Add arm64 bti pads for range extension thunks.

Large arm64 binaries like chromium use range extension thunks
for accessing plt entries. Add bti landing pads for the
additional indirection.

upstream commit: 60827df765156cee6cca3dc5049388dde9dac1c0

ok kettenis@

diff --git a/gnu/llvm/lld/ELF/Arch/AArch64.cpp b/gnu/llvm/lld/ELF/Arch/AArch64.cpp
index 1ed1227..dcea062 100644 (file)
--- a/gnu/llvm/lld/ELF/Arch/AArch64.cpp
+++ b/gnu/llvm/lld/ELF/Arch/AArch64.cpp
@@ -916,7 +916,8 @@ void AArch64BtiPac::writePlt(uint8_t *buf, const Symbol &sym,
   // escape to shared objects. isInIplt indicates a non-preemptible ifunc. Its
   // address may escape if referenced by a direct relocation. The condition is
   // conservative.
-  bool hasBti = btiHeader && (sym.hasFlag(NEEDS_COPY) || sym.isInIplt);
+  bool hasBti = btiHeader &&
+                (sym.hasFlag(NEEDS_COPY) || sym.isInIplt || sym.thunkAccessed);
   if (hasBti) {
     memcpy(buf, btiData, sizeof(btiData));
     buf += sizeof(btiData);

diff --git a/gnu/llvm/lld/ELF/Symbols.cpp b/gnu/llvm/lld/ELF/Symbols.cpp
index 96ae7a5..5addbaf 100644 (file)
--- a/gnu/llvm/lld/ELF/Symbols.cpp
+++ b/gnu/llvm/lld/ELF/Symbols.cpp
@@ -25,7 +25,7 @@ using namespace llvm::ELF;
 using namespace lld;
 using namespace lld::elf;
 
-static_assert(sizeof(SymbolUnion) <= 64, "SymbolUnion too large");
+static_assert(sizeof(SymbolUnion) <= 72, "SymbolUnion too large");
 
 template <typename T> struct AssertSymbol {
   static_assert(std::is_trivially_destructible<T>(),

diff --git a/gnu/llvm/lld/ELF/Symbols.h b/gnu/llvm/lld/ELF/Symbols.h
index 19ffc8f..865fba3 100644 (file)
--- a/gnu/llvm/lld/ELF/Symbols.h
+++ b/gnu/llvm/lld/ELF/Symbols.h
@@ -295,6 +295,9 @@ public:
   // True if defined in a DSO as protected visibility.
   uint8_t dsoProtected : 1;
 
+  // True if targeted by a range extension thunk.
+  uint8_t thunkAccessed : 1;
+
   // Temporary flags used to communicate which symbol entries need PLT and GOT
   // entries during postScanRelocations();
   std::atomic<uint16_t> flags;

diff --git a/gnu/llvm/lld/ELF/Thunks.cpp b/gnu/llvm/lld/ELF/Thunks.cpp
index 5964196..bed059b 100644 (file)
--- a/gnu/llvm/lld/ELF/Thunks.cpp
+++ b/gnu/llvm/lld/ELF/Thunks.cpp
@@ -1217,7 +1217,9 @@ bool PPC64LongBranchThunk::isCompatibleWith(const InputSection &isec,
   return rel.type == R_PPC64_REL24 || rel.type == R_PPC64_REL14;
 }
 
-Thunk::Thunk(Symbol &d, int64_t a) : destination(d), addend(a), offset(0) {}
+Thunk::Thunk(Symbol &d, int64_t a) : destination(d), addend(a), offset(0) {
+  destination.thunkAccessed = true;
+}
 
 Thunk::~Thunk() = default;