Summary:
This is the only real unwinder, and things have been this way for quite
a long time. At this point, the class has accumulated so many features
it is unlikely that anyone will want to reimplement the whole thing.

The class is also fairly closely coupled (through UnwindPlans and
FuncUnwinders) with a lot of other lldb components that it is hard to
imagine a different unwinder implementation being substantially
different without reimplementing all of those.

The existing unwinding functionality is nonetheless fairly complex and
there is space for adding more structure to it, but I believe a more
worthwhile effort would be to take the existing UnwindLLDB class and try
to break it down and introduce extension/customization points, instead
of writing a brand new Unwind implementation.

Reviewers: jasonmolenda, JDevlieghere, xiaobai

Subscribers: mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D75848

Updated the patch to only fetch $pc on a Return Address-using
target only if we're in a trap frame *and* if there is a saved
location for $pc in the trap frame's unwind rules.  If not,
we fall back to fetching the Return Address register (eg $lr).

Original commit msg:

    Unwind past an interrupt handler correctly on arm or at pc==0

    Fix RegisterContextLLDB::InitializeNonZerothFrame so that it
    will fetch a FullUnwindPlan instead of falling back to the
    architectural default unwind plan -- GetFullUnwindPlan knows
    how to spot a jmp 0x0 that results in a fault, which may be
    the case when we see a trap handler on the stack.

    Fix RegisterContextLLDB::SavedLocationForRegister so that when
    the pc value is requested from a trap handler frame, where we
    have a complete register context available to us, don't provide
    the Return Address register (lr) instead of the pc.  We have
    an actual pc value here, and it's pointing to the instruction
    that faulted.

    Differential revision: https://reviews.llvm.org/D75007
    <rdar://problem/59416588>

The aarcht64-ubuntu bot is showing a test failure in TestHandleAbort.py
with this patch.  Adding some logging to that file, it looks like
the saved register context above the trap handler does not have
save state for $pc, but it does have it for $lr on that platform.
I need to fall back to looking for $lr if the $pc cannot be retrieved.
I'll update the patch and re-commit once that's fixed.

This reverts commit edc4f4c9c9d90b2a4f8831ba4c873f08eaa5395a.

Fix RegisterContextLLDB::InitializeNonZerothFrame so that it
will fetch a FullUnwindPlan instead of falling back to the
architectural default unwind plan -- GetFullUnwindPlan knows
how to spot a jmp 0x0 that results in a fault, which may be
the case when we see a trap handler on the stack.

Fix RegisterContextLLDB::SavedLocationForRegister so that when
the pc value is requested from a trap handler frame, where we
have a complete register context available to us, don't provide
the Return Address register (lr) instead of the pc.  We have
an actual pc value here, and it's pointing to the instruction
that faulted.

Differential revision: https://reviews.llvm.org/D75007
<rdar://problem/59416588>

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

Summary:
Windows unwinding is weird. The unwind rules do not (always) describe
the precise layout of the stack, but rather expect the debugger to scan
the stack for something which looks like a plausible return address, and
the unwind based on that. The reason this works somewhat reliably is
because the the unwinder also has access to the frame sizes of the
functions on the stack. This allows it (in most cases) to skip function
pointers in local variables or function arguments, which could otherwise
be mistaken for return addresses.

Implementing this kind of unwind mechanism in lldb was a bit challenging
because we expect to be able to statically describe (in the UnwindPlan)
structure, the layout of the stack for any given instruction. Giving a
precise desription of this is not possible, because it requires
correlating information from two functions -- the pushed arguments to a
function are considered a part of the callers stack frame, and their
size needs to be considered when unwinding the caller, but they are only
present in the unwind entry of the callee. The callee may end up being
in a completely different module, or it may not even be possible to
determine it statically (indirect calls).

This patch implements this functionality by introducing a couple of new
APIs:
SymbolFile::GetParameterStackSize - return the amount of stack space
  taken up by parameters of this function.
SymbolFile::GetOwnFrameSize - the size of this function's frame. This
  excludes the parameters, but includes stuff like local variables and
  spilled registers.

These functions are then used by the unwinder to compute the estimated
location of the return address. This address is not always exact,
because the stack may contain some additional values -- for instance, if
we're getting ready to call a function then the stack will also contain
partially set up arguments, but we will not know their size because we
haven't called the function yet. For this reason the unwinder will crawl
up the stack from the return address position, and look for something
that looks like a possible return address. Currently, we assume that
something is a valid return address if it ends up pointing to an
executable section.

All of this logic kicks in when the UnwindPlan sets the value of CFA as
"isHeuristicallyDetected", which is also the final new API here. Right
now, only SymbolFileBreakpad implements these APIs, but in the future
SymbolFilePDB will use them too.

Differential Revision: https://reviews.llvm.org/D66638

llvm-svn: 373072

Summary:
The DWARFExpression methods have a lot of arguments. This removes two of
them by removing the ability to slice the expression via two offset+size
parameters. This is a functionality that it is not always needed, and
when it is, we already have a different handy way of slicing a data
extractor which we can use instead.

Reviewers: JDevlieghere, clayborg

Subscribers: aprantl, lldb-commits

Differential Revision: https://reviews.llvm.org/D66745

llvm-svn: 370027

Summary:
Update StackFrame::GetSymbolContext to mirror the logic in
RegisterContextLLDB::InitializeNonZerothFrame that knows not to do the
pc decrement when the given frame is a signal trap handler frame or the
parent of one, because the pc may not follow a call in these frames.
Accomplish this by adding a behaves_like_zeroth_frame field to
lldb_private::StackFrame, set to true for the zeroth frame, for
signal handler frames, and for parents of signal handler frames.

Also add logic to propagate the signal handler flag from UnwindPlan to
the FrameType on the RegisterContextLLDB it generates, and factor out a
helper to resolve symbol and address range for an Address now that we
need to invoke it in four places.

Reviewers: jasonmolenda, clayborg, jfb

Reviewed By: jasonmolenda

Subscribers: labath, dexonsmith, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D64993

llvm-svn: 367691

This patch replaces explicit calls to log::Printf with the new LLDB_LOGF
macro. The macro is similar to LLDB_LOG but supports printf-style format
strings, instead of formatv-style format strings.

So instead of writing:

  if (log)
    log->Printf("%s\n", str);

You'd write:

  LLDB_LOG(log, "%s\n", str);

This change was done mechanically with the command below. I replaced the
spurious if-checks with vim, since I know how to do multi-line
replacements with it.

  find . -type f -name '*.cpp' -exec \
  sed -i '' -E 's/log->Printf\(/LLDB_LOGF\(log, /g' "{}" +

Differential revision: https://reviews.llvm.org/D65128

llvm-svn: 366936