[PATCH] D55542: [llvm-xray] Support for PIE

[Petr Hosek via Phabricator via llvm-commits]

phosek updated this revision to Diff 178162.
phosek marked 3 inline comments as done.

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55542/new/

https://reviews.llvm.org/D55542

Files:
  llvm/lib/XRay/InstrumentationMap.cpp
  llvm/test/tools/llvm-xray/X86/Inputs/elf64-pie.bin
  llvm/test/tools/llvm-xray/X86/extract-instrmap-pie.ll


Index: llvm/test/tools/llvm-xray/X86/extract-instrmap-pie.ll
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-xray/X86/extract-instrmap-pie.ll
@@ -0,0 +1,11 @@
+; This test makes sure we can extract the instrumentation map from an
+; XRay-instrumented PIE file.
+;
+; RUN: llvm-xray extract %S/Inputs/elf64-pie.bin -s | FileCheck %s
+
+; CHECK:      ---
+; CHECK-NEXT: - { id: 1, address: 0x00000000000299C0, function: 0x00000000000299C0, kind: function-enter, always-instrument: true, function-name: {{.*foo.*}} }
+; CHECK-NEXT: - { id: 1, address: 0x00000000000299D0, function: 0x00000000000299C0, kind: function-exit, always-instrument: true, function-name: {{.*foo.*}} }
+; CHECK-NEXT: - { id: 2, address: 0x00000000000299E0, function: 0x00000000000299E0, kind: function-enter, always-instrument: true, function-name: {{.*bar.*}} }
+; CHECK-NEXT: - { id: 2, address: 0x00000000000299F6, function: 0x00000000000299E0, kind: function-exit, always-instrument: true, function-name: {{.*bar.*}} }
+; CHECK-NEXT: ...
Index: llvm/lib/XRay/InstrumentationMap.cpp
===================================================================
--- llvm/lib/XRay/InstrumentationMap.cpp
+++ llvm/lib/XRay/InstrumentationMap.cpp
@@ -12,12 +12,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/XRay/InstrumentationMap.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Object/Binary.h"
+#include "llvm/Object/ELFObjectFile.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/DataExtractor.h"
 #include "llvm/Support/Error.h"
@@ -79,6 +81,34 @@
     return errorCodeToError(
         std::make_error_code(std::errc::executable_format_error));
 
+  using RelocMap = DenseMap<uint64_t, uint64_t>;
+  RelocMap Relocs;
+
+  if (ObjFile.getBinary()->isELF()) {
+    uint32_t RelrRelocationType = [](object::ObjectFile *ObjFile) {
+      if (const auto *ELFObj = dyn_cast<object::ELF32LEObjectFile>(ObjFile))
+        return ELFObj->getELFFile()->getRelrRelocationType();
+      else if (const auto *ELFObj = dyn_cast<object::ELF32BEObjectFile>(ObjFile))
+        return ELFObj->getELFFile()->getRelrRelocationType();
+      else if (const auto *ELFObj = dyn_cast<object::ELF64LEObjectFile>(ObjFile))
+        return ELFObj->getELFFile()->getRelrRelocationType();
+      else if (const auto *ELFObj = dyn_cast<object::ELF64BEObjectFile>(ObjFile))
+        return ELFObj->getELFFile()->getRelrRelocationType();
+      else
+        return static_cast<uint32_t>(0);
+    }(ObjFile.getBinary());
+
+    for (const object::SectionRef &Section : Sections) {
+      for (const object::RelocationRef &Reloc : Section.relocations()) {
+        if (Reloc.getType() != RelrRelocationType)
+          continue;
+        auto AddendOrErr = object::ELFRelocationRef(Reloc).getAddend();
+        if (AddendOrErr)
+          Relocs.insert({Reloc.getOffset(), *AddendOrErr});
+      }
+    }
+  }
+
   // Copy the instrumentation map data into the Sleds data structure.
   auto C = Contents.bytes_begin();
   static constexpr size_t ELF64SledEntrySize = 32;
@@ -89,6 +119,16 @@
               "an XRay sled entry in ELF64."),
         std::make_error_code(std::errc::executable_format_error));
 
+  auto RelocateOrElse = [&](uint32_t Offset, uint64_t Address) {
+    if (!Address) {
+      uint64_t A = I->getAddress() + C - Contents.bytes_begin() + Offset;
+      RelocMap::const_iterator R = Relocs.find(A);
+      if (R != Relocs.end())
+        return R->second;
+    }
+    return Address;
+  };
+
   int32_t FuncId = 1;
   uint64_t CurFn = 0;
   for (; C != Contents.bytes_end(); C += ELF64SledEntrySize) {
@@ -98,8 +138,8 @@
     Sleds.push_back({});
     auto &Entry = Sleds.back();
     uint32_t OffsetPtr = 0;
-    Entry.Address = Extractor.getU64(&OffsetPtr);
-    Entry.Function = Extractor.getU64(&OffsetPtr);
+    Entry.Address = RelocateOrElse(OffsetPtr, Extractor.getU64(&OffsetPtr));
+    Entry.Function = RelocateOrElse(OffsetPtr, Extractor.getU64(&OffsetPtr));
     auto Kind = Extractor.getU8(&OffsetPtr);
     static constexpr SledEntry::FunctionKinds Kinds[] = {
         SledEntry::FunctionKinds::ENTRY, SledEntry::FunctionKinds::EXIT,


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