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[SR-8809] Enabling TSan causes immediate segfault on Swift 4.2 for Linux #51317

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Lukasa opened this issue Sep 20, 2018 · 10 comments
Open

[SR-8809] Enabling TSan causes immediate segfault on Swift 4.2 for Linux #51317

Lukasa opened this issue Sep 20, 2018 · 10 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@Lukasa
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Lukasa commented Sep 20, 2018

Previous ID SR-8809
Radar rdar://problem/44645777
Original Reporter @Lukasa
Type Bug
Environment

Ubuntu 18.04, Swift version 4.2 (swift-4.2-RELEASE)

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug
Assignee None
Priority Medium

md5: 87fcf099d809e6599a73947c53fb79a9

Issue Description:

Compiling any Swift program on Swift 4.2 on Linux with -sanitize=thread causes an immediate segmentation fault when the program starts.

The backtrace is:

* thread #​1, name = 'test', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
  * frame #​0: 0x0000000000000000
    frame #​1: 0x0000555555582c6b //test`::MonotonicNanoTime() at sanitizer_linux_libcdep.cc:754
    frame #​2: 0x00005555555d5588 //test`::PopulateFreeArray() at sanitizer_allocator_primary64.h:700
    frame #​3: 0x00005555555d5175 //test`::GetFromAllocator() at sanitizer_allocator_primary64.h:136
    frame #​4: 0x00005555555d4dd9 //test`::Refill() at sanitizer_allocator_local_cache.h:111
    frame #​5: 0x00005555555d4a87 //test`::Allocate() at sanitizer_allocator_local_cache.h:47
    frame #​6: 0x00005555555d35f3 //test`::Allocate() at sanitizer_allocator_combined.h:62
    frame #​7: 0x00005555555d2777 //test`::user_alloc_internal() at tsan_mman.cc:157
    frame #​8: 0x00005555555d2c67 //test`::user_calloc() at tsan_mman.cc:183
    frame #​9: 0x000055555558ca9c //test`::__interceptor_calloc() at tsan_interceptors.cc:684
    frame #​10: 0x00007ffff6ef27e5

User code has not even begun to run when this crash occurs.
@Lukasa
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Lukasa commented Sep 20, 2018

We seem to be using the system llvm's copy of the sanitizer code here, as the line numbers don't line up with swift-compiler-rt's lines, but they do line up with LLVM's compiler-rt line numbers for version 6.0, which is what Ubuntu 18.04 ships. The crash on line 754 becomes a crash on the call to real_clock_gettime(CLOCK_MONOTONIC, &ts);. That's a bit puzzling to me, as there's a check above that the address of real_clock_gettime is not NULL, yet our stack trace strongly suggests it is.

@belkadan
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cc george.karpenkov (JIRA User)

@Lukasa
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Lukasa commented Sep 20, 2018

@swift-ci create

@swift-ci
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Comment by George Karpenkov (JIRA)

@kubamracek for comments.

Sanitizers on Swift on Linux are not fully supported, and there are many known issues. That said, it still should not segfault on launch.

@jckarter
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Linking against anything from the "system LLVM" sounds like a red flag, since LLVM isn't generally ABI-stable and Swift is fairly tightly coupled to the LLVM libraries it builds alongside itself. Could this just be a build system configuration bug that we're failing to find and link to the swift compiler-rt libraries?

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Comment by George Karpenkov (JIRA)

@jckarter @Lukasa yeah, using tsan from system LLVM is definitely a bug.

To debug this, could you perhaps remove the system LLVM entirely?

Then you would get a "true" error message when it can not find a library from the toolchain.

@Lukasa
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Lukasa commented Sep 21, 2018

Removing the system LLVM entirely leads to the following error message:

root@7b6ced73e86a:/# swiftc -v test.swift
Swift version 4.2 (swift-4.2-RELEASE)
Target: x86_64-unknown-linux-gnu
/swift-4.2-RELEASE-ubuntu18.04/usr/bin/swift -frontend -c -primary-file test.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -color-diagnostics -module-name test -o /tmp/test-24c634.o
/swift-4.2-RELEASE-ubuntu18.04/usr/bin/swift-autolink-extract /tmp/test-24c634.o -o /tmp/test-a24bd9.autolink
<unknown>:0: error: unable to execute command: <unknown>

@Lukasa
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Lukasa commented Sep 21, 2018

This also happens even if I install all of Swift directly over my system libraries (e.g. tar xvf swift-4.2-RELEASE-ubuntu18.04.tar.gz -C / --strip-components=1 ): removing the system llvm breaks the Swift compiler.

@swift-ci
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Comment by George Karpenkov (JIRA)

> removing the system llvm breaks the Swift compiler.

That's the real issue then: the downloaded toolchain definitely should be self-sufficient.

"unable to execute command: <unknown>" is not very informative, there's no stack trace at all?

@Lukasa
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Lukasa commented Sep 22, 2018

There is really no stack trace at all. That’s the complete output from {{ swiftc -v }}.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@jckarter @belkadan @Lukasa @swift-ci