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[GOLD] powerpc64le-linux fails to link large Linux kernel

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Gold attaches stubs to an existing section in contrast to ld.bfd which
inserts a new section for stubs.  If we want stubs before branches,
then the stubs must be added to the previous section.  Adding to the
previous section is a disaster if there is a large gap between the
previous section and the group.

	PR gold/20878
	* powerpc.cc (Stub_control): Replace stubs_always_before_branch_
	with stubs_always_after_branch_, group_end_addr_ with
	group_start_addr_.
	(Stub_control::can_add_to_stub_group): Rewrite to suit scanning
	sections by increasing address.
	(Target_powerpc::group_sections): Scan that way.  Delete corner
	case.
	* options.h (--stub-group-size): Update help string.
This commit is contained in:
Alan Modra 2016-12-07 14:12:26 +10:30
parent dc60b26d98
commit a5018ae555
3 changed files with 66 additions and 80 deletions
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12
gold/ChangeLog
View File

@ -1,3 +1,15 @@
2016-12-07 Alan Modra <amodra@gmail.com>
PR gold/20878
* powerpc.cc (Stub_control): Replace stubs_always_before_branch_
with stubs_always_after_branch_, group_end_addr_ with
group_start_addr_.
(Stub_control::can_add_to_stub_group): Rewrite to suit scanning
sections by increasing address.
(Target_powerpc::group_sections): Scan that way. Delete corner
case.
* options.h (--stub-group-size): Update help string.
2016-12-07 Alan Modra <amodra@gmail.com>
* powerpc.cc (Stub_table_owner): Provide constructor.

3
gold/options.h
View File

@ -1216,8 +1216,7 @@ class General_options
DEFINE_int(stub_group_size, options::TWO_DASHES , '\0', 1,
N_("(ARM, PowerPC only) The maximum distance from instructions "
"in a group of sections to their stubs. Negative values mean "
"stubs are always after (PowerPC before) the group. 1 means "
"use default size"),
"stubs are always after the group. 1 means use default size"),
N_("SIZE"));
DEFINE_uint(split_stack_adjust_size, options::TWO_DASHES, '\0', 0x4000,

131
gold/powerpc.cc
View File

@ -2439,13 +2439,13 @@ class Stub_control
public:
// Determine the stub group size. The group size is the absolute
// value of the parameter --stub-group-size. If --stub-group-size
// is passed a negative value, we restrict stubs to be always before
// is passed a negative value, we restrict stubs to be always after
// the stubbed branches.
Stub_control(int32_t size, bool no_size_errors)
: state_(NO_GROUP), stub_group_size_(abs(size)),
stubs_always_before_branch_(size < 0),
stubs_always_after_branch_(size < 0),
suppress_size_errors_(no_size_errors), group_size_(0),
group_end_addr_(0), owner_(NULL), output_section_(NULL)
group_start_addr_(0), owner_(NULL), output_section_(NULL)
{
}
@ -2482,13 +2482,13 @@ class Stub_control
State state_;
uint32_t stub_group_size_;
bool stubs_always_before_branch_;
bool stubs_always_after_branch_;
bool suppress_size_errors_;
// Current max size of group. Starts at stub_group_size_ but is
// reduced to stub_group_size_/1024 on seeing a section with
// external conditional branches.
uint32_t group_size_;
uint64_t group_end_addr_;
uint64_t group_start_addr_;
// owner_ and output_section_ specify the section to which stubs are
// attached. The stubs are placed at the end of this section.
const Output_section::Input_section* owner_;
@ -2496,8 +2496,8 @@ class Stub_control
};
// Return true iff input section can be handled by current stub
// group. Sections are presented to this function in reverse order,
// so the first section is the tail of the group.
// group. Sections are presented to this function in order,
// so the first section is the head of the group.
bool
Stub_control::can_add_to_stub_group(Output_section* o,
@ -2518,6 +2518,7 @@ Stub_control::can_add_to_stub_group(Output_section* o,
this_size = i->data_size();
}
uint64_t end_addr = start_addr + this_size;
uint32_t group_size = this->stub_group_size_;
if (has14)
this->group_size_ = group_size = group_size >> 10;
@ -2532,64 +2533,56 @@ Stub_control::can_add_to_stub_group(Output_section* o,
i->relobj()->name().c_str(),
i->relobj()->section_name(i->shndx()).c_str(),
(long long) this_size,
(long long) this->group_end_addr_ - start_addr);
(this->state_ == NO_GROUP
? this_size
: (long long) end_addr - this->group_start_addr_));
uint64_t end_addr = start_addr + this_size;
if (this->state_ == HAS_STUB_SECTION)
{
// Can we add this section, which is before the stubs, to the
// Can we add this section, which is after the stubs, to the
// group?
if (this->group_end_addr_ - start_addr <= this->group_size_)
if (end_addr - this->group_start_addr_ <= this->group_size_)
return true;
}
else
else if (this->state_ == FINDING_STUB_SECTION)
{
// Stubs are added at the end of "owner_".
// The current section can always be the stub owner, except when
// whole_sec is true and the current section isn't the last of
// the pasted sections. (This restriction for the whole_sec
// case is just to simplify the corner case mentioned in
// group_sections.)
// Note that "owner_" itself is not necessarily part of the
// group of sections served by these stubs!
if (!whole_sec || this->output_section_ != o)
if ((whole_sec && this->output_section_ == o)
|| end_addr - this->group_start_addr_ <= this->group_size_)
{
// Stubs are added at the end of "owner_".
this->owner_ = i;
this->output_section_ = o;
}
if (this->state_ == FINDING_STUB_SECTION)
{
if (this->group_end_addr_ - start_addr <= this->group_size_)
return true;
// The group after the stubs has reached maximum size.
// Now see about adding sections before the stubs to the
// group. If the current section has a 14-bit branch and
// the group after the stubs exceeds group_size_ (because
// they didn't have 14-bit branches), don't add sections
// before the stubs: The size of stubs for such a large
// group may exceed the reach of a 14-bit branch.
if (!this->stubs_always_before_branch_
&& this_size <= this->group_size_
&& this->group_end_addr_ - end_addr <= this->group_size_)
{
gold_debug(DEBUG_TARGET, "adding before stubs");
this->state_ = HAS_STUB_SECTION;
this->group_end_addr_ = end_addr;
return true;
}
}
else if (this->state_ == NO_GROUP)
{
// Only here on very first use of Stub_control
this->state_ = FINDING_STUB_SECTION;
this->group_size_ = group_size;
this->group_end_addr_ = end_addr;
return true;
}
else
gold_unreachable();
// The group before the stubs has reached maximum size.
// Now see about adding sections after the stubs to the
// group. If the current section has a 14-bit branch and
// the group before the stubs exceeds group_size_ (because
// they didn't have 14-bit branches), don't add sections
// after the stubs: The size of stubs for such a large
// group may exceed the reach of a 14-bit branch.
if (!this->stubs_always_after_branch_
&& this_size <= this->group_size_
&& start_addr - this->group_start_addr_ <= this->group_size_)
{
gold_debug(DEBUG_TARGET, "adding after stubs");
this->state_ = HAS_STUB_SECTION;
this->group_start_addr_ = start_addr;
return true;
}
}
else if (this->state_ == NO_GROUP)
{
// Only here on very first use of Stub_control
this->owner_ = i;
this->output_section_ = o;
this->state_ = FINDING_STUB_SECTION;
this->group_size_ = group_size;
this->group_start_addr_ = start_addr;
return true;
}
else
gold_unreachable();
gold_debug(DEBUG_TARGET, "nope, didn't fit\n");
@ -2599,7 +2592,7 @@ Stub_control::can_add_to_stub_group(Output_section* o,
// group.
this->state_ = FINDING_STUB_SECTION;
this->group_size_ = group_size;
this->group_end_addr_ = end_addr;
this->group_start_addr_ = start_addr;
return false;
}
@ -2619,14 +2612,14 @@ Target_powerpc<size, big_endian>::group_sections(Layout* layout,
Layout::Section_list section_list;
layout->get_executable_sections(&section_list);
std::stable_sort(section_list.begin(), section_list.end(), Sort_sections());
for (Layout::Section_list::reverse_iterator o = section_list.rbegin();
o != section_list.rend();
for (Layout::Section_list::iterator o = section_list.begin();
o != section_list.end();
++o)
{
typedef Output_section::Input_section_list Input_section_list;
for (Input_section_list::const_reverse_iterator i
= (*o)->input_sections().rbegin();
i != (*o)->input_sections().rend();
for (Input_section_list::const_iterator i
= (*o)->input_sections().begin();
i != (*o)->input_sections().end();
++i)
{
if (i->is_input_section()
@ -2653,26 +2646,8 @@ Target_powerpc<size, big_endian>::group_sections(Layout* layout,
}
if (table_owner != NULL)
{
const Output_section::Input_section* i = stub_control.owner();
if (tables.size() >= 2 && tables[tables.size() - 2]->owner == i)
{
// Corner case. A new stub group was made for the first
// section (last one looked at here) for some reason, but
// the first section is already being used as the owner for
// a stub table for following sections. Force it into that
// stub group.
tables.pop_back();
delete table_owner;
Powerpc_relobj<size, big_endian>* ppcobj = static_cast
<Powerpc_relobj<size, big_endian>*>(i->relobj());
ppcobj->set_stub_table(i->shndx(), tables.size() - 1);
}
else
{
table_owner->output_section = stub_control.output_section();
table_owner->owner = i;
}
table_owner->output_section = stub_control.output_section();
table_owner->owner = stub_control.owner();;
}
for (typename std::vector<Stub_table_owner*>::iterator t = tables.begin();
t != tables.end();