[lld] r352082 - Fix broken export table if .rdata is merged with .text.

[Hans Wennborg via llvm-commits]

Merged to 8.0 in r352135.

On Thu, Jan 24, 2019 at 11:02 AM Rui Ueyama via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
> Author: ruiu
> Date: Thu Jan 24 11:02:31 2019
> New Revision: 352082
>
> URL: http://llvm.org/viewvc/llvm-project?rev=352082&view=rev
> Log:
> Fix broken export table if .rdata is merged with .text.
>
> Previously, we assumed that .rdata is zero-filled, so when writing
> an COFF import table, we didn't write anything if the data is zero.
> That assumption was wrong because .rdata can be merged with .text.
> If .rdata is merged with .text, they are initialized with 0xcc which
> is a trap instruction.
>
> This patch removes that assumption from code.
>
> Should be merged to 8.0 branch as this is a regression.
>
> Fixes https://bugs.llvm.org/show_bug.cgi?id=39826
>
> Differential Revision: https://reviews.llvm.org/D57168
>
> Modified:
>     lld/trunk/COFF/DLL.cpp
>     lld/trunk/test/COFF/imports.test
>
> Modified: lld/trunk/COFF/DLL.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/DLL.cpp?rev=352082&r1=352081&r2=352082&view=diff
> ==============================================================================
> --- lld/trunk/COFF/DLL.cpp (original)
> +++ lld/trunk/COFF/DLL.cpp Thu Jan 24 11:02:31 2019
> @@ -46,6 +46,7 @@ public:
>    }
>
>    void writeTo(uint8_t *Buf) const override {
> +    memset(Buf + OutputSectionOff, 0, getSize());
>      write16le(Buf + OutputSectionOff, Hint);
>      memcpy(Buf + OutputSectionOff + 2, Name.data(), Name.size());
>    }
> @@ -62,7 +63,10 @@ public:
>    size_t getSize() const override { return Config->Wordsize; }
>
>    void writeTo(uint8_t *Buf) const override {
> -    write32le(Buf + OutputSectionOff, HintName->getRVA());
> +    if (Config->is64())
> +      write64le(Buf + OutputSectionOff, HintName->getRVA());
> +    else
> +      write32le(Buf + OutputSectionOff, HintName->getRVA());
>    }
>
>    Chunk *HintName;
> @@ -98,6 +102,8 @@ public:
>    size_t getSize() const override { return sizeof(ImportDirectoryTableEntry); }
>
>    void writeTo(uint8_t *Buf) const override {
> +    memset(Buf + OutputSectionOff, 0, getSize());
> +
>      auto *E = (coff_import_directory_table_entry *)(Buf + OutputSectionOff);
>      E->ImportLookupTableRVA = LookupTab->getRVA();
>      E->NameRVA = DLLName->getRVA();
> @@ -117,6 +123,10 @@ public:
>    bool hasData() const override { return false; }
>    size_t getSize() const override { return Size; }
>
> +  void writeTo(uint8_t *Buf) const override {
> +    memset(Buf + OutputSectionOff, 0, Size);
> +  }
> +
>  private:
>    size_t Size;
>  };
> @@ -159,6 +169,8 @@ public:
>    }
>
>    void writeTo(uint8_t *Buf) const override {
> +    memset(Buf + OutputSectionOff, 0, getSize());
> +
>      auto *E = (delay_import_directory_table_entry *)(Buf + OutputSectionOff);
>      E->Attributes = 1;
>      E->Name = DLLName->getRVA();
> @@ -391,6 +403,8 @@ public:
>    }
>
>    void writeTo(uint8_t *Buf) const override {
> +    memset(Buf + OutputSectionOff, 0, getSize());
> +
>      auto *E = (export_directory_table_entry *)(Buf + OutputSectionOff);
>      E->NameRVA = DLLName->getRVA();
>      E->OrdinalBase = 0;
>
> Modified: lld/trunk/test/COFF/imports.test
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/imports.test?rev=352082&r1=352081&r2=352082&view=diff
> ==============================================================================
> --- lld/trunk/test/COFF/imports.test (original)
> +++ lld/trunk/test/COFF/imports.test Thu Jan 24 11:02:31 2019
> @@ -34,3 +34,16 @@ IMPORT-NEXT:   Symbol: ExitProcess (0)
>  IMPORT-NEXT:   Symbol:  (50)
>  IMPORT-NEXT:   Symbol: MessageBoxA (1)
>  IMPORT-NEXT: }
> +
> +# RUN: lld-link /out:%t.exe /entry:main /subsystem:console /merge:.rdata=.text \
> +# RUN:   %p/Inputs/hello64.obj %p/Inputs/std64.lib /include:ExitProcess
> +# RUN: llvm-readobj -coff-imports %t.exe | FileCheck -check-prefix=MERGE %s
> +
> +MERGE:      Import {
> +MERGE-NEXT:   Name: std64.dll
> +MERGE-NEXT:   ImportLookupTableRVA: 0x1090
> +MERGE-NEXT:   ImportAddressTableRVA: 0x10B0
> +MERGE-NEXT:   Symbol: ExitProcess (0)
> +MERGE-NEXT:   Symbol:  (50)
> +MERGE-NEXT:   Symbol: MessageBoxA (1)
> +MERGE-NEXT: }
>
>
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