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Unified Diff: lib/MC/MCNaCl.cpp

Issue 15067009: LLVM: Add ELF Note section to NaCl object files identifying them as such to gold (Closed) Base URL: http://git.chromium.org/native_client/pnacl-llvm.git@master
Patch Set: reviews, and add initialization to llvm-mc Created 7 years, 7 months ago
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Index: lib/MC/MCNaCl.cpp
diff --git a/lib/MC/MCNaCl.cpp b/lib/MC/MCNaCl.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..4a6363d6c0b43cfcea08de359341572b3e792a85
--- /dev/null
+++ b/lib/MC/MCNaCl.cpp
@@ -0,0 +1,74 @@
+//===- lib/MC/MCNaCl.cpp - NaCl-specific MC implementation ----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCNaCl.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/Support/ELF.h"
+
+static const char NoteNamespace[] = "NaCl";
+
+namespace llvm {
+void initializeNaClMCStreamer(MCStreamer &Streamer, MCContext &Ctx,
+ const Triple &TheTriple) {
+ assert(TheTriple.isOSNaCl());
+ const char *NoteName;
+ const char *NoteArch;
+ unsigned BundleAlign;
+ switch (TheTriple.getArch()) {
+ case Triple::arm:
+ NoteName = ".note.NaCl.ABI.arm";
+ NoteArch = "arm";
+ BundleAlign = 4;
+ break;
+ case Triple::mipsel:
+ NoteName = ".note.NaCl.ABI.mipsel";
+ NoteArch = "mipsel";
+ BundleAlign = 4;
+ break;
+ case Triple::x86:
+ NoteName = ".note.NaCl.ABI.x86-32";
+ NoteArch = "x86-32";
+ BundleAlign = 5;
+ break;
+ case Triple::x86_64:
+ NoteName = ".note.NaCl.ABI.x86-64";
+ NoteArch = "x86-64";
+ BundleAlign = 5;
+ break;
+ default:
+ report_fatal_error("Unsupported architecture for NaCl");
+ }
+
+ // Set bundle-alignment as required by the NaCl ABI for the target.
+ Streamer.EmitBundleAlignMode(BundleAlign);
+
+ // Emit an ELF Note section in its own COMDAT group which identifies NaCl
+ // object files to the gold linker, so it can use the NaCl layout.
+ const MCSection *Note = Ctx.getELFSection(
+ NoteName, ELF::SHT_NOTE, ELF::SHF_ALLOC | ELF::SHF_GROUP,
+ SectionKind::getReadOnly(), 0, NoteName);
+
+ // TODO(dschuff) This should probably use PushSection and PopSection, but
+ // PopSection will assert if there haven't been any other sections switched to
+ // yet.
+ Streamer.SwitchSection(Note);
+ Streamer.EmitIntValue(strlen(NoteNamespace) + 1, 4);
+ Streamer.EmitIntValue(strlen(NoteArch) + 1, 4);
+ Streamer.EmitIntValue(ELF::NT_VERSION, 4);
+ Streamer.EmitBytes(NoteNamespace);
+ Streamer.EmitIntValue(0, 1); // NUL terminator
+ Streamer.EmitValueToAlignment(4);
+ Streamer.EmitBytes(NoteArch);
+ Streamer.EmitIntValue(0, 1); // NUL terminator
+ Streamer.EmitValueToAlignment(4);
+}
+} // namespace llvm

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