[GOLD] PowerPC recreate eh_frame for stubs on each relax pass
There is a very small but non-zero probability that a stub group contains stubs on one relax pass, but does not on the next. In that case we would get an FDE covering a zero length address range. (Actually, it's even worse. Alignment padding for stubs can mean the address for the non-existent stubs is past the end of the original section to which stubs are attached, and due to the way do_plt_fde_location calculates the length we can get a negative length.) Fixing this properly requires removing the FDE. Also, I have been implementing the __tls_get_addr_opt support for gold, and that stub needs something other than the default FDE. The necessary FDE will depend on the offset to the __tls_get_addr_opt stub, which of course can change during relaxation. That means at the very least, rewriting the FDE on each pass, possibly changing the FDE size. I think that is better done by completely recreating PLT eh_frame FDEs. * ehframe.cc (Fde::operator==): New. (Cie::remove_fde, Eh_frame::remove_ehframe_for_plt): New. * ehframe.h (Fde::operator==): Declare. (Cie::remove_fde, Eh_frame::remove_ehframe_for_plt): Likewise. * layout.cc (Layout::remove_eh_frame_for_plt): New. * layout.h (Layout::remove_eh_frame_for_plt): Declare. * powerpc.cc (Target_powerpc::do_relax): Remove old eh_frame FDEs. (Stub_table::add_eh_frame): Delete eh_frame_added_ condition. Don't add eh_frame for empty stub section. (Stub_table::remove_eh_frame): New.
This commit is contained in:
Alan Modra
parent
51b69c74c6
commit
be897fb774
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@ -1,3 +1,16 @@
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2017-08-01 Alan Modra <amodra@gmail.com>
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* ehframe.cc (Fde::operator==): New.
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(Cie::remove_fde, Eh_frame::remove_ehframe_for_plt): New.
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* ehframe.h (Fde::operator==): Declare.
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(Cie::remove_fde, Eh_frame::remove_ehframe_for_plt): Likewise.
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* layout.cc (Layout::remove_eh_frame_for_plt): New.
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* layout.h (Layout::remove_eh_frame_for_plt): Declare.
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* powerpc.cc (Target_powerpc::do_relax): Remove old eh_frame FDEs.
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(Stub_table::add_eh_frame): Delete eh_frame_added_ condition.
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Don't add eh_frame for empty stub section.
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(Stub_table::remove_eh_frame): New.
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2017-07-31 Alan Modra <amodra@gmail.com>
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* options.h (no_tls_optimize): New powerpc option.
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@ -325,6 +325,21 @@ Eh_frame_hdr::get_fde_addresses(Output_file* of,
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// Class Fde.
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bool
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Fde::operator==(const Fde& that) const
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{
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if (this->object_ != that.object_
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|| this->contents_ != that.contents_)
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return false;
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if (this->object_ == NULL)
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return (this->u_.from_linker.plt == that.u_.from_linker.plt
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&& this->u_.from_linker.post_map == that.u_.from_linker.post_map);
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else
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return (this->u_.from_object.shndx == that.u_.from_object.shndx
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&& (this->u_.from_object.input_offset
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== that.u_.from_object.input_offset));
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}
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// Write the FDE to OVIEW starting at OFFSET. CIE_OFFSET is the
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// offset of the CIE in OVIEW. OUTPUT_OFFSET is the offset of the
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// Eh_frame section within the output section. FDE_ENCODING is the
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@ -443,6 +458,15 @@ Cie::set_output_offset(section_offset_type output_offset,
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return output_offset + length;
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}
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// Remove FDE. Only the last FDE using this CIE may be removed.
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void
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Cie::remove_fde(const Fde* fde)
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{
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gold_assert(*fde == *this->fdes_.back());
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this->fdes_.pop_back();
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}
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// Write the CIE to OVIEW starting at OFFSET. OUTPUT_OFFSET is the
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// offset of the Eh_frame section within the output section. Round up
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// the bytes to ADDRALIGN. ADDRESS is the virtual address of OVIEW.
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@ -1143,6 +1167,28 @@ Eh_frame::add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data,
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this->final_data_size_ += align_address(fde_length + 8, this->addralign());
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}
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// Remove unwind information for a PLT. Only the last FDE added may be removed.
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void
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Eh_frame::remove_ehframe_for_plt(Output_data* plt,
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const unsigned char* cie_data,
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size_t cie_length,
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const unsigned char* fde_data,
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size_t fde_length)
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{
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Cie cie(NULL, 0, 0, elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4, "",
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cie_data, cie_length);
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Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie);
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gold_assert (find_cie != this->cie_offsets_.end());
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Cie* pcie = *find_cie;
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Fde* fde = new Fde(plt, fde_data, fde_length, this->mappings_are_done_);
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pcie->remove_fde(fde);
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if (this->mappings_are_done_)
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this->final_data_size_ -= align_address(fde_length + 8, this->addralign());
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}
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// Return the number of FDEs.
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unsigned int
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@ -217,6 +217,8 @@ class Fde
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section_offset_type cie_offset, unsigned char fde_encoding,
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Eh_frame_hdr* eh_frame_hdr);
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bool operator==(const Fde&) const;
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private:
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// The object in which this FDE was seen. This will be NULL for a
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// linker generated FDE.
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@ -298,6 +300,10 @@ class Cie
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add_fde(Fde* fde)
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{ this->fdes_.push_back(fde); }
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// Remove an FDE associated with this CIE. Only the last FDE may be removed.
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void
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remove_fde(const Fde*);
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// Return the number of FDEs.
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unsigned int
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fde_count() const
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@ -405,6 +411,13 @@ class Eh_frame : public Output_section_data
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size_t cie_length, const unsigned char* fde_data,
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size_t fde_length);
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// Remove unwind information for a PLT. Only the last FDE added may
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// be removed.
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void
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remove_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data,
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size_t cie_length, const unsigned char* fde_data,
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size_t fde_length);
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// Return the number of FDEs.
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unsigned int
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fde_count() const;
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@ -1581,6 +1581,23 @@ Layout::add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
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}
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}
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// Remove .eh_frame information for a PLT. FDEs using the CIE must
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// be removed in reverse order to the order they were added.
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void
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Layout::remove_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
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size_t cie_length, const unsigned char* fde_data,
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size_t fde_length)
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{
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if (parameters->incremental())
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{
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// FIXME: Maybe this could work some day....
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return;
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}
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this->eh_frame_data_->remove_ehframe_for_plt(plt, cie_data, cie_length,
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fde_data, fde_length);
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}
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// Scan a .debug_info or .debug_types section, and add summary
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// information to the .gdb_index section.
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@ -653,6 +653,13 @@ class Layout
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size_t cie_length, const unsigned char* fde_data,
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size_t fde_length);
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// Remove .eh_frame information for a PLT. FDEs using the CIE must
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// be removed in reverse order to the order they were added.
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void
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remove_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
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size_t cie_length, const unsigned char* fde_data,
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size_t fde_length);
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// Scan a .debug_info or .debug_types section, and add summary
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// information to the .gdb_index section.
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template<int size, bool big_endian>
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@ -3333,6 +3333,16 @@ Target_powerpc<size, big_endian>::do_relax(int pass,
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if (size == 64 && again)
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this->brlt_section_->set_current_size(num_huge_branches);
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for (typename Stub_tables::reverse_iterator p = this->stub_tables_.rbegin();
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p != this->stub_tables_.rend();
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++p)
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(*p)->remove_eh_frame(layout);
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for (typename Stub_tables::iterator p = this->stub_tables_.begin();
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p != this->stub_tables_.end();
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++p)
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(*p)->add_eh_frame(layout);
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typedef Unordered_set<Output_section*> Output_sections;
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Output_sections os_need_update;
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for (typename Stub_tables::iterator p = this->stub_tables_.begin();
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@ -3342,7 +3352,6 @@ Target_powerpc<size, big_endian>::do_relax(int pass,
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if ((*p)->size_update())
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{
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again = true;
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(*p)->add_eh_frame(layout);
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os_need_update.insert((*p)->output_section());
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}
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}
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@ -4244,25 +4253,39 @@ class Stub_table : public Output_relaxed_input_section
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void
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add_eh_frame(Layout* layout)
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{
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if (!this->eh_frame_added_)
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if (!parameters->options().ld_generated_unwind_info())
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return;
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// Since we add stub .eh_frame info late, it must be placed
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// after all other linker generated .eh_frame info so that
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// merge mapping need not be updated for input sections.
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// There is no provision to use a different CIE to that used
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// by .glink.
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if (!this->targ_->has_glink())
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return;
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if (this->plt_size_ + this->branch_size_ + this->need_save_res_ == 0)
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return;
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layout->add_eh_frame_for_plt(this,
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Eh_cie<size>::eh_frame_cie,
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sizeof (Eh_cie<size>::eh_frame_cie),
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default_fde,
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sizeof (default_fde));
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this->eh_frame_added_ = true;
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}
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void
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remove_eh_frame(Layout* layout)
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{
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if (this->eh_frame_added_)
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{
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if (!parameters->options().ld_generated_unwind_info())
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return;
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// Since we add stub .eh_frame info late, it must be placed
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// after all other linker generated .eh_frame info so that
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// merge mapping need not be updated for input sections.
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// There is no provision to use a different CIE to that used
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// by .glink.
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if (!this->targ_->has_glink())
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return;
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layout->add_eh_frame_for_plt(this,
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Eh_cie<size>::eh_frame_cie,
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sizeof (Eh_cie<size>::eh_frame_cie),
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default_fde,
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sizeof (default_fde));
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this->eh_frame_added_ = true;
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layout->remove_eh_frame_for_plt(this,
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Eh_cie<size>::eh_frame_cie,
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sizeof (Eh_cie<size>::eh_frame_cie),
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default_fde,
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sizeof (default_fde));
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this->eh_frame_added_ = false;
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}
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}
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