[lld] r294252 - Handle symbol assignments before the first section switch.
Rafael Espindola via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 6 14:21:47 PST 2017
Author: rafael
Date: Mon Feb 6 16:21:46 2017
New Revision: 294252
URL: http://llvm.org/viewvc/llvm-project?rev=294252&view=rev
Log:
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.
Added:
lld/trunk/test/ELF/linkerscript/non-absolute2.s
Modified:
lld/trunk/ELF/LinkerScript.cpp
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=294252&r1=294251&r2=294252&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Mon Feb 6 16:21:46 2017
@@ -776,6 +776,19 @@ void LinkerScript<ELFT>::assignAddresses
// 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<
// 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
Added: lld/trunk/test/ELF/linkerscript/non-absolute2.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/non-absolute2.s?rev=294252&view=auto
==============================================================================
--- lld/trunk/test/ELF/linkerscript/non-absolute2.s (added)
+++ lld/trunk/test/ELF/linkerscript/non-absolute2.s Mon Feb 6 16:21:46 2017
@@ -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
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