[PATCH][GOLD] Record information about relocations for page crossing branches.
Doug Kwan (關振德)
dougkwan@google.com
Wed Jan 13 02:32:00 GMT 2010
Hi,
This patches add a class Cortex_a8_reloc to record relocations
for page crossing 32-bit THUMB branches (i.e branches at address
0x*****ffe.). We need to keep this information to determine if the
branches need the Cortex-A8 workaround. Some of the code is
controlled by a flag Target_arm::fix_cortex_a8_, which is initialized
to be false. The code to enable that flag will come in another patch
later.
-Doug
2010-01-12 Doug Kwan <dougkwan@google.com>
* arm.cc (Cortex_a8_reloc): New class.
(Target_arm::Target_arm): Initialize new data members fix_cortex_a8_
and cortex_a8_relocs_info_.
(Target_arm::fix_cortex_a8): New method definition.
(Target_arm::Cortex_a8_relocs_info): New type.
(Target_arm::fix_cortex_a8_, Target_arm::cortex_a8_relocs_info_):
New data member declarations.
(Target_arm::scan_reloc_for_stub): Record information about
relocations for THUMB branches that might be exempted from the
Cortex-A8 workaround.
(Target_arm::do_relax): Clear all Cortex-A8 relocation information
at the beginning of a relaxation pass.
-------------- next part --------------
Index: gold/arm.cc
===================================================================
RCS file: /cvs/src/src/gold/arm.cc,v
retrieving revision 1.52
diff -u -u -p -r1.52 arm.cc
--- gold/arm.cc 13 Jan 2010 02:00:39 -0000 1.52
+++ gold/arm.cc 13 Jan 2010 02:25:49 -0000
@@ -1309,6 +1309,49 @@ struct Stub_addend_reader<elfcpp::SHT_RE
{ return reloc.get_r_addend(); }
};
+// Cortex_a8_reloc class. We keep record of relocation that may need
+// the Cortex-A8 erratum workaround.
+
+class Cortex_a8_reloc
+{
+ public:
+ Cortex_a8_reloc(Reloc_stub* reloc_stub, unsigned r_type,
+ Arm_address destination)
+ : reloc_stub_(reloc_stub), r_type_(r_type), destination_(destination)
+ { }
+
+ ~Cortex_a8_reloc()
+ { }
+
+ // Accessors: This is a read-only class.
+
+ // Return the relocation stub associated with this relocation if there is
+ // one.
+ const Reloc_stub*
+ reloc_stub() const
+ { return this->reloc_stub_; }
+
+ // Return the relocation type.
+ unsigned int
+ r_type() const
+ { return this->r_type_; }
+
+ // Return the destination address of the relocation. LSB stores the THUMB
+ // bit.
+ Arm_address
+ destination() const
+ { return this->destination_; }
+
+ private:
+ // Associated relocation stub if there is one, or NULL.
+ const Reloc_stub* reloc_stub_;
+ // Relocation type.
+ unsigned int r_type_;
+ // Destination address of this relocation. LSB is used to distinguish
+ // ARM/THUMB mode.
+ Arm_address destination_;
+};
+
// Utilities for manipulating integers of up to 32-bits
namespace utils
@@ -1384,7 +1427,8 @@ class Target_arm : public Sized_target<3
copy_relocs_(elfcpp::R_ARM_COPY), dynbss_(NULL), stub_tables_(),
stub_factory_(Stub_factory::get_instance()), may_use_blx_(false),
should_force_pic_veneer_(false), arm_input_section_map_(),
- attributes_section_data_(NULL)
+ attributes_section_data_(NULL), fix_cortex_a8_(false),
+ cortex_a8_relocs_info_()
{ }
// Whether we can use BLX.
@@ -1612,6 +1656,11 @@ class Target_arm : public Sized_target<3
&& (name[2] == '\0' || name[2] == '.'));
}
+ // Whether we work around the Cortex-A8 erratum.
+ bool
+ fix_cortex_a8() const
+ { return this->fix_cortex_a8_; }
+
protected:
// Make an ELF object.
Object*
@@ -1932,6 +1981,10 @@ class Target_arm : public Sized_target<3
Input_section_specifier::equal_to>
Arm_input_section_map;
+ // Map output addresses to relocs for Cortex-A8 erratum.
+ typedef Unordered_map<Arm_address, const Cortex_a8_reloc*>
+ Cortex_a8_relocs_info;
+
// The GOT section.
Output_data_got<32, big_endian>* got_;
// The PLT section.
@@ -1956,6 +2009,10 @@ class Target_arm : public Sized_target<3
Arm_input_section_map arm_input_section_map_;
// Attributes section data in output.
Attributes_section_data* attributes_section_data_;
+ // Whether we want to fix code for Cortex-A8 erratum.
+ bool fix_cortex_a8_;
+ // Map addresses to relocs for Cortex-A8 erratum.
+ Cortex_a8_relocs_info cortex_a8_relocs_info_;
};
template<bool big_endian>
@@ -7081,34 +7138,49 @@ Target_arm<big_endian>::scan_reloc_for_s
gold_unreachable();
}
+ Reloc_stub* stub = NULL;
Stub_type stub_type =
Reloc_stub::stub_type_for_reloc(r_type, address, destination,
target_is_thumb);
-
- // This reloc does not need a stub.
- if (stub_type == arm_stub_none)
- return;
-
- // Try looking up an existing stub from a stub table.
- Stub_table<big_endian>* stub_table =
- arm_relobj->stub_table(relinfo->data_shndx);
- gold_assert(stub_table != NULL);
+ if (stub_type != arm_stub_none)
+ {
+ // Try looking up an existing stub from a stub table.
+ Stub_table<big_endian>* stub_table =
+ arm_relobj->stub_table(relinfo->data_shndx);
+ gold_assert(stub_table != NULL);
- // Locate stub by destination.
- Reloc_stub::Key stub_key(stub_type, gsym, arm_relobj, r_sym, addend);
+ // Locate stub by destination.
+ Reloc_stub::Key stub_key(stub_type, gsym, arm_relobj, r_sym, addend);
- // Create a stub if there is not one already
- Reloc_stub* stub = stub_table->find_reloc_stub(stub_key);
- if (stub == NULL)
- {
- // create a new stub and add it to stub table.
- stub = this->stub_factory().make_reloc_stub(stub_type);
- stub_table->add_reloc_stub(stub, stub_key);
- }
+ // Create a stub if there is not one already
+ stub = stub_table->find_reloc_stub(stub_key);
+ if (stub == NULL)
+ {
+ // create a new stub and add it to stub table.
+ stub = this->stub_factory().make_reloc_stub(stub_type);
+ stub_table->add_reloc_stub(stub, stub_key);
+ }
- // Record the destination address.
- stub->set_destination_address(destination
- | (target_is_thumb ? 1 : 0));
+ // Record the destination address.
+ stub->set_destination_address(destination
+ | (target_is_thumb ? 1 : 0));
+ }
+
+ // For Cortex-A8, we need to record a relocation at 4K page boundary.
+ if (this->fix_cortex_a8_
+ && (r_type == elfcpp::R_ARM_THM_JUMP24
+ || r_type == elfcpp::R_ARM_THM_JUMP19
+ || r_type == elfcpp::R_ARM_THM_CALL
+ || r_type == elfcpp::R_ARM_THM_XPC22)
+ && (address & 0xfffU) == 0xffeU)
+ {
+ // Found a candidate. Note we haven't checked the destination is
+ // within 4K here: if we do so (and don't create a record) we can't
+ // tell that a branch should have been relocated when scanning later.
+ this->cortex_a8_relocs_info_[address] =
+ new Cortex_a8_reloc(stub, r_type,
+ destination | (target_is_thumb ? 1 : 0));
+ }
}
// This function scans a relocation sections for stub generation.
@@ -7390,7 +7462,17 @@ Target_arm<big_endian>::do_relax(
}
typedef typename Stub_table_list::iterator Stub_table_iterator;
-
+ if (this->fix_cortex_a8_)
+ {
+ // Clear all Cortex-A8 reloc information.
+ for (typename Cortex_a8_relocs_info::const_iterator p =
+ this->cortex_a8_relocs_info_.begin();
+ p != this->cortex_a8_relocs_info_.end();
+ ++p)
+ delete p->second;
+ this->cortex_a8_relocs_info_.clear();
+ }
+
// scan relocs for stubs
for (Input_objects::Relobj_iterator op = input_objects->relobj_begin();
op != input_objects->relobj_end();
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