[lld] r276384 - [ELF/LinkerScript] Support ONLY_IF_{RO, RW} directive.
Davide Italiano via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 21 20:36:24 PDT 2016
Author: davide
Date: Thu Jul 21 22:36:24 2016
New Revision: 276384
URL: http://llvm.org/viewvc/llvm-project?rev=276384&view=rev
Log:
[ELF/LinkerScript] Support ONLY_IF_{RO, RW} directive.
Differential Revision: https://reviews.llvm.org/D22660
Added:
lld/trunk/test/ELF/linkerscript-sections-constraint.s
Modified:
lld/trunk/ELF/LinkerScript.cpp
lld/trunk/ELF/LinkerScript.h
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=276384&r1=276383&r2=276384&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Thu Jul 21 22:36:24 2016
@@ -262,15 +262,26 @@ std::vector<OutputSectionBase<ELFT> *>
LinkerScript<ELFT>::createSections(OutputSectionFactory<ELFT> &Factory) {
typedef const std::unique_ptr<ObjectFile<ELFT>> ObjectFile;
std::vector<OutputSectionBase<ELFT> *> Result;
+ DenseSet<OutputSectionBase<ELFT> *> Removed;
// Add input section to output section. If there is no output section yet,
// then create it and add to output section list.
- auto AddInputSec = [&](InputSectionBase<ELFT> *C, StringRef Name) {
+ auto AddInputSec = [&](InputSectionBase<ELFT> *C, StringRef Name,
+ ConstraintKind Constraint) {
OutputSectionBase<ELFT> *Sec;
bool IsNew;
std::tie(Sec, IsNew) = Factory.create(C, Name);
if (IsNew)
Result.push_back(Sec);
+ if ((!(C->getSectionHdr()->sh_flags & SHF_WRITE)) &&
+ Constraint == ReadWrite) {
+ Removed.insert(Sec);
+ return;
+ }
+ if ((C->getSectionHdr()->sh_flags & SHF_WRITE) && Constraint == ReadOnly) {
+ Removed.insert(Sec);
+ return;
+ }
Sec->addSection(C);
};
@@ -296,7 +307,7 @@ LinkerScript<ELFT>::createSections(Outpu
if (OutCmd->Name == "/DISCARD/")
S->Live = false;
else
- AddInputSec(S, OutCmd->Name);
+ AddInputSec(S, OutCmd->Name, OutCmd->Constraint);
}
}
}
@@ -308,11 +319,17 @@ LinkerScript<ELFT>::createSections(Outpu
for (InputSectionBase<ELFT> *S : F->getSections()) {
if (!isDiscarded(S)) {
if (!S->OutSec)
- AddInputSec(S, getOutputSectionName(S));
+ AddInputSec(S, getOutputSectionName(S), NoConstraint);
} else
reportDiscarded(S, F);
}
+ // Remove from the output all the sections which did not met the constraints.
+ Result.erase(std::remove_if(Result.begin(), Result.end(),
+ [&](OutputSectionBase<ELFT> *Sec) {
+ return Removed.count(Sec);
+ }),
+ Result.end());
return Result;
}
@@ -793,6 +810,12 @@ void ScriptParser::readOutputSectionDesc
OutputSectionCommand *Cmd = new OutputSectionCommand(OutSec);
Opt.Commands.emplace_back(Cmd);
expect(":");
+
+ // Parse constraints.
+ if (skip("ONLY_IF_RO"))
+ Cmd->Constraint = ReadOnly;
+ if (skip("ONLY_IF_RW"))
+ Cmd->Constraint = ReadWrite;
expect("{");
while (!Error && !skip("}")) {
Modified: lld/trunk/ELF/LinkerScript.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.h?rev=276384&r1=276383&r2=276384&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.h (original)
+++ lld/trunk/ELF/LinkerScript.h Thu Jul 21 22:36:24 2016
@@ -53,6 +53,13 @@ struct SymbolAssignment : BaseCommand {
std::vector<StringRef> Expr;
};
+// Linker scripts allow additional constraints to be put on ouput sections.
+// An output section will only be created if all of its input sections are
+// read-only
+// or all of its input sections are read-write by using the keyword ONLY_IF_RO
+// and ONLY_IF_RW respectively.
+enum ConstraintKind { NoConstraint, ReadOnly, ReadWrite };
+
struct OutputSectionCommand : BaseCommand {
OutputSectionCommand(StringRef Name)
: BaseCommand(OutputSectionKind), Name(Name) {}
@@ -61,6 +68,7 @@ struct OutputSectionCommand : BaseComman
std::vector<std::unique_ptr<BaseCommand>> Commands;
std::vector<StringRef> Phdrs;
std::vector<uint8_t> Filler;
+ ConstraintKind Constraint = NoConstraint;
};
struct InputSectionDescription : BaseCommand {
Added: lld/trunk/test/ELF/linkerscript-sections-constraint.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript-sections-constraint.s?rev=276384&view=auto
==============================================================================
--- lld/trunk/test/ELF/linkerscript-sections-constraint.s (added)
+++ lld/trunk/test/ELF/linkerscript-sections-constraint.s Thu Jul 21 22:36:24 2016
@@ -0,0 +1,35 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: echo "SECTIONS { \
+# RUN: .writable : ONLY_IF_RW { *(.writable) } \
+# RUN: .readable : ONLY_IF_RO { *(.readable) }}" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -section-headers %t1 | \
+# RUN: FileCheck -check-prefix=BASE %s
+# BASE: Sections:
+# BASE-NEXT: Idx Name Size Address Type
+# BASE-NEXT: 0 00000000 0000000000000000
+# BASE-NEXT: 1 .writable 00000004 0000000000000190 DATA
+# BASE-NEXT: 2 .readable 00000004 0000000000000194 DATA
+
+# RUN: echo "SECTIONS { \
+# RUN: .writable : ONLY_IF_RO { *(.writable) } \
+# RUN: .readable : ONLY_IF_RW { *(.readable) }}" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -section-headers %t1 | \
+# RUN: FileCheck -check-prefix=NOSECTIONS %s
+# NOSECTIONS: Sections:
+# NOSECTIONS-NOT: .writable
+# NOSECTIONS-NOT: .readable
+
+.global _start
+_start:
+ nop
+
+.section .writable, "aw"
+writable:
+ .long 1
+
+.section .readable, "a"
+readable:
+ .long 2
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