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@shiltian shiltian closed this Jun 18, 2024
shiltian pushed a commit that referenced this pull request Aug 26, 2024
…104523)

Compilers and language runtimes often use helper functions that are
fundamentally uninteresting when debugging anything but the
compiler/runtime itself. This patch introduces a user-extensible
mechanism that allows for these frames to be hidden from backtraces and
automatically skipped over when navigating the stack with `up` and
`down`.

This does not affect the numbering of frames, so `f <N>` will still
provide access to the hidden frames. The `bt` output will also print a
hint that frames have been hidden.

My primary motivation for this feature is to hide thunks in the Swift
programming language, but I'm including an example recognizer for
`std::function::operator()` that I wished for myself many times while
debugging LLDB.

rdar://126629381


Example output. (Yes, my proof-of-concept recognizer could hide even
more frames if we had a method that returned the function name without
the return type or I used something that isn't based off regex, but it's
really only meant as an example).

before:
```
(lldb) thread backtrace --filtered=false
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
  * frame #0: 0x0000000100001f04 a.out`foo(x=1, y=1) at main.cpp:4:10
    frame #1: 0x0000000100003a00 a.out`decltype(std::declval<int (*&)(int, int)>()(std::declval<int>(), std::declval<int>())) std::__1::__invoke[abi:se200000]<int (*&)(int, int), int, int>(__f=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:149:25
    frame #2: 0x000000010000399c a.out`int std::__1::__invoke_void_return_wrapper<int, false>::__call[abi:se200000]<int (*&)(int, int), int, int>(__args=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:216:12
    frame #3: 0x0000000100003968 a.out`std::__1::__function::__alloc_func<int (*)(int, int), std::__1::allocator<int (*)(int, int)>, int (int, int)>::operator()[abi:se200000](this=0x000000016fdff280, __arg=0x000000016fdff224, __arg=0x000000016fdff220) at function.h:171:12
    frame #4: 0x00000001000026bc a.out`std::__1::__function::__func<int (*)(int, int), std::__1::allocator<int (*)(int, int)>, int (int, int)>::operator()(this=0x000000016fdff278, __arg=0x000000016fdff224, __arg=0x000000016fdff220) at function.h:313:10
    frame #5: 0x0000000100003c38 a.out`std::__1::__function::__value_func<int (int, int)>::operator()[abi:se200000](this=0x000000016fdff278, __args=0x000000016fdff224, __args=0x000000016fdff220) const at function.h:430:12
    frame #6: 0x0000000100002038 a.out`std::__1::function<int (int, int)>::operator()(this= Function = foo(int, int) , __arg=1, __arg=1) const at function.h:989:10
    frame #7: 0x0000000100001f64 a.out`main(argc=1, argv=0x000000016fdff4f8) at main.cpp:9:10
    frame #8: 0x0000000183cdf154 dyld`start + 2476
(lldb) 
```

after

```
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
  * frame #0: 0x0000000100001f04 a.out`foo(x=1, y=1) at main.cpp:4:10
    frame #1: 0x0000000100003a00 a.out`decltype(std::declval<int (*&)(int, int)>()(std::declval<int>(), std::declval<int>())) std::__1::__invoke[abi:se200000]<int (*&)(int, int), int, int>(__f=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:149:25
    frame #2: 0x000000010000399c a.out`int std::__1::__invoke_void_return_wrapper<int, false>::__call[abi:se200000]<int (*&)(int, int), int, int>(__args=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:216:12
    frame #6: 0x0000000100002038 a.out`std::__1::function<int (int, int)>::operator()(this= Function = foo(int, int) , __arg=1, __arg=1) const at function.h:989:10
    frame #7: 0x0000000100001f64 a.out`main(argc=1, argv=0x000000016fdff4f8) at main.cpp:9:10
    frame #8: 0x0000000183cdf154 dyld`start + 2476
Note: Some frames were hidden by frame recognizers
```
shiltian pushed a commit that referenced this pull request Sep 12, 2024
…lvm#107294)

Random testing revealed it's possible to crash the analyzer with the
command line invocation:

clang -cc1 -analyze -analyzer-checker=nullability empty.c

where the source file, empty.c is an empty source file.

```
clang: <root>/clang/lib/StaticAnalyzer/Core/CheckerManager.cpp:56:
   void clang::ento::CheckerManager::finishedCheckerRegistration():
     Assertion `Event.second.HasDispatcher && "No dispatcher registered for an event"' failed.

PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/

Stack dump:
0.      Program arguments: clang -cc1 -analyze -analyzer-checker=nullability nullability-nocrash.c
 #0 ...
 ...
 #7 <addr> clang::ento::CheckerManager::finishedCheckerRegistration()
 #8 <addr> clang::ento::CheckerManager::CheckerManager(clang::ASTContext&,
             clang::AnalyzerOptions&, clang::Preprocessor const&,
             llvm::ArrayRef<std::__cxx11::basic_string<char, std::char_traits<char>,
             std::allocator<char>>>, llvm::ArrayRef<std::function<void (clang::ento::CheckerRegistry&)>>)
```

This commit removes the assertion which failed here, because it was
logically incorrect: it required that if an Event is handled by some
(enabled) checker, then there must be an **enabled** checker which can
emit that kind of Event. It should be OK to disable the event-producing
checkers but enable an event-consuming checker which has different
responsibilities in addition to handling the events.
 
Note that this assertion was in an `#ifndef NDEBUG` block, so this
change does not impact the non-debug builds.

Co-authored-by: Vince Bridgers <[email protected]>
shiltian pushed a commit that referenced this pull request Jan 22, 2025
llvm#123877)

Reverts llvm#122811 due to buildbot breakage e.g.,
https://lab.llvm.org/buildbot/#/builders/52/builds/5421/steps/11/logs/stdio

ASan output from local re-run:
```
==2780289==ERROR: AddressSanitizer: use-after-poison on address 0x7e0b87e28d28 at pc 0x55a979a99e7e bp 0x7ffe4b18f0b0 sp 0x7ffe4b18f0a8
READ of size 1 at 0x7e0b87e28d28 thread T0
    #0 0x55a979a99e7d in getStorageClass /usr/local/google/home/thurston/buildbot_repro/llvm-project/llvm/include/llvm/Object/COFF.h:344
    #1 0x55a979a99e7d in isSectionDefinition /usr/local/google/home/thurston/buildbot_repro/llvm-project/llvm/include/llvm/Object/COFF.h:429:9
    #2 0x55a979a99e7d in getSymbols /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/COFF/LLDMapFile.cpp:54:42
    #3 0x55a979a99e7d in lld::coff::writeLLDMapFile(lld::coff::COFFLinkerContext const&) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/COFF/LLDMapFile.cpp:103:40
    #4 0x55a979a16879 in (anonymous namespace)::Writer::run() /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/COFF/Writer.cpp:810:3
    #5 0x55a979a00aac in lld::coff::writeResult(lld::coff::COFFLinkerContext&) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/COFF/Writer.cpp:354:15
    #6 0x55a97985f7ed in lld::coff::LinkerDriver::linkerMain(llvm::ArrayRef<char const*>) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/COFF/Driver.cpp:2826:3
    #7 0x55a97984cdd3 in lld::coff::link(llvm::ArrayRef<char const*>, llvm::raw_ostream&, llvm::raw_ostream&, bool, bool) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/COFF/Driver.cpp:97:15
    #8 0x55a9797f9793 in lld::unsafeLldMain(llvm::ArrayRef<char const*>, llvm::raw_ostream&, llvm::raw_ostream&, llvm::ArrayRef<lld::DriverDef>, bool) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/Common/DriverDispatcher.cpp:163:12
    llvm#9 0x55a9797fa3b6 in operator() /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/Common/DriverDispatcher.cpp:188:15
    llvm#10 0x55a9797fa3b6 in void llvm::function_ref<void ()>::callback_fn<lld::lldMain(llvm::ArrayRef<char const*>, llvm::raw_ostream&, llvm::raw_ostream&, llvm::ArrayRef<lld::DriverDef>)::$_0>(long) /usr/local/google/home/thurston/buildbot_repro/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:46:12
    llvm#11 0x55a97966cb93 in operator() /usr/local/google/home/thurston/buildbot_repro/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:69:12
    llvm#12 0x55a97966cb93 in llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) /usr/local/google/home/thurston/buildbot_repro/llvm-project/llvm/lib/Support/CrashRecoveryContext.cpp:426:3
    llvm#13 0x55a9797f9dc3 in lld::lldMain(llvm::ArrayRef<char const*>, llvm::raw_ostream&, llvm::raw_ostream&, llvm::ArrayRef<lld::DriverDef>) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/Common/DriverDispatcher.cpp:187:14
    llvm#14 0x55a979627512 in lld_main(int, char**, llvm::ToolContext const&) /usr/local/google/home/thurston/buildbot_repro/llvm-project/lld/tools/lld/lld.cpp:103:14
    llvm#15 0x55a979628731 in main /usr/local/google/home/thurston/buildbot_repro/llvm_build_asan/tools/lld/tools/lld/lld-driver.cpp:17:10
    llvm#16 0x7ffb8b202c89 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    llvm#17 0x7ffb8b202d44 in __libc_start_main csu/../csu/libc-start.c:360:3
    llvm#18 0x55a97953ef60 in _start (/usr/local/google/home/thurston/buildbot_repro/llvm_build_asan/bin/lld+0x8fd1f60)
```
shiltian pushed a commit that referenced this pull request May 15, 2025
The mcmodel=tiny memory model is only valid on ARM targets. While trying
this on X86 compiler throws an internal error along with stack dump.
llvm#125641
This patch resolves the issue.
Reduced test case:
```
#include <stdio.h>
int main( void )
{
printf( "Hello, World!\n" ); 
return 0; 
}
```
```
0.	Program arguments: /opt/compiler-explorer/clang-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -mcmodel=tiny <source>
1.	<eof> parser at end of file
 #0 0x0000000003b10218 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3b10218)
 #1 0x0000000003b0e35c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3b0e35c)
 #2 0x0000000003a5dbc3 llvm::CrashRecoveryContext::HandleExit(int) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3a5dbc3)
 #3 0x0000000003b05cfe llvm::sys::Process::Exit(int, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3b05cfe)
 #4 0x0000000000d4e3eb LLVMErrorHandler(void*, char const*, bool) cc1_main.cpp:0:0
 #5 0x0000000003a67c93 llvm::report_fatal_error(llvm::Twine const&, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3a67c93)
 #6 0x0000000003a67df8 (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3a67df8)
 #7 0x0000000002549148 llvm::X86TargetMachine::X86TargetMachine(llvm::Target const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef, llvm::TargetOptions const&, std::optional<llvm::Reloc::Model>, std::optional<llvm::CodeModel::Model>, llvm::CodeGenOptLevel, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x2549148)
 #8 0x00000000025491fc llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef, llvm::TargetOptions const&, std::optional<llvm::Reloc::Model>, std::optional<llvm::CodeModel::Model>, llvm::CodeGenOptLevel, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x25491fc)
 llvm#9 0x0000000003db74cc clang::emitBackendOutput(clang::CompilerInstance&, clang::CodeGenOptions&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3db74cc)
llvm#10 0x0000000004460d95 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x4460d95)
llvm#11 0x00000000060005ec clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x60005ec)
llvm#12 0x00000000044614b5 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x44614b5)
llvm#13 0x0000000004737121 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x4737121)
llvm#14 0x00000000046b777b clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x46b777b)
llvm#15 0x00000000048229e3 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x48229e3)
llvm#16 0x0000000000d50621 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0xd50621)
llvm#17 0x0000000000d48e2d ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
llvm#18 0x00000000044acc99 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
llvm#19 0x0000000003a5dac3 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x3a5dac3)
llvm#20 0x00000000044aceb9 clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
llvm#21 0x00000000044710dd clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-trunk/bin/clang+++0x44710dd)
llvm#22 0x0000000004472071 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-trunk/bin/clang+++0x4472071)
llvm#23 0x000000000447c3fc clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x447c3fc)
llvm#24 0x0000000000d4d2b1 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0xd4d2b1)
llvm#25 0x0000000000c12464 main (/opt/compiler-explorer/clang-trunk/bin/clang+++0xc12464)
llvm#26 0x00007ae43b029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
llvm#27 0x00007ae43b029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
llvm#28 0x0000000000d488c5 _start (/opt/compiler-explorer/clang-trunk/bin/clang+++0xd488c5)
```

---------

Co-authored-by: Shashwathi N <[email protected]>
shiltian pushed a commit that referenced this pull request Oct 23, 2025
**Mitigation for:** google/sanitizers#749

**Disclosure:** I'm not an ASan compiler expert yet (I'm trying to
learn!), I primarily work in the runtime. Some of this PR was developed
with the help of AI tools (primarily as a "fuzzy `grep` engine"), but
I've manually refined and tested the output, and can speak for every
line. In general, I used it only to orient myself and for
"rubberducking".

**Context:**

The msvc ASan team (👋 ) has received an internal request to improve
clang's exception handling under ASan for Windows. Namely, we're
interested in **mitigating** this bug:
google/sanitizers#749

To summarize, today, clang + ASan produces a false-positive error for
this program:

```C++
#include <cstdio>
#include <exception>
int main()
{
	try	{
		throw std::exception("test");
	}catch (const std::exception& ex){
		puts(ex.what());
	}
	return 0;
}
```

The error reads as such:


```
C:\Users\dajusto\source\repros\upstream>type main.cpp
#include <cstdio>
#include <exception>
int main()
{
        try     {
                throw std::exception("test");
        }catch (const std::exception& ex){
                puts(ex.what());
        }
        return 0;
}
C:\Users\dajusto\source\repros\upstream>"C:\Users\dajusto\source\repos\llvm-project\build.runtimes\bin\clang.exe" -fsanitize=address -g -O0 main.cpp

C:\Users\dajusto\source\repros\upstream>a.exe
=================================================================
==19112==ERROR: AddressSanitizer: access-violation on unknown address 0x000000000000 (pc 0x7ff72c7c11d9 bp 0x0080000ff960 sp 0x0080000fcf50 T0)
==19112==The signal is caused by a READ memory access.
==19112==Hint: address points to the zero page.
    #0 0x7ff72c7c11d8 in main C:\Users\dajusto\source\repros\upstream\main.cpp:8
    #1 0x7ff72c7d479f in _CallSettingFrame C:\repos\msvc\src\vctools\crt\vcruntime\src\eh\amd64\handlers.asm:49
    #2 0x7ff72c7c8944 in __FrameHandler3::CxxCallCatchBlock(struct _EXCEPTION_RECORD *) C:\repos\msvc\src\vctools\crt\vcruntime\src\eh\frame.cpp:1567
    #3 0x7ffb4a90e3e5  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x18012e3e5)
    #4 0x7ff72c7c1128 in main C:\Users\dajusto\source\repros\upstream\main.cpp:6
    #5 0x7ff72c7c33db in invoke_main C:\repos\msvc\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78
    #6 0x7ff72c7c33db in __scrt_common_main_seh C:\repos\msvc\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
    #7 0x7ffb49b05c06  (C:\WINDOWS\System32\KERNEL32.DLL+0x180035c06)
    #8 0x7ffb4a8455ef  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x1800655ef)

==19112==Register values:
rax = 0  rbx = 80000ff8e0  rcx = 27d76d00000  rdx = 80000ff8e0
rdi = 80000fdd50  rsi = 80000ff6a0  rbp = 80000ff960  rsp = 80000fcf50
r8  = 100  r9  = 19930520  r10 = 8000503a90  r11 = 80000fd540
r12 = 80000fd020  r13 = 0  r14 = 80000fdeb8  r15 = 0
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: access-violation C:\Users\dajusto\source\repros\upstream\main.cpp:8 in main
==19112==ABORTING
```

The root of the issue _appears to be_ that ASan's instrumentation is
incompatible with Window's assumptions for instantiating `catch`-block's
parameters (`ex` in the snippet above).

The nitty gritty details are lost on me, but I understand that to make
this work without loss of ASan coverage, a "serious" refactoring is
needed. In the meantime, users risk false positive errors when pairing
ASan + catch-block parameters on Windows.

**To mitigate this** I think we should avoid instrumenting catch-block
parameters on Windows. It appears to me this is as "simple" as marking
catch block parameters as "uninteresting" in
`AddressSanitizer::isInterestingAlloca`. My manual tests seem to confirm
this.

I believe this is strictly better than today's status quo, where the
runtime generates false positives. Although we're now explicitly
choosing to instrument less, the benefit is that now more programs can
run with ASan without _funky_ macros that disable ASan on exception
blocks.

**This PR:** implements the mitigation above, and creates a simple new
test for it.

_Thanks!_

---------

Co-authored-by: Antonio Frighetto <[email protected]>
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2 participants