[PAC][lld][AArch64][ELF] Support signed TLSDESC (#113817)

Depends on #120010

Support `R_AARCH64_AUTH_TLSDESC_ADR_PAGE21`, `R_AARCH64_AUTH_TLSDESC_LD64_LO12`
and `R_AARCH64_AUTH_TLSDESC_LD64_LO12` static relocations and
`R_AARCH64_AUTH_TLSDESC` dynamic relocation. IE/LE optimization is not
currently supported for AUTH TLSDESC.

Author: kovdan01

lld/ELF/Arch/AArch64.cpp

@@ -157,9 +157,14 @@ RelExpr AArch64::getRelExpr(RelType type, const Symbol &s,
     return RE_AARCH64_AUTH;
   case R_AARCH64_TLSDESC_ADR_PAGE21:
     return RE_AARCH64_TLSDESC_PAGE;
+  case R_AARCH64_AUTH_TLSDESC_ADR_PAGE21:
+    return RE_AARCH64_AUTH_TLSDESC_PAGE;
   case R_AARCH64_TLSDESC_LD64_LO12:
   case R_AARCH64_TLSDESC_ADD_LO12:
     return R_TLSDESC;
+  case R_AARCH64_AUTH_TLSDESC_LD64_LO12:
+  case R_AARCH64_AUTH_TLSDESC_ADD_LO12:
+    return RE_AARCH64_AUTH_TLSDESC;
   case R_AARCH64_TLSDESC_CALL:
     return R_TLSDESC_CALL;
   case R_AARCH64_TLSLE_ADD_TPREL_HI12:
@@ -545,6 +550,7 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
   case R_AARCH64_ADR_PREL_PG_HI21:
   case R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21:
   case R_AARCH64_TLSDESC_ADR_PAGE21:
+  case R_AARCH64_AUTH_TLSDESC_ADR_PAGE21:
     checkInt(ctx, loc, val, 33, rel);
     [[fallthrough]];
   case R_AARCH64_ADR_PREL_PG_HI21_NC:
@@ -597,6 +603,7 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
   case R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC:
   case R_AARCH64_TLSLE_LDST64_TPREL_LO12_NC:
   case R_AARCH64_TLSDESC_LD64_LO12:
+  case R_AARCH64_AUTH_TLSDESC_LD64_LO12:
     checkAlignment(ctx, loc, val, 8, rel);
     write32Imm12(loc, getBits(val, 3, 11));
     break;
@@ -671,6 +678,7 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
     break;
   case R_AARCH64_TLSLE_ADD_TPREL_LO12_NC:
   case R_AARCH64_TLSDESC_ADD_LO12:
+  case R_AARCH64_AUTH_TLSDESC_ADD_LO12:
     write32Imm12(loc, val);
     break;
   case R_AARCH64_TLSDESC:

lld/ELF/InputSection.cpp

@@ -966,12 +966,14 @@ uint64_t InputSectionBase::getRelocTargetVA(Ctx &ctx, const Relocation &r,
   case R_SIZE:
     return r.sym->getSize() + a;
   case R_TLSDESC:
+  case RE_AARCH64_AUTH_TLSDESC:
     return ctx.in.got->getTlsDescAddr(*r.sym) + a;
   case R_TLSDESC_PC:
     return ctx.in.got->getTlsDescAddr(*r.sym) + a - p;
   case R_TLSDESC_GOTPLT:
     return ctx.in.got->getTlsDescAddr(*r.sym) + a - ctx.in.gotPlt->getVA();
   case RE_AARCH64_TLSDESC_PAGE:
+  case RE_AARCH64_AUTH_TLSDESC_PAGE:
     return getAArch64Page(ctx.in.got->getTlsDescAddr(*r.sym) + a) -
            getAArch64Page(p);
   case RE_LOONGARCH_TLSDESC_PAGE_PC:

lld/ELF/Relocations.cpp

@@ -1292,6 +1292,27 @@ static unsigned handleMipsTlsRelocation(Ctx &ctx, RelType type, Symbol &sym,
   return 0;
 }
 
+static unsigned handleAArch64PAuthTlsRelocation(InputSectionBase *sec,
+                                                RelExpr expr, RelType type,
+                                                uint64_t offset, Symbol &sym,
+                                                int64_t addend) {
+  // Do not optimize signed TLSDESC to LE/IE (as described in pauthabielf64).
+  // https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#general-restrictions
+  // > PAUTHELF64 only supports the descriptor based TLS (TLSDESC).
+  if (oneof<RE_AARCH64_AUTH_TLSDESC_PAGE, RE_AARCH64_AUTH_TLSDESC>(expr)) {
+    sym.setFlags(NEEDS_TLSDESC | NEEDS_TLSDESC_AUTH);
+    sec->addReloc({expr, type, offset, addend, &sym});
+    return 1;
+  }
+
+  // TLSDESC_CALL hint relocation should not be emitted by compiler with signed
+  // TLSDESC enabled.
+  if (expr == R_TLSDESC_CALL)
+    sym.setFlags(NEEDS_TLSDESC_NONAUTH);
+
+  return 0;
+}
+
 // Notes about General Dynamic and Local Dynamic TLS models below. They may
 // require the generation of a pair of GOT entries that have associated dynamic
 // relocations. The pair of GOT entries created are of the form GOT[e0] Module
@@ -1302,6 +1323,13 @@ static unsigned handleMipsTlsRelocation(Ctx &ctx, RelType type, Symbol &sym,
 unsigned RelocationScanner::handleTlsRelocation(RelExpr expr, RelType type,
                                                 uint64_t offset, Symbol &sym,
                                                 int64_t addend) {
+  bool isAArch64 = ctx.arg.emachine == EM_AARCH64;
+
+  if (isAArch64)
+    if (unsigned processed = handleAArch64PAuthTlsRelocation(
+            sec, expr, type, offset, sym, addend))
+      return processed;
+
   if (expr == R_TPREL || expr == R_TPREL_NEG) {
     if (ctx.arg.shared) {
       auto diag = Err(ctx);
@@ -1336,7 +1364,9 @@ unsigned RelocationScanner::handleTlsRelocation(RelExpr expr, RelType type,
     // R_RISCV_TLSDESC_{LOAD_LO12,ADD_LO12_I,CALL} reference a label. Do not
     // set NEEDS_TLSDESC on the label.
     if (expr != R_TLSDESC_CALL) {
-      if (!isRISCV || type == R_RISCV_TLSDESC_HI20)
+      if (isAArch64)
+        sym.setFlags(NEEDS_TLSDESC | NEEDS_TLSDESC_NONAUTH);
+      else if (!isRISCV || type == R_RISCV_TLSDESC_HI20)
         sym.setFlags(NEEDS_TLSDESC);
       sec->addReloc({expr, type, offset, addend, &sym});
     }
@@ -1847,10 +1877,21 @@ void elf::postScanRelocations(Ctx &ctx) {
     GotSection *got = ctx.in.got.get();
 
     if (flags & NEEDS_TLSDESC) {
+      if ((flags & NEEDS_TLSDESC_AUTH) && (flags & NEEDS_TLSDESC_NONAUTH)) {
+        Err(ctx)
+            << "both AUTH and non-AUTH TLSDESC entries for '" << sym.getName()
+            << "' requested, but only one type of TLSDESC entry per symbol is "
+               "supported";
+        return;
+      }
       got->addTlsDescEntry(sym);
+      RelType tlsDescRel = ctx.target->tlsDescRel;
+      if (flags & NEEDS_TLSDESC_AUTH) {
+        got->addTlsDescAuthEntry();
+        tlsDescRel = ELF::R_AARCH64_AUTH_TLSDESC;
+      }
       ctx.mainPart->relaDyn->addAddendOnlyRelocIfNonPreemptible(
-          ctx.target->tlsDescRel, *got, got->getTlsDescOffset(sym), sym,
-          ctx.target->tlsDescRel);
+          tlsDescRel, *got, got->getTlsDescOffset(sym), sym, tlsDescRel);
     }
     if (flags & NEEDS_TLSGD) {
       got->addDynTlsEntry(sym);

lld/ELF/Relocations.h

@@ -99,6 +99,8 @@ enum RelExpr {
   RE_AARCH64_PAGE_PC,
   RE_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
   RE_AARCH64_TLSDESC_PAGE,
+  RE_AARCH64_AUTH_TLSDESC_PAGE,
+  RE_AARCH64_AUTH_TLSDESC,
   RE_AARCH64_AUTH,
   RE_ARM_PCA,
   RE_ARM_SBREL,

lld/ELF/Symbols.h

@@ -53,6 +53,8 @@ enum {
   NEEDS_TLSIE = 1 << 8,
   NEEDS_GOT_AUTH = 1 << 9,
   NEEDS_GOT_NONAUTH = 1 << 10,
+  NEEDS_TLSDESC_AUTH = 1 << 11,
+  NEEDS_TLSDESC_NONAUTH = 1 << 12,
 };
 
 // The base class for real symbol classes.

lld/ELF/SyntheticSections.cpp

@@ -681,6 +681,11 @@ bool GotSection::addTlsDescEntry(const Symbol &sym) {
   return true;
 }
 
+void GotSection::addTlsDescAuthEntry() {
+  authEntries.push_back({(numEntries - 2) * ctx.arg.wordsize, true});
+  authEntries.push_back({(numEntries - 1) * ctx.arg.wordsize, false});
+}
+
 bool GotSection::addDynTlsEntry(const Symbol &sym) {
   assert(sym.auxIdx == ctx.symAux.size() - 1);
   ctx.symAux.back().tlsGdIdx = numEntries;

lld/ELF/SyntheticSections.h

@@ -114,6 +114,7 @@ class GotSection final : public SyntheticSection {
   void addEntry(const Symbol &sym);
   void addAuthEntry(const Symbol &sym);
   bool addTlsDescEntry(const Symbol &sym);
+  void addTlsDescAuthEntry();
   bool addDynTlsEntry(const Symbol &sym);
   bool addTlsIndex();
   uint32_t getTlsDescOffset(const Symbol &sym) const;

lld/test/ELF/aarch64-tlsdesc-pauth.s

@@ -0,0 +1,134 @@
+// REQUIRES: aarch64
+// RUN: rm -rf %t && split-file %s %t && cd %t
+
+//--- a.s
+.section .tbss,"awT",@nobits
+.global a
+a:
+.xword 0
+
+//--- ok.s
+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-linux -mattr=+pauth ok.s -o ok.o
+// RUN: ld.lld -shared ok.o -o ok.so
+// RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn ok.so | \
+// RUN:   FileCheck -DP=20 -DA=896 -DB=912 -DC=928 %s
+// RUN: llvm-readobj -r -x .got ok.so | FileCheck --check-prefix=REL \
+// RUN:   -DP1=20 -DA1=380 -DB1=390 -DC1=3A0 -DP2=020 -DA2=380 -DB2=390 -DC2=3a0 %s
+
+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-linux -mattr=+pauth a.s -o a.so.o
+// RUN: ld.lld -shared a.so.o -soname=so -o a.so
+// RUN: ld.lld ok.o a.so -o ok
+// RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn ok | \
+// RUN:   FileCheck -DP=220 -DA=936 -DB=952 -DC=968 %s
+// RUN: llvm-readobj -r -x .got ok | FileCheck --check-prefix=REL \
+// RUN:   -DP1=220 -DA1=3A8 -DB1=3B8 -DC1=3C8 -DP2=220 -DA2=3a8 -DB2=3b8 -DC2=3c8 %s
+
+        .text
+        adrp    x0, :tlsdesc_auth:a
+        ldr     x16, [x0, :tlsdesc_auth_lo12:a]
+        add     x0, x0, :tlsdesc_auth_lo12:a
+        blraa   x16, x0
+
+// CHECK:      adrp    x0, 0x[[P]]000
+// CHECK-NEXT: ldr     x16, [x0, #[[A]]]
+// CHECK-NEXT: add     x0, x0, #[[A]]
+// CHECK-NEXT: blraa   x16, x0
+
+/// Create relocation against local TLS symbols where linker should
+/// create target specific dynamic TLSDESC relocation where addend is
+/// the symbol VMA in tls block.
+
+        adrp    x0, :tlsdesc_auth:local1
+        ldr     x16, [x0, :tlsdesc_auth_lo12:local1]
+        add     x0, x0, :tlsdesc_auth_lo12:local1
+        blraa   x16, x0
+
+// CHECK:      adrp    x0, 0x[[P]]000
+// CHECK-NEXT: ldr     x16, [x0, #[[B]]]
+// CHECK-NEXT: add     x0, x0, #[[B]]
+// CHECK-NEXT: blraa   x16, x0
+
+        adrp    x0, :tlsdesc_auth:local2
+        ldr     x16, [x0, :tlsdesc_auth_lo12:local2]
+        add     x0, x0, :tlsdesc_auth_lo12:local2
+        blraa   x16, x0
+
+// CHECK:      adrp    x0, 0x[[P]]000
+// CHECK-NEXT: ldr     x16, [x0, #[[C]]]
+// CHECK-NEXT: add     x0, x0, #[[C]]
+// CHECK-NEXT: blraa   x16, x0
+
+        .section .tbss,"awT",@nobits
+        .type   local1,@object
+        .p2align 2
+local1:
+        .word   0
+        .size   local1, 4
+
+        .type   local2,@object
+        .p2align 3
+local2:
+        .xword  0
+        .size   local2, 8
+
+
+// R_AARCH64_AUTH_TLSDESC - 0x0 -> start of tls block
+// R_AARCH64_AUTH_TLSDESC - 0x8 -> align (sizeof (local1), 8)
+
+// REL:      Relocations [
+// REL-NEXT:   Section (5) .rela.dyn {
+// REL-NEXT:     0x[[P1]][[B1]] R_AARCH64_AUTH_TLSDESC - 0x0
+// REL-NEXT:     0x[[P1]][[C1]] R_AARCH64_AUTH_TLSDESC - 0x8
+// REL-NEXT:     0x[[P1]][[A1]] R_AARCH64_AUTH_TLSDESC a 0x0
+// REL-NEXT:   }
+// REL-NEXT: ]
+
+// REL:      Hex dump of section '.got':
+// REL-NEXT: 0x00[[P2]][[A2]] 00000000 00000080 00000000 000000a0
+// REL-NEXT: 0x00[[P2]][[B2]] 00000000 00000080 00000000 000000a0
+// REL-NEXT: 0x00[[P2]][[C2]] 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
+
+//--- err1.s
+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-linux -mattr=+pauth err1.s -o err1.o
+// RUN: not ld.lld -shared err1.o 2>&1 | FileCheck --check-prefix=ERR1 --implicit-check-not=error: %s
+// ERR1: error: both AUTH and non-AUTH TLSDESC entries for 'a' requested, but only one type of TLSDESC entry per symbol is supported
+        .text
+        adrp    x0, :tlsdesc_auth:a
+        ldr     x16, [x0, :tlsdesc_auth_lo12:a]
+        add     x0, x0, :tlsdesc_auth_lo12:a
+        blraa   x16, x0
+
+        adrp    x0, :tlsdesc:a
+        ldr     x1, [x0, :tlsdesc_lo12:a]
+        add     x0, x0, :tlsdesc_lo12:a
+        blr     x1
+
+//--- err2.s
+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-linux -mattr=+pauth err2.s -o err2.o
+// RUN: not ld.lld -shared err2.o 2>&1 | FileCheck --check-prefix=ERR2 --implicit-check-not=error: %s
+// ERR2: error: both AUTH and non-AUTH TLSDESC entries for 'a' requested, but only one type of TLSDESC entry per symbol is supported
+        .text
+        adrp    x0, :tlsdesc:a
+        ldr     x1, [x0, :tlsdesc_lo12:a]
+        add     x0, x0, :tlsdesc_lo12:a
+        blr     x1
+
+        adrp    x0, :tlsdesc_auth:a
+        ldr     x16, [x0, :tlsdesc_auth_lo12:a]
+        add     x0, x0, :tlsdesc_auth_lo12:a
+        blraa   x16, x0
+
+//--- err3.s
+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-linux -mattr=+pauth err3.s -o err3.o
+// RUN: not ld.lld -shared err3.o 2>&1 | FileCheck --check-prefix=ERR3 --implicit-check-not=error: %s
+// ERR3: error: both AUTH and non-AUTH TLSDESC entries for 'a' requested, but only one type of TLSDESC entry per symbol is supported
+        .text
+        adrp    x0, :tlsdesc_auth:a
+        ldr     x16, [x0, :tlsdesc_auth_lo12:a]
+        add     x0, x0, :tlsdesc_auth_lo12:a
+        .tlsdesccall a
+        blraa   x16, x0