From 210e76c6de4c9ffbc2a66f7eaa53434288bb59f2 Mon Sep 17 00:00:00 2001
From: Dmitri Makarov <dmakarov@users.noreply.github.com>
Date: Thu, 4 Feb 2021 08:36:04 +0100
Subject: [PATCH] [SOL] Enable BPF shared object creation

---
 lld/ELF/Arch/BPF.cpp                          | 85 +++++++++++++++++++
 lld/ELF/CMakeLists.txt                        |  1 +
 lld/ELF/Target.cpp                            |  2 +
 lld/ELF/Target.h                              |  1 +
 .../llvm/BinaryFormat/ELFRelocs/BPF.def       |  1 +
 5 files changed, 90 insertions(+)
 create mode 100644 lld/ELF/Arch/BPF.cpp

diff --git a/lld/ELF/Arch/BPF.cpp b/lld/ELF/Arch/BPF.cpp
new file mode 100644
index 00000000000000..aba173e22b979f
--- /dev/null
+++ b/lld/ELF/Arch/BPF.cpp
@@ -0,0 +1,85 @@
+//===- BPF.cpp ------------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InputFiles.h"
+#include "Symbols.h"
+#include "Target.h"
+#include "lld/Common/ErrorHandler.h"
+#include "llvm/Object/ELF.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::object;
+using namespace llvm::support::endian;
+using namespace llvm::ELF;
+
+namespace lld {
+namespace elf {
+
+namespace {
+class BPF final : public TargetInfo {
+public:
+  BPF();
+  RelExpr getRelExpr(RelType type, const Symbol &s,
+                     const uint8_t *loc) const override;
+  RelType getDynRel(RelType type) const override;
+  void relocateOne(uint8_t *loc, RelType type, uint64_t val) const override;
+};
+} // namespace
+
+BPF::BPF() {
+  noneRel = R_BPF_NONE;
+  relativeRel = R_BPF_64_RELATIVE;
+  symbolicRel = R_BPF_64_64;
+}
+
+RelExpr BPF::getRelExpr(RelType type, const Symbol &s,
+                        const uint8_t *loc) const {
+  switch (type) {
+    case R_BPF_64_32:
+      return R_PC;
+    case R_BPF_64_64:
+      return R_ABS;
+    default:
+      error(getErrorLocation(loc) + "unrecognized reloc " + toString(type));
+  }
+  return R_NONE;
+}
+
+RelType BPF::getDynRel(RelType type) const {
+  return type;
+}
+
+void BPF::relocateOne(uint8_t *loc, RelType type, uint64_t val) const {
+  switch (type) {
+    case R_BPF_64_32: {
+      // Relocation of a symbol
+      write32le(loc + 4, ((val - 8) / 8) & 0xFFFFFFFF);
+      break;
+    }
+    case R_BPF_64_64: {
+      // Relocation of a lddw instruction
+      // 64 bit address is divided into the imm of this and the following
+      // instructions, lower 32 first.
+      write32le(loc + 4, val & 0xFFFFFFFF);
+      write32le(loc + 8 + 4, val >> 32);
+      break;
+    }
+    default:
+      error(getErrorLocation(loc) + "unrecognized reloc " + toString(type));
+  }
+}
+
+TargetInfo *getBPFTargetInfo() {
+  static BPF target;
+  return &target;
+}
+
+} // namespace elf
+} // namespace lld
diff --git a/lld/ELF/CMakeLists.txt b/lld/ELF/CMakeLists.txt
index 83d816ddb0601e..1910343cc6a2f9 100644
--- a/lld/ELF/CMakeLists.txt
+++ b/lld/ELF/CMakeLists.txt
@@ -24,6 +24,7 @@ add_lld_library(lldELF
   Arch/AMDGPU.cpp
   Arch/ARM.cpp
   Arch/AVR.cpp
+  Arch/BPF.cpp
   Arch/Hexagon.cpp
   Arch/LoongArch.cpp
   Arch/Mips.cpp
diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
index b7922425a34e43..34b780c1596953 100644
--- a/lld/ELF/Target.cpp
+++ b/lld/ELF/Target.cpp
@@ -60,6 +60,8 @@ TargetInfo *elf::getTarget() {
     return getARMTargetInfo();
   case EM_AVR:
     return getAVRTargetInfo();
+  case EM_BPF:
+    return getBPFTargetInfo();
   case EM_HEXAGON:
     return getHexagonTargetInfo();
   case EM_LOONGARCH:
diff --git a/lld/ELF/Target.h b/lld/ELF/Target.h
index 0cefa318135662..42d146fc1dfc9a 100644
--- a/lld/ELF/Target.h
+++ b/lld/ELF/Target.h
@@ -181,6 +181,7 @@ TargetInfo *getAArch64TargetInfo();
 TargetInfo *getAMDGPUTargetInfo();
 TargetInfo *getARMTargetInfo();
 TargetInfo *getAVRTargetInfo();
+TargetInfo *getBPFTargetInfo();
 TargetInfo *getHexagonTargetInfo();
 TargetInfo *getLoongArchTargetInfo();
 TargetInfo *getMSP430TargetInfo();
diff --git a/llvm/include/llvm/BinaryFormat/ELFRelocs/BPF.def b/llvm/include/llvm/BinaryFormat/ELFRelocs/BPF.def
index cc18a65d1fd2f7..3ec043d5896ced 100644
--- a/llvm/include/llvm/BinaryFormat/ELFRelocs/BPF.def
+++ b/llvm/include/llvm/BinaryFormat/ELFRelocs/BPF.def
@@ -8,4 +8,5 @@ ELF_RELOC(R_BPF_64_64,       1)
 ELF_RELOC(R_BPF_64_ABS64,    2)
 ELF_RELOC(R_BPF_64_ABS32,    3)
 ELF_RELOC(R_BPF_64_NODYLD32, 4)
+ELF_RELOC(R_BPF_64_RELATIVE, 8)  // B + A
 ELF_RELOC(R_BPF_64_32,      10)