[llvm] [BOLT] Support runtime library hook via DT_INIT_ARRAY (PR #167467)

[Maksim Panchenko via llvm-commits]

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@@ -1448,26 +1536,101 @@ Error RewriteInstance::discoverRtFiniAddress() {
                            "No relocation for first DT_FINI_ARRAY slot");
 }
 
-void RewriteInstance::updateRtFiniReloc() {
+Error RewriteInstance::updateRtInitReloc() {
+  if (BC->HasInterpHeader && opts::RuntimeLibInitHook == opts::RLIH_ENTRY_POINT)
+    return Error::success();
+
+  // Updating DT_INIT is handled by patchELFDynamic.
+  if (BC->InitAddress && opts::RuntimeLibInitHook <= opts::RLIH_INIT)
+    return Error::success();
+
+  const RuntimeLibrary *RT = BC->getRuntimeLibrary();
+  if (!RT || !RT->getRuntimeStartAddress())
+    return Error::success();
+
+  if (!BC->InitArrayAddress)
+    return Error::success();
+
+  if (!BC->InitArrayAddress || !BC->InitArraySize)
+    return createStringError(std::errc::not_supported,
+                             "inconsistent .init_array state");
+
+  ErrorOr<BinarySection &> InitArraySection =
+      BC->getSectionForAddress(*BC->InitArrayAddress);
+  if (!InitArraySection)
+    return createStringError(std::errc::not_supported, ".init_array removed");
+
+  if (std::optional<Relocation> Reloc =
+          InitArraySection->takeDynamicRelocationAt(0)) {
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maksfb wrote:

Same assumption here for offset 0.

https://github.com/llvm/llvm-project/pull/167467