[lld] [PAC][lld][AArch64][ELF] Support signed GOT (PR #96169)
via llvm-commits
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Thu Jun 20 04:27:23 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lld-elf
Author: Daniil Kovalev (kovdan01)
<details>
<summary>Changes</summary>
Depends on #<!-- -->96164
Support `R_AARCH64_AUTH_ADR_GOT_PAGE`, `R_AARCH64_AUTH_GOT_LO12_NC` and `R_AARCH64_AUTH_GOT_ADD_LO12_NC` GOT-generating relocations. For preemptible symbols, dynamic relocation `R_AARCH64_AUTH_GLOB_DAT` is emitted. Otherwise, we unconditionally emit `R_AARCH64_AUTH_RELATIVE` dynamic relocation since pointers in signed GOT needs to be signed during dynamic link time.
---
Full diff: https://github.com/llvm/llvm-project/pull/96169.diff
8 Files Affected:
- (modified) lld/ELF/Arch/AArch64.cpp (+9)
- (modified) lld/ELF/InputSection.cpp (+2)
- (modified) lld/ELF/Relocations.cpp (+33-9)
- (modified) lld/ELF/Relocations.h (+2)
- (modified) lld/ELF/Symbols.h (+1)
- (modified) lld/ELF/SyntheticSections.cpp (+19)
- (modified) lld/ELF/SyntheticSections.h (+5)
- (added) lld/test/ELF/aarch64-auth-got-relocations.s (+94)
``````````diff
diff --git a/lld/ELF/Arch/AArch64.cpp b/lld/ELF/Arch/AArch64.cpp
index 47e6ea1ff7756..45d21e777f2d8 100644
--- a/lld/ELF/Arch/AArch64.cpp
+++ b/lld/ELF/Arch/AArch64.cpp
@@ -169,11 +169,16 @@ RelExpr AArch64::getRelExpr(RelType type, const Symbol &s,
case R_AARCH64_LD64_GOT_LO12_NC:
case R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC:
return R_GOT;
+ case R_AARCH64_AUTH_GOT_LO12_NC:
+ case R_AARCH64_AUTH_GOT_ADD_LO12_NC:
+ return R_AARCH64_AUTH_GOT;
case R_AARCH64_LD64_GOTPAGE_LO15:
return R_AARCH64_GOT_PAGE;
case R_AARCH64_ADR_GOT_PAGE:
case R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21:
return R_AARCH64_GOT_PAGE_PC;
+ case R_AARCH64_AUTH_ADR_GOT_PAGE:
+ return R_AARCH64_AUTH_GOT_PAGE_PC;
case R_AARCH64_GOTPCREL32:
case R_AARCH64_GOT_LD_PREL19:
return R_GOT_PC;
@@ -225,6 +230,7 @@ int64_t AArch64::getImplicitAddend(const uint8_t *buf, RelType type) const {
return read64(buf + 8);
case R_AARCH64_NONE:
case R_AARCH64_GLOB_DAT:
+ case R_AARCH64_AUTH_GLOB_DAT:
case R_AARCH64_JUMP_SLOT:
return 0;
case R_AARCH64_ABS16:
@@ -430,9 +436,11 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
write64(loc, val);
break;
case R_AARCH64_ADD_ABS_LO12_NC:
+ case R_AARCH64_AUTH_GOT_ADD_LO12_NC:
or32AArch64Imm(loc, val);
break;
case R_AARCH64_ADR_GOT_PAGE:
+ case R_AARCH64_AUTH_ADR_GOT_PAGE:
case R_AARCH64_ADR_PREL_PG_HI21:
case R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21:
case R_AARCH64_TLSDESC_ADR_PAGE21:
@@ -482,6 +490,7 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
break;
case R_AARCH64_LDST64_ABS_LO12_NC:
case R_AARCH64_LD64_GOT_LO12_NC:
+ case R_AARCH64_AUTH_GOT_LO12_NC:
case R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC:
case R_AARCH64_TLSLE_LDST64_TPREL_LO12_NC:
case R_AARCH64_TLSDESC_LD64_LO12:
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index be12218d9948c..f3b54e7f72855 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -694,6 +694,7 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
case R_ARM_SBREL:
return sym.getVA(a) - getARMStaticBase(sym);
case R_GOT:
+ case R_AARCH64_AUTH_GOT:
case R_RELAX_TLS_GD_TO_IE_ABS:
return sym.getGotVA() + a;
case R_LOONGARCH_GOT:
@@ -721,6 +722,7 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
case R_RELAX_TLS_GD_TO_IE_GOT_OFF:
return sym.getGotOffset() + a;
case R_AARCH64_GOT_PAGE_PC:
+ case R_AARCH64_AUTH_GOT_PAGE_PC:
case R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC:
return getAArch64Page(sym.getGotVA() + a) - getAArch64Page(p);
case R_AARCH64_GOT_PAGE:
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 1b08339e3996a..5840b8ead5af0 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -209,8 +209,9 @@ static bool needsPlt(RelExpr expr) {
}
bool lld::elf::needsGot(RelExpr expr) {
- return oneof<R_GOT, R_GOT_OFF, R_MIPS_GOT_LOCAL_PAGE, R_MIPS_GOT_OFF,
- R_MIPS_GOT_OFF32, R_AARCH64_GOT_PAGE_PC, R_GOT_PC, R_GOTPLT,
+ return oneof<R_GOT, R_AARCH64_AUTH_GOT, R_GOT_OFF, R_MIPS_GOT_LOCAL_PAGE,
+ R_MIPS_GOT_OFF, R_MIPS_GOT_OFF32, R_AARCH64_GOT_PAGE_PC,
+ R_AARCH64_AUTH_GOT_PAGE_PC, R_GOT_PC, R_GOTPLT,
R_AARCH64_GOT_PAGE, R_LOONGARCH_GOT, R_LOONGARCH_GOT_PAGE_PC>(
expr);
}
@@ -924,13 +925,25 @@ void elf::addGotEntry(Symbol &sym) {
// If preemptible, emit a GLOB_DAT relocation.
if (sym.isPreemptible) {
- mainPart->relaDyn->addReloc({target->gotRel, in.got.get(), off,
+ RelType gotRel = target->gotRel;
+ if (sym.hasFlag(NEEDS_GOT_AUTH)) {
+ assert(config->emachine == EM_AARCH64);
+ gotRel = R_AARCH64_AUTH_GLOB_DAT;
+ }
+ mainPart->relaDyn->addReloc({gotRel, in.got.get(), off,
DynamicReloc::AgainstSymbol, sym, 0, R_ABS});
return;
}
// Otherwise, the value is either a link-time constant or the load base
- // plus a constant.
+ // plus a constant. Signed GOT requires dynamic relocation.
+ if (sym.hasFlag(NEEDS_GOT_AUTH)) {
+ in.got->getPartition().relaDyn->addReloc(
+ {R_AARCH64_AUTH_RELATIVE, in.got.get(), off,
+ DynamicReloc::AddendOnlyWithTargetVA, sym, 0, R_ABS});
+ return;
+ }
+
if (!config->isPic || isAbsolute(sym))
in.got->addConstant({R_ABS, target->symbolicRel, off, 0, &sym});
else
@@ -983,10 +996,11 @@ bool RelocationScanner::isStaticLinkTimeConstant(RelExpr e, RelType type,
// These expressions always compute a constant
if (oneof<R_GOTPLT, R_GOT_OFF, R_RELAX_HINT, R_MIPS_GOT_LOCAL_PAGE,
R_MIPS_GOTREL, R_MIPS_GOT_OFF, R_MIPS_GOT_OFF32, R_MIPS_GOT_GP_PC,
- R_AARCH64_GOT_PAGE_PC, R_GOT_PC, R_GOTONLY_PC, R_GOTPLTONLY_PC,
- R_PLT_PC, R_PLT_GOTREL, R_PLT_GOTPLT, R_GOTPLT_GOTREL, R_GOTPLT_PC,
- R_PPC32_PLTREL, R_PPC64_CALL_PLT, R_PPC64_RELAX_TOC, R_RISCV_ADD,
- R_AARCH64_GOT_PAGE, R_LOONGARCH_PLT_PAGE_PC, R_LOONGARCH_GOT,
+ R_AARCH64_GOT_PAGE_PC, R_AARCH64_AUTH_GOT_PAGE_PC, R_GOT_PC,
+ R_GOTONLY_PC, R_GOTPLTONLY_PC, R_PLT_PC, R_PLT_GOTREL, R_PLT_GOTPLT,
+ R_GOTPLT_GOTREL, R_GOTPLT_PC, R_PPC32_PLTREL, R_PPC64_CALL_PLT,
+ R_PPC64_RELAX_TOC, R_RISCV_ADD, R_AARCH64_GOT_PAGE,
+ R_AARCH64_AUTH_GOT, R_LOONGARCH_PLT_PAGE_PC, R_LOONGARCH_GOT,
R_LOONGARCH_GOT_PAGE_PC>(e))
return true;
@@ -1099,7 +1113,17 @@ void RelocationScanner::processAux(RelExpr expr, RelType type, uint64_t offset,
} else if (!sym.isTls() || config->emachine != EM_LOONGARCH) {
// Many LoongArch TLS relocs reuse the R_LOONGARCH_GOT type, in which
// case the NEEDS_GOT flag shouldn't get set.
- sym.setFlags(NEEDS_GOT);
+ bool needsGotAuth =
+ (expr == R_AARCH64_AUTH_GOT || expr == R_AARCH64_AUTH_GOT_PAGE_PC);
+ if (!sym.hasFlag(NEEDS_GOT)) {
+ sym.setFlags(NEEDS_GOT);
+ if (needsGotAuth)
+ sym.setFlags(NEEDS_GOT_AUTH);
+ } else if (needsGotAuth != sym.hasFlag(NEEDS_GOT_AUTH)) {
+ fatal("both AUTH and non-AUTH GOT entries for '" + sym.getName() +
+ "' requested, but only one type of GOT entry per symbol is "
+ "supported");
+ }
}
} else if (needsPlt(expr)) {
sym.setFlags(NEEDS_PLT);
diff --git a/lld/ELF/Relocations.h b/lld/ELF/Relocations.h
index e299d23dd7db3..fb1973b19f485 100644
--- a/lld/ELF/Relocations.h
+++ b/lld/ELF/Relocations.h
@@ -83,7 +83,9 @@ enum RelExpr {
// of a relocation type, there are some relocations whose semantics are
// unique to a target. Such relocation are marked with R_<TARGET_NAME>.
R_AARCH64_GOT_PAGE_PC,
+ R_AARCH64_AUTH_GOT_PAGE_PC,
R_AARCH64_GOT_PAGE,
+ R_AARCH64_AUTH_GOT,
R_AARCH64_PAGE_PC,
R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
R_AARCH64_TLSDESC_PAGE,
diff --git a/lld/ELF/Symbols.h b/lld/ELF/Symbols.h
index c65c5d6cd0dca..c8aa3d937af0e 100644
--- a/lld/ELF/Symbols.h
+++ b/lld/ELF/Symbols.h
@@ -54,6 +54,7 @@ enum {
NEEDS_TLSGD_TO_IE = 1 << 6,
NEEDS_GOT_DTPREL = 1 << 7,
NEEDS_TLSIE = 1 << 8,
+ NEEDS_GOT_AUTH = 1 << 9,
};
// Some index properties of a symbol are stored separately in this auxiliary
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index cc423d152e912..b4212b4962634 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -655,6 +655,10 @@ void GotSection::addConstant(const Relocation &r) { relocations.push_back(r); }
void GotSection::addEntry(const Symbol &sym) {
assert(sym.auxIdx == symAux.size() - 1);
symAux.back().gotIdx = numEntries++;
+ if (sym.hasFlag(NEEDS_GOT_AUTH)) {
+ assert(config->emachine == EM_AARCH64);
+ authEntries.push_back({(numEntries - 1) * config->wordsize, sym.isFunc()});
+ }
}
bool GotSection::addTlsDescEntry(const Symbol &sym) {
@@ -718,6 +722,21 @@ void GotSection::writeTo(uint8_t *buf) {
return;
target->writeGotHeader(buf);
target->relocateAlloc(*this, buf);
+ for (const AuthEntryInfo &authEntry : authEntries) {
+ // https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#default-signing-schema
+ // Signed GOT entries use the IA key for symbols of type STT_FUNC and the
+ // DA key for all other symbol types, with the address of the GOT entry as
+ // the modifier. The static linker must encode the signing schema into the
+ // GOT slot.
+ //
+ // https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#encoding-the-signing-schema
+ // If address diversity is set and the discriminator
+ // is 0 then modifier = Place
+ uint8_t *dest = buf + authEntry.offset;
+ uint64_t key = authEntry.isSymbolFunc ? /*IA*/ 0b00 : /*DA*/ 0b10;
+ uint64_t addrDiversity = 1;
+ write64(dest, (addrDiversity << 63) | (key << 60));
+ }
}
static uint64_t getMipsPageAddr(uint64_t addr) {
diff --git a/lld/ELF/SyntheticSections.h b/lld/ELF/SyntheticSections.h
index 34949025a45f7..7cc6a34c5dc8a 100644
--- a/lld/ELF/SyntheticSections.h
+++ b/lld/ELF/SyntheticSections.h
@@ -131,6 +131,11 @@ class GotSection final : public SyntheticSection {
size_t numEntries = 0;
uint32_t tlsIndexOff = -1;
uint64_t size = 0;
+ struct AuthEntryInfo {
+ size_t offset;
+ bool isSymbolFunc;
+ };
+ SmallVector<AuthEntryInfo> authEntries;
};
// .note.GNU-stack section.
diff --git a/lld/test/ELF/aarch64-auth-got-relocations.s b/lld/test/ELF/aarch64-auth-got-relocations.s
new file mode 100644
index 0000000000000..f04e3d953388c
--- /dev/null
+++ b/lld/test/ELF/aarch64-auth-got-relocations.s
@@ -0,0 +1,94 @@
+# REQUIRES: aarch64
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux %p/Inputs/shared.s -o a.o
+# RUN: ld.lld -shared a.o -o a.so
+
+#--- ok.s
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux ok.s -o ok.o
+
+# RUN: ld.lld ok.o a.so -pie -o external
+# RUN: llvm-readelf -r -S -x .got external | FileCheck %s --check-prefix=EXTERNAL
+
+# RUN: ld.lld ok.o a.o -pie -o local
+# RUN: llvm-readelf -r -S -x .got -s local | FileCheck %s --check-prefix=LOCAL
+
+# EXTERNAL: Offset Info Type Symbol's Value Symbol's Name + Addend
+# EXTERNAL-NEXT: 0000000000020380 000000010000e201 R_AARCH64_AUTH_GLOB_DAT 0000000000000000 bar + 0
+# EXTERNAL-NEXT: 0000000000020388 000000020000e201 R_AARCH64_AUTH_GLOB_DAT 0000000000000000 zed + 0
+
+## Symbol's values for bar and zed are equal since they contain no content (see Inputs/shared.s)
+# LOCAL: Offset Info Type Symbol's Value Symbol's Name + Addend
+# LOCAL-NEXT: 0000000000020320 0000000000000411 R_AARCH64_AUTH_RELATIVE 10260
+# LOCAL-NEXT: 0000000000020328 0000000000000411 R_AARCH64_AUTH_RELATIVE 10260
+
+# EXTERNAL: Hex dump of section '.got':
+# EXTERNAL-NEXT: 0x00020380 00000000 00000080 00000000 000000a0
+# ^^
+# 0b10000000 bit 63 address diversity = true, bits 61..60 key = IA
+# ^^
+# 0b10100000 bit 63 address diversity = true, bits 61..60 key = DA
+
+# LOCAL: Symbol table '.symtab' contains {{.*}} entries:
+# LOCAL: Num: Value Size Type Bind Vis Ndx Name
+# LOCAL: 0000000000010260 0 FUNC GLOBAL DEFAULT 6 bar
+# LOCAL: 0000000000010260 0 NOTYPE GLOBAL DEFAULT 6 zed
+
+# LOCAL: Hex dump of section '.got':
+# LOCAL-NEXT: 0x00020320 00000000 00000080 00000000 000000a0
+# ^^
+# 0b10000000 bit 63 address diversity = true, bits 61..60 key = IA
+# ^^
+# 0b10100000 bit 63 address diversity = true, bits 61..60 key = DA
+
+# RUN: llvm-objdump -d external | FileCheck %s --check-prefix=EXTERNAL-ASM
+
+# EXTERNAL-ASM: <_start>:
+# EXTERNAL-ASM-NEXT: adrp x0, 0x20000
+# EXTERNAL-ASM-NEXT: ldr x0, [x0, #0x380]
+# EXTERNAL-ASM-NEXT: adrp x1, 0x20000
+# EXTERNAL-ASM-NEXT: add x1, x1, #0x380
+# EXTERNAL-ASM-NEXT: adrp x0, 0x20000
+# EXTERNAL-ASM-NEXT: ldr x0, [x0, #0x388]
+# EXTERNAL-ASM-NEXT: adrp x1, 0x20000
+# EXTERNAL-ASM-NEXT: add x1, x1, #0x388
+
+# RUN: llvm-objdump -d local | FileCheck %s --check-prefix=LOCAL-ASM
+
+# LOCAL-ASM: <_start>:
+# LOCAL-ASM-NEXT: adrp x0, 0x20000
+# LOCAL-ASM-NEXT: ldr x0, [x0, #0x320]
+# LOCAL-ASM-NEXT: adrp x1, 0x20000
+# LOCAL-ASM-NEXT: add x1, x1, #0x320
+# LOCAL-ASM-NEXT: adrp x0, 0x20000
+# LOCAL-ASM-NEXT: ldr x0, [x0, #0x328]
+# LOCAL-ASM-NEXT: adrp x1, 0x20000
+# LOCAL-ASM-NEXT: add x1, x1, #0x328
+
+.globl _start
+_start:
+ adrp x0, :got_auth:bar
+ ldr x0, [x0, :got_auth_lo12:bar]
+ adrp x1, :got_auth:bar
+ add x1, x1, :got_auth_lo12:bar
+ adrp x0, :got_auth:zed
+ ldr x0, [x0, :got_auth_lo12:zed]
+ adrp x1, :got_auth:zed
+ add x1, x1, :got_auth_lo12:zed
+
+#--- err.s
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux err.s -o err.o
+
+# RUN: not ld.lld err.o a.so -pie -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
+
+# ERR: error: both AUTH and non-AUTH GOT entries for 'bar' requested, but only one type of GOT entry per symbol is supported
+
+.globl _start
+_start:
+ adrp x0, :got_auth:bar
+ ldr x0, [x0, :got_auth_lo12:bar]
+ adrp x0, :got:bar
+ ldr x0, [x0, :got_lo12:bar]
``````````
</details>
https://github.com/llvm/llvm-project/pull/96169
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