[llvm-dev] initialization-order-fiasco in MCTargetDesc/X86MCAsmInfo.cpp

[Mehdi Amini via llvm-dev]

It seems that the culprit is llvm/unittests/MC/DwarfLineTables.cpp, which has a global variable “Context” that initializes all of LLVM (InitializeAllTargetInfos(), InitializeAllTargetMCs(), InitializeAllDisassemblers(), etc.).

It seems to have been there forever, but just got uncovered by “luck” (or lack of thereof) by ASAN.

Fixed in r286647 hopefully.

> On Nov 11, 2016, at 1:44 PM, Kostya Serebryany <kcc at google.com> wrote:
> 
> Mehdi, Teresa, 
> 
> Not sure if this is caused by one of your recent commits, or by someone else's,
> please excuse me if that's unrelated to your work... 
> 
> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/542/steps/check-llvm%20asan/logs/stdio <http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/542/steps/check-llvm%20asan/logs/stdio>
> 
> ==26383==ERROR: AddressSanitizer: initialization-order-fiasco on address 0x000002ef41d8 at pc 0x0000009d1aa5 bp 0x7ffd0cd72b50 sp 0x7ffd0cd72b48
> READ of size 4 at 0x000002ef41d8 thread T0
>     #0 0x9d1aa4 in getValue /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Support/CommandLine.h:1229:38
>     #1 0x9d1aa4 in operator AsmWriterFlavorTy /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Support/CommandLine.h:1233
>     #2 0x9d1aa4 in llvm::X86ELFMCAsmInfo::X86ELFMCAsmInfo(llvm::Triple const&) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp:100
>     #3 0x9cf3e1 in createX86MCAsmInfo(llvm::MCRegisterInfo const&, llvm::Triple const&) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp:179:15
>     #4 0x421020 in createMCAsmInfo /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Support/TargetRegistry.h:298:12
>     #5 0x421020 in Context /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/unittests/MC/DwarfLineTables.cpp:41
>     #6 0x421020 in __cxx_global_var_init /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/unittests/MC/DwarfLineTables.cpp:49
>     #7 0x421020 in _GLOBAL__sub_I_DwarfLineTables.cpp /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/unittests/MC/DwarfLineTables.cpp
>     #8 0x102efcc in __libc_csu_init (/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_asan/unittests/MC/MCTests+0x102efcc)
>     #9 0x7f57fa3d8ed4 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21ed4)
>     #10 0x4b4222 in _start (/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_asan/unittests/MC/MCTests+0x4b4222)
> 
> 0x000002ef41d8 is located 152 bytes inside of global variable 'AsmWriterFlavor' defined in '/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp:31:1' (0x2ef4140) of size 600
>   registered at:
>     #0 0x4c63fd in __asan_register_globals.part.15 /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/projects/compiler-rt/lib/asan/asan_globals.cc:338
>     #1 0x9d3f9b in asan.module_ctor (/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_asan/unittests/MC/MCTests+0x9d3f9b)
> 
> The reports seems correct. 
> The flag object AsmWriterFlavor is used before it is initialized in initialization of some other global object. 
> 
> This makes the asan bot red... :( 
> 
> Thanks, 
> --kcc

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