llvm-capstone/lld/test/COFF/merge.test
Alexandre Ganea 45b8a741fb [LLD][COFF] When using LLD-as-a-library, always prevent re-entrance on failures
This is a follow-up for D70378 (Cover usage of LLD as a library).

While debugging an intermittent failure on a bot, I recalled this scenario which
causes the issue:

1.When executing lld/test/ELF/invalid/symtab-sh-info.s L45, we reach
  lld:🧝:Obj-File::ObjFile() which goes straight into its base ELFFileBase(),
  then ELFFileBase::init().
2.At that point fatal() is thrown in lld/ELF/InputFiles.cpp L381, leaving a
  half-initialized ObjFile instance.
3.We then end up in lld::exitLld() and since we are running with LLD_IN_TEST, we
  hapily restore the control flow to CrashRecoveryContext::RunSafely() then back
  in lld::safeLldMain().
4.Before this patch, we called errorHandler().reset() just after, and this
  attempted to reset the associated SpecificAlloc<ObjFile<ELF64LE>>. That tried
  to free the half-initialized ObjFile instance, and more precisely its
  ObjFile::dwarf member.

Sometimes that worked, sometimes it failed and was catched by the
CrashRecoveryContext. This scenario was the reason we called
errorHandler().reset() through a CrashRecoveryContext.

But in some rare cases, the above repro somehow corrupted the heap, creating a
stack overflow. When the CrashRecoveryContext's filter (that is,
__except (ExceptionFilter(GetExceptionInformation()))) tried to handle the
exception, it crashed again since the stack was exhausted -- and that took the
whole application down. That is the issue seen on the bot. Locally it happens
about 1 times out of 15.

Now this situation can happen anywhere in LLD. Since catching stack overflows is
not a reliable scenario ATM when using CrashRecoveryContext, we're now
preventing further re-entrance when such failures occur, by signaling
lld::SafeReturn::canRunAgain=false. When running with LLD_IN_TEST=2 (or above),
only one iteration will be executed, instead of two.

Differential Revision: https://reviews.llvm.org/D88348
2020-11-12 08:14:43 -05:00

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# RUN: yaml2obj %s -o %t.obj
# RUN: lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.foo=.abc /merge:.bar=.def %t.obj /debug
# RUN: llvm-readobj --sections %t.exe | FileCheck %s
# RUN: lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.foo=.bar /merge:.bar=.abc %t.obj /debug
# RUN: llvm-readobj --sections %t.exe | FileCheck --check-prefix=CHECK2 %s
# RUN: env LLD_IN_TEST=1 not lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.rsrc=.foo %t.obj /debug 2>&1 | FileCheck --check-prefix=NO-RSRC %s
# RUN: env LLD_IN_TEST=1 not lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.foo=.rsrc %t.obj /debug 2>&1 | FileCheck --check-prefix=NO-RSRC %s
# RUN: env LLD_IN_TEST=1 not lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.reloc=.foo %t.obj /debug 2>&1 | FileCheck --check-prefix=NO-RELOC %s
# RUN: env LLD_IN_TEST=1 not lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.foo=.reloc %t.obj /debug 2>&1 | FileCheck --check-prefix=NO-RELOC %s
# RUN: env LLD_IN_TEST=1 not lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.foo=.foo1 /merge:.foo1=.foo %t.obj /debug 2>&1 | FileCheck --check-prefix=NO-CYCLE %s
# RUN: env LLD_IN_TEST=1 not lld-link /out:%t.exe /entry:main /subsystem:console /force \
# RUN: /merge:.foo=.foo1 /merge:.foo1=.foo2 /merge:.foo2=.foo1 %t.obj /debug 2>&1 | FileCheck --check-prefix=NO-CYCLE %s
# CHECK: Name: .def
# CHECK: Name: .abc
# CHECK2-NOT: Name: .bar
# CHECK2: Name: .abc
# CHECK2-NOT: Name: .bar
# NO-RSRC: /merge: cannot merge '.rsrc' with any section
# NO-RELOC: /merge: cannot merge '.reloc' with any section
# NO-CYCLE: /merge: cycle found for section '.foo'
--- !COFF
header:
Machine: IMAGE_FILE_MACHINE_AMD64
Characteristics: []
sections:
- Name: .foo
Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
Alignment: 4
SectionData: 000000000000
- Name: .bar
Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
Alignment: 4
SectionData: 000000000000
symbols:
- Name: .foo
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
SectionDefinition:
Length: 6
NumberOfRelocations: 0
NumberOfLinenumbers: 0
CheckSum: 0
Number: 0
- Name: .bar
Value: 0
SectionNumber: 2
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
SectionDefinition:
Length: 6
NumberOfRelocations: 0
NumberOfLinenumbers: 0
CheckSum: 0
Number: 0
- Name: main
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_FUNCTION
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
...