The IT instruction can specify condition code for up to 4 consecutive
instruction and it is used quite often by clang in epilogues causing
an issue when trying to unwind from locations covered by the IT
instruction and for locatins inmediately after the IT instruction.
Changes made to fix it:
* Introduce the concept of conditional instruction block what is a list
of consecutive instructions with the same condition. We update the
unwind information during the conditional instruction block and when
we reach the end of it (first instruction with a differemt condition)
then we restore the unwind information we had before the condition.
* Fix a bug in the ARM instruction emulator where neither PC nor the
ITSTATE was advanced when we reached an instruction what we can't
decode.
After the change we have no regression on android-arm running the
regular test suit and TestStandardUnwind also passes when running it
with clang as the compiler (previously it failed on an IT instruction).
Differential revision: http://reviews.llvm.org/D16814
llvm-svn: 260368
* 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:
This patch enables evaluation of DWARF expressions setting the CFA during stack unwinding.
This makes TestSigtrampUnwind "almost" pass on linux. I am not enabling the test yet since the
symbol name for the signal trampoline does not get resolved properly due to a different bug, but
apart from that, the backtrace is sane.
I am unsure how this change affects Mac. I think it makes the unwinder prefer the DWARF unwind
plan instead of some custom platform-dependant plan. However, it does not affect the end result
- the stack unwinding works as expected.
Reviewers: jasonmolenda
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D7792
llvm-svn: 230211
Summary:
This change refactors UnwindPlan::Row to be able to store the fact that the CFA is value is set
by evaluating a dwarf expression (DW_CFA_def_cfa_expression). This is achieved by creating a new
class CFAValue and moving all CFA setting/getting code there. Note that code using the new
CFAValue::isDWARFExpression is not yet present and will be added in a follow-up patch. Therefore,
this patch should not change the functionality in any way.
Test Plan: Ran tests on Mac and Linux. No regressions detected.
Reviewers: jasonmolenda, clayborg
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D7755
llvm-svn: 230210
step through the complete function looking for any epilogue
instructions. If we find an epilogue sequence, re-instate
the correct unwind instructions if there is more code past
that epilogue -- this will correctly handle an x86 function
with multiple epilogues in it.
NB there is still a bug with the "eh_frame augmented"
UnwindPlans and mid-function epilogues. Looking at that next.
<rdar://problem/18863406>
llvm-svn: 225770
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
Summary:
PowerPC handles the stack chain with the current stack pointer being a pointer
to the backchain (CFA). LLDB currently has no way of handling this, so this
adds a "CFA is dereferenced from a register" type.
Discussed with Jason Molenda, who also provided the initial patch for this.
Reviewers: jasonmolenda
Reviewed By: jasonmolenda
Subscribers: emaste, lldb-commits
Differential Revision: http://reviews.llvm.org/D6182
llvm-svn: 221788
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
This is a mechanical change addressing the various sign comparison warnings that
are identified by both clang and gcc. This helps cleanup some of the warning
spew that occurs during builds.
llvm-svn: 205390
indications that the UnwindPlan is invalid -- for instance, a
complete lack of rows, or a row that fails to define a register to
base the CFA off of.
<rdar://problem/15246247>
llvm-svn: 196201
Full UnwindPlan is trying to do an impossible unwind; in that case
invalidate the Full UnwindPlan and replace it with the architecture
default unwind plan.
This is a scenario that happens occasionally with arm unwinds in
particular; the instruction analysis based full unwindplan can
mis-parse the functions and the stack walk stops prematurely. Now
we can do a simpleminded frame-chain walk to find the caller frame
and continue the unwind. It's not ideal but given the complicated
nature of analyzing the arm functions, and the lack of eh_frame
information on iOS, it is a distinct improvement and fixes some
long-standing problems with the unwinder on that platform.
This is fixing <rdar://problem/12091421>. I may re-use this
invalidate feature in the future if I can identify other cases where
the full unwindplan's unwind information is clearly incorrect.
This checkin also includes some cleanup for the volatile register
definition in the arm ABI plugin for <rdar://problem/10652166>
although work remains to be done for that bug.
llvm-svn: 166757
the state of the unwind instructions once the prologue has finished. If it hits an
early return epilogue in the middle of the function, re-instate the prologue after that
epilogue has completed so that we can still unwind for cases where the flow of control
goes past that early-return. <rdar://problem/11775059>
Move the UnwindPlan operator== definition into the .cpp file, expand the definition a bit.
Add some casts to a SBCommandInterpreter::HandleCompletion() log statement so it builds without
warning on 64- and 32-bit systems.
llvm-svn: 160337
a shared pointer to ease some memory management issues with a patch
I'm working on.
The main complication with using SPs for these objects is that most
methods that build up an UnwindPlan will construct a Row to a given
instruction point in a function, then add additional regsaves in
the next instruction point to that row and push it again. A little
care is needed to not mutate the previous instruction point's Row
once these are switched to being held behing shared pointers.
llvm-svn: 160214
objects for the backlink to the lldb_private::Process. The issues we were
running into before was someone was holding onto a shared pointer to a
lldb_private::Thread for too long, and the lldb_private::Process parent object
would get destroyed and the lldb_private::Thread had a "Process &m_process"
member which would just treat whatever memory that used to be a Process as a
valid Process. This was mostly happening for lldb_private::StackFrame objects
that had a member like "Thread &m_thread". So this completes the internal
strong/weak changes.
Documented the ExecutionContext and ExecutionContextRef classes so that our
LLDB developers can understand when and where to use ExecutionContext and
ExecutionContextRef objects.
llvm-svn: 151009
stdarg formats to use __attribute__ format so the compiler can flag
incorrect uses. Fix all incorrect uses. Most of these are innocuous,
a few were resulting in crashes.
llvm-svn: 140185
respective ABI plugins as they were plug-ins that supplied ABI specfic info.
Also hookep up the UnwindAssemblyInstEmulation so that it can generate the
unwind plans for ARM.
Changed the way ABI plug-ins are handed out when you get an instance from
the plug-in manager. They used to return pointers that would be mananged
individually by each client that requested them, but now they are handed out
as shared pointers since there is no state in the ABI objects, they can be
shared.
llvm-svn: 131193
Switch the EmulateInstruction to use the standard RegisterInfo structure
that is defined in the lldb private types intead of passing the reg kind and
reg num everywhere. EmulateInstruction subclasses also need to provide
RegisterInfo structs given a reg kind and reg num. This eliminates the need
for the GetRegisterName() virtual function and allows more complete information
to be passed around in the read/write register callbacks. Subclasses should
always provide RegiterInfo structs with the generic register info filled in as
well as at least one kind of register number in the RegisterInfo.kinds[] array.
llvm-svn: 130256
an issue with the way the UnwindLLDB was handing out RegisterContexts: it
was making shared pointers to register contexts and then handing out just
the pointers (which would get put into shared pointers in the thread and
stack frame classes) and cause double free issues. MallocScribble helped to
find these issues after I did some other cleanup. To help avoid any
RegisterContext issue in the future, all code that deals with them now
returns shared pointers to the register contexts so we don't end up with
multiple deletions. Also now that the RegisterContext class doesn't require
a stack frame, we patched a memory leak where a StackFrame object was being
created and leaked.
Made the RegisterContext class not have a pointer to a StackFrame object as
one register context class can be used for N inlined stack frames so there is
not a 1 - 1 mapping. Updates the ExecutionContextScope part of the
RegisterContext class to never return a stack frame to indicate this when it
is asked to recreate the execution context. Now register contexts point to the
concrete frame using a concrete frame index. Concrete frames are all of the
frames that are actually formed on the stack of a thread. These concrete frames
can be turned into one or more user visible frames due to inlining. Each
inlined stack frame has the exact same register context (shared via shared
pointers) as any parent inlined stack frames all the way up to the concrete
frame itself.
So now the stack frames and the register contexts should behave much better.
llvm-svn: 122976
RegisterContextLLDB holds a reference to the SymbolContext
in the vector of Cursors that UnwindLLDB maintains. Switch
UnwindLLDB to hold a vector of shared pointers of Cursors
so this reference doesn't become invalid.
Correctly falling back from the "fast" UnwindPlan to the
"full" UnwindPlan when additional registers need to be
retrieved.
llvm-svn: 118218
Not yet enabled as the default unwinder but there are no known
backtrace problems with the code at this point.
Added 'log enable lldb unwind' to help diagnose backtrace problems;
this output needs a little refining but it's a good first step.
eh_frame information is currently read unconditionally - the code
is structured to allow this to be delayed until it's actually needed.
There is a performance hit when you have to parse the eh_frame
information for any largeish executable/library so it's necessary
to avoid if possible.
It's confusing having both the UnwindPlan::RegisterLocation struct
and the RegisterConextLLDB::RegisterLocation struct, I need to rename
one of them.
The writing of registers isn't done in the RegisterConextLLDB subclass
yet; neither is the running of complex DWARF expressions from eh_frame
(e.g. used for _sigtramp on Mac OS X).
llvm-svn: 117256
The Unwind and RegisterContext subclasses still need
to be finished; none of this code is used by lldb at
this point (unless you call into it by hand).
The ObjectFile class now has an UnwindTable object.
The UnwindTable object has a series of FuncUnwinders
objects (Function Unwinders) -- one for each function
in that ObjectFile we've backtraced through during this
debug session.
The FuncUnwinders object has a few different UnwindPlans.
UnwindPlans are a generic way of describing how to find
the canonical address of a given function's stack frame
(the CFA idea from DWARF/eh_frame) and how to restore the
caller frame's register values, if they have been saved
by this function.
UnwindPlans are created from different sources. One source is the
eh_frame exception handling information generated by the compiler
for unwinding an exception throw. Another source is an assembly
language inspection class (UnwindAssemblyProfiler, uses the Plugin
architecture) which looks at the instructions in the funciton
prologue and describes the stack movements/register saves that are
done.
Two additional types of UnwindPlans that are worth noting are
the "fast" stack UnwindPlan which is useful for making a first
pass over a thread's stack, determining how many stack frames there
are and retrieving the pc and CFA values for each frame (enough
to create StackFrameIDs). Only a minimal set of registers is
recovered during a fast stack walk.
The final UnwindPlan is an architectural default unwind plan.
These are provided by the ArchDefaultUnwindPlan class (which uses
the plugin architecture). When no symbol/function address range can
be found for a given pc value -- when we have no eh_frame information
and when we don't have a start address so we can't examine the assembly
language instrucitons -- we have to make a best guess about how to
unwind. That's when we use the architectural default UnwindPlan.
On x86_64, this would be to assume that rbp is used as a stack pointer
and we can use that to find the caller's frame pointer and pc value.
It's a last-ditch best guess about how to unwind out of a frame.
There are heuristics about when to use one UnwindPlan versues the other --
this will all happen in the still-begin-written UnwindLLDB subclass of
Unwind which runs the UnwindPlans.
llvm-svn: 113581
Tamas Berghammer