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Improved support for --icf=safe when used with -pie. 

gold/
	* x86_64.cc (Target_x86_64::do_can_check_for_function_pointers):
	Return true even when building pie binaries.
	(Target_x86_64::possible_function_pointer_reloc): Check opcode
	for R_X86_64_PC32 relocations.
	(Target_x86_64::local_reloc_may_be_function_pointer): Pass
	extra arguments to local_reloc_may_be_function_pointer.
	(Target_x86_64::global_reloc_may_be_function_pointer): Likewise.
	* gc.h (gc_process_relocs): Add check for STT_FUNC.
	* testsuite/Makefile.am (icf_safe_pie_test): New test case.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/icf_safe_pie_test.sh: New shell script.
This commit is contained in:
Rahul Chaudhry 2017-02-15 00:37:10 -08:00 committed by Cary Coutant
parent 4e746bb689
commit 4aebb6312e
6 changed files with 191 additions and 17 deletions
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14
gold/ChangeLog
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@ -1,3 +1,17 @@
2017-02-03 Rahul Chaudhry <rahulchaudhry@google.com>
* x86_64.cc (Target_x86_64::do_can_check_for_function_pointers):
Return true even when building pie binaries.
(Target_x86_64::possible_function_pointer_reloc): Check opcode
for R_X86_64_PC32 relocations.
(Target_x86_64::local_reloc_may_be_function_pointer): Pass
extra arguments to local_reloc_may_be_function_pointer.
(Target_x86_64::global_reloc_may_be_function_pointer): Likewise.
* gc.h (gc_process_relocs): Add check for STT_FUNC.
* testsuite/Makefile.am (icf_safe_pie_test): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/icf_safe_pie_test.sh: New shell script.
2017-02-03 Alan Modra <amodra@gmail.com>
* powerpc.cc (Powerpc_relobj::make_toc_relative): Don't crash

1
gold/gc.h
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@ -295,6 +295,7 @@ gc_process_relocs(
// When doing safe folding, check to see if this relocation is that
// of a function pointer being taken.
if (gsym->source() == Symbol::FROM_OBJECT
&& gsym->type() == elfcpp::STT_FUNC
&& check_section_for_function_pointers
&& dst_obj != NULL
&& (!is_ordinary

14
gold/testsuite/Makefile.am
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@ -274,6 +274,20 @@ icf_safe_test_1.stdout: icf_safe_test
icf_safe_test_2.stdout: icf_safe_test
$(TEST_READELF) -h $< > $@
check_SCRIPTS += icf_safe_pie_test.sh
check_DATA += icf_safe_pie_test_1.stdout icf_safe_pie_test_2.stdout icf_safe_pie_test.map
MOSTLYCLEANFILES += icf_safe_pie_test icf_safe_pie_test.map
icf_safe_pie_test.o: icf_safe_test.cc
$(CXXCOMPILE) -O0 -c -ffunction-sections -fPIE -g -o $@ $<
icf_safe_pie_test: icf_safe_pie_test.o gcctestdir/ld
$(CXXLINK) -o icf_safe_pie_test -Bgcctestdir/ -Wl,--icf=safe,-Map,icf_safe_pie_test.map icf_safe_pie_test.o -pie
icf_safe_pie_test.map: icf_safe_pie_test
@touch icf_safe_pie_test.map
icf_safe_pie_test_1.stdout: icf_safe_pie_test
$(TEST_NM) $< > $@
icf_safe_pie_test_2.stdout: icf_safe_pie_test
$(TEST_READELF) -h $< > $@
check_SCRIPTS += icf_safe_so_test.sh
check_DATA += icf_safe_so_test_1.stdout icf_safe_so_test_2.stdout icf_safe_so_test.map
MOSTLYCLEANFILES += icf_safe_so_test icf_safe_so_test.map

18
gold/testsuite/Makefile.in
View File

@ -82,6 +82,7 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_test.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_keep_unique_test.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_test.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_pie_test.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_so_test.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ final_layout.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_section_grouping.sh \
@ -103,6 +104,9 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_test_1.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_test_2.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_test.map \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_pie_test_1.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_pie_test_2.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_pie_test.map \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_so_test_1.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_so_test_2.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_so_test.map \
@ -125,6 +129,8 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_test icf_test.map \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_keep_unique_test \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_test icf_safe_test.map \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_pie_test \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_pie_test.map \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_so_test \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_safe_so_test.map \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ final_layout \
@ -5093,6 +5099,8 @@ icf_keep_unique_test.sh.log: icf_keep_unique_test.sh
@p='icf_keep_unique_test.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
icf_safe_test.sh.log: icf_safe_test.sh
@p='icf_safe_test.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
icf_safe_pie_test.sh.log: icf_safe_pie_test.sh
@p='icf_safe_pie_test.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
icf_safe_so_test.sh.log: icf_safe_so_test.sh
@p='icf_safe_so_test.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
final_layout.sh.log: final_layout.sh
@ -5910,6 +5918,16 @@ uninstall-am:
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_NM) $< > $@
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_test_2.stdout: icf_safe_test
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_READELF) -h $< > $@
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_pie_test.o: icf_safe_test.cc
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXCOMPILE) -O0 -c -ffunction-sections -fPIE -g -o $@ $<
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_pie_test: icf_safe_pie_test.o gcctestdir/ld
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXLINK) -o icf_safe_pie_test -Bgcctestdir/ -Wl,--icf=safe,-Map,icf_safe_pie_test.map icf_safe_pie_test.o -pie
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_pie_test.map: icf_safe_pie_test
@GCC_TRUE@@NATIVE_LINKER_TRUE@ @touch icf_safe_pie_test.map
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_pie_test_1.stdout: icf_safe_pie_test
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_NM) $< > $@
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_pie_test_2.stdout: icf_safe_pie_test
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_READELF) -h $< > $@
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_so_test.o: icf_safe_so_test.cc
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXCOMPILE) -O0 -c -ffunction-sections -fPIC -g -o $@ $<
@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_safe_so_test: icf_safe_so_test.o gcctestdir/ld

76
gold/testsuite/icf_safe_pie_test.sh Executable file
View File

@ -0,0 +1,76 @@
#!/bin/sh
# icf_safe_pie_test.sh -- test --icf=safe -pie
# Copyright (C) 2009-2017 Free Software Foundation, Inc.
# Written by Sriraman Tallam <tmsriram@google.com>.
# Modified by Rahul Chaudhry <rahulchaudhry@google.com>.
# This file is part of gold.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
# MA 02110-1301, USA.
# The goal of this program is to verify if --icf=safe works with
# -pie as expected. File icf_safe_test.cc is in this test. This
# program checks if only ctors and dtors are folded, except for
# the architectures which use relocation types and instruction
# opcodes to detect if function pointers are taken.
set -e
check_nofold()
{
func_addr_1=`grep $2 $1 | awk '{print $1}'`
func_addr_2=`grep $3 $1 | awk '{print $1}'`
if [ $func_addr_1 = $func_addr_2 ]
then
echo "Safe Identical Code Folding folded" $2 "and" $3
exit 1
fi
}
check_fold()
{
awk "
BEGIN { discard = 0; }
/^Discarded input/ { discard = 1; }
/^Memory map/ { discard = 0; }
/.*\\.text\\..*($2|$3).*/ { act[discard] = act[discard] \" \" \$0; }
END {
# printf \"kept\" act[0] \"\\nfolded\" act[1] \"\\n\";
if (length(act[0]) == 0 || length(act[1]) == 0)
{
printf \"Safe Identical Code Folding did not fold $2 and $3\\n\"
exit 1;
}
}" $1
}
arch_specific_safe_fold()
{
if grep -q -e "Advanced Micro Devices X86-64" -e "Intel 80386" -e "ARM" -e "TILE" -e "PowerPC" -e "AArch64" -e "IBM S/390" $2;
then
check_fold $3 $4 $5
else
check_nofold $1 $4 $5
fi
}
arch_specific_safe_fold icf_safe_pie_test_1.stdout icf_safe_pie_test_2.stdout \
icf_safe_pie_test.map "kept_func_1" "kept_func_2"
check_fold icf_safe_pie_test.map "_ZN1AD2Ev" "_ZN1AC2Ev"
check_nofold icf_safe_pie_test_1.stdout "kept_func_3" "kept_func_1"
check_nofold icf_safe_pie_test_1.stdout "kept_func_3" "kept_func_2"

85
gold/x86_64.cc
View File

@ -729,10 +729,13 @@ class Target_x86_64 : public Sized_target<size, false>
// and global_reloc_may_be_function_pointer)
// if a function's pointer is taken. ICF uses this in safe mode to only
// fold those functions whose pointer is defintely not taken. For x86_64
// pie binaries, safe ICF cannot be done by looking at relocation types.
// pie binaries, safe ICF cannot be done by looking at only relocation
// types, and for certain cases (e.g. R_X86_64_PC32), the instruction
// opcode is checked as well to distinguish a function call from taking
// a function's pointer.
bool
do_can_check_for_function_pointers() const
{ return !parameters->options().pie(); }
{ return true; }
// Return the base for a DW_EH_PE_datarel encoding.
uint64_t
@ -924,7 +927,10 @@ class Target_x86_64 : public Sized_target<size, false>
check_non_pic(Relobj*, unsigned int r_type, Symbol*);
inline bool
possible_function_pointer_reloc(unsigned int r_type);
possible_function_pointer_reloc(Sized_relobj_file<size, false>* src_obj,
unsigned int src_indx,
unsigned int r_offset,
unsigned int r_type);
bool
reloc_needs_plt_for_ifunc(Sized_relobj_file<size, false>*,
@ -3277,7 +3283,11 @@ Target_x86_64<size>::Scan::unsupported_reloc_global(
// Returns true if this relocation type could be that of a function pointer.
template<int size>
inline bool
Target_x86_64<size>::Scan::possible_function_pointer_reloc(unsigned int r_type)
Target_x86_64<size>::Scan::possible_function_pointer_reloc(
Sized_relobj_file<size, false>* src_obj,
unsigned int src_indx,
unsigned int r_offset,
unsigned int r_type)
{
switch (r_type)
{
@ -3296,6 +3306,41 @@ Target_x86_64<size>::Scan::possible_function_pointer_reloc(unsigned int r_type)
{
return true;
}
case elfcpp::R_X86_64_PC32:
{
// This relocation may be used both for function calls and
// for taking address of a function. We distinguish between
// them by checking the opcodes.
uint64_t sh_flags = src_obj->section_flags(src_indx);
bool is_executable = (sh_flags & elfcpp::SHF_EXECINSTR) != 0;
if (is_executable)
{
section_size_type stype;
const unsigned char* view = src_obj->section_contents(src_indx,
&stype,
true);
// call
if (r_offset >= 1
&& view[r_offset - 1] == 0xe8)
return false;
// jmp
if (r_offset >= 1
&& view[r_offset - 1] == 0xe9)
return false;
// jo/jno/jb/jnb/je/jne/jna/ja/js/jns/jp/jnp/jl/jge/jle/jg
if (r_offset >= 2
&& view[r_offset - 2] == 0x0f
&& view[r_offset - 1] >= 0x80
&& view[r_offset - 1] <= 0x8f)
return false;
}
// Be conservative and treat all others as function pointers.
return true;
}
}
return false;
}
@ -3310,18 +3355,21 @@ Target_x86_64<size>::Scan::local_reloc_may_be_function_pointer(
Symbol_table* ,
Layout* ,
Target_x86_64<size>* ,
Sized_relobj_file<size, false>* ,
unsigned int ,
Sized_relobj_file<size, false>* src_obj,
unsigned int src_indx,
Output_section* ,
const elfcpp::Rela<size, false>& ,
const elfcpp::Rela<size, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<size, false>&)
{
// When building a shared library, do not fold any local symbols as it is
// not possible to distinguish pointer taken versus a call by looking at
// the relocation types.
return (parameters->options().shared()
|| possible_function_pointer_reloc(r_type));
if (parameters->options().shared())
return true;
return possible_function_pointer_reloc(src_obj, src_indx,
reloc.get_r_offset(), r_type);
}
// For safe ICF, scan a relocation for a global symbol to check if it
@ -3334,20 +3382,23 @@ Target_x86_64<size>::Scan::global_reloc_may_be_function_pointer(
Symbol_table*,
Layout* ,
Target_x86_64<size>* ,
Sized_relobj_file<size, false>* ,
unsigned int ,
Sized_relobj_file<size, false>* src_obj,
unsigned int src_indx,
Output_section* ,
const elfcpp::Rela<size, false>& ,
const elfcpp::Rela<size, false>& reloc,
unsigned int r_type,
Symbol* gsym)
{
// When building a shared library, do not fold symbols whose visibility
// is hidden, internal or protected.
return ((parameters->options().shared()
&& (gsym->visibility() == elfcpp::STV_INTERNAL
|| gsym->visibility() == elfcpp::STV_PROTECTED
|| gsym->visibility() == elfcpp::STV_HIDDEN))
|| possible_function_pointer_reloc(r_type));
if (parameters->options().shared()
&& (gsym->visibility() == elfcpp::STV_INTERNAL
|| gsym->visibility() == elfcpp::STV_PROTECTED
|| gsym->visibility() == elfcpp::STV_HIDDEN))
return true;
return possible_function_pointer_reloc(src_obj, src_indx,
reloc.get_r_offset(), r_type);
}
// Scan a relocation for a global symbol.