Commit Graph

651 Commits

Author SHA1 Message Date
Jonas Devlieghere bba9ba8d95 [lldb/Plugin] s/LLDB_PLUGIN/LLDB_PLUGIN_DEFINE/ (NFC)
Rename LLDB_PLUGIN to LLDB_PLUGIN_DEFINE as Pavel suggested in D73067 to
avoid name conflict.
2020-02-14 09:58:24 -08:00
Jan Kratochvil 98c940bf51 [NFC] [lldb] Remove unused declaration
ObjectFileELF::GetSectionIndexByType declaration without definition was
added by commit 17220c1886.
2020-02-11 14:59:52 +01:00
Martin Storsjö 6115bd9ba2 [LLDB] Fix GCC warnings about extra semicolons. NFC. 2020-02-10 11:20:44 +02:00
Jonas Devlieghere fbb4d1e43d [lldb/Plugins] Use external functions to (de)initialize plugins
This is a step towards making the initialize and terminate calls be
generated by CMake, which in turn is towards making it possible to
disable plugins at configuration time.

Differential revision: https://reviews.llvm.org/D74245
2020-02-07 15:28:27 -08:00
Pavel Labath 40efa65de8 Revert "[LLDB] Add DynamicLoaderWasmDYLD plugin for WebAssembly debugging"
This patch has a couple of outstanding issues. The test is not python3
compatible, and it also seems to fail with python2 (at least under some
circumstances) due to an overambitious assertion.

This reverts the patch as well as subsequent fixup attempts:
014ea93376,
f5f70d1c8f.
4697e701b8.
5c15e8e682.
3ec28da6d6.
2020-02-05 16:22:19 -08:00
Paolo Severini 3ec28da6d6 [LLDB] Add DynamicLoaderWasmDYLD plugin for WebAssembly debugging
Add a dynamic loader plug-in class for WebAssembly modules.

Differential Revision: https://reviews.llvm.org/D72751
2020-02-05 14:49:36 -08:00
Michał Górny 98594a44aa [lldb] [ObjectFile/ELF] Fix negated seg ids on 32-bit arches
Scale segment identifier up to user_id_t before negating it.  This fixes
the identifers being wrongly e.g. 0x00000000fffffffe instead of
0xfffffffffffffffe.  Fix suggested by Pavel Labath.

This fixes 5 tests failing on i386 (PR #44748):

  lldb-shell :: ObjectFile/ELF/PT_LOAD-overlap-PT_INTERP.yaml
  lldb-shell :: ObjectFile/ELF/PT_LOAD-overlap-PT_TLS.yaml
  lldb-shell :: ObjectFile/ELF/PT_LOAD-overlap-section.yaml
  lldb-shell :: ObjectFile/ELF/PT_LOAD.yaml
  lldb-shell :: ObjectFile/ELF/PT_TLS-overlap-PT_LOAD.yaml

Differential Revision: https://reviews.llvm.org/D73914
2020-02-04 05:50:56 +01:00
Alex Langford 22b044877d [lldb][NFCI] Remove unused LanguageType parameters
These parameters are unused in these methods, and some of them only had a
LanguageType parameter to pipe to other methods that don't use it
either.
2020-01-30 21:57:23 -08:00
Benjamin Kramer adcd026838 Make llvm::StringRef to std::string conversions explicit.
This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.

This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.

This doesn't actually modify StringRef yet, I'll do that in a follow-up.
2020-01-28 23:25:25 +01:00
Raphael Isemann 808142876c [lldb][NFC] Fix all formatting errors in .cpp file headers
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
2020-01-24 08:52:55 +01:00
Derek Schuff d34e4152e3 [LLDB] Convert Plugins/ObjectFile/wasm/ObjectFileWasm.h to unix line endings 2020-01-16 09:38:37 -08:00
Paolo Severini 9b3254dbf9 [LLDB] Add SymbolVendorWasm plugin for WebAssembly debugging
Add plugin class SymbolVendorWasm, with the logic to manage debug symbols
for Wasm modules.

Reviewers: clayborg, labath, aprantl, sbc100, teemperor

Reviewed By: labath

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D72650
2020-01-16 09:36:17 -08:00
Jim Ingham cd9e5c3230 Fix the macos build after D71575.
size_t and uint64_t are spelled slightly differently on macOS, which was
causing the compiler to error out calling std::min - since the two types have
to be the same.

I fixed this by casting the uint64_t computation to a size_t.  That's probably
not the cleanest solution, but it gets us back to building.
2020-01-15 18:13:44 -08:00
Paolo Severini 4bafceced6 [LLDB] Add ObjectFileWasm plugin for WebAssembly debugging
Summary:
This is the first in a series of patches to enable LLDB debugging of
WebAssembly targets.

Current versions of Clang emit (partial) DWARF debug information in WebAssembly
modules and we can leverage this debug information to give LLDB the ability to
do source-level debugging of Wasm code that runs in a WebAssembly engine.

A way to do this could be to use the remote debugging functionalities provided
by LLDB via the GDB-remote protocol. Remote debugging can indeed be useful not
only to connect a debugger to a process running on a remote machine, but also to
connect the debugger to a managed VM or script engine that runs locally,
provided that the engine implements a GDB-remote stub that offers the ability to
access the engine runtime internal state.

To make this work, the GDB-remote protocol would need to be extended with a few
Wasm-specific custom query commands, used to access aspects of the Wasm engine
state (like the Wasm memory, Wasm local and global variables, and so on).
Furthermore, the DWARF format would need to be enriched with a few Wasm-specific
extensions, here detailed: https://yurydelendik.github.io/webassembly-dwarf.

This CL introduce classes **ObjectFileWasm**, a file plugin to represent a Wasm
module loaded in a debuggee process. It knows how to parse Wasm modules and
store the Code section and the DWARF-specific sections.

Reviewers: jasonmolenda, clayborg, labath

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D71575
2020-01-15 16:25:35 -08:00
Pavel Labath 4b5bc38802 [lldb/DWARF] Move location list sections into DWARFContext
These are the last sections not managed by the DWARFContext object. I
also introduce separate SectionType enums for dwo section variants, as
this is necessary for proper handling of single-file split dwarf.
2020-01-14 15:19:29 +01:00
Jan Kratochvil bf7225888a [lldb] Fix lookup of symbols with the same address range but different binding
This fixes a failing testcase on Fedora 30 x86_64 (regression Fedora 29->30):

PASS:
./bin/lldb ./lldb-test-build.noindex/functionalities/unwind/noreturn/TestNoreturnUnwind.test_dwarf/a.out -o 'settings set symbols.enable-external-lookup false' -o r -o bt -o quit
  * frame #0: 0x00007ffff7aa6e75 libc.so.6`__GI_raise + 325
    frame #1: 0x00007ffff7a91895 libc.so.6`__GI_abort + 295
    frame #2: 0x0000000000401140 a.out`func_c at main.c:12:2
    frame #3: 0x000000000040113a a.out`func_b at main.c:18:2
    frame #4: 0x0000000000401134 a.out`func_a at main.c:26:2
    frame #5: 0x000000000040112e a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:32:2
    frame #6: 0x00007ffff7a92f33 libc.so.6`__libc_start_main + 243
    frame #7: 0x000000000040106e a.out`_start + 46

vs.

FAIL - unrecognized abort() function:
./bin/lldb ./lldb-test-build.noindex/functionalities/unwind/noreturn/TestNoreturnUnwind.test_dwarf/a.out -o 'settings set symbols.enable-external-lookup false' -o r -o bt -o quit
  * frame #0: 0x00007ffff7aa6e75 libc.so.6`.annobin_raise.c + 325
    frame #1: 0x00007ffff7a91895 libc.so.6`.annobin_loadmsgcat.c_end.unlikely + 295
    frame #2: 0x0000000000401140 a.out`func_c at main.c:12:2
    frame #3: 0x000000000040113a a.out`func_b at main.c:18:2
    frame #4: 0x0000000000401134 a.out`func_a at main.c:26:2
    frame #5: 0x000000000040112e a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:32:2
    frame #6: 0x00007ffff7a92f33 libc.so.6`.annobin_libc_start.c + 243
    frame #7: 0x000000000040106e a.out`.annobin_init.c.hot + 46

The extra ELF symbols are there due to Annobin (I did not investigate why this
problem happened specifically since F-30 and not since F-28).

It is due to:

Symbol table '.dynsym' contains 2361 entries:
Valu e          Size Type   Bind   Vis     Name
0000000000022769   5 FUNC   LOCAL  DEFAULT _nl_load_domain.cold
000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_abort.c.unlikely
...
000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_loadmsgcat.c_end.unlikely
...
000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_textdomain.c_end.unlikely
000000000002276e 548 FUNC   GLOBAL DEFAULT abort
000000000002276e 548 FUNC   GLOBAL DEFAULT abort@@GLIBC_2.2.5
000000000002276e 548 FUNC   LOCAL  DEFAULT __GI_abort
0000000000022992   0 NOTYPE LOCAL  HIDDEN  .annobin_abort.c_end.unlikely

GDB has some more complicated preferences between overlapping and/or sharing
address symbols, I have made here so far the most simple fix for this case.

Differential revision: https://reviews.llvm.org/D63540
2020-01-13 12:05:26 +01:00
Jason Molenda 7026b34702 make err msg in MachSymtabSectionInfo::GetSection clear about the file
This error message didn't specify which file was malformed, so
there's some hunting-around required if it comes up.  We have the
filename; include it in the error message.
2019-12-18 16:13:17 -08:00
Jonas Devlieghere e194d89012 [lldb/MachO] "Fix" intentional out-of-bounds error (NFC)
Remove the hack that populates the cpsr register in the gpr struct by
writing past the end of the array. This was tripping up ASan.

Patch by: Reva Cuthbertson
2019-12-18 12:54:04 -08:00
Martin Storsjö a0f72441c8 [LLDB] [PECOFF] Make sure to set the address byte size in m_data after parsing headers
If not set, the address byte size was implied to be the one of the
host process.

This allows reverting the functional change from 31087b2ae9154, since
now PECOFF does the same as ELF and MachO wrt setting both byte order
and address size on m_data within ParseHeader.

Differential Revision: https://reviews.llvm.org/D71108
2019-12-10 13:55:38 +02:00
Pavel Labath 28e4942b2c [lldb] Remove FileSpec(FileSpec*) constructor
This constructor was the cause of some pretty weird behavior. Remove it,
and update all code to properly dereference the argument instead.
2019-12-04 10:49:25 +01:00
Martin Storsjö 934c025e9b [LLDB] [PECOFF] Look for the truncated ".eh_fram" section name
COFF section names can either be stored truncated to 8 chars, in the
section header, or as a longer section name, stored separately in the
string table.

libunwind locates the .eh_frame section by runtime introspection,
which only works for section names stored in the section header (as
the string table isn't mapped at runtime). To support this behaviour,
lld always truncates the section names for sections that will be
mapped, like .eh_frame.

Differential Revision: https://reviews.llvm.org/D70745
2019-11-28 11:27:00 +02:00
Martin Storsjö 2e5bb6d8d9 [LLDB] [PECOFF] Factorize mapping section names to types using StringSwitch. NFCI.
Keep the existing special cases based on combinations of section name,
flags and sizes/offsets.

Differential Revision: https://reviews.llvm.org/D70778
2019-11-28 11:27:00 +02:00
Pavel Labath 4023bd05fc [lldb] Add boilerplate to recognize the .debug_rnglists.dwo section 2019-11-26 13:58:26 +01:00
Davide Italiano 96915495f9 [ObjectFileMachO] Fix the build for __arm64__.
Catch up with an API change.
2019-11-12 11:10:36 -08:00
Pavel Labath f71e35dc1f lldb/breakpad: add suppport for the "x86_64h" architecture 2019-11-05 11:41:20 +01:00
Martin Storsjö 3db1d138b1 [LLDB] [PECOFF] Fix error handling for executables that object::createBinary errors out on
llvm::object::createBinary returns an Expected<>, which requires
not only checking the object for success, but also requires consuming
the Error, if one was set.

Use LLDB_LOG_ERROR for this case, and change an existing similar log
statement to use it as well, to make sure the Error is consumed even
if the log channel is disabled.

Differential Revision: https://reviews.llvm.org/D69646
2019-10-31 11:26:21 +02:00
Martin Storsjö 7e1a307641 [LLDB] [PECOFF] Don't crash in ReadImageDataByRVA for addresses out of range
This can happen e.g. when unwinding doesn't work perfectly.

Differential Revision: https://reviews.llvm.org/D69502
2019-10-31 11:26:06 +02:00
Pavel Labath f1e0ae3420 COFF: Set section permissions
Summary:
This enables us to reason about whether a given address can be
executable, for instance during unwinding.

Reviewers: amccarth, mstorsjo

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D69102
2019-10-30 14:13:21 +01:00
Martin Storsjö 4394b5bee6 [LLDB] [PECOFF] Use FindSectionByID to associate symbols to sections
The virtual container/header section caused the section list to be
offset by one, but by using FindSectionByID, the layout of the
section list shouldn't matter.

Differential Revision: https://reviews.llvm.org/D69366
2019-10-29 14:48:35 +02:00
Pavel Labath 73a7a55c0e lldb/COFF: Create a separate "section" for the file header
In an attempt to ensure that every part of the module's memory image is
accounted for, D56537 created a special "container section" spanning the
entire image. While that seemed reasonable at the time (and it still
mostly does), it did create a problem of what to put as the "file size"
of the section, because the image is not continuous on disk, as we
generally assume (which is why I put zero there). Additionally, this
arrangement makes it unclear what kind of permissions should be assigned
to that section (which is what my next patch does).

To get around these, this patch partially reverts D56537, and goes back
to top-level sections. Instead, what I do is create a new "section" for
the object file header, which is also being loaded into memory, though
its not considered to be a section in the strictest sense. This makes it
possible to correctly assign file size section, and we can later assign
permissions to it as well.

Reviewers: amccarth, mstorsjo

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D69100
2019-10-25 22:11:53 +00:00
Vedant Kumar 72105b9dcd Fix compilation error in ObjectFileMachO::ParseSymtab 2019-10-25 11:16:51 -07:00
Adrian Prantl 1ad655e255 Modernize the rest of the Find.* API (NFC)
This patch removes the size_t return value and the append parameter
from the remainder of the Find.* functions in LLDB's internal API. As
in the previous patches, this is motivated by the fact that these
parameters aren't really used, and in the case of the append parameter
were frequently implemented incorrectly.

Differential Revision: https://reviews.llvm.org/D69119

llvm-svn: 375160
2019-10-17 19:56:40 +00:00
Jason Molenda 7dd7a36075 Add arm64_32 support to lldb, an ILP32 codegen
that runs on arm64 ISA targets, specifically 
Apple watches.


Differential Revision: https://reviews.llvm.org/D68858

llvm-svn: 375032
2019-10-16 19:14:49 +00:00
Martin Storsjo 674d55438d [LLDB] [PECOFF] Use a "pc" vendor name in aarch64 triples
This matches all other architectures listed in the same file.

This fixes debugging aarch64 executables with lldb-server, which
otherwise fails, with log messages like these:

Target::SetArchitecture changing architecture to aarch64 (aarch64-pc-windows-msvc)
Target::SetArchitecture Trying to select executable file architecture aarch64 (aarch64-pc-windows-msvc)

ArchSpec::SetArchitecture sets the vendor to llvm::Triple::PC
for any coff/win32 combination, and if this doesn't match the triple
set by the PECOFF module, things doesn't seem to work with when
using lldb-server.

Differential Revision: https://reviews.llvm.org/D68939

llvm-svn: 374867
2019-10-15 08:32:46 +00:00
Kadir Cetinkaya cb5324c462 [lldb] Insert break to avoid unannotated fall-through
llvm-svn: 374545
2019-10-11 12:33:47 +00:00
Aleksandr Urakov 30c2441a32 [Windows] Use information from the PE32 exceptions directory to construct unwind plans
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
2019-10-11 09:03:29 +00:00
Adrian Prantl f98606f177 Remove obsolete parameter.
llvm-svn: 374185
2019-10-09 16:55:27 +00:00
Adrian Prantl 939411c1aa Remove the is_mangled flag from Mangled and Symbol
Testing whether a name is mangled or not is extremely cheap and can be
done by looking at the first two characters. Mangled knows how to do
it. On the flip side, many call sites that currently pass in an
is_mangled determination do not know how to correctly do it (for
example, they leave out Swift mangling prefixes).

This patch removes this entry point and just forced Mangled to
determine the mangledness of a string itself.

Differential Revision: https://reviews.llvm.org/D68674

llvm-svn: 374180
2019-10-09 16:22:14 +00:00
Hans Wennborg 1e1e3ba252 Unify the two CRC implementations
David added the JamCRC implementation in r246590. More recently, Eugene
added a CRC-32 implementation in r357901, which falls back to zlib's
crc32 function if present.

These checksums are essentially the same, so having multiple
implementations seems unnecessary. This replaces the CRC-32
implementation with the simpler one from JamCRC, and implements the
JamCRC interface in terms of CRC-32 since this means it can use zlib's
implementation when available, saving a few bytes and potentially making
it faster.

JamCRC took an ArrayRef<char> argument, and CRC-32 took a StringRef.
This patch changes it to ArrayRef<uint8_t> which I think is the best
choice, and simplifies a few of the callers nicely.

Differential revision: https://reviews.llvm.org/D68570

llvm-svn: 374148
2019-10-09 09:06:30 +00:00
Antonio Afonso ad6690afa3 Explicitly set entry point arch when it's thumb [Second Try]
Summary:
This is a redo of D68069 because I reverted it due to some concerns that were now addressed along with the new comments that @labath added.

I found a case where the main android binary (app_process32) had thumb code at its entry point but no entry in the symbol table indicating this. This made lldb set a 4 byte breakpoint at that address (we default to arm code) instead of a 2 byte one (like we should for thumb).
The big deal with this is that the expression evaluator uses the entry point as a way to know when a JITed expression has finished executing by putting a breakpoint there. Because of this, evaluating expressions on certain android devices (Google Pixel something) made the process crash.
This was fixed by checking this specific situation when we parse the symbol table and add an artificial symbol for this 2 byte range and indicating that it's arm thumb.

I created 2 unit tests for this, one to check that now we know that the entry point is arm thumb, and the other to make sure we didn't change the behaviour for arm code.

I also run the following on the command line with the `app_process32` where I found the issue:
**Before:**
```
(lldb) dis -s 0x1640 -e 0x1644
app_process32[0x1640]: .long  0xf0004668                ; unknown opcode
```
**After:**
```
(lldb) dis -s 0x1640 -e 0x1644
app_process32`:
app_process32[0x1640] <+0>: mov    r0, sp
app_process32[0x1642]:      andeq  r0, r0, r0
```

Reviewers: clayborg, labath, wallace, espindola

Reviewed By: labath

Subscribers: labath, lldb-commits, MaskRay, kristof.beyls, arichardson, emaste, srhines

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D68533

llvm-svn: 374132
2019-10-08 23:44:49 +00:00
Adrian Prantl 8db229e287 ObjectFileMachO: Replace std::map with llvm::DenseMap (NFC)
This makes parsing the symbol table of clang marginally faster. (Hashtable versus tree).

Differential Revision: https://reviews.llvm.org/D68605

llvm-svn: 374084
2019-10-08 16:59:24 +00:00
Adrian Prantl 917b8df0e5 Replace static const StringRef with StringRef (NFC)
Differential Revision: https://reviews.llvm.org/D68597

llvm-svn: 374081
2019-10-08 16:29:36 +00:00
Adrian Prantl bde5a6a45a Remove constructor and unused method (NFC).
Differential Revision: https://reviews.llvm.org/D68595

llvm-svn: 374080
2019-10-08 16:29:33 +00:00
Jonas Devlieghere 4bddca306a [MachO] Fix symbol merging during symtab parsing.
The symtab parser in ObjectFileMachO has logic to coalesce debug (STAB)
and non-debug symbols, based on the address and the symbol name for
static (STSYM) and global symbols (GSYM) respectively. It makes the
assumption that the debug variant is always encountered first. Rather
than creating a second entry in the symbol table for the non-debug
symbol, the latter gets merged into the existing debug symbol.

This breaks when the linker emits the non-debug symbol first. We'd end
up with two entries in the symbol table, each containing part of the
information LLDB relies on. Indeed, commenting out the merging logic
breaks the test suite spectacularly.

This patch solves that problem by always parsing the debug symbols
first. This guarantees that the assumption for merging holds.

I'm not particularly happy with  adding a lambda, but after numerous
attempts this is the best solution I could come up with. The symtab
parsing logic is pretty complex in that it touches a lot of things. I've
experienced first hand that it's very easy to break things. I believe
this approach strikes a balance between fixing the issue while limiting
the risk of regressions.

Differential revision: https://reviews.llvm.org/D68536

llvm-svn: 373994
2019-10-08 00:13:59 +00:00
Jonas Devlieghere 369407fc52 [MachO] Shuffle some things around in ParseSymtab (NFC)
llvm-svn: 373954
2019-10-07 20:31:22 +00:00
Konrad Kleine 2c082b4827 [lldb][ELF] Read symbols from .gnu_debugdata sect.
Summary:
If the .symtab section is stripped from the binary it might be that
there's a .gnu_debugdata section which contains a smaller .symtab in
order to provide enough information to create a backtrace with function
names or to set and hit a breakpoint on a function name.

This change looks for a .gnu_debugdata section in the ELF object file.
The .gnu_debugdata section contains a xz-compressed ELF file with a
.symtab section inside. Symbols from that compressed .symtab section
are merged with the main object file's .dynsym symbols (if any).
In addition we always load the .dynsym even if there's a .symtab
section.

For example, the Fedora and RHEL operating systems strip their binaries
but keep a .gnu_debugdata section. While gdb already can read this
section, LLDB until this patch couldn't. To test this patch on a
Fedora or RHEL operating system, try to set a breakpoint on the "help"
symbol in the "zip" binary. Before this patch, only GDB can set this
breakpoint; now LLDB also can do so without installing extra debug
symbols:

    lldb /usr/bin/zip -b -o "b help" -o "r" -o "bt" -- -h

The above line runs LLDB in batch mode and on the "/usr/bin/zip -h"
target:

    (lldb) target create "/usr/bin/zip"
    Current executable set to '/usr/bin/zip' (x86_64).
    (lldb) settings set -- target.run-args  "-h"

Before the program starts, we set a breakpoint on the "help" symbol:

    (lldb) b help
    Breakpoint 1: where = zip`help, address = 0x00000000004093b0

Once the program is run and has hit the breakpoint we ask for a
backtrace:

    (lldb) r
    Process 10073 stopped
    * thread #1, name = 'zip', stop reason = breakpoint 1.1
        frame #0: 0x00000000004093b0 zip`help
    zip`help:
    ->  0x4093b0 <+0>:  pushq  %r12
        0x4093b2 <+2>:  movq   0x2af5f(%rip), %rsi       ;  + 4056
        0x4093b9 <+9>:  movl   $0x1, %edi
        0x4093be <+14>: xorl   %eax, %eax

    Process 10073 launched: '/usr/bin/zip' (x86_64)
    (lldb) bt
    * thread #1, name = 'zip', stop reason = breakpoint 1.1
      * frame #0: 0x00000000004093b0 zip`help
        frame #1: 0x0000000000403970 zip`main + 3248
        frame #2: 0x00007ffff7d8bf33 libc.so.6`__libc_start_main + 243
        frame #3: 0x0000000000408cee zip`_start + 46

In order to support the .gnu_debugdata section, one has to have LZMA
development headers installed. The CMake section, that controls this
part looks for the LZMA headers and enables .gnu_debugdata support by
default if they are found; otherwise or if explicitly requested, the
minidebuginfo support is disabled.

GDB supports the "mini debuginfo" section .gnu_debugdata since v7.6
(2013).

Reviewers: espindola, labath, jankratochvil, alexshap

Reviewed By: labath

Subscribers: rnkovacs, wuzish, shafik, emaste, mgorny, arichardson, hiraditya, MaskRay, lldb-commits

Tags: #lldb, #llvm

Differential Revision: https://reviews.llvm.org/D66791

llvm-svn: 373891
2019-10-07 10:32:16 +00:00
Jonas Devlieghere 4e5d9e120b [MachO] Reduce indentation further in ParseSymtab (NFC)
llvm-svn: 373810
2019-10-04 23:09:55 +00:00
Jonas Devlieghere 5042882698 [MachO] Move nlist parsing into helper function (NFC)
llvm-svn: 373803
2019-10-04 22:21:32 +00:00
Jonas Devlieghere e973fc0056 [MachO] Add early returns to save some indentation.
This file really suffered from the Great Reformat. I'm adding a few
early returns to give the deeply nested code some more breathing room.

llvm-svn: 373778
2019-10-04 19:37:59 +00:00
Jonas Devlieghere 845292cba3 [MachO] Reformat before making changes to this file (NFC)
llvm-svn: 373777
2019-10-04 19:37:52 +00:00