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[ELF][PPC32] Fix canonical PLTs when the order does not match the PLT order 

Reviewed By: Bdragon28

Differential Revision: https://reviews.llvm.org/D75394
This commit is contained in:
Fangrui Song 2020-02-28 17:22:29 -08:00
parent 718cbd394a
commit 00925aadb3
7 changed files with 69 additions and 39 deletions
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11
lld/ELF/Arch/PPC.cpp
View File

@ -76,12 +76,11 @@ void writePPC32GlinkSection(uint8_t *buf, size_t numEntries) {
// non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE.
uint32_t glink = in.plt->getVA(); // VA of .glink
if (!config->isPic) {
for (const Symbol *sym : in.plt->entries)
if (sym->needsPltAddr) {
writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0);
buf += 16;
glink += 16;
}
for (const Symbol *sym : cast<PPC32GlinkSection>(in.plt)->canonical_plts) {
writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0);
buf += 16;
glink += 16;
}
}
// On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an

1
lld/ELF/Relocations.cpp
View File

@ -1226,6 +1226,7 @@ static void processRelocAux(InputSectionBase &sec, RelExpr expr, RelType type,
// PPC32 canonical PLT entries are at the beginning of .glink
cast<Defined>(sym).value = in.plt->headerSize;
in.plt->headerSize += 16;
cast<PPC32GlinkSection>(in.plt)->canonical_plts.push_back(&sym);
}
}
sym.needsPltAddr = true;

25
lld/ELF/SyntheticSections.cpp
View File

@ -2447,12 +2447,9 @@ PltSection::PltSection()
: SyntheticSection(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, 16, ".plt"),
headerSize(target->pltHeaderSize) {
// On PowerPC, this section contains lazy symbol resolvers.
if (config->emachine == EM_PPC || config->emachine == EM_PPC64) {
if (config->emachine == EM_PPC64) {
name = ".glink";
alignment = 4;
// PLTresolve is at the end.
if (config->emachine == EM_PPC)
footerSize = 64;
}
// On x86 when IBT is enabled, this section contains the second PLT (lazy
@ -2468,11 +2465,6 @@ PltSection::PltSection()
}
void PltSection::writeTo(uint8_t *buf) {
if (config->emachine == EM_PPC) {
writePPC32GlinkSection(buf, entries.size());
return;
}
// At beginning of PLT, we have code to call the dynamic
// linker to resolve dynsyms at runtime. Write such code.
target->writePltHeader(buf);
@ -2490,7 +2482,7 @@ void PltSection::addEntry(Symbol &sym) {
}
size_t PltSection::getSize() const {
return headerSize + entries.size() * target->pltEntrySize + footerSize;
return headerSize + entries.size() * target->pltEntrySize;
}
bool PltSection::isNeeded() const {
@ -2544,6 +2536,19 @@ void IpltSection::addSymbols() {
}
}
PPC32GlinkSection::PPC32GlinkSection() {
name = ".glink";
alignment = 4;
}
void PPC32GlinkSection::writeTo(uint8_t *buf) {
writePPC32GlinkSection(buf, entries.size());
}
size_t PPC32GlinkSection::getSize() const {
return headerSize + entries.size() * target->pltEntrySize + footerSize;
}
// This is an x86-only extra PLT section and used only when a security
// enhancement feature called CET is enabled. In this comment, I'll explain what
// the feature is and why we have two PLT sections if CET is enabled.

11
lld/ELF/SyntheticSections.h
View File

@ -684,7 +684,6 @@ public:
size_t getNumEntries() const { return entries.size(); }
size_t headerSize;
size_t footerSize = 0;
std::vector<const Symbol *> entries;
};
@ -705,6 +704,16 @@ public:
void addEntry(Symbol &sym);
};
class PPC32GlinkSection : public PltSection {
public:
PPC32GlinkSection();
void writeTo(uint8_t *buf) override;
size_t getSize() const override;
std::vector<const Symbol *> canonical_plts;
static constexpr size_t footerSize = 64;
};
// This is x86-only.
class IBTPltSection : public SyntheticSection {
public:

3
lld/ELF/Writer.cpp
View File

@ -525,7 +525,8 @@ template <class ELFT> void createSyntheticSections() {
add(in.ibtPlt);
}
in.plt = make<PltSection>();
in.plt = config->emachine == EM_PPC ? make<PPC32GlinkSection>()
: make<PltSection>();
add(in.plt);
in.iplt = make<IpltSection>();
add(in.iplt);

4
lld/test/ELF/Inputs/canonical-plt-pcrel.s
View File

@ -1,5 +1,7 @@
.globl func, ifunc
.globl func, func2, ifunc
.type func, @function
.type func2, @function
.type ifunc, @gnu_indirect_function
func:
func2:
ifunc:

53
lld/test/ELF/ppc32-canonical-plt.s
View File

@ -14,49 +14,59 @@
# REL: Relocations [
# REL-NEXT: .rela.plt {
# REL-NEXT: R_PPC_JMP_SLOT func 0x0
# REL-NEXT: R_PPC_JMP_SLOT ifunc 0x0
# REL-NEXT: 0x10030318 R_PPC_JMP_SLOT func 0x0
# REL-NEXT: 0x1003031C R_PPC_JMP_SLOT func2 0x0
# REL-NEXT: 0x10030320 R_PPC_JMP_SLOT ifunc 0x0
# REL-NEXT: }
# REL-NEXT: ]
# SYM: .glink PROGBITS 100101dc
# SYM: .glink PROGBITS 1001022c
## st_value points to the canonical PLT entry in .glink
# SYM: Symbol table '.dynsym'
# SYM: 100101dc 0 FUNC GLOBAL DEFAULT UND func
# SYM: 100101ec 0 FUNC GLOBAL DEFAULT UND ifunc
# SYM: 1001023c 0 FUNC GLOBAL DEFAULT UND func
# SYM: 1001022c 0 FUNC GLOBAL DEFAULT UND func2
# SYM: 1001024c 0 FUNC GLOBAL DEFAULT UND ifunc
# SYM: Symbol table '.symtab'
# SYM: 100101dc 0 FUNC GLOBAL DEFAULT UND func
# SYM: 100101ec 0 FUNC GLOBAL DEFAULT UND ifunc
# SYM: 1001023c 0 FUNC GLOBAL DEFAULT UND func
# SYM: 1001022c 0 FUNC GLOBAL DEFAULT UND func2
# SYM: 1001024c 0 FUNC GLOBAL DEFAULT UND ifunc
# HEX: 0x100302b4 100101fc 10010200
# HEX: 0x10030318 1001025c 10010260 10010264
## Canonical PLT entry of func2.
## 0x1003031C = 65536*4099+796
# CHECK: 1001022c .glink:
# CHECK-NEXT: lis 11, 4099
# CHECK-NEXT: lwz 11, 796(11)
# CHECK-NEXT: mtctr 11
# CHECK-NEXT: bctr
## Canonical PLT entry of func.
## 0x100101dc + 4*2 + 64 = 0x10010224
## 0x1001021c = 65536*4099+692
# CHECK: 100101dc .glink:
# CHECK-NEXT: lis 11, 4099
# CHECK-NEXT: lwz 11, 692(11)
## 0x10030318 = 65536*4099+792
# CHECK-NEXT: 1001023c: lis 11, 4099
# CHECK-NEXT: lwz 11, 792(11)
# CHECK-NEXT: mtctr 11
# CHECK-NEXT: bctr
## Canonical PLT entry of ifunc.
## 0x10010220 = 65536*4099+696
# CHECK-NEXT: 100101ec: lis 11, 4099
# CHECK-NEXT: lwz 11, 696(11)
## 0x10030320 = 65536*4099+800
# CHECK-NEXT: 1001024c: lis 11, 4099
# CHECK-NEXT: lwz 11, 800(11)
# CHECK-NEXT: mtctr 11
# CHECK-NEXT: bctr
## The 2 b instructions are referenced by .plt entries.
# CHECK-NEXT: 100101fc: b .+8
## The 3 b instructions are referenced by .plt entries.
# CHECK-NEXT: 1001025c: b .+12
# CHECK-NEXT: b .+8
# CHECK-NEXT: b .+4
## PLTresolve of 64 bytes is at the end.
## Operands of addis & addi: -0x100101fc = 65536*-4097-508
## Operands of addis & addi: -0x1001025c = 65536*-4097-604
# CHECK-NEXT: lis 12, 0
# CHECK-NEXT: addis 11, 11, -4097
# CHECK-NEXT: lwz 0, 4(12)
# CHECK-NEXT: addi 11, 11, -508
# CHECK-NEXT: addi 11, 11, -604
# CHECK-NEXT: mtctr 0
# CHECK-NEXT: add 0, 11, 11
# CHECK-NEXT: lwz 12, 8(12)
@ -66,6 +76,9 @@
.globl _start
_start:
b func
lis 3, func2@ha
la 3, func2@l(3)
lis 3, func@ha
la 3, func@l(3)
lis 4, ifunc@ha