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-rw-r--r--lld/ELF/OutputSections.cpp121
-rw-r--r--lld/ELF/OutputSections.h13
-rw-r--r--lld/test/ELF/eh-frame-hdr-icf.s2
3 files changed, 69 insertions, 67 deletions
diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 03688d439ab..86bf3a38237 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -720,42 +720,6 @@ EhFrameHeader<ELFT>::EhFrameHeader()
this->Header.sh_size = 12;
}
-// We have to get PC values of FDEs. They depend on relocations
-// which are target specific, so we run this code after performing
-// all relocations. We read the values from ouput buffer according to the
-// encoding given for FDEs. Return value is an offset to the initial PC value
-// for the FDE.
-template <class ELFT>
-typename EhFrameHeader<ELFT>::uintX_t
-EhFrameHeader<ELFT>::getFdePc(uintX_t EhVA, const FdeData &F) {
- const endianness E = ELFT::TargetEndianness;
- uint8_t Size = F.Enc & 0x7;
- if (Size == DW_EH_PE_absptr)
- Size = sizeof(uintX_t) == 8 ? DW_EH_PE_udata8 : DW_EH_PE_udata4;
- uint64_t PC;
- switch (Size) {
- case DW_EH_PE_udata2:
- PC = read16<E>(F.PCRel);
- break;
- case DW_EH_PE_udata4:
- PC = read32<E>(F.PCRel);
- break;
- case DW_EH_PE_udata8:
- PC = read64<E>(F.PCRel);
- break;
- default:
- fatal("unknown FDE size encoding");
- }
- switch (F.Enc & 0x70) {
- case DW_EH_PE_absptr:
- return PC;
- case DW_EH_PE_pcrel:
- return PC + EhVA + F.Off + 8;
- default:
- fatal("unknown FDE size relative encoding");
- }
-}
-
// .eh_frame_hdr contains a binary search table of pointers to FDEs.
// Each entry of the search table consists of two values,
// the starting PC from where FDEs covers, and the FDE's address.
@@ -763,36 +727,32 @@ EhFrameHeader<ELFT>::getFdePc(uintX_t EhVA, const FdeData &F) {
template <class ELFT> void EhFrameHeader<ELFT>::writeTo(uint8_t *Buf) {
const endianness E = ELFT::TargetEndianness;
- uintX_t EhVA = Sec->getVA();
- uintX_t VA = this->getVA();
-
- // InitialPC -> Offset in .eh_frame, sorted by InitialPC, and deduplicate PCs.
- // FIXME: Deduplication leaves unneeded null bytes at the end of the section.
- std::map<uintX_t, size_t> PcToOffset;
- for (const FdeData &F : FdeList)
- PcToOffset[getFdePc(EhVA, F)] = F.Off;
+ // Sort the FDE list by their PC and uniqueify. Usually there is only
+ // one FDE for a PC (i.e. function), but if ICF merges two functions
+ // into one, there can be more than one FDEs pointing to the address.
+ auto Less = [](const FdeData &A, const FdeData &B) { return A.Pc < B.Pc; };
+ std::stable_sort(Fdes.begin(), Fdes.end(), Less);
+ auto Eq = [](const FdeData &A, const FdeData &B) { return A.Pc == B.Pc; };
+ Fdes.erase(std::unique(Fdes.begin(), Fdes.end(), Eq), Fdes.end());
- // Write a header.
Buf[0] = 1;
Buf[1] = DW_EH_PE_pcrel | DW_EH_PE_sdata4;
Buf[2] = DW_EH_PE_udata4;
Buf[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4;
- uintX_t EhOff = EhVA - VA - 4;
- write32<E>(Buf + 4, EhOff);
- write32<E>(Buf + 8, PcToOffset.size());
+ write32<E>(Buf + 4, Sec->getVA() - this->getVA() - 4);
+ write32<E>(Buf + 8, Fdes.size());
Buf += 12;
- for (auto &I : PcToOffset) {
- // The first four bytes are an offset to the initial PC value for the FDE.
- write32<E>(Buf, I.first - VA);
- // The last four bytes are an offset to the FDE data itself.
- write32<E>(Buf + 4, EhVA + I.second - VA);
+ uintX_t VA = this->getVA();
+ for (FdeData &Fde : Fdes) {
+ write32<E>(Buf, Fde.Pc - VA);
+ write32<E>(Buf + 4, Fde.FdeVA - VA);
Buf += 8;
}
}
template <class ELFT>
-void EhFrameHeader<ELFT>::assignEhFrame(EHOutputSection<ELFT> *Sec) {
+void EhFrameHeader<ELFT>::add(EHOutputSection<ELFT> *Sec) {
assert((!this->Sec || this->Sec == Sec) &&
"multiple .eh_frame sections not supported for .eh_frame_hdr");
Live = Config->EhFrameHdr;
@@ -800,10 +760,8 @@ void EhFrameHeader<ELFT>::assignEhFrame(EHOutputSection<ELFT> *Sec) {
}
template <class ELFT>
-void EhFrameHeader<ELFT>::addFde(uint8_t Enc, size_t Off, uint8_t *PCRel) {
- if (Live && (Enc & 0xF0) == DW_EH_PE_datarel)
- fatal("DW_EH_PE_datarel encoding unsupported for FDEs by .eh_frame_hdr");
- FdeList.push_back(FdeData{Enc, Off, PCRel});
+void EhFrameHeader<ELFT>::addFde(uint32_t Pc, uint32_t FdeVA) {
+ Fdes.push_back({Pc, FdeVA});
}
template <class ELFT> void EhFrameHeader<ELFT>::reserveFde() {
@@ -966,7 +924,7 @@ template <class ELFT>
EHOutputSection<ELFT>::EHOutputSection(StringRef Name, uint32_t Type,
uintX_t Flags)
: OutputSectionBase<ELFT>(Name, Type, Flags) {
- Out<ELFT>::EhFrameHdr->assignEhFrame(this);
+ Out<ELFT>::EhFrameHdr->add(this);
}
template <class ELFT>
@@ -1217,6 +1175,39 @@ template <class ELFT> void EHOutputSection<ELFT>::finalize() {
this->Header.sh_size = Off;
}
+template <class ELFT> static uint64_t readFdeAddr(uint8_t *Buf, int Size) {
+ const endianness E = ELFT::TargetEndianness;
+ switch (Size) {
+ case DW_EH_PE_udata2:
+ return read16<E>(Buf);
+ case DW_EH_PE_udata4:
+ return read32<E>(Buf);
+ case DW_EH_PE_udata8:
+ return read64<E>(Buf);
+ case DW_EH_PE_absptr:
+ if (ELFT::Is64Bits)
+ return read64<E>(Buf);
+ return read32<E>(Buf);
+ }
+ fatal("unknown FDE size encoding");
+}
+
+// Returns the VA to which a given FDE (on a mmap'ed buffer) is applied to.
+// We need it to create .eh_frame_hdr section.
+template <class ELFT>
+typename ELFT::uint EHOutputSection<ELFT>::getFdePc(uint8_t *Buf, size_t FdeOff,
+ uint8_t Enc) {
+ // The starting address to which this FDE applies to is
+ // stored at FDE + 8 byte.
+ size_t Off = FdeOff + 8;
+ uint64_t Addr = readFdeAddr<ELFT>(Buf + Off, Enc & 0x7);
+ if ((Enc & 0x70) == DW_EH_PE_absptr)
+ return Addr;
+ if ((Enc & 0x70) == DW_EH_PE_pcrel)
+ return Addr + this->getVA() + Off;
+ fatal("unknown FDE size relative encoding");
+}
+
template <class ELFT> void EHOutputSection<ELFT>::writeTo(uint8_t *Buf) {
const endianness E = ELFT::TargetEndianness;
for (CieRecord *Cie : Cies) {
@@ -1230,12 +1221,22 @@ template <class ELFT> void EHOutputSection<ELFT>::writeTo(uint8_t *Buf) {
// FDE's second word should have the offset to an associated CIE.
// Write it.
write32<E>(Buf + Off + 4, Off + 4 - CieOffset);
- Out<ELFT>::EhFrameHdr->addFde(Cie->FdeEncoding, Off, Buf + Off + 8);
}
}
for (EHInputSection<ELFT> *S : Sections)
S->relocate(Buf, nullptr);
+
+ // Construct .eh_frame_hdr. .eh_frame_hdr is a binary search table
+ // to get a FDE from an address to which FDE is applied to. So here
+ // we obtain two addresses and pass them to EhFrameHdr object.
+ for (CieRecord *Cie : Cies) {
+ for (SectionPiece *Fde : Cie->FdePieces) {
+ uintX_t Pc = getFdePc(Buf, Fde->OutputOff, Cie->FdeEncoding);
+ uintX_t FdeVA = this->getVA() + Fde->OutputOff;
+ Out<ELFT>::EhFrameHdr->addFde(Pc, FdeVA);
+ }
+ }
}
template <class ELFT>
diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h
index 084c2c3d319..61330c77fde 100644
--- a/lld/ELF/OutputSections.h
+++ b/lld/ELF/OutputSections.h
@@ -363,6 +363,8 @@ private:
uint8_t getFdeEncoding(ArrayRef<uint8_t> D);
+ uintX_t getFdePc(uint8_t *Buf, size_t Off, uint8_t Enc);
+
std::vector<EHInputSection<ELFT> *> Sections;
std::vector<CieRecord *> Cies;
@@ -536,8 +538,8 @@ public:
EhFrameHeader();
void writeTo(uint8_t *Buf) override;
- void addFde(uint8_t Enc, size_t Off, uint8_t *PCRel);
- void assignEhFrame(EHOutputSection<ELFT> *Sec);
+ void addFde(uint32_t Pc, uint32_t FdeVA);
+ void add(EHOutputSection<ELFT> *Sec);
void reserveFde();
bool Live = false;
@@ -546,14 +548,13 @@ public:
private:
struct FdeData {
- uint8_t Enc;
- size_t Off;
- uint8_t *PCRel;
+ uint32_t Pc;
+ uint32_t FdeVA;
};
uintX_t getFdePc(uintX_t EhVA, const FdeData &F);
- std::vector<FdeData> FdeList;
+ std::vector<FdeData> Fdes;
};
template <class ELFT> class BuildIdSection : public OutputSectionBase<ELFT> {
diff --git a/lld/test/ELF/eh-frame-hdr-icf.s b/lld/test/ELF/eh-frame-hdr-icf.s
index 09b76458e53..2e7b335fb46 100644
--- a/lld/test/ELF/eh-frame-hdr-icf.s
+++ b/lld/test/ELF/eh-frame-hdr-icf.s
@@ -7,7 +7,7 @@
# CHECK: Contents of section .eh_frame_hdr:
# CHECK-NEXT: 101a0 011b033b b4ffffff 01000000 600e0000
# ^ FDE count
-# CHECK-NEXT: 101b0 e8ffffff 00000000 00000000
+# CHECK-NEXT: 101b0 d0ffffff 00000000 00000000
# ^ FDE for f2
.globl _start, f1, f2
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