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[GOLD] PowerPC64 huge branch dynamic relocs

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PowerPC64 gold and ld.bfd implement an indirect branch trampoline,
used when the destination of a branch exceeds a bounce through another
"b" instruction.  When generating PIEs or shared libraries, the
addresses need dynamic relocations.  This was implemented in gold
using a dedicated relocation section, but this means the relative
relocations for these addresses are not sorted properly with other
dynamic relative relocations: gold doesn't support merging relocation
sections, then sorting.  Instead we need to use a single .rela.dyn
section.

This is done by increasing the size of rela_dyn_ during do_relax to
account for needed dynamic relocations, delaying adding the actual
relocations until the end of relaxation once the layout has
stabilised.

	* powerpc.cc (Target_powerpc): Add rela_dyn_size_;
	(update_current_size): New function.
	(Target_powerpc::do_relax): Capture the size of rela_dyn_ at
	the start of relaxation.  Artifically increase its size during
	relaxation to account for needed indirect branches, and add
	those relocations at the end.
	(Output_data_brlt_powerpc::rel_, reset_brlt_sizes),
	(finalize_brlt_sizes, add_reloc, set_current_size): Delete.
	(Target_powerpc::make_brlt_section): Don't make reloc section.
This commit is contained in:
Alan Modra 2023-06-23 10:37:53 +09:30
parent bdad2ad579
commit 5a97377e55
1 changed files with 38 additions and 61 deletions
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99
gold/powerpc.cc
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@ -1763,6 +1763,8 @@ class Target_powerpc : public Sized_target<size, big_endian>
Branches branch_info_;
Tocsave_loc tocsave_loc_;
off_t rela_dyn_size_;
bool power10_relocs_;
bool plt_thread_safe_;
bool plt_localentry0_;
@ -3687,6 +3689,18 @@ Target_powerpc<size, big_endian>::Branch_info::make_stub(
return ok;
}
// Helper for do_relax, avoiding checks that size, address and offset
// are not set more than once.
static inline void
update_current_size(Output_section_data_build* od, off_t cur_size)
{
od->reset_address_and_file_offset();
od->set_current_data_size(cur_size);
od->finalize_data_size();
od->output_section()->set_section_offsets_need_adjustment();
}
// Relaxation hook. This is where we do stub generation.
template<int size, bool big_endian>
@ -3752,10 +3766,11 @@ Target_powerpc<size, big_endian>::do_relax(int pass,
}
}
this->plt_thread_safe_ = thread_safe;
}
if (pass == 1)
{
if (parameters->options().output_is_position_independent())
this->rela_dyn_size_
= this->rela_dyn_section(layout)->current_data_size();
this->stub_group_size_ = parameters->options().stub_group_size();
bool no_size_errors = true;
if (this->stub_group_size_ == 1)
@ -3868,7 +3883,15 @@ Target_powerpc<size, big_endian>::do_relax(int pass,
if (size == 64 && num_huge_branches != 0)
this->make_brlt_section(layout);
if (size == 64 && again)
this->brlt_section_->set_current_size(num_huge_branches);
{
update_current_size(this->brlt_section_, num_huge_branches * 16);
if (parameters->options().output_is_position_independent())
{
const unsigned int reloc_size = elfcpp::Elf_sizes<size>::rela_size;
off_t cur = this->rela_dyn_size_ + num_huge_branches * reloc_size;
update_current_size(this->rela_dyn_, cur);
}
}
for (typename Stub_tables::reverse_iterator p = this->stub_tables_.rbegin();
p != this->stub_tables_.rend();
@ -3937,15 +3960,21 @@ Target_powerpc<size, big_endian>::do_relax(int pass,
&& parameters->options().output_is_position_independent())
{
// Fill in the BRLT relocs.
this->brlt_section_->reset_brlt_sizes();
this->rela_dyn_->reset_data_size();
this->rela_dyn_->set_current_data_size(this->rela_dyn_size_);
for (typename Branch_lookup_table::const_iterator p
= this->branch_lookup_table_.begin();
p != this->branch_lookup_table_.end();
++p)
{
this->brlt_section_->add_reloc(p->first, p->second);
this->rela_dyn_->add_relative(elfcpp::R_POWERPC_RELATIVE,
this->brlt_section_, p->second,
p->first);
}
this->brlt_section_->finalize_brlt_sizes();
this->rela_dyn_->finalize_data_size();
const unsigned int reloc_size = elfcpp::Elf_sizes<size>::rela_size;
gold_assert(this->rela_dyn_->data_size()
== this->rela_dyn_size_ + num_huge_branches * reloc_size);
}
if (!again
@ -4554,52 +4583,11 @@ class Output_data_brlt_powerpc : public Output_section_data_build
typedef Output_data_reloc<elfcpp::SHT_RELA, true,
size, big_endian> Reloc_section;
Output_data_brlt_powerpc(Target_powerpc<size, big_endian>* targ,
Reloc_section* brlt_rel)
Output_data_brlt_powerpc(Target_powerpc<size, big_endian>* targ)
: Output_section_data_build(size == 32 ? 4 : 8),
rel_(brlt_rel),
targ_(targ)
{ }
void
reset_brlt_sizes()
{
this->reset_data_size();
this->rel_->reset_data_size();
}
void
finalize_brlt_sizes()
{
this->finalize_data_size();
this->rel_->finalize_data_size();
}
// Add a reloc for an entry in the BRLT.
void
add_reloc(Address to, unsigned int off)
{ this->rel_->add_relative(elfcpp::R_POWERPC_RELATIVE, this, off, to); }
// Update section and reloc section size.
void
set_current_size(unsigned int num_branches)
{
this->reset_address_and_file_offset();
this->set_current_data_size(num_branches * 16);
this->finalize_data_size();
Output_section* os = this->output_section();
os->set_section_offsets_need_adjustment();
if (this->rel_ != NULL)
{
const unsigned int reloc_size = elfcpp::Elf_sizes<size>::rela_size;
this->rel_->reset_address_and_file_offset();
this->rel_->set_current_data_size(num_branches * reloc_size);
this->rel_->finalize_data_size();
Output_section* os = this->rel_->output_section();
os->set_section_offsets_need_adjustment();
}
}
protected:
void
do_adjust_output_section(Output_section* os)
@ -4617,8 +4605,6 @@ class Output_data_brlt_powerpc : public Output_section_data_build
void
do_write(Output_file*);
// The reloc section.
Reloc_section* rel_;
Target_powerpc<size, big_endian>* targ_;
};
@ -4630,24 +4616,15 @@ Target_powerpc<size, big_endian>::make_brlt_section(Layout* layout)
{
if (size == 64 && this->brlt_section_ == NULL)
{
Reloc_section* brlt_rel = NULL;
bool is_pic = parameters->options().output_is_position_independent();
if (is_pic)
{
// When PIC we can't fill in .branch_lt but must initialise at
// runtime via dynamic relocations.
this->rela_dyn_section(layout);
// FIXME: This reloc section won't have its relative relocs
// sorted properly among the other relative relocs in rela_dyn_
// but it must be a separate section due to needing to call
// reset_data_size().
brlt_rel = new Reloc_section(false);
if (this->rela_dyn_->output_section())
this->rela_dyn_->output_section()
->add_output_section_data(brlt_rel);
}
this->brlt_section_
= new Output_data_brlt_powerpc<size, big_endian>(this, brlt_rel);
= new Output_data_brlt_powerpc<size, big_endian>(this);
if (this->plt_ && is_pic && this->plt_->output_section())
this->plt_->output_section()
->add_output_section_data(this->brlt_section_);