From 220f99066d6ce2a6caf17692fcc57d714d8f6910 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Mon, 1 Jul 2019 14:37:49 +0930 Subject: [GOLD] PowerPC notoc eh_frame When generating notoc call and branch stubs without the benefit of pc-relative insns, the stubs need to use LR to access the run time PC. All LR changes must be described in .eh_frame if we're to support unwinding through asynchronous exceptions. That's what this patch does. The patch has gone through way too many iterations. At first I attempted to add multiple FDEs, one for each stub. That ran into difficulties with do_plt_fde_location which is only capable of setting the address of a single FDE per Output_data section, and with removing any FDEs added on a previous do_relax pass. Removing FDEs (git commit be897fb774) went overboard in matching the FDE contents. That means either stashing the contents created for add_eh_frame_for_plt to use when calling remove_eh_frame_for_plt, or recreating contents on the fly (*) just to remove FDEs. In fact, FDE content matching is quite unnecesary. FDEs added by a previous do_relax pass are those with u_.from_linker.post_map set. So they can easily be recognised just by looking at that flag. This patch keeps that part of the multiple FDE changes. In the end I went for just one FDE per stub group to describe the call stubs. That's reasonably efficient for the common case of only needing to describe the __tls_get_addr_opt call stub. We don't expect to be making many calls using notoc stubs without pc-relative insns. *) Which has it's own set of problems. The contents must be recreated using the old stub layout, but .eh_frame size can affect stub requirements so you need to temporarily keep the old .eh_frame size when creating new stubs, then reset .eh_frame size before adding new FDEs. * ehframe.cc (Fde::operator==): Delete. (Cie::remove_fde): Delete. (Eh_frame::remove_ehframe_for_plt): Delete fde_data and fde_length parameters. Remove all post-map plt FDEs. * ehframe.h (Fde:post_map): Make const, add variant to compare plt. (Fde::operator==): Delete. (Cie::remove_fde): Implement here. (Cie::last_fde): New accessor. (Eh_frame::remove_ehframe_for_plt): Update prototype. * layout.cc (Layout::remove_eh_frame_for_plt): Delete fde_data and fde_length parameters. * layout.h (Layout::remove_eh_frame_for_plt): Update prototype. * powerpc.cc (Stub_table::tls_get_addr_opt_bctrl_): Delete. (Stub_table::plt_fde_len_, plt_fde_, init_plt_fde): Delete. (Stub_table::add_plt_call_entry): Don't set tls_get_addr_opt_bctrl_. (eh_advance): New function. (stub_sort): New function. (Stub_table::add_eh_frame): Emit eh_frame for notoc plt calls and branches as well as __tls_get_addr_opt plt call stub. (Stub_table::remove_eh_frame): Update to suit. --- gold/ehframe.cc | 47 ++++++++++++++--------------------------------- 1 file changed, 14 insertions(+), 33 deletions(-) (limited to 'gold/ehframe.cc') diff --git a/gold/ehframe.cc b/gold/ehframe.cc index df056d3..51490e0 100644 --- a/gold/ehframe.cc +++ b/gold/ehframe.cc @@ -325,21 +325,6 @@ 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 @@ -458,15 +443,6 @@ 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. @@ -1167,26 +1143,31 @@ 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. +// Remove all post-map unwind information for a PLT. 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) + size_t cie_length) { + if (!this->mappings_are_done_) + return; + 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()); + while (pcie->fde_count() != 0) + { + const Fde* fde = pcie->last_fde(); + if (!fde->post_map(plt)) + break; + size_t length = fde->length(); + this->final_data_size_ -= align_address(length + 8, this->addralign()); + pcie->remove_fde(); + } } // Return the number of FDEs. -- cgit v1.1