[lld] r302186 - Simplify the header allocation.
Rafael Espindola via llvm-commits
llvm-commits at lists.llvm.org
Thu May 4 12:34:17 PDT 2017
Author: rafael
Date: Thu May 4 14:34:17 2017
New Revision: 302186
URL: http://llvm.org/viewvc/llvm-project?rev=302186&view=rev
Log:
Simplify the header allocation.
In the non linker script case we would try very early to find out if
we could allocate the headers. Failing to do that would add extra
alignment to the first ro section, since we would set PageAlign
thinking it was the first section in the PT_LOAD.
In the linker script case the header allocation must be done in the
end, causing some duplication.
We now tentatively add the headers to the first PT_LOAD and if it
turns out they don't fit, remove them. With this we only need to
allocate the headers in one place in the code.
Modified:
lld/trunk/ELF/LinkerScript.cpp
lld/trunk/ELF/LinkerScript.h
lld/trunk/ELF/Writer.cpp
lld/trunk/ELF/Writer.h
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=302186&r1=302185&r2=302186&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Thu May 4 14:34:17 2017
@@ -420,13 +420,11 @@ void LinkerScript::processCommands(Outpu
CurOutSec = nullptr;
}
-void LinkerScript::fabricateDefaultCommands(bool AllocateHeader) {
+void LinkerScript::fabricateDefaultCommands() {
std::vector<BaseCommand *> Commands;
// Define start address
- uint64_t StartAddr = Config->ImageBase;
- if (AllocateHeader)
- StartAddr += elf::getHeaderSize();
+ uint64_t StartAddr = Config->ImageBase + elf::getHeaderSize();
// The Sections with -T<section> have been sorted in order of ascending
// address. We must lower StartAddr if the lowest -T<section address> as
@@ -892,6 +890,48 @@ void LinkerScript::synchronize() {
}
}
+static bool allocateHeaders(std::vector<PhdrEntry> &Phdrs,
+ ArrayRef<OutputSection *> OutputSections,
+ uint64_t Min) {
+ auto FirstPTLoad =
+ std::find_if(Phdrs.begin(), Phdrs.end(),
+ [](const PhdrEntry &E) { return E.p_type == PT_LOAD; });
+ if (FirstPTLoad == Phdrs.end())
+ return false;
+
+ uint64_t HeaderSize = getHeaderSize();
+ if (HeaderSize <= Min || Script->hasPhdrsCommands()) {
+ Min = alignDown(Min - HeaderSize, Config->MaxPageSize);
+ Out::ElfHeader->Addr = Min;
+ Out::ProgramHeaders->Addr = Min + Out::ElfHeader->Size;
+ return true;
+ }
+
+ assert(FirstPTLoad->First == Out::ElfHeader);
+ OutputSection *ActualFirst = nullptr;
+ for (OutputSection *Sec : OutputSections) {
+ if (Sec->FirstInPtLoad == Out::ElfHeader) {
+ ActualFirst = Sec;
+ break;
+ }
+ }
+ if (ActualFirst) {
+ for (OutputSection *Sec : OutputSections)
+ if (Sec->FirstInPtLoad == Out::ElfHeader)
+ Sec->FirstInPtLoad = ActualFirst;
+ FirstPTLoad->First = ActualFirst;
+ } else {
+ Phdrs.erase(FirstPTLoad);
+ }
+
+ auto PhdrI = std::find_if(Phdrs.begin(), Phdrs.end(), [](const PhdrEntry &E) {
+ return E.p_type == PT_PHDR;
+ });
+ if (PhdrI != Phdrs.end())
+ Phdrs.erase(PhdrI);
+ return false;
+}
+
void LinkerScript::assignAddresses(std::vector<PhdrEntry> &Phdrs) {
// Assign addresses as instructed by linker script SECTIONS sub-commands.
Dot = 0;
Modified: lld/trunk/ELF/LinkerScript.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.h?rev=302186&r1=302185&r2=302186&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.h (original)
+++ lld/trunk/ELF/LinkerScript.h Thu May 4 14:34:17 2017
@@ -253,7 +253,7 @@ public:
bool isDefined(StringRef S);
std::vector<OutputSection *> *OutputSections;
- void fabricateDefaultCommands(bool AllocateHeader);
+ void fabricateDefaultCommands();
void addOrphanSections(OutputSectionFactory &Factory);
void removeEmptyCommands();
void adjustSectionsBeforeSorting();
Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=302186&r1=302185&r2=302186&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Thu May 4 14:34:17 2017
@@ -62,7 +62,6 @@ private:
void assignFileOffsets();
void assignFileOffsetsBinary();
void setPhdrs();
- void fixHeaders();
void fixSectionAlignments();
void fixPredefinedSymbols();
void openFile();
@@ -86,7 +85,6 @@ private:
uint64_t FileSize;
uint64_t SectionHeaderOff;
- bool AllocateHeader = true;
};
} // anonymous namespace
@@ -252,7 +250,7 @@ template <class ELFT> void Writer<ELFT>:
} else {
if (!Script->Opt.HasSections) {
fixSectionAlignments();
- Script->fabricateDefaultCommands(AllocateHeader);
+ Script->fabricateDefaultCommands();
}
Script->synchronize();
Script->assignAddresses(Phdrs);
@@ -1176,7 +1174,7 @@ template <class ELFT> void Writer<ELFT>:
if (!Config->Relocatable && !Config->OFormatBinary) {
Phdrs = Script->hasPhdrsCommands() ? Script->createPhdrs() : createPhdrs();
addPtArmExid(Phdrs);
- fixHeaders();
+ Out::ProgramHeaders->Size = sizeof(Elf_Phdr) * Phdrs.size();
}
// Dynamic section must be the last one in this list and dynamic
@@ -1321,6 +1319,11 @@ template <class ELFT> std::vector<PhdrEn
// Add the first PT_LOAD segment for regular output sections.
uint64_t Flags = computeFlags(PF_R);
PhdrEntry *Load = AddHdr(PT_LOAD, Flags);
+
+ // Add the headers. We will remove them if they don't fit.
+ Load->add(Out::ElfHeader);
+ Load->add(Out::ProgramHeaders);
+
for (OutputSection *Sec : OutputSections) {
if (!(Sec->Flags & SHF_ALLOC))
break;
@@ -1447,64 +1450,6 @@ template <class ELFT> void Writer<ELFT>:
}
}
-bool elf::allocateHeaders(std::vector<PhdrEntry> &Phdrs,
- ArrayRef<OutputSection *> OutputSections,
- uint64_t Min) {
- auto FirstPTLoad =
- std::find_if(Phdrs.begin(), Phdrs.end(),
- [](const PhdrEntry &E) { return E.p_type == PT_LOAD; });
- if (FirstPTLoad == Phdrs.end())
- return false;
-
- uint64_t HeaderSize = getHeaderSize();
- if (HeaderSize > Min) {
- auto PhdrI =
- std::find_if(Phdrs.begin(), Phdrs.end(),
- [](const PhdrEntry &E) { return E.p_type == PT_PHDR; });
- if (PhdrI != Phdrs.end())
- Phdrs.erase(PhdrI);
- return false;
- }
- Min = alignDown(Min - HeaderSize, Config->MaxPageSize);
-
- if (!Script->Opt.HasSections)
- Config->ImageBase = Min = std::min(Min, Config->ImageBase);
-
- Out::ElfHeader->Addr = Min;
- Out::ProgramHeaders->Addr = Min + Out::ElfHeader->Size;
-
- if (Script->hasPhdrsCommands())
- return true;
-
- if (FirstPTLoad->First)
- for (OutputSection *Sec : OutputSections)
- if (Sec->FirstInPtLoad == FirstPTLoad->First)
- Sec->FirstInPtLoad = Out::ElfHeader;
- FirstPTLoad->First = Out::ElfHeader;
- if (!FirstPTLoad->Last)
- FirstPTLoad->Last = Out::ProgramHeaders;
- return true;
-}
-
-// We should set file offsets and VAs for elf header and program headers
-// sections. These are special, we do not include them into output sections
-// list, but have them to simplify the code.
-template <class ELFT> void Writer<ELFT>::fixHeaders() {
- Out::ProgramHeaders->Size = sizeof(Elf_Phdr) * Phdrs.size();
- // If the script has SECTIONS, assignAddresses will compute the values.
- if (Script->Opt.HasSections)
- return;
-
- // When -T<section> option is specified, lower the base to make room for those
- // sections.
- uint64_t Min = -1;
- if (!Config->SectionStartMap.empty())
- for (const auto &P : Config->SectionStartMap)
- Min = std::min(Min, P.second);
-
- AllocateHeader = allocateHeaders(Phdrs, OutputSections, Min);
-}
-
// Adjusts the file alignment for a given output section and returns
// its new file offset. The file offset must be the same with its
// virtual address (modulo the page size) so that the loader can load
Modified: lld/trunk/ELF/Writer.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.h?rev=302186&r1=302185&r2=302186&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.h (original)
+++ lld/trunk/ELF/Writer.h Thu May 4 14:34:17 2017
@@ -49,9 +49,6 @@ struct PhdrEntry {
llvm::StringRef getOutputSectionName(llvm::StringRef Name);
-bool allocateHeaders(std::vector<PhdrEntry> &, llvm::ArrayRef<OutputSection *>,
- uint64_t Min);
-
template <class ELFT> uint32_t getMipsEFlags();
uint8_t getMipsFpAbiFlag(uint8_t OldFlag, uint8_t NewFlag,
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