- it is always passed as zero
- a lot of plugins aren't using it correctly
- the data extractor class already has the capability to look at a
subset of bytes
Some plugins were returning the number of specifications they have
added, while others were returning the total final number. Particularly
devious plugins (Minidump) were clearing the specification list
altogether. This resulted in nondeterministic failures (depending on
plugin ininitialization order) in TestSBModule.
This PR defines the problem away by having each plugin only return the
specifications it is responsible for. If the caller wants to merge them,
it is free to do so. This *might* be slighly less efficient, but this is
hardly hot code.
I'm not touching the ObjectFile::GetModuleSpecifications function (the
caller of all these functions) as the PR is big enough, although the
same approach might be warranted there as well.
Fixes https://github.com/llvm/llvm-project/issues/178625.
In a PR last month I changed the ObjectFile CreateInstance etc methods
to accept an optional DataExtractorSP instead of a DataBufferSP, and
retain the extractor in a shared pointer internally in all of the
ObjectFile subclasses. This is laying the groundwork for using a
VirtualDataExtractor for some Mach-O binaries on macOS, where the
segments of the binary are out-of-order in actual memory, and we add a
lookup table to make it appear that the TEXT segment is at offset 0 in
the Extractor, etc. Working on the actual implementation, I realized we
were still using DataBufferSP's in ModuleSpec and Module, as well as in
ObjectFile::GetModuleSpecifications.
I originally was making a much larger NFC change where I had all
ObjectFile subclasses operating on DataExtractors throughout their
implementation, as well as in the DWARF parser. It was a very large
patchset. Many subclasses start with their DataExtractor, then create
smaller DataExtractors for parts of the binary image - the string table,
the symbol table, etc., for processing.
After consideration and discussion with Jonas, we agreed that a
segment/section of a binary will never require a lookup table to access
the bytes within it, so I changed
VirtualDataExtractor::GetSubsetExtractorSP to (1) require that the
Subset be contained within a single lookup table entry, and (2) return a
simple DataExtractor bounded on that byte range. By doing this, I was
able to remove all of my very-invasive changes to the ObjectFile
subclass internals; it's only when they are operating on the entire
binary image that care is needed.
One pattern that subclasses like ObjectFileBreakpad use is to take an
ArrayRef of the DataBuffer for a binary, then create a StringRef of
that, then look for strings in it. With a VirtualDataExtractor and
out-of-order binary segments, with gaps between them, this allows us to
search the entire buffer looking for a string, and segfault when it gets
to an unmapped region of the buffer. I added a
VirtualDataExtractor::GetSubsetExtractorSP(0) which gets the largest
contiguous memory region starting at offset 0 for this use case, and I
added a comment about what was being done there because I know it is not
obvious, and people not working on macOS wouldn't be familiar with the
requirement. (when we have a ModuleSpec with a DataExtractor, any of the
ObjectFile subclasses get a shot at Creating, so they all have to be
able to iterate on these)
rdar://148939795
The ObjectFile plugin interface accepts an optional DataBufferSP
argument. If the caller has the contents of the binary, it can provide
this in that DataBufferSP. The ObjectFile subclasses in their
CreateInstance methods will fill in the DataBufferSP with the actual
binary contents if it is not set.
ObjectFile base class creates an ivar DataExtractor from the
DataBufferSP passed in.
My next patch will be a caller that creates a VirtualDataExtractor with
the binary data, and needs to pass that in to the ObjectFile plugin,
instead of the bag-of-bytes DataBufferSP. It builds on the previous
patch changing ObjectFile's ivar from DataExtractor to DataExtractorSP
so I could pass in a subclass in the shared ptr. And it will be using
the VirtualDataExtractor that Jonas added in
https://github.com/llvm/llvm-project/pull/168802
No behavior is changed by the patch; we're simply moving the creation of
the DataExtractor to the caller, instead of a DataBuffer that is
immediately used to set up the ObjectFile DataExtractor. The patch is a
bit complicated because all of the ObjectFile subclasses have to
initialize their DataExtractor to pass in to the base class.
I ran the testsuite on macOS and on AArch64 Ubutnu. (btw David, I ran it
under qemu on my M4 mac with SME-no-SVE again, Ubuntu 25.10, checked
lshw(1) cpu capabilities, and qemu doesn't seem to be virtualizing the
SME, that explains why the testsuite passes)
rdar://148939795
---------
Co-authored-by: Jonas Devlieghere <jonas@devlieghere.com>
ObjectFile has an m_data DataExtractor ivar which may be default
constructed initially, or initialized with a DataBuffer passed in to its
ctor. If the DataExtractor does not get a DataBuffer source passed in,
the subclass will initialize it with access to the object file's data.
When a DataBuffer is passed in to the base class ctor, the DataExtractor
only has its buffer initialized; ObjectFile doesn't yet know the address
size and endianness to fully initialize the DataExtractor.
This patch changes ObjectFile to instead have a DataExtractorSP ivar
which is always initialized with at least a default-constructed
DataExtractor object in the base class ctor. The next patch I will be
writing is to change the ObjectFile ctor to take an optional
DataExtractorSP, so the caller can pass a DataExtractor subclass -- the
VirtualizeDataExtractor being added via
https://github.com/llvm/llvm-project/pull/168802
instead of a DataBuffer which is trivially saved into the DataExtractor.
The change is otherwise mechanical; all `m_data.` changed to
`m_data_sp->` and all the places where `m_data` was passed in for a
by-ref call were changed to `*m_data_sp.get()`. The shared pointer is
always initialized to contain an object.
I built & ran the testsuite on macOS and on aarch64-Ubuntu (thanks for
getting the Linux testsuite to run on SME-only systems David). All of
the ObjectFile subclasses I modifed compile cleanly, but I haven't
tested them beyond any unit tests they may have (prob breakpad).
rdar://148939795
Lots of code around LLDB was directly accessing the target's section
load list. This NFC patch makes the section load list private so the
Target class can access it, but everyone else now uses accessor
functions. This allows us to control the resolving of addresses and will
allow for functionality in LLDB which can lazily resolve addresses in
JIT plug-ins with a future patch.
This commit does a few related things:
- Removes unused function `uuid_is_null`
- Removes unneeded includes of UuidCompatibility.h
- Renames UuidCompatibility to AppleUuidCompatibility and adds a comment
to clarify intent of header.
- Moves AppleUuidCompatibility to the include directory
Differential Revision: https://reviews.llvm.org/D156562
In the spirit of not having lldbExpression rely on plugins, this move
makes the most sense. ObjectFileJIT is not really a "plugin" in the
sense that without it, expression evaluation doesn't work at all. This
is different than something like ObjectFileELF where lldb can still
technically debug non-ELF targets without it. For that reason, moving
ObjectFileJIT into Expression where it will be used in conjunction with
IRExecutionUnit makes the most sense.
Differential Revision: https://reviews.llvm.org/D147084
