[libunwind] r352016 - [libunwind] Don't abort if encoutering invalid .eh_frame_hdr

[Hans Wennborg via cfe-commits]

Should we merge this to 8.0?

On Wed, Jan 23, 2019 at 10:04 PM Petr Hosek via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
>
> Author: phosek
> Date: Wed Jan 23 19:04:42 2019
> New Revision: 352016
>
> URL: http://llvm.org/viewvc/llvm-project?rev=352016&view=rev
> Log:
> [libunwind] Don't abort if encoutering invalid .eh_frame_hdr
>
> Recent Linux kernel release has introduced a bug as part of the ORC
> rollout where the vDSO has a valid .eh_frame section, but it's missing
> the .eh_frame_hdr section and GNU_EH_FRAME segment has zero size. This
> causes libunwind to abort which breaks programs that use libunwind.
>
> The other unwinder implementation (libgcc, non-gnu) instead silently
> bail out unless being compiled as debug. This change modifies libunwind
> to use the same strategy.
>
> Differential Revision: https://reviews.llvm.org/D57081
>
> Modified:
>     libunwind/trunk/src/AddressSpace.hpp
>     libunwind/trunk/src/EHHeaderParser.hpp
>
> Modified: libunwind/trunk/src/AddressSpace.hpp
> URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/src/AddressSpace.hpp?rev=352016&r1=352015&r2=352016&view=diff
> ==============================================================================
> --- libunwind/trunk/src/AddressSpace.hpp (original)
> +++ libunwind/trunk/src/AddressSpace.hpp Wed Jan 23 19:04:42 2019
> @@ -535,11 +535,11 @@ inline bool LocalAddressSpace::findUnwin
>  #endif
>              cbdata->sects->dwarf_index_section = eh_frame_hdr_start;
>              cbdata->sects->dwarf_index_section_length = phdr->p_memsz;
> -            EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
> +            found_hdr = EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
>                  *cbdata->addressSpace, eh_frame_hdr_start, phdr->p_memsz,
>                  hdrInfo);
> -            cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
> -            found_hdr = true;
> +            if (found_hdr)
> +              cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
>            }
>          }
>
>
> Modified: libunwind/trunk/src/EHHeaderParser.hpp
> URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/src/EHHeaderParser.hpp?rev=352016&r1=352015&r2=352016&view=diff
> ==============================================================================
> --- libunwind/trunk/src/EHHeaderParser.hpp (original)
> +++ libunwind/trunk/src/EHHeaderParser.hpp Wed Jan 23 19:04:42 2019
> @@ -35,7 +35,7 @@ public:
>      uint8_t table_enc;
>    };
>
> -  static void decodeEHHdr(A &addressSpace, pint_t ehHdrStart, pint_t ehHdrEnd,
> +  static bool decodeEHHdr(A &addressSpace, pint_t ehHdrStart, pint_t ehHdrEnd,
>                            EHHeaderInfo &ehHdrInfo);
>    static bool findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
>                        uint32_t sectionLength,
> @@ -52,12 +52,14 @@ private:
>  };
>
>  template <typename A>
> -void EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart,
> +bool EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart,
>                                      pint_t ehHdrEnd, EHHeaderInfo &ehHdrInfo) {
>    pint_t p = ehHdrStart;
>    uint8_t version = addressSpace.get8(p++);
> -  if (version != 1)
> -    _LIBUNWIND_ABORT("Unsupported .eh_frame_hdr version");
> +  if (version != 1) {
> +    _LIBUNWIND_LOG0("Unsupported .eh_frame_hdr version");
> +    return false;
> +  }
>
>    uint8_t eh_frame_ptr_enc = addressSpace.get8(p++);
>    uint8_t fde_count_enc = addressSpace.get8(p++);
> @@ -70,6 +72,8 @@ void EHHeaderParser<A>::decodeEHHdr(A &a
>            ? 0
>            : addressSpace.getEncodedP(p, ehHdrEnd, fde_count_enc, ehHdrStart);
>    ehHdrInfo.table = p;
> +
> +  return true;
>  }
>
>  template <typename A>
> @@ -101,7 +105,9 @@ bool EHHeaderParser<A>::findFDE(A &addre
>    pint_t ehHdrEnd = ehHdrStart + sectionLength;
>
>    EHHeaderParser<A>::EHHeaderInfo hdrInfo;
> -  EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, ehHdrEnd, hdrInfo);
> +  if (!EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, ehHdrEnd,
> +                                      hdrInfo))
> +    return false;
>
>    size_t tableEntrySize = getTableEntrySize(hdrInfo.table_enc);
>    pint_t tableEntry;
>
>
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