[LLD][ELF][AArch64] Add support for R_AARCH64_LD64_GOTPAGE_LO15 relocation

It is not used by LLVM, but GCC might generates it when compiling
with -fpie, as indicated by PR#40357 [1].

[1] https://bugs.llvm.org/show_bug.cgi?id=40357

lld/ELF/Arch/AArch64.cpp

@@ -147,6 +147,8 @@ 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_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;
@@ -399,6 +401,10 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
     checkAlignment(loc, val, 16, rel);
     or32AArch64Imm(loc, getBits(val, 4, 11));
     break;
+  case R_AARCH64_LD64_GOTPAGE_LO15:
+    checkAlignment(loc, val, 8, rel);
+    or32AArch64Imm(loc, getBits(val, 3, 14));
+    break;
   case R_AARCH64_MOVW_UABS_G0:
     checkUInt(loc, val, 16, rel);
     LLVM_FALLTHROUGH;

lld/ELF/InputSection.cpp

@@ -705,6 +705,8 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
   case R_AARCH64_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:
+    return sym.getGotVA() + a - getAArch64Page(in.got->getVA());
   case R_GOT_PC:
   case R_RELAX_TLS_GD_TO_IE:
     return sym.getGotVA() + a - p;

lld/ELF/Relocations.cpp

@@ -381,8 +381,8 @@ static bool needsPlt(RelExpr expr) {
 // TLS variables uses GOT differently than the regular variables.
 static bool 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>(
-      expr);
+               R_MIPS_GOT_OFF32, R_AARCH64_GOT_PAGE_PC, R_GOT_PC, R_GOTPLT,
+               R_AARCH64_GOT_PAGE>(expr);
 }
 
 // True if this expression is of the form Sym - X, where X is a position in the
@@ -411,7 +411,8 @@ static bool isStaticLinkTimeConstant(RelExpr e, RelType type, const Symbol &sym,
             R_AARCH64_GOT_PAGE_PC, R_GOT_PC, R_GOTONLY_PC, R_GOTPLTONLY_PC,
             R_PLT_PC, R_TLSGD_GOT, R_TLSGD_GOTPLT, R_TLSGD_PC, R_PPC32_PLTREL,
             R_PPC64_CALL_PLT, R_PPC64_RELAX_TOC, R_RISCV_ADD, R_TLSDESC_CALL,
-            R_TLSDESC_PC, R_AARCH64_TLSDESC_PAGE, R_TLSLD_HINT, R_TLSIE_HINT>(
+            R_TLSDESC_PC, R_AARCH64_TLSDESC_PAGE, R_TLSLD_HINT, R_TLSIE_HINT,
+            R_AARCH64_GOT_PAGE>(
           e))
     return true;
 

lld/ELF/Relocations.h

@@ -78,6 +78,7 @@ 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_GOT_PAGE,
   R_AARCH64_PAGE_PC,
   R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
   R_AARCH64_TLSDESC_PAGE,

lld/test/ELF/aarch64-gotpage.s

@@ -0,0 +1,46 @@
+# REQUIRES: aarch64
+# RUN: split-file %s %t
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-unknown-linux %t/test.s -o %t.o
+# RUN: ld.lld -shared --script %t/script %t.o -o %t.so
+# RUN: ld.lld -pie --script %t/script %t.o -o %t.exe
+# RUN: llvm-readobj -r %t.so | FileCheck --check-prefix=RELOCS-SHARED %s
+# RUN: llvm-readobj -r %t.exe | FileCheck --check-prefix=RELOCS-PIE %s
+# RUN: llvm-objdump --no-show-raw-insn -d %t.so | FileCheck --check-prefix=DISAS %s
+
+## Check if the R_AARCH64_LD64_GOTPAGE_LO15 generates the GOT entries.
+# RELOCS-SHARED:      Relocations [
+# RELOCS-SHARED-NEXT:   Section (5) .rela.dyn {
+# RELOCS-SHARED-NEXT:     0x{{[0-9A-F]+}} R_AARCH64_GLOB_DAT global1 0x{{[0-9A-F]+}}
+# RELOCS-SHARED-NEXT:     0x{{[0-9A-F]+}} R_AARCH64_GLOB_DAT global2 0x{{[0-9A-F]+}}
+# RELOCS-SHARED-NEXT:   }
+# RELOCS-SHARED-NEXT: ]
+
+# RELOCS-PIE:      Relocations [
+# RELOCS-PIE-NEXT:   Section (5) .rela.dyn {
+# RELOCS-PIE-NEXT:     0x{{[0-9A-F]+}} R_AARCH64_RELATIVE - 0x{{[0-9A-F]+}}
+# RELOCS-PIE-NEXT:     0x{{[0-9A-F]+}} R_AARCH64_RELATIVE - 0x{{[0-9A-F]+}}
+# RELOCS-PIE-NEXT:   }
+# RELOCS-PIE-NEXT: ]
+
+# DISAS:      adrp    x0, 0xf000
+# DISAS-NEXT: ldr     x0, [x0, #4088]
+# DISAS-NEXT: ldr     x1, [x0, #4096]
+
+#--- script
+SECTIONS {
+  .got (0x10000 - 8) : { *.got }
+}
+
+#--- test.s
+.globl	_start
+.type	_start,@function
+_start:
+	adrp    x0, _GLOBAL_OFFSET_TABLE_
+	ldr     x0, [x0, #:gotpage_lo15:global1]
+	ldr     x1, [x0, #:gotpage_lo15:global2]
+
+.type   global1,@object
+.comm   global1,8,8
+.type   global2,@object
+.comm   global2,8,8