9aea164457
There are number of changes in the way IFUNC related relocations are done:
1. IRELATIVE relocations are now supported for x86/x86_64 and arm64.
2. IFUNC relocations are now relying on static linker to generate
them in correct order - this removes necessety of additional
relocation pass for ifuncs.
3. Related to 2: rela?.dyn relocations are preformed before .plt ones.
4. Ifunc are resolved on symbol lookup this approach allowed to avoid
mprotect(PROT_WRITE) call on r-x program segments.
Bug: 17399706
Bug: 17177284
Change-Id: I414dd3e82bd47cc03442c5dfc7c279949aec51ed
65 lines
1.6 KiB
C
65 lines
1.6 KiB
C
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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static int g_flag = 0;
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static void __attribute__((constructor)) init_flag() {
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g_flag = 1;
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}
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static const char* is_ctor_called() __attribute__ ((ifunc("is_ctor_called_ifun")));
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const char* foo() __attribute__ ((ifunc ("foo_ifunc")));
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// Static linker creates GLOBAL/IFUNC symbol and JUMP_SLOT relocation type for plt segment
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const char* is_ctor_called_jump_slot() __attribute__ ((ifunc("is_ctor_called_ifun")));
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const char* is_ctor_called_irelative() {
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// Call internal ifunc-resolved function with IRELATIVE reloc
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return is_ctor_called();
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}
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const char* return_true() {
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return "true";
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}
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const char* return_false() {
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return "false";
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}
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const char* f1() {
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return "unset";
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}
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const char* f2() {
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return "set";
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}
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void* is_ctor_called_ifun() {
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return g_flag == 0 ? return_false : return_true;
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}
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void* foo_ifunc() {
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char* choice = getenv("IFUNC_CHOICE");
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return choice == NULL ? f1 : f2;
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}
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const char* foo_library() {
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return foo();
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}
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