[JITLink] Improve llvm-jitlink regression testing support for ELF.

This patch adds a jitlink pass, 'registerELFGraphInfo', that records section
and symbol information about each LinkGraph in the llvm-jitlink session object.
This allows symbols and sections to be referred to by name in llvm-jitlink
regression tests. This will enable a testcase to be written for
https://reviews.llvm.org/D80613.

lib/ExecutionEngine/JITLink/ELF_x86_64.cpp

@@ -344,6 +344,9 @@ void jitLink_ELF_x86_64(std::unique_ptr<JITLinkContext> Ctx) {
   else
     Config.PrePrunePasses.push_back(markAllSymbolsLive);
 
+  if (auto Err = Ctx->modifyPassConfig(TT, Config))
+    return Ctx->notifyFailed(std::move(Err));
+
   ELFJITLinker_x86_64::link(std::move(Ctx), std::move(Config));
 }
 

tools/llvm-jitlink/CMakeLists.txt

@@ -14,6 +14,7 @@ set(LLVM_LINK_COMPONENTS
 
 add_llvm_tool(llvm-jitlink
   llvm-jitlink.cpp
+  llvm-jitlink-elf.cpp
   llvm-jitlink-macho.cpp
   )
 

tools/llvm-jitlink/llvm-jitlink-elf.cpp

@@ -0,0 +1,100 @@
+//===---- llvm-jitlink-elf.cpp -- ELF parsing support for llvm-jitlink ----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// ELF parsing support for llvm-jitlink.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-jitlink.h"
+
+#include "llvm/Support/Error.h"
+#include "llvm/Support/Path.h"
+
+#define DEBUG_TYPE "llvm_jitlink"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+
+namespace llvm {
+
+Error registerELFGraphInfo(Session &S, LinkGraph &G) {
+  auto FileName = sys::path::filename(G.getName());
+  if (S.FileInfos.count(FileName)) {
+    return make_error<StringError>("When -check is passed, file names must be "
+                                   "distinct (duplicate: \"" +
+                                       FileName + "\")",
+                                   inconvertibleErrorCode());
+  }
+
+  auto &FileInfo = S.FileInfos[FileName];
+  LLVM_DEBUG({
+    dbgs() << "Registering ELF file info for \"" << FileName << "\"\n";
+  });
+  for (auto &Sec : G.sections()) {
+    LLVM_DEBUG({
+      dbgs() << "  Section \"" << Sec.getName() << "\": "
+             << (llvm::empty(Sec.symbols()) ? "empty. skipping."
+                                            : "processing...")
+             << "\n";
+    });
+
+    // Skip empty sections.
+    if (llvm::empty(Sec.symbols()))
+      continue;
+
+    if (FileInfo.SectionInfos.count(Sec.getName()))
+      return make_error<StringError>("Encountered duplicate section name \"" +
+                                         Sec.getName() + "\" in \"" + FileName +
+                                         "\"",
+                                     inconvertibleErrorCode());
+
+    bool SectionContainsContent = false;
+    bool SectionContainsZeroFill = false;
+
+    auto *FirstSym = *Sec.symbols().begin();
+    auto *LastSym = FirstSym;
+    for (auto *Sym : Sec.symbols()) {
+      if (Sym->getAddress() < FirstSym->getAddress())
+        FirstSym = Sym;
+      if (Sym->getAddress() > LastSym->getAddress())
+        LastSym = Sym;
+
+      if (Sym->hasName()) {
+        dbgs() << "Symbol: " << Sym->getName() << "\n";
+        if (Sym->isSymbolZeroFill()) {
+          S.SymbolInfos[Sym->getName()] = {Sym->getSize(), Sym->getAddress()};
+          SectionContainsZeroFill = true;
+        } else {
+          S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
+                                           Sym->getAddress()};
+          SectionContainsContent = true;
+        }
+      }
+    }
+
+    JITTargetAddress SecAddr = FirstSym->getAddress();
+    uint64_t SecSize =
+        (LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
+        SecAddr;
+
+    if (SectionContainsZeroFill && SectionContainsContent)
+      return make_error<StringError>("Mixed zero-fill and content sections not "
+                                     "supported yet",
+                                     inconvertibleErrorCode());
+    if (SectionContainsZeroFill)
+      FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr};
+    else
+      FileInfo.SectionInfos[Sec.getName()] = {
+          StringRef(FirstSym->getBlock().getContent().data(), SecSize),
+          SecAddr};
+  }
+
+  return Error::success();
+}
+
+} // end namespace llvm

tools/llvm-jitlink/llvm-jitlink-macho.cpp

@@ -74,7 +74,7 @@ static Expected<Symbol &> getMachOStubTarget(LinkGraph &G, Block &B) {
 
 namespace llvm {
 
-Error registerMachOStubsAndGOT(Session &S, LinkGraph &G) {
+Error registerMachOGraphInfo(Session &S, LinkGraph &G) {
   auto FileName = sys::path::filename(G.getName());
   if (S.FileInfos.count(FileName)) {
     return make_error<StringError>("When -check is passed, file names must be "

tools/llvm-jitlink/llvm-jitlink.cpp

@@ -467,8 +467,13 @@ void Session::modifyPassConfig(const Triple &FTT,
                                PassConfiguration &PassConfig) {
   if (!CheckFiles.empty())
     PassConfig.PostFixupPasses.push_back([this](LinkGraph &G) {
+
+      if (TT.getObjectFormat() == Triple::ELF)
+        return registerELFGraphInfo(*this, G);
+
       if (TT.getObjectFormat() == Triple::MachO)
-        return registerMachOStubsAndGOT(*this, G);
+        return registerMachOGraphInfo(*this, G);
+
       return make_error<StringError>("Unsupported object format for GOT/stub "
                                      "registration",
                                      inconvertibleErrorCode());

tools/llvm-jitlink/llvm-jitlink.h

@@ -69,7 +69,11 @@ private:
   Session(Triple TT, Error &Err);
 };
 
-Error registerMachOStubsAndGOT(Session &S, jitlink::LinkGraph &G);
+/// Record symbols, GOT entries, stubs, and sections for ELF file.
+Error registerELFGraphInfo(Session &S, jitlink::LinkGraph &G);
+
+/// Record symbols, GOT entries, stubs, and sections for MachO file.
+Error registerMachOGraphInfo(Session &S, jitlink::LinkGraph &G);
 
 } // end namespace llvm