[PATCH] D101451: [ELF] Implement X86_64::getImplicitAddend()

[Alexander Richardson via Phabricator via llvm-commits]

arichardson created this revision.
arichardson added a reviewer: MaskRay.
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This allows checking dynamic relocation addends for -z rel and
--apply-dynamic-relocs output.

Depends on D101450 <https://reviews.llvm.org/D101450>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101451

Files:
  lld/ELF/Arch/X86_64.cpp
  lld/ELF/Driver.cpp


Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -1385,7 +1385,8 @@
   // enable the debug checks for all targets, but currently not all targets
   // have support for reading Elf_Rel addends, so we only enable for a subset.
 #ifndef NDEBUG
-  bool checkDynamicRelocsDefault = m == EM_ARM || m == EM_386 || m == EM_MIPS;
+  bool checkDynamicRelocsDefault =
+      m == EM_ARM || m == EM_386 || m == EM_MIPS || m == EM_X86_64;
 #else
   bool checkDynamicRelocsDefault = false;
 #endif
Index: lld/ELF/Arch/X86_64.cpp
===================================================================
--- lld/ELF/Arch/X86_64.cpp
+++ lld/ELF/Arch/X86_64.cpp
@@ -37,6 +37,7 @@
                 uint64_t pltEntryAddr) const override;
   void relocate(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
+  int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
   void applyJumpInstrMod(uint8_t *loc, JumpModType type,
                          unsigned size) const override;
 
@@ -674,6 +675,54 @@
   }
 }
 
+int64_t X86_64::getImplicitAddend(const uint8_t *buf, RelType type) const {
+  switch (type) {
+  case R_X86_64_8:
+  case R_X86_64_PC8:
+    return SignExtend64<8>(*buf);
+  case R_X86_64_16:
+  case R_X86_64_PC16:
+    return SignExtend64<16>(read16le(buf));
+  case R_X86_64_32:
+  case R_X86_64_32S:
+  case R_X86_64_TPOFF32:
+  case R_X86_64_GOT32:
+  case R_X86_64_GOTPC32:
+  case R_X86_64_GOTPC32_TLSDESC:
+  case R_X86_64_GOTPCREL:
+  case R_X86_64_GOTPCRELX:
+  case R_X86_64_REX_GOTPCRELX:
+  case R_X86_64_PC32:
+  case R_X86_64_GOTTPOFF:
+  case R_X86_64_PLT32:
+  case R_X86_64_TLSGD:
+  case R_X86_64_TLSLD:
+  case R_X86_64_DTPOFF32:
+  case R_X86_64_SIZE32:
+    return SignExtend64<32>(read32le(buf));
+  case R_X86_64_64:
+  case R_X86_64_TPOFF64:
+  case R_X86_64_DTPOFF64:
+  case R_X86_64_DTPMOD64:
+  case R_X86_64_PC64:
+  case R_X86_64_SIZE64:
+  case R_X86_64_GLOB_DAT:
+  case R_X86_64_GOT64:
+  case R_X86_64_GOTOFF64:
+  case R_X86_64_GOTPC64:
+  case R_X86_64_IRELATIVE:
+  case R_X86_64_RELATIVE:
+    return read64le(buf);
+  case R_X86_64_JUMP_SLOT:
+  case R_X86_64_NONE:
+    return 0; // The stored value at this location is not the addend.
+  default:
+    internalLinkerError(getErrorLocation(buf),
+                        "cannot read addend for relocation " + toString(type));
+    return 0;
+  }
+}
+
 void X86_64::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
   switch (rel.type) {
   case R_X86_64_8:


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