intel/llvm
1
0
Fork 0
mirror of https://github.com/intel/llvm.git synced 2026-01-22 23:49:22 +08:00
Code Issues Packages Projects Releases Wiki Activity

ELF: Add basic partition data structures and behaviours.

Browse Source 
This change causes us to read partition specifications from partition
specification sections and split output sections into partitions according
to their reachability from partition entry points.

This is only the first step towards a full implementation of partitions. Later
changes will add additional synthetic sections to each partition so that
they can be loaded independently.

Differential Revision: https://reviews.llvm.org/D60353

llvm-svn: 361925
This commit is contained in:
Peter Collingbourne
2019-05-29 03:55:20 +00:00
parent e8698ead9d
commit ba2816be82
18 changed files with 387 additions and 70 deletions
Download Patch File Download Diff File Expand all files Collapse all files

71
lld/ELF/Driver.cpp
View File

@@ -98,6 +98,8 @@ bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly,
Tar = nullptr;
memset(&In, 0, sizeof(In));
Partitions = {Partition()};
SharedFile::VernauxNum = 0;
Config->ProgName = Args[0];
@@ -1344,7 +1346,7 @@ static void replaceCommonSymbols() {
auto *Bss = make<BssSection>("COMMON", S->Size, S->Alignment);
Bss->File = S->File;
Bss->Live = !Config->GcSections;
Bss->markDead();
InputSections.push_back(Bss);
S->replace(Defined{S->File, S->getName(), S->Binding, S->StOther, S->Type,
/*Value=*/0, S->Size, Bss});
@@ -1432,6 +1434,55 @@ static void findKeepUniqueSections(opt::InputArgList &Args) {
}
}
// This function reads a symbol partition specification section. These sections
// are used to control which partition a symbol is allocated to. See
// https://lld.llvm.org/Partitions.html for more details on partitions.
template <typename ELFT>
static void readSymbolPartitionSection(InputSectionBase *S) {
// Read the relocation that refers to the partition's entry point symbol.
Symbol *Sym;
if (S->AreRelocsRela)
Sym = &S->getFile<ELFT>()->getRelocTargetSym(S->template relas<ELFT>()[0]);
else
Sym = &S->getFile<ELFT>()->getRelocTargetSym(S->template rels<ELFT>()[0]);
if (!isa<Defined>(Sym) || !Sym->includeInDynsym())
return;
StringRef PartName = reinterpret_cast<const char *>(S->data().data());
for (Partition &Part : Partitions) {
if (Part.Name == PartName) {
Sym->Partition = Part.getNumber();
return;
}
}
// Forbid partitions from being used on incompatible targets, and forbid them
// from being used together with various linker features that assume a single
// set of output sections.
if (Script->HasSectionsCommand)
error(toString(S->File) +
": partitions cannot be used with the SECTIONS command");
if (Script->hasPhdrsCommands())
error(toString(S->File) +
": partitions cannot be used with the PHDRS command");
if (!Config->SectionStartMap.empty())
error(toString(S->File) + ": partitions cannot be used with "
"--section-start, -Ttext, -Tdata or -Tbss");
if (Config->EMachine == EM_MIPS)
error(toString(S->File) + ": partitions cannot be used on this target");
// Impose a limit of no more than 254 partitions. This limit comes from the
// sizes of the Partition fields in InputSectionBase and Symbol, as well as
// the amount of space devoted to the partition number in RankFlags.
if (Partitions.size() == 254)
fatal("may not have more than 254 partitions");
Partitions.emplace_back();
Partition &NewPart = Partitions.back();
NewPart.Name = PartName;
Sym->Partition = NewPart.getNumber();
}
template <class ELFT> static Symbol *addUndefined(StringRef Name) {
return Symtab->addSymbol(
Undefined{nullptr, Name, STB_GLOBAL, STV_DEFAULT, 0});
@@ -1700,13 +1751,17 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
for (InputSectionBase *S : F->getSections())
InputSections.push_back(cast<InputSection>(S));
// We do not want to emit debug sections if --strip-all
// or -strip-debug are given.
if (Config->Strip != StripPolicy::None) {
llvm::erase_if(InputSections, [](InputSectionBase *S) {
return S->Name.startswith(".debug") || S->Name.startswith(".zdebug");
});
}
llvm::erase_if(InputSections, [](InputSectionBase *S) {
if (S->Type == SHT_LLVM_SYMPART) {
readSymbolPartitionSection<ELFT>(S);
return true;
}
// We do not want to emit debug sections if --strip-all
// or -strip-debug are given.
return Config->Strip != StripPolicy::None &&
(S->Name.startswith(".debug") || S->Name.startswith(".zdebug"));
});
Config->EFlags = Target->calcEFlags();
// MaxPageSize (sometimes called abi page size) is the maximum page size that