From be897fb774abfb0a44b3b87fe77bccafa336e638 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Tue, 1 Aug 2017 14:08:53 +0930 Subject: [PATCH] [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. --- gold/ChangeLog | 13 +++++++++++ gold/ehframe.cc | 46 ++++++++++++++++++++++++++++++++++++++ gold/ehframe.h | 13 +++++++++++ gold/layout.cc | 17 ++++++++++++++ gold/layout.h | 7 ++++++ gold/powerpc.cc | 59 ++++++++++++++++++++++++++++++++++--------------- 6 files changed, 137 insertions(+), 18 deletions(-) diff --git a/gold/ChangeLog b/gold/ChangeLog index 869a01ddd52..c886cc1ca4f 100644 --- a/gold/ChangeLog +++ b/gold/ChangeLog @@ -1,3 +1,16 @@ +2017-08-01 Alan Modra + + * 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. + 2017-07-31 Alan Modra * options.h (no_tls_optimize): New powerpc option. diff --git a/gold/ehframe.cc b/gold/ehframe.cc index fd72a4fd06c..61b51932bcf 100644 --- a/gold/ehframe.cc +++ b/gold/ehframe.cc @@ -325,6 +325,21 @@ Eh_frame_hdr::get_fde_addresses(Output_file* of, // Class Fde. +bool +Fde::operator==(const Fde& that) const +{ + if (this->object_ != that.object_ + || this->contents_ != that.contents_) + return false; + if (this->object_ == NULL) + return (this->u_.from_linker.plt == that.u_.from_linker.plt + && this->u_.from_linker.post_map == that.u_.from_linker.post_map); + else + return (this->u_.from_object.shndx == that.u_.from_object.shndx + && (this->u_.from_object.input_offset + == that.u_.from_object.input_offset)); +} + // Write the FDE to OVIEW starting at OFFSET. CIE_OFFSET is the // offset of the CIE in OVIEW. OUTPUT_OFFSET is the offset of the // Eh_frame section within the output section. FDE_ENCODING is the @@ -443,6 +458,15 @@ Cie::set_output_offset(section_offset_type output_offset, return output_offset + length; } +// Remove FDE. Only the last FDE using this CIE may be removed. + +void +Cie::remove_fde(const Fde* fde) +{ + gold_assert(*fde == *this->fdes_.back()); + this->fdes_.pop_back(); +} + // Write the CIE to OVIEW starting at OFFSET. OUTPUT_OFFSET is the // offset of the Eh_frame section within the output section. Round up // the bytes to ADDRALIGN. ADDRESS is the virtual address of OVIEW. @@ -1143,6 +1167,28 @@ Eh_frame::add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data, this->final_data_size_ += align_address(fde_length + 8, this->addralign()); } +// Remove unwind information for a PLT. Only the last FDE added may be removed. + +void +Eh_frame::remove_ehframe_for_plt(Output_data* plt, + const unsigned char* cie_data, + size_t cie_length, + const unsigned char* fde_data, + size_t fde_length) +{ + Cie cie(NULL, 0, 0, elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4, "", + cie_data, cie_length); + Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie); + gold_assert (find_cie != this->cie_offsets_.end()); + Cie* pcie = *find_cie; + + Fde* fde = new Fde(plt, fde_data, fde_length, this->mappings_are_done_); + pcie->remove_fde(fde); + + if (this->mappings_are_done_) + this->final_data_size_ -= align_address(fde_length + 8, this->addralign()); +} + // Return the number of FDEs. unsigned int diff --git a/gold/ehframe.h b/gold/ehframe.h index 347ce46e45b..f501634c2f6 100644 --- a/gold/ehframe.h +++ b/gold/ehframe.h @@ -217,6 +217,8 @@ class Fde section_offset_type cie_offset, unsigned char fde_encoding, Eh_frame_hdr* eh_frame_hdr); + bool operator==(const Fde&) const; + private: // The object in which this FDE was seen. This will be NULL for a // linker generated FDE. @@ -298,6 +300,10 @@ class Cie add_fde(Fde* fde) { this->fdes_.push_back(fde); } + // Remove an FDE associated with this CIE. Only the last FDE may be removed. + void + remove_fde(const Fde*); + // Return the number of FDEs. unsigned int fde_count() const @@ -405,6 +411,13 @@ class Eh_frame : public Output_section_data size_t cie_length, const unsigned char* fde_data, size_t fde_length); + // Remove unwind information for a PLT. Only the last FDE added may + // be removed. + void + remove_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data, + size_t cie_length, const unsigned char* fde_data, + size_t fde_length); + // Return the number of FDEs. unsigned int fde_count() const; diff --git a/gold/layout.cc b/gold/layout.cc index 963ae523ca8..5f25faea553 100644 --- a/gold/layout.cc +++ b/gold/layout.cc @@ -1581,6 +1581,23 @@ Layout::add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data, } } +// Remove .eh_frame information for a PLT. FDEs using the CIE must +// be removed in reverse order to the order they were added. + +void +Layout::remove_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data, + size_t cie_length, const unsigned char* fde_data, + size_t fde_length) +{ + if (parameters->incremental()) + { + // FIXME: Maybe this could work some day.... + return; + } + this->eh_frame_data_->remove_ehframe_for_plt(plt, cie_data, cie_length, + fde_data, fde_length); +} + // Scan a .debug_info or .debug_types section, and add summary // information to the .gdb_index section. diff --git a/gold/layout.h b/gold/layout.h index 5f58c2c67f6..15ee9246788 100644 --- a/gold/layout.h +++ b/gold/layout.h @@ -653,6 +653,13 @@ class Layout size_t cie_length, const unsigned char* fde_data, size_t fde_length); + // Remove .eh_frame information for a PLT. FDEs using the CIE must + // be removed in reverse order to the order they were added. + void + remove_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data, + size_t cie_length, const unsigned char* fde_data, + size_t fde_length); + // Scan a .debug_info or .debug_types section, and add summary // information to the .gdb_index section. template diff --git a/gold/powerpc.cc b/gold/powerpc.cc index 9a200ab63e1..6f610cbe8cb 100644 --- a/gold/powerpc.cc +++ b/gold/powerpc.cc @@ -3333,6 +3333,16 @@ Target_powerpc::do_relax(int pass, if (size == 64 && again) this->brlt_section_->set_current_size(num_huge_branches); + for (typename Stub_tables::reverse_iterator p = this->stub_tables_.rbegin(); + p != this->stub_tables_.rend(); + ++p) + (*p)->remove_eh_frame(layout); + + for (typename Stub_tables::iterator p = this->stub_tables_.begin(); + p != this->stub_tables_.end(); + ++p) + (*p)->add_eh_frame(layout); + typedef Unordered_set Output_sections; Output_sections os_need_update; for (typename Stub_tables::iterator p = this->stub_tables_.begin(); @@ -3342,7 +3352,6 @@ Target_powerpc::do_relax(int pass, if ((*p)->size_update()) { again = true; - (*p)->add_eh_frame(layout); os_need_update.insert((*p)->output_section()); } } @@ -4244,25 +4253,39 @@ class Stub_table : public Output_relaxed_input_section void add_eh_frame(Layout* layout) { - if (!this->eh_frame_added_) - { - if (!parameters->options().ld_generated_unwind_info()) - return; + if (!parameters->options().ld_generated_unwind_info()) + return; - // Since we add stub .eh_frame info late, it must be placed - // after all other linker generated .eh_frame info so that - // merge mapping need not be updated for input sections. - // There is no provision to use a different CIE to that used - // by .glink. - if (!this->targ_->has_glink()) - return; + // Since we add stub .eh_frame info late, it must be placed + // after all other linker generated .eh_frame info so that + // merge mapping need not be updated for input sections. + // There is no provision to use a different CIE to that used + // by .glink. + if (!this->targ_->has_glink()) + return; - layout->add_eh_frame_for_plt(this, - Eh_cie::eh_frame_cie, - sizeof (Eh_cie::eh_frame_cie), - default_fde, - sizeof (default_fde)); - this->eh_frame_added_ = true; + if (this->plt_size_ + this->branch_size_ + this->need_save_res_ == 0) + return; + + layout->add_eh_frame_for_plt(this, + Eh_cie::eh_frame_cie, + sizeof (Eh_cie::eh_frame_cie), + default_fde, + sizeof (default_fde)); + this->eh_frame_added_ = true; + } + + void + remove_eh_frame(Layout* layout) + { + if (this->eh_frame_added_) + { + layout->remove_eh_frame_for_plt(this, + Eh_cie::eh_frame_cie, + sizeof (Eh_cie::eh_frame_cie), + default_fde, + sizeof (default_fde)); + this->eh_frame_added_ = false; } } -- 2.30.2