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Handle symbol assignments before the first section switch. 

We now create a dummy section with index 1 before processing the
linker script.

Thanks to George Rimar for finding the bug and providing the initial
testcase.

llvm-svn: 294252
This commit is contained in:
Rafael Espindola 2017-02-06 22:21:46 +00:00
parent 383c5c228f
commit 06f4743a48
2 changed files with 28 additions and 8 deletions
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24
lld/ELF/LinkerScript.cpp
View File

@ -776,6 +776,19 @@ void LinkerScript<ELFT>::assignAddresses(std::vector<PhdrEntry> &Phdrs) {
// Assign addresses as instructed by linker script SECTIONS sub-commands.
Dot = 0;
// A symbol can be assigned before any section is mentioned in the linker
// script. In an DSO, the symbol values are addresses, so the only important
// section values are:
// * SHN_UNDEF
// * SHN_ABS
// * Any value meaning a regular section.
// To handle that, create a dummy aether section that fills the void before
// the linker scripts switches to another section. It has an index of one
// which will map to whatever the first actual section is.
auto *Aether = make<OutputSectionBase>("", 0, SHF_ALLOC);
Aether->SectionIndex = 1;
switchTo(Aether);
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base.get())) {
if (Cmd->Name == ".") {
@ -973,14 +986,9 @@ template <class ELFT> bool LinkerScript<ELFT>::isAbsolute(StringRef S) {
// to find suitable section for it as well.
template <class ELFT>
const OutputSectionBase *LinkerScript<ELFT>::getSymbolSection(StringRef S) {
SymbolBody *Sym = Symtab<ELFT>::X->find(S);
if (!Sym) {
if (OutputSections->empty())
return nullptr;
return CurOutSec ? CurOutSec : (*OutputSections)[0];
}
return SymbolTableSection<ELFT>::getOutputSection(Sym);
if (SymbolBody *Sym = Symtab<ELFT>::X->find(S))
return SymbolTableSection<ELFT>::getOutputSection(Sym);
return CurOutSec;
}
// Returns indices of ELF headers containing specific section, identified

12
lld/test/ELF/linkerscript/non-absolute2.s Normal file
View File

@ -0,0 +1,12 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1.o
# RUN: echo "SECTIONS { A = . + 0x1; . += 0x1000; }" > %t.script
# RUN: ld.lld -shared %t1.o --script %t.script -o %t
# RUN: llvm-objdump -section-headers -t %t | FileCheck %s
# CHECK: Sections:
# CHECK-NEXT: Idx Name Size Address
# CHECK-NEXT: 0 00000000 0000000000000000
# CHECK-NEXT: 1 .text 00000000 0000000000001000
# CHECK: 0000000000000001 .text 00000000 A