Proper support for primitive types #5
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Hello @bcardosolopes , I started hacking ClangIR to test adding bitfields support for ClangIR. I work with specific proprietary instructions that can be very useful with bitfields, however, premature lowering of bitfields accesses to arithmetic/logical instructions makes optimizations very hard to the backend. However, I looked in other MLIR projects to see how bitfields have been handled and I did not find anything. Does anyone in the project already have a possible path on how to solve this for ClangIR? Kind regards, |
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@felipealmeida great to hear you played a bit with bitfields.
Nothing set in stone from our discussions but we surely don't wanna lower them in terms of logical operations right away, but instead proxy it out (and hide the details) over an operation |
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@felipealmeida Created #13 to track bitfields! |
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It might also be worth checking out how polygeist does some of that lowering, could provide interesting insights. |
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@bcardosolopes as I am now lowering vast to cir, I might add something similar to vast high-level types to cir: https://github.com/trailofbits/vast/blob/master/include/vast/Dialect/HighLevel/HighLevelTypes.td Do you want to retain type qualifiers in cir? Also a tricky part is to define constants with high-level types, they do not cooperate nicely with attributes, and our lowering of their attribute types is a bit hackish at the moment :( |
This is great to hear!
This information will be good to have, for sure. The way I was planning to get type qualifiers would be through ASTContext queries on types (which should do the right thing on top of its Something like HighLevelTypes.td in CIR would be helpful, specially cause we also want to add something like your CharType, ShortType, etc (purpose of this github issue). How about adding these first and qualifiers as a second step? Regarding qualifiers, since we don't usually add things without use cases, I'm curious about some pieces:
Oh, what kind of problems on high-level-types+attributes you've been running into? |
I don't mind dropping the qualifiers for now. My main goal at the moment is to see whether VAST -> CIR -> LLVM is a viable path. As we discussed, if there is some common part I am happy to add it to CIR. And this seemed to me as one of them :)
I would need to investigate whether we can reconstruct ASTContext, I don't have answer for that now.
Maybe with newer MLIR version and |
Sweet, @lanza just started to work on CIR -> LLVM, so I guess we are all going towards the same goal, and adding qualifiers is a big step on that too!
Perfect.
Yea, I remember he had to change a lot because of a change past few months ago that decoupled types and attributes, but I'm not sure how much it addresses the problem you are describing :( |
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For the following program,
$ cat t.c
struct t {
int (__attribute__((btf_type_tag("rcu"))) *f)();
int a;
};
int foo(struct t *arg) {
return arg->a;
}
Compiling with 'clang -g -O2 -S t.c' will cause a failure like below:
clang: /home/yhs/work/llvm-project/clang/lib/Sema/SemaType.cpp:6391: void {anonymous}::DeclaratorLocFiller::VisitParenTypeLoc(clang::ParenTypeLoc):
Assertion `Chunk.Kind == DeclaratorChunk::Paren' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
......
#5 0x00007f89e4280ea5 abort (/lib64/libc.so.6+0x21ea5)
#6 0x00007f89e4280d79 _nl_load_domain.cold.0 (/lib64/libc.so.6+0x21d79)
#7 0x00007f89e42a6456 (/lib64/libc.so.6+0x47456)
#8 0x00000000045c2596 GetTypeSourceInfoForDeclarator((anonymous namespace)::TypeProcessingState&, clang::QualType, clang::TypeSourceInfo*) SemaType.cpp:0:0
#9 0x00000000045ccfa5 GetFullTypeForDeclarator((anonymous namespace)::TypeProcessingState&, clang::QualType, clang::TypeSourceInfo*) SemaType.cpp:0:0
......
The reason of the failure is due to the mismatch of TypeLoc and D.getTypeObject().Kind. For example,
the TypeLoc is
BTFTagAttributedType 0x88614e0 'int btf_type_tag(rcu)()' sugar
|-ParenType 0x8861480 'int ()' sugar
| `-FunctionNoProtoType 0x8861450 'int ()' cdecl
| `-BuiltinType 0x87fd500 'int'
while corresponding D.getTypeObject().Kind points to DeclaratorChunk::Paren, and
this will cause later assertion.
To fix the issue, similar to AttributedTypeLoc, let us skip BTFTagAttributedTypeLoc in
GetTypeSourceInfoForDeclarator().
Differential Revision: https://reviews.llvm.org/D136807
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The Assignment Tracking debug-info feature is outlined in this RFC: https://discourse.llvm.org/t/ rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir Add initial revision of assignment tracking analysis pass --------------------------------------------------------- This patch squashes five individually reviewed patches into one: #1 https://reviews.llvm.org/D136320 #2 https://reviews.llvm.org/D136321 #3 https://reviews.llvm.org/D136325 #4 https://reviews.llvm.org/D136331 #5 https://reviews.llvm.org/D136335 Patch #1 introduces 2 new files: AssignmentTrackingAnalysis.h and .cpp. The two subsequent patches modify those files only. Patch #4 plumbs the analysis into SelectionDAG, and patch #5 is a collection of tests for the analysis as a whole. The analysis was broken up into smaller chunks for review purposes but for the most part the tests were written using the whole analysis. It would be possible to break up the tests for patches #1 through #3 for the purpose of landing the patches seperately. However, most them would require an update for each patch. In addition, patch #4 - which connects the analysis to SelectionDAG - is required by all of the tests. If there is build-bot trouble, we might try a different landing sequence. Analysis problem and goal ------------------------- Variables values can be stored in memory, or available as SSA values, or both. Using the Assignment Tracking metadata, it's not possible to determine a variable location just by looking at a debug intrinsic in isolation. Instructions without any metadata can change the location of a variable. The meaning of dbg.assign intrinsics changes depending on whether there are linked instructions, and where they are relative to those instructions. So we need to analyse the IR and convert the embedded information into a form that SelectionDAG can consume to produce debug variable locations in MIR. The solution is a dataflow analysis which, aiming to maximise the memory location coverage for variables, outputs a mapping of instruction positions to variable location definitions. API usage --------- The analysis is named `AssignmentTrackingAnalysis`. It is added as a required pass for SelectionDAGISel when assignment tracking is enabled. The results of the analysis are exposed via `getResults` using the returned `const FunctionVarLocs *`'s const methods: const VarLocInfo *single_locs_begin() const; const VarLocInfo *single_locs_end() const; const VarLocInfo *locs_begin(const Instruction *Before) const; const VarLocInfo *locs_end(const Instruction *Before) const; void print(raw_ostream &OS, const Function &Fn) const; Debug intrinsics can be ignored after running the analysis. Instead, variable location definitions that occur between an instruction `Inst` and its predecessor (or block start) can be found by looping over the range: locs_begin(Inst), locs_end(Inst) Similarly, variables with a memory location that is valid for their lifetime can be iterated over using the range: single_locs_begin(), single_locs_end() Further detail -------------- For an explanation of the dataflow implementation and the integration with SelectionDAG, please see the reviews linked at the top of this commit message. Reviewed By: jmorse
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…ak ordering
`std::sort` requires a comparison operator that obides by strict weak
ordering. `operator<=` on pointer does not and leads to undefined
behaviour. Specifically, when we grow the `scratch_type_systems` vector
slightly larger (and thus take `std::sort` down a slightly different
codepath), we segfault. This happened while working on a patch that
would in fact grow this vector. In such a case ASAN reports:
```
$ ./bin/lldb ./lldb-test-build.noindex/lang/cpp/complete-type-check/TestCppIsTypeComplete.test_builtin_types/a.out -o "script -- lldb.target.FindFirstType(\"void\")"
(lldb) script -- lldb.target.FindFirstType("void")
=================================================================
==59975==ERROR: AddressSanitizer: container-overflow on address 0x000108f6b510 at pc 0x000280177b4c bp 0x00016b7d7430 sp 0x00016b7d7428
READ of size 8 at 0x000108f6b510 thread T0
#0 0x280177b48 in std::__1::shared_ptr<lldb_private::TypeSystem>::shared_ptr[abi:v15006](std::__1::shared_ptr<lldb_private::TypeSystem> const&)+0xb4 (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0x177b48)
(BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#1 0x280dcc008 in void std::__1::__introsort<std::__1::_ClassicAlgPolicy, lldb_private::Target::GetScratchTypeSystems(bool)::$_3&, std::__1::shared_ptr<lldb_private::TypeSystem>*>(std::__1::shared_ptr<lldb_private::TypeSystem>*, std::__1::shared_
ptr<lldb_private::TypeSystem>*, lldb_private::Target::GetScratchTypeSystems(bool)::$_3&, std::__1::iterator_traits<std::__1::shared_ptr<lldb_private::TypeSystem>*>::difference_type)+0x1050 (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblld
b.17.0.0git.dylib:arm64+0xdcc008) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#2 0x280d88788 in lldb_private::Target::GetScratchTypeSystems(bool)+0x5a4 (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0xd88788) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#3 0x28021f0b4 in lldb::SBTarget::FindFirstType(char const*)+0x624 (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0x21f0b4) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#4 0x2804e9590 in _wrap_SBTarget_FindFirstType(_object*, _object*)+0x26c (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0x4e9590) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#5 0x1062d3ad4 in cfunction_call+0x5c (/opt/homebrew/Cellar/python@3.11/3.11.1/Frameworks/Python.framework/Versions/3.11/Python:arm64+0xcfad4) (BuildId: c9efc4bbb1943f9a9b7cc4e91fce477732000000200000000100000000000d00)
<--- snipped --->
0x000108f6b510 is located 400 bytes inside of 512-byte region [0x000108f6b380,0x000108f6b580)
allocated by thread T0 here:
#0 0x105209414 in wrap__Znwm+0x74 (/Applications/Xcode2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/14.0.3/lib/darwin/libclang_rt.asan_osx_dynamic.dylib:arm64e+0x51414) (BuildId: 0a44828ceb64337bbfff60b22cd838f0320000
00200000000100000000000b00)
#1 0x280dca3b4 in std::__1::__split_buffer<std::__1::shared_ptr<lldb_private::TypeSystem>, std::__1::allocator<std::__1::shared_ptr<lldb_private::TypeSystem>>&>::__split_buffer(unsigned long, unsigned long, std::__1::allocator<std::__1::shared_pt
r<lldb_private::TypeSystem>>&)+0x11c (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0xdca3b4) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#2 0x280dc978c in void std::__1::vector<std::__1::shared_ptr<lldb_private::TypeSystem>, std::__1::allocator<std::__1::shared_ptr<lldb_private::TypeSystem>>>::__push_back_slow_path<std::__1::shared_ptr<lldb_private::TypeSystem> const&>(std::__1::s
hared_ptr<lldb_private::TypeSystem> const&)+0x13c (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0xdc978c) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#3 0x280d88dec in std::__1::vector<std::__1::shared_ptr<lldb_private::TypeSystem>, std::__1::allocator<std::__1::shared_ptr<lldb_private::TypeSystem>>>::push_back[abi:v15006](std::__1::shared_ptr<lldb_private::TypeSystem> const&)+0x80 (/Users/mic
haelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0xd88dec) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#4 0x280d8857c in lldb_private::Target::GetScratchTypeSystems(bool)+0x398 (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0xd8857c) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#5 0x28021f0b4 in lldb::SBTarget::FindFirstType(char const*)+0x624 (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0x21f0b4) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#6 0x2804e9590 in _wrap_SBTarget_FindFirstType(_object*, _object*)+0x26c (/Users/michaelbuch/Git/lldb-build-main-no-modules/lib/liblldb.17.0.0git.dylib:arm64+0x4e9590) (BuildId: ea963d2c0d47354fb647f5c5f32b76d932000000200000000100000000000d00)
#7 0x1062d3ad4 in cfunction_call+0x5c (/opt/homebrew/Cellar/python@3.11/3.11.1/Frameworks/Python.framework/Versions/3.11/Python:arm64+0xcfad4) (BuildId: c9efc4bbb1943f9a9b7cc4e91fce477732000000200000000100000000000d00)
#8 0x10627fff0 in _PyObject_MakeTpCall+0x7c (/opt/homebrew/Cellar/python@3.11/3.11.1/Frameworks/Python.framework/Versions/3.11/Python:arm64+0x7bff0) (BuildId: c9efc4bbb1943f9a9b7cc4e91fce477732000000200000000100000000000d00)
#9 0x106378a98 in _PyEval_EvalFrameDefault+0xbcf8 (/opt/homebrew/Cellar/python@3.11/3.11.1/Frameworks/Python.framework/Versions/3.11/Python:arm64+0x174a98) (BuildId: c9efc4bbb1943f9a9b7cc4e91fce477732000000200000000100000000000d00)
```
Differential Revision: https://reviews.llvm.org/D142709
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This change prevents rare deadlocks observed for specific macOS/iOS GUI
applications which issue many `dlopen()` calls from multiple different
threads at startup and where TSan finds and reports a race during
startup. Providing a reliable test for this has been deemed infeasible.
Although I've only observed this deadlock on Apple platforms,
conceptually the cause is not confined to Apple code so the fix lives in
platform-independent code.
Deadlock scenario:
```
Thread 2 | Thread 4
ReportRace() |
Lock internal TSan mutexes |
&ctx->slot_mtx |
| dlopen() interceptor
| OnLibraryLoaded()
| MemoryMappingLayout::DumpListOfModules()
| calls dyld API, which takes internal lock
| lock() interceptor
| TSan tries to take internal mutexes again
| &ctx->slot_mtx
call into symbolizer |
MemoryMappingLayout::DumpListOfModules()
calls dyld API, which hangs on trying to take lock
```
Resulting in:
* Thread 2 has internal TSan mutex, blocked on dyld lock
* Thread 4 has dyld lock, blocked on internal TSan mutex
The fix prevents this situation by not intercepting any of the calls
originating from `MemoryMappingLayout::DumpListOfModules()`.
Stack traces for deadlock between ReportRace() and dlopen() interceptor:
```
thread #2, queue = 'com.apple.root.default-qos'
frame #0: libsystem_kernel.dylib
frame #1: libclang_rt.tsan_osx_dynamic.dylib`::wrap_os_unfair_lock_lock_with_options(lock=<unavailable>, options=<unavailable>) at tsan_interceptors_mac.cpp:306:3
frame #2: dyld`dyld4::RuntimeLocks::withLoadersReadLock(this=0x000000016f21b1e0, work=0x00000001814523c0) block_pointer) at DyldRuntimeState.cpp:227:28
frame #3: dyld`dyld4::APIs::_dyld_get_image_header(this=0x0000000101012a20, imageIndex=614) at DyldAPIs.cpp:240:11
frame #4: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::CurrentImageHeader(this=<unavailable>) at sanitizer_procmaps_mac.cpp:391:35
frame #5: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::Next(this=0x000000016f2a2800, segment=0x000000016f2a2738) at sanitizer_procmaps_mac.cpp:397:51
frame #6: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::DumpListOfModules(this=0x000000016f2a2800, modules=0x00000001011000a0) at sanitizer_procmaps_mac.cpp:460:10
frame #7: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::ListOfModules::init(this=0x00000001011000a0) at sanitizer_mac.cpp:610:18
frame #8: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Symbolizer::FindModuleForAddress(unsigned long) [inlined] __sanitizer::Symbolizer::RefreshModules(this=0x0000000101100078) at sanitizer_symbolizer_libcdep.cpp:185:12
frame #9: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Symbolizer::FindModuleForAddress(this=0x0000000101100078, address=6465454512) at sanitizer_symbolizer_libcdep.cpp:204:5
frame #10: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Symbolizer::SymbolizePC(this=0x0000000101100078, addr=6465454512) at sanitizer_symbolizer_libcdep.cpp:88:15
frame #11: libclang_rt.tsan_osx_dynamic.dylib`__tsan::SymbolizeCode(addr=6465454512) at tsan_symbolize.cpp:106:35
frame #12: libclang_rt.tsan_osx_dynamic.dylib`__tsan::SymbolizeStack(trace=StackTrace @ 0x0000600002d66d00) at tsan_rtl_report.cpp:112:28
frame #13: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedReportBase::AddMemoryAccess(this=0x000000016f2a2a90, addr=4381057136, external_tag=<unavailable>, s=<unavailable>, tid=<unavailable>, stack=<unavailable>, mset=0x00000001012fc310) at tsan_rtl_report.cpp:190:16
frame #14: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ReportRace(thr=0x00000001012fc000, shadow_mem=0x000008020a4340e0, cur=<unavailable>, old=<unavailable>, typ0=1) at tsan_rtl_report.cpp:795:9
frame #15: libclang_rt.tsan_osx_dynamic.dylib`__tsan::DoReportRace(thr=0x00000001012fc000, shadow_mem=0x000008020a4340e0, cur=Shadow @ x22, old=Shadow @ 0x0000600002d6b4f0, typ=1) at tsan_rtl_access.cpp:166:3
frame #16: libclang_rt.tsan_osx_dynamic.dylib`::__tsan_read8(void *) at tsan_rtl_access.cpp:220:5
frame #17: libclang_rt.tsan_osx_dynamic.dylib`::__tsan_read8(void *) [inlined] __tsan::MemoryAccess(thr=0x00000001012fc000, pc=<unavailable>, addr=<unavailable>, size=8, typ=1) at tsan_rtl_access.cpp:442:3
frame #18: libclang_rt.tsan_osx_dynamic.dylib`::__tsan_read8(addr=<unavailable>) at tsan_interface.inc:34:3
<call into TSan from from instrumented code>
thread #4, queue = 'com.apple.dock.fullscreen'
frame #0: libsystem_kernel.dylib
frame #1: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::FutexWait(p=<unavailable>, cmp=<unavailable>) at sanitizer_mac.cpp:540:3
frame #2: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Semaphore::Wait(this=<unavailable>) at sanitizer_mutex.cpp:35:7
frame #3: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Mutex::Lock(this=0x0000000102992a80) at sanitizer_mutex.h:196:18
frame #4: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock(this=<unavailable>, mu=0x0000000102992a80) at sanitizer_mutex.h:383:10
frame #5: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock(this=<unavailable>, mu=0x0000000102992a80) at sanitizer_mutex.h:382:77
frame #6: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() at tsan_rtl.h:708:10
frame #7: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __tsan::TryTraceFunc(thr=0x000000010f084000, pc=0) at tsan_rtl.h:751:7
frame #8: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __tsan::FuncExit(thr=0x000000010f084000) at tsan_rtl.h:798:7
frame #9: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor(this=0x000000016f3ba280) at tsan_interceptors_posix.cpp:300:5
frame #10: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor(this=<unavailable>) at tsan_interceptors_posix.cpp:293:41
frame #11: libclang_rt.tsan_osx_dynamic.dylib`::wrap_os_unfair_lock_lock_with_options(lock=0x000000016f21b1e8, options=OS_UNFAIR_LOCK_NONE) at tsan_interceptors_mac.cpp:310:1
frame #12: dyld`dyld4::RuntimeLocks::withLoadersReadLock(this=0x000000016f21b1e0, work=0x00000001814525d4) block_pointer) at DyldRuntimeState.cpp:227:28
frame #13: dyld`dyld4::APIs::_dyld_get_image_vmaddr_slide(this=0x0000000101012a20, imageIndex=412) at DyldAPIs.cpp:273:11
frame #14: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::Next(__sanitizer::MemoryMappedSegment*) at sanitizer_procmaps_mac.cpp:286:17
frame #15: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::Next(this=0x000000016f3ba560, segment=0x000000016f3ba498) at sanitizer_procmaps_mac.cpp:432:15
frame #16: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::DumpListOfModules(this=0x000000016f3ba560, modules=0x000000016f3ba618) at sanitizer_procmaps_mac.cpp:460:10
frame #17: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::ListOfModules::init(this=0x000000016f3ba618) at sanitizer_mac.cpp:610:18
frame #18: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::LibIgnore::OnLibraryLoaded(this=0x0000000101f3aa40, name="<some library>") at sanitizer_libignore.cpp:54:11
frame #19: libclang_rt.tsan_osx_dynamic.dylib`::wrap_dlopen(filename="<some library>", flag=<unavailable>) at sanitizer_common_interceptors.inc:6466:3
<library code>
```
rdar://106766395
Differential Revision: https://reviews.llvm.org/D146593
This was referenced May 24, 2023
|
The main parts of this are done, other issues will track further improvements. |
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Running this on Amazon Ubuntu the final backtrace is: ``` (lldb) thread backtrace * thread #1, name = 'a.out', stop reason = breakpoint 1.1 * frame #0: 0x0000aaaaaaaa07d0 a.out`func_c at main.c:10:3 frame #1: 0x0000aaaaaaaa07c4 a.out`func_b at main.c:14:3 frame #2: 0x0000aaaaaaaa07b4 a.out`func_a at main.c:18:3 frame #3: 0x0000aaaaaaaa07a4 a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:22:3 frame #4: 0x0000fffff7b373fc libc.so.6`___lldb_unnamed_symbol2962 + 108 frame #5: 0x0000fffff7b374cc libc.so.6`__libc_start_main + 152 frame #6: 0x0000aaaaaaaa06b0 a.out`_start + 48 ``` This causes the test to fail because of the extra ___lldb_unnamed_symbol2962 frame (an inlined function?). To fix this, strictly check all the frames in main.c then for the rest just check we find __libc_start_main and _start in that order regardless of other frames in between. Reviewed By: omjavaid Differential Revision: https://reviews.llvm.org/D154204
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… on (#74207) lld string tail merging interacts badly with ASAN on Windows, as is reported in llvm/llvm-project#62078. A similar error was found when building LLVM with `-DLLVM_USE_SANITIZER=Address`: ```console [2/2] Building GenVT.inc... FAILED: include/llvm/CodeGen/GenVT.inc C:/Dev/llvm-project/Build_asan/include/llvm/CodeGen/GenVT.inc cmd.exe /C "cd /D C:\Dev\llvm-project\Build_asan && C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe -gen-vt -I C:/Dev/llvm-project/llvm/include/llvm/CodeGen -IC:/Dev/llvm-project/Build_asan/include -IC:/Dev/llvm-project/llvm/include C:/Dev/llvm-project/llvm/include/llvm/CodeGen/ValueTypes.td --write-if-changed -o include/llvm/CodeGen/GenVT.inc -d include/llvm/CodeGen/GenVT.inc.d" ================================================================= ==31944==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7ff6cff80d20 at pc 0x7ff6cfcc7378 bp 0x00e8bcb8e990 sp 0x00e8bcb8e9d8 READ of size 1 at 0x7ff6cff80d20 thread T0 #0 0x7ff6cfcc7377 in strlen (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1400a7377) #1 0x7ff6cfde50c2 in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1401c50c2) #2 0x7ff6cfdd75ef in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1401b75ef) #3 0x7ff6cfde59f9 in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1401c59f9) #4 0x7ff6cff03f6c in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1402e3f6c) #5 0x7ff6cfefbcbc in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1402dbcbc) #6 0x7ffb7f247343 (C:\WINDOWS\System32\KERNEL32.DLL+0x180017343) #7 0x7ffb800826b0 (C:\WINDOWS\SYSTEM32\ntdll.dll+0x1800526b0) 0x7ff6cff80d20 is located 31 bytes after global variable '"#error \"ArgKind is not defined\"\n"...' defined in 'C:\Dev\llvm-project\llvm\utils\TableGen\IntrinsicEmitter.cpp' (0x7ff6cff80ce0) of size 33 '"#error \"ArgKind is not defined\"\n"...' is ascii string '#error "ArgKind is not defined" ' 0x7ff6cff80d20 is located 0 bytes inside of global variable '""' defined in 'C:\Dev\llvm-project\llvm\utils\TableGen\IntrinsicEmitter.cpp' (0x7ff6cff80d20) of size 1 '""' is ascii string '' SUMMARY: AddressSanitizer: global-buffer-overflow (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1400a7377) in strlen Shadow bytes around the buggy address: 0x7ff6cff80a80: 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 01 f9 f9 f9 0x7ff6cff80b00: f9 f9 f9 f9 00 00 00 00 00 00 00 00 01 f9 f9 f9 0x7ff6cff80b80: f9 f9 f9 f9 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 0x7ff6cff80c00: 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 0x7ff6cff80c80: 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 =>0x7ff6cff80d00: 01 f9 f9 f9[f9]f9 f9 f9 00 00 00 00 00 00 00 00 0x7ff6cff80d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x7ff6cff80e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x7ff6cff80e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x7ff6cff80f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x7ff6cff80f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==31944==ABORTING ``` This is reproducible with the 17.0.3 release: ```console $ clang-cl --version clang version 17.0.3 Target: x86_64-pc-windows-msvc Thread model: posix InstalledDir: C:\Program Files\LLVM\bin $ cmake -S llvm -B Build -G Ninja -DLLVM_USE_SANITIZER=Address -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded -DCMAKE_BUILD_TYPE=Release $ cd Build $ ninja all ```
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## Motivation Since we don't need the metadata sections at runtime, we can somehow offload them from memory at runtime. Initially, I explored [debug info correlation](https://discourse.llvm.org/t/instrprofiling-lightweight-instrumentation/59113), which is used for PGO with value profiling disabled. However, it currently only works with DWARF and it's be hard to add such artificial debug info for every function in to CodeView which is used on Windows. So, offloading profile metadata sections at runtime seems to be a platform independent option. ## Design The idea is to use new section names for profile name and data sections and mark them as metadata sections. Under this mode, the new sections are non-SHF_ALLOC in ELF. So, they are not loaded into memory at runtime and can be stripped away as a post-linking step. After the process exits, the generated raw profiles will contains only headers + counters. llvm-profdata can be used correlate raw profiles with the unstripped binary to generate indexed profile. ## Data For chromium base_unittests with code coverage on linux, the binary size overhead due to instrumentation reduced from 64M to 38.8M (39.4%) and the raw profile files size reduce from 128M to 68M (46.9%) ``` $ bloaty out/cov/base_unittests.stripped -- out/no-cov/base_unittests.stripped FILE SIZE VM SIZE -------------- -------------- +121% +30.4Mi +121% +30.4Mi .text [NEW] +14.6Mi [NEW] +14.6Mi __llvm_prf_data [NEW] +10.6Mi [NEW] +10.6Mi __llvm_prf_names [NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts +95% +1.75Mi +95% +1.75Mi .eh_frame +108% +400Ki +108% +400Ki .eh_frame_hdr +9.5% +211Ki +9.5% +211Ki .rela.dyn +9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro +5.0% +87.3Ki +5.0% +87.3Ki .rodata [ = ] 0 +13% +47.0Ki .bss +40% +1.78Ki +40% +1.78Ki .got +12% +1.49Ki +12% +1.49Ki .gcc_except_table [ = ] 0 +65% +1.23Ki .relro_padding +62% +1.20Ki [ = ] 0 [Unmapped] +13% +448 +19% +448 .init_array +8.8% +192 [ = ] 0 [ELF Section Headers] +0.0% +136 +0.0% +80 [7 Others] +0.1% +96 +0.1% +96 .dynsym +1.2% +96 +1.2% +96 .rela.plt +1.5% +80 +1.2% +64 .plt [ = ] 0 -99.2% -3.68Ki [LOAD #5 [RW]] +195% +64.0Mi +194% +64.0Mi TOTAL $ bloaty out/cov-cor/base_unittests.stripped -- out/no-cov/base_unittests.stripped FILE SIZE VM SIZE -------------- -------------- +121% +30.4Mi +121% +30.4Mi .text [NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts +95% +1.75Mi +95% +1.75Mi .eh_frame +108% +400Ki +108% +400Ki .eh_frame_hdr +9.5% +211Ki +9.5% +211Ki .rela.dyn +9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro +5.0% +87.3Ki +5.0% +87.3Ki .rodata [ = ] 0 +13% +47.0Ki .bss +40% +1.78Ki +40% +1.78Ki .got +12% +1.49Ki +12% +1.49Ki .gcc_except_table +13% +448 +19% +448 .init_array +0.1% +96 +0.1% +96 .dynsym +1.2% +96 +1.2% +96 .rela.plt +1.2% +64 +1.2% +64 .plt +2.9% +64 [ = ] 0 [ELF Section Headers] +0.0% +40 +0.0% +40 .data +1.2% +32 +1.2% +32 .got.plt +0.0% +24 +0.0% +8 [5 Others] [ = ] 0 -22.9% -872 [LOAD #5 [RW]] -74.5% -1.44Ki [ = ] 0 [Unmapped] [ = ] 0 -76.5% -1.45Ki .relro_padding +118% +38.8Mi +117% +38.8Mi TOTAL ``` A few things to note: 1. llvm-profdata doesn't support filter raw profiles by binary id yet, so when a raw profile doesn't belongs to the binary being digested by llvm-profdata, merging will fail. Once this is implemented, llvm-profdata should be able to only merge raw profiles with the same binary id as the binary and discard the rest (with mismatched/missing binary id). The workflow I have in mind is to have scripts invoke llvm-profdata to get all binary ids for all raw profiles, and selectively choose the raw pnrofiles with matching binary id and the binary to llvm-profdata for merging. 2. Note: In COFF, currently they are still loaded into memory but not used. I didn't do it in this patch because I noticed that `.lcovmap` and `.lcovfunc` are loaded into memory. A separate patch will address it. 3. This should works with PGO when value profiling is disabled as debug info correlation currently doing, though I haven't tested this yet.
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Internal builds of the unittests with msan flagged mempcpy_test.
==6862==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x55e34d7d734a in length
llvm-project/libc/src/__support/CPP/string_view.h:41:11
#1 0x55e34d7d734a in string_view
llvm-project/libc/src/__support/CPP/string_view.h:71:24
#2 0x55e34d7d734a in
__llvm_libc_9999_0_0_git::testing::Test::testStrEq(char const*, char
const*, char const*, char const*,
__llvm_libc_9999_0_0_git::testing::internal::Location)
llvm-project/libc/test/UnitTest/LibcTest.cpp:284:13
#3 0x55e34d7d4e09 in LlvmLibcMempcpyTest_Simple::Run()
llvm-project/libc/test/src/string/mempcpy_test.cpp:20:3
#4 0x55e34d7d6dff in
__llvm_libc_9999_0_0_git::testing::Test::runTests(char const*)
llvm-project/libc/test/UnitTest/LibcTest.cpp:133:8
#5 0x55e34d7d86e0 in main
llvm-project/libc/test/UnitTest/LibcTestMain.cpp:21:10
SUMMARY: MemorySanitizer: use-of-uninitialized-value
llvm-project/libc/src/__support/CPP/string_view.h:41:11 in length
What's going on here is that mempcpy_test.cpp's Simple test is using
ASSERT_STREQ with a partially initialized char array. ASSERT_STREQ calls
Test::testStrEq which constructs a cpp:string_view. That constructor
calls the
private method cpp::string_view::length. When built with msan, the loop
is
transformed into multi-byte access, which then fails upon access.
I took a look at libc++'s __constexpr_strlen which just calls
__builtin_strlen(). Replacing the implementation of
cpp::string_view::length
with a call to __builtin_strlen() may still result in out of bounds
access when
the test is built with msan.
It's not safe to use ASSERT_STREQ with a partially initialized array.
Initialize the whole array so that the test passes.
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We'd like a way to select the current thread by its thread ID (rather than its internal LLDB thread index). This PR adds a `-t` option (`--thread_id` long option) that tells the `thread select` command to interpret the `<thread-index>` argument as a thread ID. Here's an example of it working: ``` michristensen@devbig356 llvm/llvm-project (thread-select-tid) » ../Debug/bin/lldb ~/scratch/cpp/threading/a.out (lldb) target create "/home/michristensen/scratch/cpp/threading/a.out" Current executable set to '/home/michristensen/scratch/cpp/threading/a.out' (x86_64). (lldb) b 18 Breakpoint 1: where = a.out`main + 80 at main.cpp:18:12, address = 0x0000000000000850 (lldb) run Process 215715 launched: '/home/michristensen/scratch/cpp/threading/a.out' (x86_64) This is a thread, i=1 This is a thread, i=2 This is a thread, i=3 This is a thread, i=4 This is a thread, i=5 Process 215715 stopped * thread #1, name = 'a.out', stop reason = breakpoint 1.1 frame #0: 0x0000555555400850 a.out`main at main.cpp:18:12 15 for (int i = 0; i < 5; i++) { 16 pthread_create(&thread_ids[i], NULL, foo, NULL); 17 } -> 18 for (int i = 0; i < 5; i++) { 19 pthread_join(thread_ids[i], NULL); 20 } 21 return 0; (lldb) thread select 2 * thread #2, name = 'a.out' frame #0: 0x00007ffff68f9918 libc.so.6`__nanosleep + 72 libc.so.6`__nanosleep: -> 0x7ffff68f9918 <+72>: cmpq $-0x1000, %rax ; imm = 0xF000 0x7ffff68f991e <+78>: ja 0x7ffff68f9952 ; <+130> 0x7ffff68f9920 <+80>: movl %edx, %edi 0x7ffff68f9922 <+82>: movl %eax, 0xc(%rsp) (lldb) thread info thread #2: tid = 216047, 0x00007ffff68f9918 libc.so.6`__nanosleep + 72, name = 'a.out' (lldb) thread list Process 215715 stopped thread #1: tid = 215715, 0x0000555555400850 a.out`main at main.cpp:18:12, name = 'a.out', stop reason = breakpoint 1.1 * thread #2: tid = 216047, 0x00007ffff68f9918 libc.so.6`__nanosleep + 72, name = 'a.out' thread #3: tid = 216048, 0x00007ffff68f9918 libc.so.6`__nanosleep + 72, name = 'a.out' thread #4: tid = 216049, 0x00007ffff68f9918 libc.so.6`__nanosleep + 72, name = 'a.out' thread #5: tid = 216050, 0x00007ffff68f9918 libc.so.6`__nanosleep + 72, name = 'a.out' thread #6: tid = 216051, 0x00007ffff68f9918 libc.so.6`__nanosleep + 72, name = 'a.out' (lldb) thread select 215715 error: invalid thread #215715. (lldb) thread select -t 215715 * thread #1, name = 'a.out', stop reason = breakpoint 1.1 frame #0: 0x0000555555400850 a.out`main at main.cpp:18:12 15 for (int i = 0; i < 5; i++) { 16 pthread_create(&thread_ids[i], NULL, foo, NULL); 17 } -> 18 for (int i = 0; i < 5; i++) { 19 pthread_join(thread_ids[i], NULL); 20 } 21 return 0; (lldb) thread select -t 216051 * thread #6, name = 'a.out' frame #0: 0x00007ffff68f9918 libc.so.6`__nanosleep + 72 libc.so.6`__nanosleep: -> 0x7ffff68f9918 <+72>: cmpq $-0x1000, %rax ; imm = 0xF000 0x7ffff68f991e <+78>: ja 0x7ffff68f9952 ; <+130> 0x7ffff68f9920 <+80>: movl %edx, %edi 0x7ffff68f9922 <+82>: movl %eax, 0xc(%rsp) (lldb) thread select 3 * thread #3, name = 'a.out' frame #0: 0x00007ffff68f9918 libc.so.6`__nanosleep + 72 libc.so.6`__nanosleep: -> 0x7ffff68f9918 <+72>: cmpq $-0x1000, %rax ; imm = 0xF000 0x7ffff68f991e <+78>: ja 0x7ffff68f9952 ; <+130> 0x7ffff68f9920 <+80>: movl %edx, %edi 0x7ffff68f9922 <+82>: movl %eax, 0xc(%rsp) (lldb) thread select -t 216048 * thread #3, name = 'a.out' frame #0: 0x00007ffff68f9918 libc.so.6`__nanosleep + 72 libc.so.6`__nanosleep: -> 0x7ffff68f9918 <+72>: cmpq $-0x1000, %rax ; imm = 0xF000 0x7ffff68f991e <+78>: ja 0x7ffff68f9952 ; <+130> 0x7ffff68f9920 <+80>: movl %edx, %edi 0x7ffff68f9922 <+82>: movl %eax, 0xc(%rsp) (lldb) thread select --thread_id 216048 * thread #3, name = 'a.out' frame #0: 0x00007ffff68f9918 libc.so.6`__nanosleep + 72 libc.so.6`__nanosleep: -> 0x7ffff68f9918 <+72>: cmpq $-0x1000, %rax ; imm = 0xF000 0x7ffff68f991e <+78>: ja 0x7ffff68f9952 ; <+130> 0x7ffff68f9920 <+80>: movl %edx, %edi 0x7ffff68f9922 <+82>: movl %eax, 0xc(%rsp) (lldb) help thread select Change the currently selected thread. Syntax: thread select <cmd-options> <thread-index> Command Options Usage: thread select [-t] <thread-index> -t ( --thread_id ) Provide a thread ID instead of a thread index. This command takes options and free-form arguments. If your arguments resemble option specifiers (i.e., they start with a - or --), you must use ' -- ' between the end of the command options and the beginning of the arguments. (lldb) c Process 215715 resuming Process 215715 exited with status = 0 (0x00000000) ```
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Right now we use MLIR's ints, floats, etc. Just like we have
cir.boolandcir.ptrwe should havecir.int ...like type and track more language level info (signedness, etc)The text was updated successfully, but these errors were encountered: