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[GOLD] PowerPC recreate eh_frame for stubs on each relax pass

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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
2017-08-01 14:08:53 +09:30
parent 51b69c74c6
commit be897fb774
6 changed files with 138 additions and 19 deletions
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61
gold/powerpc.cc
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@@ -3333,6 +3333,16 @@ Target_powerpc<size, big_endian>::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_section*> Output_sections;
Output_sections os_need_update;
for (typename Stub_tables::iterator p = this->stub_tables_.begin();
@@ -3342,7 +3352,6 @@ Target_powerpc<size, big_endian>::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;
// 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;
if (this->plt_size_ + this->branch_size_ + this->need_save_res_ == 0)
return;
layout->add_eh_frame_for_plt(this,
Eh_cie<size>::eh_frame_cie,
sizeof (Eh_cie<size>::eh_frame_cie),
default_fde,
sizeof (default_fde));
this->eh_frame_added_ = true;
}
void
remove_eh_frame(Layout* layout)
{
if (this->eh_frame_added_)
{
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;
layout->add_eh_frame_for_plt(this,
Eh_cie<size>::eh_frame_cie,
sizeof (Eh_cie<size>::eh_frame_cie),
default_fde,
sizeof (default_fde));
this->eh_frame_added_ = true;
layout->remove_eh_frame_for_plt(this,
Eh_cie<size>::eh_frame_cie,
sizeof (Eh_cie<size>::eh_frame_cie),
default_fde,
sizeof (default_fde));
this->eh_frame_added_ = false;
}
}