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authorAlan Modra <amodra@gmail.com>2019-07-01 14:37:49 +0930
committerAlan Modra <amodra@gmail.com>2019-07-13 09:57:50 +0930
commit220f99066d6ce2a6caf17692fcc57d714d8f6910 (patch)
tree81dbd577f8116359ab582788dd808abaf08da32a /gold
parent32f598441988e5a086ba8580e82f4944c3692eb5 (diff)
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[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.
Diffstat (limited to 'gold')
-rw-r--r--gold/ChangeLog23
-rw-r--r--gold/ehframe.cc47
-rw-r--r--gold/ehframe.h25
-rw-r--r--gold/layout.cc9
-rw-r--r--gold/layout.h6
-rw-r--r--gold/powerpc.cc197
6 files changed, 190 insertions, 117 deletions
diff --git a/gold/ChangeLog b/gold/ChangeLog
index e8bfea9..355ffc5 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,5 +1,28 @@
2019-07-13 Alan Modra <amodra@gmail.com>
+ * 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.
+
+2019-07-13 Alan Modra <amodra@gmail.com>
+
* powerpc.cc (Target_powerpc::maybe_skip_tls_get_addr_call): Handle
notoc calls.
(is_branch_reloc): Template on size. Return true for REL24_NOTOC.
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.
diff --git a/gold/ehframe.h b/gold/ehframe.h
index ba65083..4fd8f3e 100644
--- a/gold/ehframe.h
+++ b/gold/ehframe.h
@@ -203,9 +203,14 @@ class Fde
// Return whether this FDE was added after merge mapping.
bool
- post_map()
+ post_map() const
{ return this->object_ == NULL && this->u_.from_linker.post_map; }
+ // Return whether this FDE was added for the PLT after merge mapping.
+ bool
+ post_map(const Output_data* plt) const
+ { return this->post_map() && this->u_.from_linker.plt == plt; }
+
// Write the FDE to OVIEW starting at OFFSET. FDE_ENCODING is the
// encoding, from the CIE. Round up the bytes to ADDRALIGN if
// necessary. ADDRESS is the virtual address of OVIEW. Record the
@@ -217,8 +222,6 @@ 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.
@@ -300,9 +303,15 @@ 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.
+ // Remove the last FDE associated with this CIE.
void
- remove_fde(const Fde*);
+ remove_fde()
+ { this->fdes_.pop_back(); }
+
+ // Access the last FDE associated with this CIE.
+ const Fde*
+ last_fde() const
+ { return this->fdes_.back(); }
// Return the number of FDEs.
unsigned int
@@ -411,12 +420,10 @@ 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.
+ // Remove all post-map unwind information for a PLT.
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);
+ size_t cie_length);
// Return the number of FDEs.
unsigned int
diff --git a/gold/layout.cc b/gold/layout.cc
index b83e8e6..fc7cdf8 100644
--- a/gold/layout.cc
+++ b/gold/layout.cc
@@ -1604,21 +1604,18 @@ 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.
+// Remove all post-map .eh_frame information for a PLT.
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)
+ size_t cie_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);
+ this->eh_frame_data_->remove_ehframe_for_plt(plt, cie_data, cie_length);
}
// Scan a .debug_info or .debug_types section, and add summary
diff --git a/gold/layout.h b/gold/layout.h
index c4f1f8c..bfd44e1 100644
--- a/gold/layout.h
+++ b/gold/layout.h
@@ -666,12 +666,10 @@ 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.
+ // Remove all post-map .eh_frame information for a PLT.
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);
+ size_t cie_length);
// Scan a .debug_info or .debug_types section, and add summary
// information to the .gdb_index section.
diff --git a/gold/powerpc.cc b/gold/powerpc.cc
index 1b62f55..494a1fd 100644
--- a/gold/powerpc.cc
+++ b/gold/powerpc.cc
@@ -4542,7 +4542,7 @@ class Stub_table : public Output_relaxed_input_section
plt_size_(0), last_plt_size_(0),
branch_size_(0), last_branch_size_(0), min_size_threshold_(0),
need_save_res_(false), need_resize_(false), resizing_(false),
- uniq_(id), tls_get_addr_opt_bctrl_(-1u), plt_fde_len_(0)
+ uniq_(id)
{
this->set_output_section(output_section);
@@ -4724,10 +4724,6 @@ class Stub_table : public Output_relaxed_input_section
return false;
}
- // Generate a suitable FDE to describe code in this stub group.
- void
- init_plt_fde();
-
// Add .eh_frame info for this stub section.
void
add_eh_frame(Layout* layout);
@@ -4932,11 +4928,6 @@ class Stub_table : public Output_relaxed_input_section
bool resizing_;
// Per stub table unique identifier.
uint32_t uniq_;
- // The bctrl in the __tls_get_addr_opt stub, if present.
- unsigned int tls_get_addr_opt_bctrl_;
- // FDE unwind info for this stub group.
- unsigned int plt_fde_len_;
- unsigned char plt_fde_[20];
};
// Add a plt call stub, if we do not already have one for this
@@ -4986,10 +4977,7 @@ Stub_table<size, big_endian>::add_plt_call_entry(
}
this->plt_size_ += this->plt_call_size(p.first);
if (this->targ_->is_tls_get_addr_opt(gsym))
- {
- this->targ_->set_has_tls_get_addr_opt();
- this->tls_get_addr_opt_bctrl_ = this->plt_size_ - 5 * 4;
- }
+ this->targ_->set_has_tls_get_addr_opt();
this->plt_size_ = this->plt_call_align(this->plt_size_);
}
return this->can_reach_stub(from, p.first->second.off_, r_type);
@@ -5159,48 +5147,39 @@ Stub_table<size, big_endian>::find_long_branch_entry(
return &p->second;
}
-// Generate a suitable FDE to describe code in this stub group.
-// The __tls_get_addr_opt call stub needs to describe where it saves
-// LR, to support exceptions that might be thrown from __tls_get_addr.
-
-template<int size, bool big_endian>
-void
-Stub_table<size, big_endian>::init_plt_fde()
+template<bool big_endian>
+static void
+eh_advance (std::vector<unsigned char>& fde, unsigned int delta)
{
- unsigned char* p = this->plt_fde_;
- // offset pcrel sdata4, size udata4, and augmentation size byte.
- memset (p, 0, 9);
- p += 9;
- if (this->tls_get_addr_opt_bctrl_ != -1u)
+ delta /= 4;
+ if (delta < 64)
+ fde.push_back(elfcpp::DW_CFA_advance_loc + delta);
+ else if (delta < 256)
{
- unsigned int to_bctrl = this->tls_get_addr_opt_bctrl_ / 4;
- if (to_bctrl < 64)
- *p++ = elfcpp::DW_CFA_advance_loc + to_bctrl;
- else if (to_bctrl < 256)
- {
- *p++ = elfcpp::DW_CFA_advance_loc1;
- *p++ = to_bctrl;
- }
- else if (to_bctrl < 65536)
- {
- *p++ = elfcpp::DW_CFA_advance_loc2;
- elfcpp::Swap<16, big_endian>::writeval(p, to_bctrl);
- p += 2;
- }
- else
- {
- *p++ = elfcpp::DW_CFA_advance_loc4;
- elfcpp::Swap<32, big_endian>::writeval(p, to_bctrl);
- p += 4;
- }
- *p++ = elfcpp::DW_CFA_offset_extended_sf;
- *p++ = 65;
- *p++ = -(this->targ_->stk_linker() / 8) & 0x7f;
- *p++ = elfcpp::DW_CFA_advance_loc + 4;
- *p++ = elfcpp::DW_CFA_restore_extended;
- *p++ = 65;
+ fde.push_back(elfcpp::DW_CFA_advance_loc1);
+ fde.push_back(delta);
}
- this->plt_fde_len_ = p - this->plt_fde_;
+ else if (delta < 65536)
+ {
+ fde.resize(fde.size() + 3);
+ unsigned char *p = &*fde.end() - 3;
+ *p++ = elfcpp::DW_CFA_advance_loc2;
+ elfcpp::Swap<16, big_endian>::writeval(p, delta);
+ }
+ else
+ {
+ fde.resize(fde.size() + 5);
+ unsigned char *p = &*fde.end() - 5;
+ *p++ = elfcpp::DW_CFA_advance_loc4;
+ elfcpp::Swap<32, big_endian>::writeval(p, delta);
+ }
+}
+
+template<typename T>
+static bool
+stub_sort(T s1, T s2)
+{
+ return s1->second.off_ < s2->second.off_;
}
// Add .eh_frame info for this stub section. Unlike other linker
@@ -5212,7 +5191,8 @@ template<int size, bool big_endian>
void
Stub_table<size, big_endian>::add_eh_frame(Layout* layout)
{
- if (!parameters->options().ld_generated_unwind_info())
+ if (size != 64
+ || !parameters->options().ld_generated_unwind_info())
return;
// Since we add stub .eh_frame info late, it must be placed
@@ -5223,28 +5203,115 @@ Stub_table<size, big_endian>::add_eh_frame(Layout* layout)
if (!this->targ_->has_glink())
return;
- if (this->plt_size_ + this->branch_size_ + this->need_save_res_ == 0)
+ typedef typename Plt_stub_entries::const_iterator plt_iter;
+ std::vector<plt_iter> calls;
+ if (!this->plt_call_stubs_.empty())
+ for (plt_iter cs = this->plt_call_stubs_.begin();
+ cs != this->plt_call_stubs_.end();
+ ++cs)
+ if ((this->targ_->is_tls_get_addr_opt(cs->first.sym_)
+ && cs->second.r2save_
+ && !cs->second.localentry0_)
+ || cs->second.notoc_)
+ calls.push_back(cs);
+ if (calls.size() > 1)
+ std::stable_sort(calls.begin(), calls.end(),
+ stub_sort<plt_iter>);
+
+ typedef typename Branch_stub_entries::const_iterator branch_iter;
+ std::vector<branch_iter> branches;
+ if (!this->long_branch_stubs_.empty())
+ for (branch_iter bs = this->long_branch_stubs_.begin();
+ bs != this->long_branch_stubs_.end();
+ ++bs)
+ if (bs->second.notoc_)
+ branches.push_back(bs);
+ if (branches.size() > 1)
+ std::stable_sort(branches.begin(), branches.end(),
+ stub_sort<branch_iter>);
+
+ if (calls.empty() && branches.empty())
return;
- this->init_plt_fde();
+ unsigned int last_eh_loc = 0;
+ // offset pcrel sdata4, size udata4, and augmentation size byte.
+ std::vector<unsigned char> fde(9, 0);
+
+ for (unsigned int i = 0; i < calls.size(); i++)
+ {
+ plt_iter cs = calls[i];
+ unsigned int off = cs->second.off_;
+ // The __tls_get_addr_opt call stub needs to describe where
+ // it saves LR, to support exceptions that might be thrown
+ // from __tls_get_addr, and to support asynchronous exceptions.
+ if (this->targ_->is_tls_get_addr_opt(cs->first.sym_))
+ {
+ off += 7 * 4;
+ if (cs->second.r2save_
+ && !cs->second.localentry0_)
+ {
+ off += 2 * 4;
+ eh_advance<big_endian>(fde, off - last_eh_loc);
+ fde.resize(fde.size() + 6);
+ unsigned char* p = &*fde.end() - 6;
+ *p++ = elfcpp::DW_CFA_offset_extended_sf;
+ *p++ = 65;
+ *p++ = -(this->targ_->stk_linker() / 8) & 0x7f;
+ unsigned int delta = this->plt_call_size(cs) - 4 - 9 * 4;
+ *p++ = elfcpp::DW_CFA_advance_loc + delta / 4;
+ *p++ = elfcpp::DW_CFA_restore_extended;
+ *p++ = 65;
+ last_eh_loc = off + delta;
+ continue;
+ }
+ }
+ // notoc stubs also should describe LR changes, to support
+ // asynchronous exceptions.
+ off += (cs->second.r2save_ ? 4 : 0) + 8;
+ eh_advance<big_endian>(fde, off - last_eh_loc);
+ fde.resize(fde.size() + 6);
+ unsigned char* p = &*fde.end() - 6;
+ *p++ = elfcpp::DW_CFA_register;
+ *p++ = 65;
+ *p++ = 12;
+ *p++ = elfcpp::DW_CFA_advance_loc + 8 / 4;
+ *p++ = elfcpp::DW_CFA_restore_extended;
+ *p++ = 65;
+ last_eh_loc = off + 8;
+ }
+
+ for (unsigned int i = 0; i < branches.size(); i++)
+ {
+ branch_iter bs = branches[i];
+ unsigned int off = bs->second.off_ + 8;
+ eh_advance<big_endian>(fde, off - last_eh_loc);
+ fde.resize(fde.size() + 6);
+ unsigned char* p = &*fde.end() - 6;
+ *p++ = elfcpp::DW_CFA_register;
+ *p++ = 65;
+ *p++ = 12;
+ *p++ = elfcpp::DW_CFA_advance_loc + 8 / 4;
+ *p++ = elfcpp::DW_CFA_restore_extended;
+ *p++ = 65;
+ last_eh_loc = off + 8;
+ }
+
layout->add_eh_frame_for_plt(this,
Eh_cie<size>::eh_frame_cie,
sizeof (Eh_cie<size>::eh_frame_cie),
- this->plt_fde_, this->plt_fde_len_);
+ &*fde.begin(), fde.size());
}
template<int size, bool big_endian>
void
Stub_table<size, big_endian>::remove_eh_frame(Layout* layout)
{
- if (this->plt_fde_len_ != 0)
- {
- layout->remove_eh_frame_for_plt(this,
- Eh_cie<size>::eh_frame_cie,
- sizeof (Eh_cie<size>::eh_frame_cie),
- this->plt_fde_, this->plt_fde_len_);
- this->plt_fde_len_ = 0;
- }
+ if (size == 64
+ && parameters->options().ld_generated_unwind_info()
+ && this->targ_->has_glink())
+ layout->remove_eh_frame_for_plt(this,
+ Eh_cie<size>::eh_frame_cie,
+ sizeof (Eh_cie<size>::eh_frame_cie));
}
// A class to handle .glink.