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[PATCH] gold: Implement --long-plt flag.
- From: Peter Collingbourne <pcc at google dot com>
- To: binutils at sourceware dot org
- Cc: Peter Collingbourne <pcc at google dot com>
- Date: Fri, 20 Nov 2015 15:45:09 -0800
- Subject: [PATCH] gold: Implement --long-plt flag.
- Authentication-results: sourceware.org; auth=none
gold/
PR gold/18780
* arm.cc (Target_arm::do_make_data_plt): Choose PLT generator based
on value of --long-plt flag.
(Output_data_plt_arm_standard::do_get_plt_entry_size): Moved to
Output_data_plt_arm_short.
(Output_data_plt_arm_standard::do_fill_plt_entry): Likewise.
(Output_data_plt_arm_standard::plt_entry): Likewise.
(Output_data_plt_arm_standard::do_fill_first_plt_entry): Fix
variable reference.
(Output_data_plt_arm_short): New class.
(Output_data_plt_arm_long): New class.
* options.h (General_options): Define --long-plt flag.
---
gold/arm.cc | 124 +++++++++++++++++++++++++++++++++++++++++++++++----------
gold/options.h | 4 ++
2 files changed, 108 insertions(+), 20 deletions(-)
diff --git a/gold/arm.cc b/gold/arm.cc
index 4a6d414..2381442 100644
--- a/gold/arm.cc
+++ b/gold/arm.cc
@@ -62,7 +62,10 @@ template<bool big_endian>
class Output_data_plt_arm;
template<bool big_endian>
-class Output_data_plt_arm_standard;
+class Output_data_plt_arm_short;
+
+template<bool big_endian>
+class Output_data_plt_arm_long;
template<bool big_endian>
class Stub_table;
@@ -2555,7 +2558,11 @@ class Target_arm : public Sized_target<32, big_endian>
Output_data_space* got_irelative)
{
gold_assert(got_plt != NULL && got_irelative != NULL);
- return new Output_data_plt_arm_standard<big_endian>(
+ if (parameters->options().long_plt())
+ return new Output_data_plt_arm_long<big_endian>(
+ layout, got, got_plt, got_irelative);
+ else
+ return new Output_data_plt_arm_short<big_endian>(
layout, got, got_plt, got_irelative);
}
@@ -7719,29 +7726,14 @@ class Output_data_plt_arm_standard : public Output_data_plt_arm<big_endian>
do_first_plt_entry_offset() const
{ return sizeof(first_plt_entry); }
- // Return the size of a PLT entry.
- virtual unsigned int
- do_get_plt_entry_size() const
- { return sizeof(plt_entry); }
-
virtual void
do_fill_first_plt_entry(unsigned char* pov,
Arm_address got_address,
Arm_address plt_address);
- virtual void
- do_fill_plt_entry(unsigned char* pov,
- Arm_address got_address,
- Arm_address plt_address,
- unsigned int got_offset,
- unsigned int plt_offset);
-
private:
// Template for the first PLT entry.
static const uint32_t first_plt_entry[5];
-
- // Template for subsequent PLT entries.
- static const uint32_t plt_entry[3];
};
// ARM PLTs.
@@ -7769,7 +7761,7 @@ Output_data_plt_arm_standard<big_endian>::do_fill_first_plt_entry(
{
// Write first PLT entry. All but the last word are constants.
const size_t num_first_plt_words = (sizeof(first_plt_entry)
- / sizeof(plt_entry[0]));
+ / sizeof(first_plt_entry[0]));
for (size_t i = 0; i < num_first_plt_words - 1; i++)
elfcpp::Swap<32, big_endian>::writeval(pov + i * 4, first_plt_entry[i]);
// Last word in first PLT entry is &GOT[0] - .
@@ -7778,9 +7770,39 @@ Output_data_plt_arm_standard<big_endian>::do_fill_first_plt_entry(
}
// Subsequent entries in the PLT.
+// This class generates short (12-byte) entries, for displacements up to 2^28.
template<bool big_endian>
-const uint32_t Output_data_plt_arm_standard<big_endian>::plt_entry[3] =
+class Output_data_plt_arm_short : public Output_data_plt_arm_standard<big_endian>
+{
+ public:
+ Output_data_plt_arm_short(Layout* layout,
+ Arm_output_data_got<big_endian>* got,
+ Output_data_space* got_plt,
+ Output_data_space* got_irelative)
+ : Output_data_plt_arm_standard<big_endian>(layout, got, got_plt, got_irelative)
+ { }
+
+ protected:
+ // Return the size of a PLT entry.
+ virtual unsigned int
+ do_get_plt_entry_size() const
+ { return sizeof(plt_entry); }
+
+ virtual void
+ do_fill_plt_entry(unsigned char* pov,
+ Arm_address got_address,
+ Arm_address plt_address,
+ unsigned int got_offset,
+ unsigned int plt_offset);
+
+ private:
+ // Template for subsequent PLT entries.
+ static const uint32_t plt_entry[3];
+};
+
+template<bool big_endian>
+const uint32_t Output_data_plt_arm_short<big_endian>::plt_entry[3] =
{
0xe28fc600, // add ip, pc, #0xNN00000
0xe28cca00, // add ip, ip, #0xNN000
@@ -7789,7 +7811,7 @@ const uint32_t Output_data_plt_arm_standard<big_endian>::plt_entry[3] =
template<bool big_endian>
void
-Output_data_plt_arm_standard<big_endian>::do_fill_plt_entry(
+Output_data_plt_arm_short<big_endian>::do_fill_plt_entry(
unsigned char* pov,
Arm_address got_address,
Arm_address plt_address,
@@ -7808,6 +7830,68 @@ Output_data_plt_arm_standard<big_endian>::do_fill_plt_entry(
elfcpp::Swap<32, big_endian>::writeval(pov + 8, plt_insn2);
}
+// This class generates long (16-byte) entries, for arbitrary displacements.
+
+template<bool big_endian>
+class Output_data_plt_arm_long : public Output_data_plt_arm_standard<big_endian>
+{
+ public:
+ Output_data_plt_arm_long(Layout* layout,
+ Arm_output_data_got<big_endian>* got,
+ Output_data_space* got_plt,
+ Output_data_space* got_irelative)
+ : Output_data_plt_arm_standard<big_endian>(layout, got, got_plt, got_irelative)
+ { }
+
+ protected:
+ // Return the size of a PLT entry.
+ virtual unsigned int
+ do_get_plt_entry_size() const
+ { return sizeof(plt_entry); }
+
+ virtual void
+ do_fill_plt_entry(unsigned char* pov,
+ Arm_address got_address,
+ Arm_address plt_address,
+ unsigned int got_offset,
+ unsigned int plt_offset);
+
+ private:
+ // Template for subsequent PLT entries.
+ static const uint32_t plt_entry[4];
+};
+
+template<bool big_endian>
+const uint32_t Output_data_plt_arm_long<big_endian>::plt_entry[4] =
+{
+ 0xe28fc200, // add ip, pc, #0xN0000000
+ 0xe28cc600, // add ip, ip, #0xNN00000
+ 0xe28cca00, // add ip, ip, #0xNN000
+ 0xe5bcf000, // ldr pc, [ip, #0xNNN]!
+};
+
+template<bool big_endian>
+void
+Output_data_plt_arm_long<big_endian>::do_fill_plt_entry(
+ unsigned char* pov,
+ Arm_address got_address,
+ Arm_address plt_address,
+ unsigned int got_offset,
+ unsigned int plt_offset)
+{
+ int32_t offset = ((got_address + got_offset)
+ - (plt_address + plt_offset + 8));
+
+ uint32_t plt_insn0 = plt_entry[0] | (offset >> 28);
+ elfcpp::Swap<32, big_endian>::writeval(pov, plt_insn0);
+ uint32_t plt_insn1 = plt_entry[1] | ((offset >> 20) & 0xff);
+ elfcpp::Swap<32, big_endian>::writeval(pov + 4, plt_insn1);
+ uint32_t plt_insn2 = plt_entry[2] | ((offset >> 12) & 0xff);
+ elfcpp::Swap<32, big_endian>::writeval(pov + 8, plt_insn2);
+ uint32_t plt_insn3 = plt_entry[3] | (offset & 0xfff);
+ elfcpp::Swap<32, big_endian>::writeval(pov + 12, plt_insn3);
+}
+
// Write out the PLT. This uses the hand-coded instructions above,
// and adjusts them as needed. This is all specified by the arm ELF
// Processor Supplement.
diff --git a/gold/options.h b/gold/options.h
index ffc44e6..d83ea54 100644
--- a/gold/options.h
+++ b/gold/options.h
@@ -834,6 +834,10 @@ class General_options
"veneer"),
NULL);
+ DEFINE_bool(long_plt, options::TWO_DASHES, '\0', false,
+ N_("(ARM only) Generate long PLT entries."),
+ N_("(ARM only) Do not generate long PLT entries."));
+
DEFINE_bool(g, options::EXACTLY_ONE_DASH, '\0', false,
N_("Ignored"), NULL);
--
2.6.0.rc2.230.g3dd15c0