From fc5a9bd57cbb974b8fc3aeb9a15d644cd9103451 Mon Sep 17 00:00:00 2001 From: Cary Coutant Date: Fri, 26 Feb 2016 07:50:15 -0800 Subject: [PATCH] Discard FDEs for zero-length address ranges. 2016-02-26 Egor Kochetov Cary Coutant gold/ PR gold/19735 * ehframe.h (Cie::fde_encoding): New method. * ehframe.cc (Eh_frame::read_fde): Discard FDEs for zero-length address ranges. --- gold/ChangeLog | 8 ++++++++ gold/ehframe.cc | 39 ++++++++++++++++++++++++++++++++++----- gold/ehframe.h | 5 +++++ 3 files changed, 47 insertions(+), 5 deletions(-) diff --git a/gold/ChangeLog b/gold/ChangeLog index 45d02bf064..53c1ceb8ae 100644 --- a/gold/ChangeLog +++ b/gold/ChangeLog @@ -1,3 +1,11 @@ +2016-02-26 Egor Kochetov + Cary Coutant + + PR gold/19735 + * ehframe.h (Cie::fde_encoding): New method. + * ehframe.cc (Eh_frame::read_fde): Discard FDEs for zero-length + address ranges. + 2016-02-15 H.J. Lu * testsuite/Makefile.am (x86_64_mov_to_lea5.o): Pass diff --git a/gold/ehframe.cc b/gold/ehframe.cc index 71bcc2053f..57eb031faf 100644 --- a/gold/ehframe.cc +++ b/gold/ehframe.cc @@ -1010,6 +1010,8 @@ Eh_frame::read_fde(Sized_relobj_file* object, // pointer to a PC relative offset when generating a shared library. relocs->advance(pfdeend - pcontents); + // Find the section index for code that this FDE describes. + // If we have discarded the section, we can also discard the FDE. unsigned int fde_shndx; const int sym_size = elfcpp::Elf_sizes::sym_size; if (symndx >= symbols_size / sym_size) @@ -1018,13 +1020,40 @@ Eh_frame::read_fde(Sized_relobj_file* object, bool is_ordinary; fde_shndx = object->adjust_sym_shndx(symndx, sym.get_st_shndx(), &is_ordinary); + bool is_discarded = (is_ordinary + && fde_shndx != elfcpp::SHN_UNDEF + && fde_shndx < object->shnum() + && !object->is_section_included(fde_shndx)); - if (is_ordinary - && fde_shndx != elfcpp::SHN_UNDEF - && fde_shndx < object->shnum() - && !object->is_section_included(fde_shndx)) + // Fetch the address range field from the FDE. The offset and size + // of the field depends on the PC encoding given in the CIE, but + // it is always an absolute value. If the address range is 0, this + // FDE corresponds to a function that was discarded during optimization + // (too late to discard the corresponding FDE). + uint64_t address_range = 0; + int pc_size = cie->fde_encoding() & 7; + if (pc_size == elfcpp::DW_EH_PE_absptr) + pc_size = size == 32 ? elfcpp::DW_EH_PE_udata4 : elfcpp::DW_EH_PE_udata8; + switch (pc_size) { - // This FDE applies to a section which we are discarding. We + case elfcpp::DW_EH_PE_udata2: + address_range = elfcpp::Swap<16, big_endian>::readval(pfde + 2); + break; + case elfcpp::DW_EH_PE_udata4: + address_range = elfcpp::Swap<32, big_endian>::readval(pfde + 4); + break; + case elfcpp::DW_EH_PE_udata8: + gold_assert(size == 64); + address_range = elfcpp::Swap_unaligned<64, big_endian>::readval(pfde + 8); + break; + default: + // All other cases were rejected in Eh_frame::read_cie. + gold_unreachable(); + } + + if (is_discarded || address_range == 0) + { + // This FDE applies to a discarded function. We // can discard this FDE. object->add_merge_mapping(this, shndx, (pfde - 8) - pcontents, pfdeend - (pfde - 8), -1); diff --git a/gold/ehframe.h b/gold/ehframe.h index a32b55089c..14281b0d33 100644 --- a/gold/ehframe.h +++ b/gold/ehframe.h @@ -323,6 +323,11 @@ class Cie unsigned int addralign, Eh_frame_hdr* eh_frame_hdr, Post_fdes* post_fdes); + // Return the FDE encoding. + unsigned char + fde_encoding() const + { return this->fde_encoding_; } + friend bool operator<(const Cie&, const Cie&); friend bool operator==(const Cie&, const Cie&);