewers: aprantl, espindola, jfb, shafik, JDevlieghere
Reviewed By: JDevlieghere
Subscribers: dexonsmith, wuzish, emaste, sdardis, nemanjai, kbarton, MaskRay, atanasyan, arphaman, jfb, abidh, jsji, JDevlieghere, usaxena95, lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D73258
This patch adds an implementation of unwinding using PE EH info. It allows to
get almost ideal call stacks on 64-bit Windows systems (except some epilogue
cases, but I believe that they can be fixed with unwind plan disassembly
augmentation in the future).
To achieve the goal the CallFrameInfo abstraction was made. It is based on the
DWARFCallFrameInfo class interface with a few changes to make it less
DWARF-specific.
To implement the new interface for PECOFF object files the class PECallFrameInfo
was written. It uses the next helper classes:
- UnwindCodesIterator helps to iterate through UnwindCode structures (and
processes chained infos transparently);
- EHProgramBuilder with the use of UnwindCodesIterator constructs EHProgram;
- EHProgram is, by fact, a vector of EHInstructions. It creates an abstraction
over the low-level unwind codes and simplifies work with them. It contains
only the information that is relevant to unwinding in the unified form. Also
the required unwind codes are read from the object file only once with it;
- EHProgramRange allows to take a range of EHProgram and to build an unwind row
for it.
So, PECallFrameInfo builds the EHProgram with EHProgramBuilder, takes the ranges
corresponding to every offset in prologue and builds the rows of the resulted
unwind plan. The resulted plan covers the whole range of the function except the
epilogue.
Reviewers: jasonmolenda, asmith, amccarth, clayborg, JDevlieghere, stella.stamenova, labath, espindola
Reviewed By: jasonmolenda
Subscribers: leonid.mashinskiy, emaste, mgorny, aprantl, arichardson, MaskRay, lldb-commits, llvm-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D67347
llvm-svn: 374528
The two sections usually contain the same information, and we rarely
have both kinds of entries for a single function. However, in theory the
debug_frame plan can be more complete, whereas eh_frame is only required
to be correct at places where exceptions can be thrown.
Reviewers: jasonmolenda, clayborg
Subscribers: lldb-commits
Differential Revision: https://reviews.llvm.org/D62374
llvm-svn: 361758
Summary:
Previous patch (r360409) introduced the "symbol file unwind plan"
concept, but that plan wasn't used for unwinding yet. With this patch,
we start to consider the new plan as a possible strategy for both
synchronous and asynchronous unwinding. I also add a test that asserts
that unwinding via breakpad STACK CFI info works end-to-end.
Reviewers: jasonmolenda, clayborg
Subscribers: lldb-commits, amccarth, markmentovai
Differential Revision: https://reviews.llvm.org/D61853
llvm-svn: 361618
Summary:
some unwind formats are specific to a single symbol file and so it does
not make sense for their parsing code live in the general Symbol library
(as is the case with eh_frame for instance). This is the case for the
unwind information in breakpad files, but the same will probably be true
for PDB unwind info (once we are able to parse that).
This patch adds the ability to fetch an unwind plan provided by a symbol
file plugin, as discussed in the RFC at
<http://lists.llvm.org/pipermail/lldb-dev/2019-February/014703.html>.
I've kept the set of changes to a minimum, as there is no way to test
them until we have a symbol file which implements this API -- that is
comming in a follow-up patch, which will also implicitly test this
change.
The interesting part here is the introduction of the
"RegisterInfoResolver" interface. The reason for this is that breakpad
needs to be able to resolve register names (which are present as strings
in the file) into register enums so that it can construct the unwind
plan. This is normally done via the RegisterContext class, handing this
over to the SymbolFile plugin would mean that it has full access to the
debugged process, which is not something we want it to have. So instead,
I create a facade, which only provides the ability to query register
names, and hide the RegisterContext behind the facade.
Also note that this only adds the ability to dump the unwind plan
created by the symbol file plugin -- the plan is not used for unwinding
yet -- this will be added in a third patch, which will add additional
tests which makes sure the unwinding works as a whole.
Reviewers: jasonmolenda, clayborg
Subscribers: markmentovai, amccarth, lldb-commits
Differential Revision: https://reviews.llvm.org/D61732
llvm-svn: 360409
Summary:
This argument was added back in 2010 (r118882) to support the ability to unwind
from functions whose eh_frame entry does not cover the entire range of
the function.
However, due to the caching happening in FuncUnwinders, this solution is
very fragile. FuncUnwinders will cache the plan it got from eh_frame
regardless of the value of the current_offset, so our ability to unwind
from a given function depended what was the value of "current_offset" the
first time that this function was called.
Furthermore, since the "image show-unwind" command did not know what's
the right offset to pass, this created an unfortunate situation where
"image show-unwind" would show no valid plans for a function, even
though they were available and being used.
In this patch I implement the feature slightly differently. Instead of
giving just a base address to the eh_frame unwinder, I give it the
entire range we are interested in. Then, I change the unwinder to return
the first plan that covers (even partially) that range. This way even a
partial plan will be returned, regardless of the address in the function
where we are stopped at.
This solution is still not 100% correct, as it will not handle a
function which is covered by two independent fde entries. However, I
don't expect anybody will write this kind of functions, and this wasn't
handled by the previous implementation either. If this is ever needed in
the future. The eh_frame unwinder can be extended to return "composite"
unwind plans created by merging sevelar fde entries.
I also create a test which triggers this scenario. As doing this is
virtually impossible without hand-written assembly, the test only works
on x86 linux.
Reviewers: jasonmolenda, clayborg
Subscribers: lldb-commits
Differential Revision: https://reviews.llvm.org/D60829
llvm-svn: 358964
A lot of comments in LLDB are surrounded by an ASCII line to delimit the
begging and end of the comment.
Its use is not really consistent across the code base, sometimes the
lines are longer, sometimes they are shorter and sometimes they are
omitted. Furthermore, it looks kind of weird with the 80 column limit,
where the comment actually extends past the line, but not by much.
Furthermore, when /// is used for Doxygen comments, it looks
particularly odd. And when // is used, it incorrectly gives the
impression that it's actually a Doxygen comment.
I assume these lines were added to improve distinguishing between
comments and code. However, given that todays editors and IDEs do a
great job at highlighting comments, I think it's worth to drop this for
the sake of consistency. The alternative is fixing all the
inconsistencies, which would create a lot more churn.
Differential revision: https://reviews.llvm.org/D60508
llvm-svn: 358135
Unlike std::make_unique, which is only available since C++14,
std::make_shared is available since C++11. Not only is std::make_shared
a lot more readable compared to ::reset(new), it also performs a single
heap allocation for the object and control block.
Differential revision: https://reviews.llvm.org/D57990
llvm-svn: 353764
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
instead of returning the architecture through by-ref argument and a
boolean value indicating success, we can just return the ArchSpec
directly. Since the ArchSpec already has an invalid state, it can be
used to denote the failure without the additional bool.
Reviewers: clayborg, zturner, espindola
Subscribers: emaste, arichardson, JDevlieghere, lldb-commits
Differential Revision: https://reviews.llvm.org/D56129
llvm-svn: 350291
This patch simplifies boolean expressions acorss LLDB. It was generated
using clang-tidy with the following command:
run-clang-tidy.py -checks='-*,readability-simplify-boolean-expr' -format -fix $PWD
Differential revision: https://reviews.llvm.org/D55584
llvm-svn: 349215
This is intended as a clean up after the big clang-format commit
(r280751), which unfortunately resulted in many of the comment
paragraphs in LLDB being very hard to read.
FYI, the script I used was:
import textwrap
import commands
import os
import sys
import re
tmp = "%s.tmp"%sys.argv[1]
out = open(tmp, "w+")
with open(sys.argv[1], "r") as f:
header = ""
text = ""
comment = re.compile(r'^( *//) ([^ ].*)$')
special = re.compile(r'^((([A-Z]+[: ])|([0-9]+ )).*)|(.*;)$')
for line in f:
match = comment.match(line)
if match and not special.match(match.group(2)):
# skip intentionally short comments.
if not text and len(match.group(2)) < 40:
out.write(line)
continue
if text:
text += " " + match.group(2)
else:
header = match.group(1)
text = match.group(2)
continue
if text:
filled = textwrap.wrap(text, width=(78-len(header)),
break_long_words=False)
for l in filled:
out.write(header+" "+l+'\n')
text = ""
out.write(line)
os.rename(tmp, sys.argv[1])
Differential Revision: https://reviews.llvm.org/D46144
llvm-svn: 331197
Summary:
This is a beefed-up version of D33504, which adds support for dwarf 4
debug_frame section format.
The main difference here is that the decision whether to use eh_frame or
debug_frame is done on a per-function basis instead of per-object file.
This is necessary because one module can contain both sections (for
example, the start files added by the linker will typically pull in
eh_frame), but we want to be able to access both, for maximum
information.
I also add unit test for parsing various CFI formats (eh_frame,
debug_frame v3 and debug_frame v4).
Reviewers: jasonmolenda, clayborg
Subscribers: mgorny, aprantl, abidh, lldb-commits, tatyana-krasnukha
Differential Revision: https://reviews.llvm.org/D34613
llvm-svn: 306397
acquired only after checking if the ivar shared pointer was already
filled in. But when I assign an UnwindPlan object to the shared
pointer, I assign an empty object and then fill it in. That leaves
a window where another thread could get the shared pointer to the
empty (but quickly being-filled-in) object and lead to a crash.
Also two changes from Greg for correctness on the TestMultipleDebuggers
test case.
<rdar://problem/30564102>
llvm-svn: 296084
With this patch, the only dependency left is from Utility
to Host. After this is broken, Utility will finally be
standalone.
Differential Revision: https://reviews.llvm.org/D29909
llvm-svn: 295088
*** to conform to clang-format’s LLVM style. This kind of mass change has
*** two obvious implications:
Firstly, merging this particular commit into a downstream fork may be a huge
effort. Alternatively, it may be worth merging all changes up to this commit,
performing the same reformatting operation locally, and then discarding the
merge for this particular commit. The commands used to accomplish this
reformatting were as follows (with current working directory as the root of
the repository):
find . \( -iname "*.c" -or -iname "*.cpp" -or -iname "*.h" -or -iname "*.mm" \) -exec clang-format -i {} +
find . -iname "*.py" -exec autopep8 --in-place --aggressive --aggressive {} + ;
The version of clang-format used was 3.9.0, and autopep8 was 1.2.4.
Secondly, “blame” style tools will generally point to this commit instead of
a meaningful prior commit. There are alternatives available that will attempt
to look through this change and find the appropriate prior commit. YMMV.
llvm-svn: 280751
may be in a function that is non-ABI conformant, and the eh_frame
instructions correctly describe how to unwind out of this function,
but the assembly parsing / arch default unwind plans would be
incorrect.
This is to address a problem that Ravitheja Addepally reported in
http://reviews.llvm.org/D21221 - I wanted to try handling the problem
with this approach which I think may be more generally helpful,
Ravitheja tested it and said it solves the problem on Linux/FreeBSD.
Ravi has a test case in http://reviews.llvm.org/D21221 that will
be committed separately.
Thanks for all the help on this one, Ravi.
llvm-svn: 274700
This is a pretty straightforward first pass over removing a number of uses of
Mutex in favor of std::mutex or std::recursive_mutex. The problem is that there
are interfaces which take Mutex::Locker & to lock internal locks. This patch
cleans up most of the easy cases. The only non-trivial change is in
CommandObjectTarget.cpp where a Mutex::Locker was split into two.
llvm-svn: 269877
should not be used for this module -- for use when an ObjectFile
knows that it does not have meaningful or accurate function start
addresses.
More commonly, it is not clear that function start addresses are
missing in a module. There are certain cases on Mac OS X where we
can tell that a Mach-O binary has been stripped of this essential
information, and the unwinder can end up emulating many megabytes
of instructions for a single "function" in the binary.
When a Mach-O binary is missing both an LC_FUNCTION_STARTS load
command (very unusual) and an eh_frame section, then we will assume
it has also been stripped of symbols and that instruction emulation
will not be useful on this module.
<rdar://problem/25988067>
llvm-svn: 268475
.ARM.exidx/.ARM.extab sections contain unwind information used on ARM
architecture from unwinding from an exception.
Differential revision: http://reviews.llvm.org/D13245
llvm-svn: 248903
* Add and fix the emulation of several instruction.
* Disable frame pointer usage on Android.
* Specify return address register for the unwind plan instead of explict
tracking the value of RA.
* Replace prologue detection heuristics (unreliable in several cases)
with a logic to follow the branch instructions and restore the CFI
value based on them. The target address for a branch should have the
same CFI as the source address (if they are in the same function).
* Handle symbols in ELF files where the symbol size is not specified
with calcualting their size based on the next symbol (already done
in MachO files).
* Fix architecture in FuncUnwinders with filling up the inforamtion
missing from the object file with the architecture of the target.
* Add code to read register wehn the value is set to "IsSame" as it
meanse the value of a register in the parent frame is the same as the
value in the current frame.
Differential revision: http://reviews.llvm.org/D10447
llvm-svn: 240533
Summary:
GetEHFrameAugmentedUnwindPlan duplicated the work of GetEHFrameUnwindPlan in getting the original
plan from DWARF CFI. This changes the function to call GetEHFrameUnwindPlan instead of doing all
the work itself. A copy constructor is added to UnwindPlan to enable plan copying.
Test Plan: No regressions on linux test suite.
Reviewers: jasonmolenda, clayborg
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D9369
llvm-svn: 236607
Most of the changes are to the FuncUnwinders class -- as we've added
more types of unwind information, the way this class was written was
making it a mess to maintain. Instead of trying to keep one
"non-call site" unwind plan and one "call site" unwind plan, track
all the different types of unwind plans we can possibly retrieve for
each function and have the call-site/non-call-site accessor methods
retrieve those.
Add a real "fast unwind plan" for x86_64 / i386 -- when doing an
unwind through a function, this only has to read the first 4 bytes
to tell if the function has a standard prologue sequence. If so,
we can use the architecture default unwind plan to backtrace
through this function. If we try to retrieve the save location for
other registers later on, a real unwind plan will be used. This
one is just for doing fast backtraces.
Change the compact unwind plan importer to fill in the valid address
range it is valid for.
Compact unwind, in theory, may have multiple entries for a single
function. The FuncUnwinders rewrite includes the start of supporting
this correctly. In practice compact unwind encodings are used for
the entire range of the function today -- in fact, sometimes the same
encoding is used for multiple functions that have the same unwind
rules. But I want to handle a single function that has multiple
different compact unwind UnwindPlans eventually.
llvm-svn: 224689
section for x86_64 and i386 targets on Darwin systems. Currently only the
compact unwind encoding for normal frame-using functions is supported but it
will be easy handle frameless functions when I have a bit more free time to
test it. The LSDA and personality routines for functions are also retrieved
correctly for functions from the compact unwind section.
This new code is very fresh -- it passes the lldb testsuite and I've done
by-hand inspection of many functions and am getting correct behavior for all
of them. There may need to be some bug fixing over the next couple weeks as
I exercise and test it further. But I think it's fine right now so I'm
committing it.
<rdar://problem/13220837>
llvm-svn: 223625
retrieves the personality routine addr and the
LSDA addr. Don't bother checking with the
"non-call site" unwind plan - this kind of
information is only going to come from the
call site unwind plan.
llvm-svn: 222226
eh_frame data. These two pieces of information are used in the
process of exception handler unwinding on SysV ABI systems.
This patch reads the data from the eh_frame section
(DWARFCallFrameInfo.cpp), allows for it to be saved & read out
of a given UnwindPlan (UnwindPlan.h, UnwindPlan.cpp) - as well
as printing the information in the UnwindPlan::Dump method - and
adds methods to the FuncUnwinders object so that higher levels
can query if a given function has an LSDA / personality routine
defined.
It's only lightly tested, but seems to be working correctly as long
as your have this information in eh_frame. Does not address getting
this information from compact unwind yet on Darwin systems.
<rdar://problem/18742797>
llvm-svn: 222214
let's let lldb try the arch default unwind every time but not destructively --
it doesn't permanently replace the main unwind method for that function from
now on.
This fix is for <rdar://problem/18683658>.
I tested it against Ryan Brown's go program test case and also a
collection of core files of tricky unwind scenarios
<rdar://problem/15664282> <rdar://problem/15835846>
<rdar://problem/15982682> <rdar://problem/16099440>
<rdar://problem/17364005> <rdar://problem/18556719>
that I've fixed over the last 6-9 months.
llvm-svn: 221238
We decided to use assmbly profiler instead of eh_frame for frame 0 because for compiler generated code, eh_frame is usually synchronous(a.k.a. only valid at call site); and we have no way to tell if it's asynchronous or not.
But for x86 & x86_64 compiler generated code:
1. clang & GCC describes all prologue instructions in eh_frame;
2. mid-function stack pointer altering instructions can be easily detected.
So we can grab eh_frame, and use assembly profiler to augment it into asynchronous unwind table.
This change also benefits hand-written assembly; eh_frame for hand-written assembly is often asynchronous,so we have a much better chance to successfully unwind through them.
Change by Tong Shen.
llvm-svn: 216406
and sharing it with all of its FuncUnwinders, have each FuncUnwinder
create an AssemblyProfiler on demand as needed. I was worried that
the cost of creating the llvm disassemblers would be high for this
approach but it's not supposed to be an expensive operation, and it
means we don't need to add locks around this section of code.
<rdar://problem/16992332>
llvm-svn: 209493
to its unwind assembly profiler to all of the FuncUnwinders (one
per symbol) under it. If lldb is running multiple targets, you
could get two different FuncUnwinders in the same Module trying
to use the same llvm disassembler simultaneously and that may be
a re-entrancy problem.
Instead, the UnwindTable has the unwind assembly profiler and when
the FuncUnwinders want to use it, they get exclusive access to
the assembly profiler until they're done using it.
<rdar://problem/16992332>
llvm-svn: 209488
