and made attempts to allocate memory in the process
fall back to FindSpace and just allocate memory on
the host (but with real-looking pointers, hence
FindSpace) if the process doesn't allow allocation.
This allows expressions to run on processes that don't
support allocation, like core files.
This introduces an extremely rare potential problem:
If all of the following are true:
- The Process doesn't support allocation;
- the user writes an expression that refers to an
address that does not yet map to anything, or is
dynamically generated (e.g., the result of calling
a function); and
- the randomly-selected address for the static data
for that specific expression runs into the
address the user was expecting to work with;
then dereferencing the pointer later results
in the user seeing something unexpected. This is
unlikely but possible; as a future piece of work,
we should have processes be able to hint to the
expression parser where it can allocate temporary data
of this kind.
llvm-svn: 179827
expressions.
Previously, ClangUserExpression assumed that if
there was a constant result for an expression
then it could be determined during parsing. In
particular, the IRInterpreter ran while parser
state (in particular, ClangExpressionDeclMap)
was present. This approach is flawed, because
the IRInterpreter actually is capable of using
external variables, and hence the result might
be different each run. Until now, we papered
over this flaw by re-parsing the expression each
time we ran it.
I have rewritten the IRInterpreter to be
completely independent of the ClangExpressionDeclMap.
Instead of special-casing external variable lookup,
which ties the IRInterpreter closely to LLDB,
we now interpret the exact same IR that the JIT
would see. This IR assumes that materialization
has occurred; hence the recent implementation of the
Materializer, which does not require parser state
(in the form of ClangExpressionDeclMap) to be
present.
Materialization, interpretation, and dematerialization
are now all independent of parsing. This means that
in theory we can parse expressions once and run them
many times. I have three outstanding tasks before
shutting this down:
- First, I will ensure that all of this works with
core files. Core files have a Process but do not
allow allocating memory, which currently confuses
materialization.
- Second, I will make expression breakpoint
conditions remember their ClangUserExpression and
re-use it.
- Third, I will tear out all the redundant code
(for example, materialization logic in
ClangExpressionDeclMap) that is no longer used.
While implementing this fix, I also found a bug in
IRForTarget's handling of floating-point constants.
This should be fixed.
llvm-svn: 179801
IRMemoryMap rather than through its own memory
abstraction. This considerably simplifies the
code, and makes it possible to run the
IRInterpreter multiple times on an already-parsed
expression in the absence of a ClangExpressionDeclMap.
Changes include:
- ClangExpressionDeclMap's interface methods
for the IRInterpreter now take IRMemoryMap
arguments. They are not long for this world,
however, since the IRInterpreter will soon be
working with materialized variables.
- As mentioned above, removed the Memory class
from the IR interpreter altogether. It had a
few functions that remain useful, such as
keeping track of Values that have been placed
in memory, so I moved those into methods on
InterpreterStackFrame.
- Changed IRInterpreter to work with lldb::addr_t
rather than Memory::Region as its primary
currency.
- Fixed a bug in the IRMemoryMap where it did not
report correct address byte size and byte order
if no process was present, because it was using
Target::GetDefaultArchitecture() rather than
Target::GetArchitecture().
- Made IRMemoryMap methods clear the Errors they
receive before running. Having to do this by
hand is just annoying.
The testsuite seems happy with these changes, but
please let me know if you see problems (especially
in use cases without a process).
llvm-svn: 179675
Materializer for all expressions that need to
run in the target. This includes the following
changes:
- Removed a bunch of (de-)materialization code
from ClangExpressionDeclMap and assumed the
presence of a Materializer where we previously
had a fallback.
- Ensured that an IRMemoryMap is passed into
ClangExpressionDeclMap::Materialize().
- Fixed object ownership on LLVMContext; it is
now owned by the IRExecutionUnit, since the
Module and the ExecutionEngine both depend on
its existence.
- Fixed a few bugs in IRMemoryMap and the
Materializer that showed up during testing.
llvm-svn: 179649
- If an allocation is mirrored between the host
and the process, update the host's version
before returning a DataExtractor pointing to
it.
- If anyone attempts to access memory in a
process/target that does not have a corresponding
allocation, try accessing the memory directly
before erroring out.
llvm-svn: 179561
for variables in the new Materializer. This is
much easier now that the ValueObject API is solid.
I still have to implement reading bytes into a
ValueObject, but committing what I have so far.
This code is not yet used, so there will be fixes
when I switch the expression parser over to use the
new Materializer.
llvm-svn: 179416
from IRExecutionUnit into a superclass called
IRMemoryMap. IRMemoryMap handles all reading and
writing, ensuring that areas are kept track of and
memory is properly cached (and deleted).
Also fixed several cases where we would simply leak
binary data in the target process over time. Now
the expression objects explicitly own their
IRExecutionUnit and delete it when they go away. This
is why I had to modify ClangUserExpression,
ClangUtilityFunction, and ClangFunction.
As a side effect of this, I am removing the JIT
mutex for an IRMemoryMap. If it turns out that we
need this mutex, I'll add it in then, but right now
it's just adding complexity.
This is part of a more general project to make
expressions fully reusable. The next step is to
make materialization and dematerialization use
the IRMemoryMap API rather than writing and
reading directly from the process's memory.
This will allow the IR interpreter to use the
same data, but in the host's memory, without having
to use a different set of pointers.
llvm-svn: 178832
