[lld] r320817 - Handle a VersymIndex of 0 as an error.

[Simon Atanasyan via llvm-commits]

Hi Rafael,

Starting from this commit I get the following error in attempt to
build MIPS executable:
[[
error: corrupt input file: version definition index 0 for symbol
_gp_disp is out of bounds
>>> defined in ..../code-2017.10-mti/lib/gcc/mips-mti-linux-gnu/6.3.0/../../../../mips-mti-linux-gnu/lib/mipsel-r2-hard/lib/libgcc_s.so.1
]]

The "_gp_disp" symbol defined in the "libgcc_s.so.1" as "SECTION
GLOBAL DEFAULT ABS". The "libgcc_s.so.1" is a part of CodeScape
toolchain and linked using GNU tools.

Do you think that libgcc_s.so.1 has broken version info or global
section symbol is a corner case and zero VersymIndex is a correct
value?

For the reference here is the link to the "libgcc_s.so.1":
https://drive.google.com/open?id=1xp3eU34G4N6oSY5HeVKBHNLXwzXJK5O6

Regards,
Simon

On Fri, Dec 15, 2017 at 5:52 PM, Rafael Espindola via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: rafael
> Date: Fri Dec 15 06:52:40 2017
> New Revision: 320817
>
> URL: http://llvm.org/viewvc/llvm-project?rev=320817&view=rev
> Log:
> Handle a VersymIndex of 0 as an error.
>
> I noticed that the continue this patch deletes was not tested. Trying
> to add a test I realized that we never put a VER_NDX_LOCAL symbol in
> the dynamic symbol table. There doesn't seem to be any reason for a
> linker to use VER_NDX_LOCAL for a defined shared symbol.
>
> Modified:
>     lld/trunk/ELF/InputFiles.cpp
>     lld/trunk/test/ELF/corrupted-version-reference.s
>
> Modified: lld/trunk/ELF/InputFiles.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=320817&r1=320816&r2=320817&view=diff
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.cpp (original)
> +++ lld/trunk/ELF/InputFiles.cpp Fri Dec 15 06:52:40 2017
> @@ -793,7 +793,7 @@ template <class ELFT> void SharedFile<EL
>    // Add symbols to the symbol table.
>    Elf_Sym_Range Syms = this->getGlobalELFSyms();
>    for (const Elf_Sym &Sym : Syms) {
> -    unsigned VersymIndex = 0;
> +    unsigned VersymIndex = VER_NDX_GLOBAL;
>      if (Versym) {
>        VersymIndex = Versym->vs_index;
>        ++Versym;
> @@ -813,12 +813,9 @@ template <class ELFT> void SharedFile<EL
>        continue;
>      }
>
> -    // Ignore local symbols.
> -    if (Versym && VersymIndex == VER_NDX_LOCAL)
> -      continue;
>      const Elf_Verdef *Ver = nullptr;
>      if (VersymIndex != VER_NDX_GLOBAL) {
> -      if (VersymIndex >= Verdefs.size()) {
> +      if (VersymIndex >= Verdefs.size() || VersymIndex == VER_NDX_LOCAL) {
>          error("corrupt input file: version definition index " +
>                Twine(VersymIndex) + " for symbol " + Name +
>                " is out of bounds\n>>> defined in " + toString(this));