Summary:
Currently bitcode produced with `sledge buck link` can have missing
symbols that are clearly defined in the source. For example consider a
symbol `awesome_function` that is defined in the libraries linked in but
not in the produced binary (despite being reachable from main).
`llvm-nm` of the bitcode produced by `llvm-link` might look like:
```
U awesome_function
t awesome_function.1892
```
Some our `awesome_function` is undefined and its definition is called
`awsome_function.1892` for some reason and is local. I think this is because symbol get internalized too early and then they get renamed and somehow lost. Not sure why `llvm-link` behaves this way sometimes.
This patch removes internalization from `llvm-link` and puts it into `opt`, where it doesn't cause problems.
Reviewed By: jvillard
Differential Revision: D16494153
fbshipit-source-id: aad9053a4
Summary:
`__llair_alloc` is meant to be a drop-in non-failing replacement for
`mallco`. Currently `__llair_alloc(1)` allocates 8 bytes instead of 1 as
`malloc(1)` would. This is because handling of `__llair_alloc` was
merged with handling of `new`. This patch reverts changes to handling of
`new` in D15778817 and adds a new case for `__llair_alloc`.
Reviewed By: jvillard
Differential Revision: D16356865
fbshipit-source-id: 3878d87c3
Summary:
When using summaries we first garbage collect the precondition and then
ask the solver to infer the frame of the precondition with respect to
grabage-collected footprint.
Currently if the solver fails to show the frame, we just give it an
empty frame. This is bad, because if grabage collection removed some
segments, they don't get added back on.
This patch throws an exception instead to be very explicit when the
solver cannot show the frame in this case.
Reviewed By: ngorogiannis
Differential Revision: D16339587
fbshipit-source-id: b88d0689c
Summary:
The actual implementation of folly::usingJEMalloc() tests if malloc is
jemalloc using internal knowledge of the jemalloc implemenation of
malloc. This internal behavior is not reflected in the analyzer's
spec, so the detection fails.
Additionally, folly::usingJEMalloc is implemented using mallctl to
query internal state of jemalloc. Depending on the key string passed
to mallctl, it might return a pointer to jemalloc internal state, or a
scalar, which means that the spec needs to essentially allocate that
state in those cases.
Since the jemalloc detection fails, and the analyzer is not always
able to reason precisely about string equality, this diff models
folly::usingJEMalloc directly (as nondet).
Reviewed By: kren1
Differential Revision: D16059776
fbshipit-source-id: 7e7156d7d
Summary:
It seems that functions internalized by llvm no longer have valid
mangled names, and instead have a `.<int>` suffix. This diff removes
these unpredictable suffixes when checking if a called function is a
specified/modeled intrinsic.
Reviewed By: kren1
Differential Revision: D16059781
fbshipit-source-id: a4b9f6c73
Summary:
A frame inference query `Minuend ⊢ ∃xs. Subtrahend` returns a
`∃zs. Remainder` formula such that `Minuend ⊢ ∃xs. Subtrahend *
∃zs. Remainder` when successful. Currently if the subtrahend is itself
existentially quantified, its existentials are treated trivially: they
must witness themselves. This diff allows the solver to find witnesses
as the `xs`. They are still existentially quantified in the remainder,
so clients that need to constrain them should still name them before
calling the solver.
Reviewed By: kren1
Differential Revision: D16269630
fbshipit-source-id: 65136edd1
Summary:
Add a global merge pass that merges globals into a single big global. It
replaces the uses of globals merged, with offsets into the big global.
Function summarisationis a big benefactor of this as it greatly reduces
the number of implicit formals (ie. globals).
Reviewed By: jvillard
Differential Revision: D16260098
fbshipit-source-id: 1b936f02f
Summary:
Fix a bug where summaries would be created even if summarisation option
is disabled.
Reviewed By: jvillard
Differential Revision: D16259761
fbshipit-source-id: f7319ef03
Summary:
If function summaries are enabled calling a function first tries to
apply a summary, if succesful, it directly jumps to the return site of
the call. Otherwise it proceeds as before.
Reviewed By: jvillard
Differential Revision: D16201251
fbshipit-source-id: cec52e0e5
Summary:
Define a new function summary type and compute it on function return.
As an intermediary step also apply the just computed summary to function
pre so it can be compared to what was actually computed.
Reviewed By: jvillard
Differential Revision: D16149833
fbshipit-source-id: b826c17e8
Summary:
Fix a crash that occurs when subtrahend has an existential variable that
was renamed as in the test.
The crash is due to an assertion in `Sh.exists` that says only variables
in the vocabulary can be existentialy quantifed out.
The problem was `Sh.exists` call in Solver.ml:611. Where `ws`
(existentials of the subthrehend) are not present in the vocabulary of
the remainder. This is because remainder "inheirts" the vocabulary of
the minued.
This fix simply extends the vocabulary of minued with `ws`, which
means the remaainder has the correct vocabulary. This should have no
externally visible effect as `ws` are then existentialed out.
Another option would be to try to change all the `excise_seg` functions,
to keep the vocabulary, but that looked annoying to implement.
Reviewed By: jvillard
Differential Revision: D16201423
fbshipit-source-id: b88c3abc4
Summary:
Add a `-color` option to sledge, that prints variable that are
existentially bound as bold.
Reviewed By: ngorogiannis
Differential Revision: D16088750
fbshipit-source-id: bd21cb8a0
Summary:
This fixes two bugs:
* All local variables would get existentially quantified out, that means
the the local variables of the caller couldn't be restored properly
* Frame was added back on after the formals were killed. Which meant
that if frame talked about formals (in pure for example), those
formals would remain to be free variables.
Reviewed By: ngorogiannis
Differential Revision: D16091157
fbshipit-source-id: dfe12ed82
Summary:
This fixes two issues with function summarization when calling a
function multiple times.
* Previously on return, the actuals wouldn't get added back in, so
their name would be "lost" (that is existentially quantified out),
this patch adds the formals to actuals equalities back on return,
before quantifying the formals out.
* Previously the entry state of the function would be lost if there were
multiple calls to other functions.
Reviewed By: jberdine
Differential Revision: D16071656
fbshipit-source-id: 9df7b1d4b
Summary:
Currently alarms are reported to stdout while the debug trace is
written to stderr. This makes synchronizing the two difficult. With
this diff, the alarm reports can also be included in the debug trace,
and analysis can be stopped when an alarm is encountered by tracing
the `Stop` module, e.g.:
```
sledge -trace Report+Stop.on_invalid_access
```
Reviewed By: kren1
Differential Revision: D16072611
fbshipit-source-id: 32c3639a2
Summary:
There are many assumptions on the behavior of mutexes, condition
variables, etc. in the implementation of the cxxabi with threads
support. So compile with `_LIBCXXABI_HAS_NO_THREADS` defined to select
the much simpler code paths for the single-threaded case.
Reviewed By: kren1
Differential Revision: D16069454
fbshipit-source-id: 9f975e0e6
Summary:
Each call to __cxa_allocate_exception, in practice, is shortly
followed by raising an exception. With -skip-throw, execution will not
proceed past the throw. Since the concrete implementation of
__cxa_allocate_exception and the following initialization of the
exception object is very low-level code that plays tricks, the
analyzer has trouble with it. So model __cxa_allocate_exception as
unreachable to avoid (needlessly) executing that code and potentially
failing spuriously.
Reviewed By: kren1
Differential Revision: D16069451
fbshipit-source-id: bea1dae09
Summary:
Allow intrinsics to return an inconsistent state, to specify that they
do not return.
Reviewed By: kren1
Differential Revision: D16069453
fbshipit-source-id: deb5d2a22
Summary:
This adds an optimized debug build mode, which is compiled with
optimizations, and without assertions, but still has tracing enabled.
Reviewed By: kren1
Differential Revision: D16069452
fbshipit-source-id: 445cfa329
Summary:
The report output got disturbed by the change from predicate to
relational Domain, and the tricky control of printing simplified
states. After this diff by default states are printed in full, and in
simplified form with `-t State_domain.pp_simp`.
Also includes some minor output improvements.
Reviewed By: kren1
Differential Revision: D16059780
fbshipit-source-id: b33289887
Summary:
Trivial renamings to use the standard "libFuzzer" name instead of "lib
fuzzer".
Reviewed By: kren1
Differential Revision: D16067881
fbshipit-source-id: 3ff2a8f86
Summary:
On function return add the computed summary (pre/post) condition to a
hashtable.
Reviewed By: jberdine
Differential Revision: D16052136
fbshipit-source-id: 0c5c9bafb
Summary:
Outputting the list of bitcode inputs when no output flag is ok for
`sledge buck bitcode` but does not make sense when it is composed as
part of other commands. So only output to stdout if `-` is given as
the output file name.
Reviewed By: kren1
Differential Revision: D16059782
fbshipit-source-id: abac9c36f
Summary:
To easily monitor and track changes to the help generated by the
command line interface, generate it in full and add it to the repo.
Reviewed By: kren1
Differential Revision: D16059783
fbshipit-source-id: be15f9943
Summary:
This diff enhances `-function-summaries` to remember the frame computed by
the solver and actually execute the function using the summary. Upon
return the frame is added back on the computed post condition.
Reviewed By: ngorogiannis
Differential Revision: D15900318
fbshipit-source-id: 8bb56b771
Summary:
This diff is preparation for function summarization and focuses on
function calls and function summary precondition computation.
It introduces `-function-summaries` flag behind most of functionality is
hidden, when enabled on each call
* A function summary is computed by quantifying all the non-formal/global variables
and removing all the segments that are not reachable from them
* `pre` and `foot` are computed from function summary and the calling context
by replacing formals with actuals again.
* A solver is asked if `pre` entails `foot` and a frame is printed if it
does
Currently this only works for formulas without disjunctions, so when
function summaries are enabled, that state is first moved to dnf and then
the call is done for each disjunct.
Reviewed By: ngorogiannis
Differential Revision: D15898928
fbshipit-source-id: 49d32504c
Summary: For buck targets that contain at least one of the substrings in `buck-target-pattern` option in config, change the buck target to add `_sledge` suffix.
Reviewed By: jberdine
Differential Revision: D15920018
fbshipit-source-id: 44c242e99
Summary: And fix test Makefile to call the C++ compiler on .cpp files.
Reviewed By: kren1
Differential Revision: D15972426
fbshipit-source-id: 719de755f
Summary:
Simplify all conversions between castable types to the identity. The
backend treats castable types as equal, so distinguishing conversions
between them is incomplete.
Reviewed By: kren1
Differential Revision: D15972427
fbshipit-source-id: fa09859ac
Summary:
The entry block contains all locals of the entire function, as
required by the backend. This makes the manipulation of the locals of
each block redundant.
This diff moves the locals from the entry block to the function
itself, removes the Locals frames of the Control.Stack, and adds a
locals field to Return frames.
This is part cleanup and part preparation for removing the
Control.Stack.
Reviewed By: ngorogiannis
Differential Revision: D15963503
fbshipit-source-id: 523ebc260
Summary:
Adds `-mergefunc` and `-dce` passes to `Frontend.translate` to match
the `buck link` flow with `opt`
Reviewed By: ngorogiannis
Differential Revision: D15938641
fbshipit-source-id: 128cb89cd
Summary:
The current handling of the formal return variable scope is not
correct. Since it is passed as an actual argument to the return
continuation, it is manipulated as if it was a local variable of the
caller. However, its scope is not ended with the caller's locals,
leading to clashes.
This diff reworks the passing of return values to avoid this problem,
mainly by introducing a notion of temporary variables during parameter
passing. This essentially has the effect of taking a function spec
{ P } f(x) { λv. Q }
and generating a "temporary" variable v, applying the post λv. Q to it
to obtain the pre-state for the call to the return continuation
k(v). Being a temporary variable just means that it goes out of scope
just after parameter passing. This amounts to a long-winded way of
applying the post-state to the formal parameter of the return
continuation without violating scopes or SSA.
This diff also separates the manipulation of the symbolic states as they
proceed from:
1. the pre-state before the return instruction;
2. the exit-state after the return instruction (including the binding
of the returned value to the return formal variable);
3. the post-state, where the locals are existentially quantified; and
4. the return-state, which is expressed in terms of actual args
instead of formal parameters.
Also in support of summarization, formal return and throw parameters
are no longer tracked on the analyzer's stack.
Note that these changes involve changing the locals of blocks and
functions to no longer include the formal parameters.
Reviewed By: kren1
Differential Revision: D15912148
fbshipit-source-id: e41dd6e42
Summary:
The solver couldn't deal with `∃ a,b . a = b` , so this diff adds
a special case to deal with it.
Reviewed By: ngorogiannis
Differential Revision: D15897953
fbshipit-source-id: d841d3557
Summary:
:
This patch adds several passes that reduce the amount of bitcode
making sledge's job easier, more info:
https://llvm.org/docs/Passes.html
`-mergefunc`
This pass merges functions that do the same thing, this can be because of
templating or casts (ie. same functionality but on 32bit and 64bit ints,
which is the same in machine code). More details at
http://llvm.org/docs/MergeFunctions.html
Note that this pass is currently not available through C/OCaml API.
`-constmerge`
This merges constants that have the same value, this is possible to do
when the constants are internalized.
`-argpromotion`
```
This pass promotes “by reference” arguments to be “by value” arguments.
In practice, this means looking for internal functions that have pointer
arguments. If it can prove, through the use of alias analysis, that an
argument is only loaded, then it can pass the value into the function
instead of the address of the value. This can cause recursive
simplification of code and lead to the elimination of allocas
(especially in C++ template code like the STL).
```
`-ipsccp`
```
Sparse conditional constant propagation and merging, which can be
summarized as:
Assumes values are constant unless proven otherwise
Assumes BasicBlocks are dead unless proven otherwise
Proves values to be constant, and replaces them with constants
Proves conditional branches to be unconditional
```
`-deadargelim`
Removes dead arguments of internal functions, good to run after other inter-procedural
passes. Seems to crash llvm if run directly after `ipsccp`.
Note that while this might look like doing full link-time optimisation,
we are actually picking relatively cheap optimisations that mostly look
at globals and walk their use chains. The main reason link-time
optimisations are expensive is due to inlining and then running the full
optimisation again from there.
Reviewed By: jberdine
Differential Revision: D15851408
fbshipit-source-id: be7191683
Summary:
This diff introduces a `-lib-fuzz` flag to `buck link`, which links in a
simple main that calls the LLVMFuzzerTestOneInput function, which is the
entry point of libFuzzer fuzzer.
Reviewed By: jberdine, jvillard
Differential Revision: D15821512
fbshipit-source-id: cff731ed3
Summary:
Previous change to allow bitcasts in call instructions was too strict
and did not allow for indirect calls.
Reviewed By: jberdine
Differential Revision: D15803262
fbshipit-source-id: 40d828b59
Summary:
Currently printing symbolic heaps is unreadable, because there are too
many quantified variables, that are mostly just equal to other
variables.
This diff tries to replace all variables in an equivalence class with a
single variable and remove the unneccesary variables.
It also introduces two modes for printing state domains:
`-t +State_domain.pp_full` prints the state domain as is
`-t +State_domain.pp` uses the simplification before printing.
Reviewed By: jberdine
Differential Revision: D15738748
fbshipit-source-id: 7c85b580e
Summary:
Print pre- and post- conditions (aka, summaries) when analyzer hits a
function return
- plumbing the precondition through the analyzer
so that it is available when return is hit
Reviewed By: jberdine
Differential Revision: D15713725
fbshipit-source-id: b10b6206f
Summary:
This diff adds a `__llair_alloc` intrinsic which is modeled
as a non-failing malloc. Using it instead of `malloc` increases
the readbility of symbolic heaps, because it removes all the cases
where malloc failed.
Note that `assert(malloc())` does not have the desired effect.
Reviewed By: ngorogiannis
Differential Revision: D15778817
fbshipit-source-id: d02784077
Timotej Kapus
Josh Berdine