[binutils-gdb] [GOLD] PowerPC recreate eh_frame for stubs on each relax pass
Alan Modra
amodra@sourceware.org
Tue Aug 1 04:41:00 GMT 2017
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=be897fb774abfb0a44b3b87fe77bccafa336e638
commit be897fb774abfb0a44b3b87fe77bccafa336e638
Author: Alan Modra <amodra@gmail.com>
Date: Tue Aug 1 14:08:53 2017 +0930
[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.
Diff:
---
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 869a01d..c886cc1 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,3 +1,16 @@
+2017-08-01 Alan Modra <amodra@gmail.com>
+
+ * 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 <amodra@gmail.com>
* options.h (no_tls_optimize): New powerpc option.
diff --git a/gold/ehframe.cc b/gold/ehframe.cc
index fd72a4f..61b5193 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 347ce46..f501634 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 963ae52..5f25fae 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 5f58c2c..15ee924 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<int size, bool big_endian>
diff --git a/gold/powerpc.cc b/gold/powerpc.cc
index 9a200ab..6f610cb 100644
--- a/gold/powerpc.cc
+++ b/gold/powerpc.cc
@@ -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;
+ 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<size>::eh_frame_cie,
- sizeof (Eh_cie<size>::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<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_)
+ {
+ 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;
}
}
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