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LibELF: Implement x86_64 relocation support

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There are definitely some relocations missing and this is untested
for now.
This commit is contained in:
Gunnar Beutner 2021-05-02 01:32:28 +02:00 committed by Andreas Kling
parent 6990ab41c8
commit a050b43290
3 changed files with 38 additions and 0 deletions
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6
Userland/Libraries/LibC/elf.h
View file

@ -791,3 +791,9 @@ struct elf_args {
#define R_386_RELATIVE 8 /* Base address + Addned */
#define R_386_TLS_TPOFF 14 /* Negative offset into the static TLS storage */
#define R_386_TLS_TPOFF32 37
#define R_X86_64_NONE 0
#define R_X86_64_64 1
#define R_X86_64_GLOB_DAT 6
#define R_X86_64_JUMP_SLOT 7
#define R_X86_64_RELATIVE 8

12
Userland/Libraries/LibELF/Arch/x86_64/plt_trampoline.S Normal file
View file

@ -0,0 +1,12 @@
/*
* Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
.align 4
.globl _plt_trampoline
.hidden _plt_trampoline
.type _plt_trampoline,@function
_plt_trampoline:
int3

20
Userland/Libraries/LibELF/DynamicLoader.cpp
View file

@ -398,11 +398,19 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
patch_ptr = (FlatPtr*)(FlatPtr)relocation.offset();
switch (relocation.type()) {
#ifndef __LP64__
case R_386_NONE:
#else
case R_X86_64_NONE:
#endif
// Apparently most loaders will just skip these?
// Seems if the 'link editor' generates one something is funky with your code
break;
#ifndef __LP64__
case R_386_32: {
#else
case R_X86_64_64: {
#endif
auto symbol = relocation.symbol();
auto res = lookup_symbol(symbol);
if (!res.has_value()) {
@ -415,6 +423,7 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
*patch_ptr += symbol_address.get();
break;
}
#ifndef __LP64__
case R_386_PC32: {
auto symbol = relocation.symbol();
auto result = lookup_symbol(symbol);
@ -425,6 +434,9 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
break;
}
case R_386_GLOB_DAT: {
#else
case R_X86_64_GLOB_DAT: {
#endif
auto symbol = relocation.symbol();
auto res = lookup_symbol(symbol);
VirtualAddress symbol_location;
@ -444,13 +456,18 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
*patch_ptr = symbol_location.get();
break;
}
#ifndef __LP64__
case R_386_RELATIVE: {
#else
case R_X86_64_RELATIVE: {
#endif
// FIXME: According to the spec, R_386_relative ones must be done first.
// We could explicitly do them first using m_number_of_relocations from DT_RELCOUNT
// However, our compiler is nice enough to put them at the front of the relocations for us :)
*patch_ptr += (FlatPtr)m_dynamic_object->base_address().as_ptr(); // + addend for RelA (addend for Rel is stored at addr)
break;
}
#ifndef __LP64__
case R_386_TLS_TPOFF32:
case R_386_TLS_TPOFF: {
auto symbol = relocation.symbol();
@ -466,6 +483,9 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
break;
}
case R_386_JMP_SLOT: {
#else
case R_X86_64_JUMP_SLOT: {
#endif
// FIXME: Or BIND_NOW flag passed in?
if (m_dynamic_object->must_bind_now()) {
// Eagerly BIND_NOW the PLT entries, doing all the symbol looking goodness