[PATCH] D80856: [lld-macho] Support X86_64_RELOC_GOT

[Jez Ng via Phabricator via llvm-commits]

int3 created this revision.
int3 added reviewers: ruiu, pcc, MaskRay, smeenai, alexshap, gkm, Ktwu, christylee.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.
int3 added a child revision: D80857: [lld-macho] Handle GOT relocations of non-dylib symbols.

As far as I can tell, it's identical to _GOT_LOAD. llvm-mc has the following
comment explaining why _GOT exists:

  // x86_64 distinguishes movq foo at GOTPCREL so that the linker can
  // rewrite the movq to an leaq at link time if the symbol ends up in
  // the same linkage unit.

Depends on D80855 <https://reviews.llvm.org/D80855>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80856

Files:
  lld/MachO/Arch/X86_64.cpp
  lld/test/MachO/dylink.s


Index: lld/test/MachO/dylink.s
===================================================================
--- lld/test/MachO/dylink.s
+++ lld/test/MachO/dylink.s
@@ -19,7 +19,7 @@
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/dylink.o
 # RUN: lld -flavor darwinnew -o %t/dylink -Z -L%t -lhello -lgoodbye %t/dylink.o
-# RUN: llvm-objdump --bind -d %t/dylink | FileCheck %s
+# RUN: llvm-objdump --bind -d --no-show-raw-insn %t/dylink | FileCheck %s
 
 # CHECK: movq [[#%u, HELLO_OFF:]](%rip), %rsi
 # CHECK-NEXT: [[#%x, HELLO_RIP:]]:
@@ -27,8 +27,8 @@
 # CHECK: movq [[#%u, HELLO_ITS_ME_OFF:]](%rip), %rsi
 # CHECK-NEXT: [[#%x, HELLO_ITS_ME_RIP:]]:
 
-# CHECK: movq [[#%u, GOODBYE_OFF:]](%rip), %rsi
-# CHECK-NEXT: [[#%x, GOODBYE_RIP:]]:
+# CHECK: pushq [[#%u, GOODBYE_OFF:]](%rip)
+# CHECK-NEXT: [[#%x, GOODBYE_RIP:]]: popq %rsi
 
 # CHECK-LABEL: Bind table:
 # CHECK-DAG: __DATA_CONST __got 0x{{0*}}[[#%x, HELLO_RIP + HELLO_OFF]]               pointer 0 libhello   _hello_world
@@ -53,7 +53,8 @@
 
   movl $0x2000004, %eax # write() syscall
   mov $1, %rdi # stdout
-  movq _goodbye_world at GOTPCREL(%rip), %rsi
+  pushq _goodbye_world at GOTPCREL(%rip)
+  popq %rsi
   mov $15, %rdx # length of str
   syscall
   mov $0, %rax
Index: lld/MachO/Arch/X86_64.cpp
===================================================================
--- lld/MachO/Arch/X86_64.cpp
+++ lld/MachO/Arch/X86_64.cpp
@@ -81,6 +81,7 @@
   case X86_64_RELOC_SIGNED_2:
   case X86_64_RELOC_SIGNED_4:
   case X86_64_RELOC_GOT_LOAD:
+  case X86_64_RELOC_GOT:
     if (!rel.r_pcrel)
       fatal(getErrorLocation(mb, sec, rel) + ": relocations of type " +
             std::to_string(rel.r_type) + " must be pcrel");
@@ -119,6 +120,7 @@
   case X86_64_RELOC_SIGNED_2:
   case X86_64_RELOC_SIGNED_4:
   case X86_64_RELOC_GOT_LOAD:
+  case X86_64_RELOC_GOT:
     // These types are only used for pc-relative relocations, so offset by 4
     // since the RIP has advanced by 4 at this point.
     val -= 4;
@@ -207,13 +209,12 @@
 void X86_64::prepareDylibSymbolRelocation(DylibSymbol &sym, uint8_t type) {
   switch (type) {
   case X86_64_RELOC_GOT_LOAD:
+  case X86_64_RELOC_GOT:
     in.got->addEntry(sym);
     break;
   case X86_64_RELOC_BRANCH:
     in.stubs->addEntry(sym);
     break;
-  case X86_64_RELOC_GOT:
-    fatal("TODO: Unhandled dylib symbol relocation X86_64_RELOC_GOT");
   default:
     llvm_unreachable("Unexpected dylib relocation type");
   }
@@ -222,11 +223,10 @@
 uint64_t X86_64::getDylibSymbolVA(const DylibSymbol &sym, uint8_t type) const {
   switch (type) {
   case X86_64_RELOC_GOT_LOAD:
+  case X86_64_RELOC_GOT:
     return in.got->addr + sym.gotIndex * WordSize;
   case X86_64_RELOC_BRANCH:
     return in.stubs->addr + sym.stubsIndex * sizeof(stub);
-  case X86_64_RELOC_GOT:
-    fatal("TODO: Unhandled dylib symbol relocation X86_64_RELOC_GOT");
   default:
     llvm_unreachable("Unexpected dylib relocation type");
   }


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