Modify header of object file generated by the LLVM backend to match the target architecture

Author: Zeavee

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/elf/ELFMachine.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -44,8 +44,17 @@ Class<? extends Enum<? extends RelocationMethod>> relocationTypes() {
         Class<? extends Enum<? extends RelocationMethod>> relocationTypes() {
             return ELFAArch64Relocation.class;
         }
+    },
+    RISCV64 {
+        @Override
+        Class<? extends Enum<? extends RelocationMethod>> relocationTypes() {
+            return ELFRISCV64Relocation.class;
+        }
     };
 
+    private static final int NO_FLAGS = 0;
+    private static final int RVC_DOUBLE_FLOAT_ABI = 5;
+
     abstract Class<? extends Enum<? extends RelocationMethod>> relocationTypes();
 
     public static ELFMachine from(String s) {
@@ -56,6 +65,8 @@ public static ELFMachine from(String s) {
             case "arm64":
             case "aarch64":
                 return AArch64;
+            case "riscv64":
+                return RISCV64;
         }
         throw new IllegalStateException("unknown CPU type: " + s);
     }
@@ -129,6 +140,14 @@ public static ELFRelocationMethod getRelocation(ELFMachine m, RelocationKind k)
                         throw new IllegalArgumentException("cannot map unknown relocation kind to an ELF aarch64 relocation type: " + k);
 
                 }
+            case RISCV64:
+                switch (k) {
+                    case DIRECT_8:
+                        return ELFRISCV64Relocation.R_RISCV_64;
+                    default:
+                    case UNKNOWN:
+                        throw new IllegalArgumentException("cannot map unknown relocation kind to an ELF riscv64 relocation type: " + k);
+                }
             default:
                 throw new IllegalStateException("unknown ELF machine type");
         }
@@ -141,6 +160,8 @@ public static ELFMachine from(int m) {
                 return X86_64;
             case 0xB7:
                 return AArch64;
+            case 0xF3:
+                return RISCV64;
             default:
                 throw new IllegalStateException("unknown ELF machine type");
         }
@@ -151,6 +172,8 @@ public short toShort() {
             return 0xB7;
         } else if (this == X86_64) {
             return 0x3E;
+        } else if (this == RISCV64) {
+            return 0xF3;
         } else {
             throw new IllegalStateException("should not reach here");
         }
@@ -159,10 +182,34 @@ public short toShort() {
     public static ELFMachine getSystemNativeValue() {
         if (System.getProperty("os.arch").equals("aarch64")) {
             return AArch64;
+        } else if (System.getProperty("os.arch").equals("riscv64")) {
+            return RISCV64;
         } else {
             return X86_64;
         }
     }
+
+    public int flags() {
+        if (this == AArch64) {
+            /*
+             * e_flags are always 0 for AArch64
+             */
+            return NO_FLAGS;
+        } else if (this == X86_64) {
+            /*
+             * e_flags are always 0 for X86
+             */
+            return NO_FLAGS;
+        } else if (this == RISCV64) {
+            /*
+             * Since we use the most powerful rv64gc model variant, we need to set e_flags to 5,
+             * which are RVC and double-float ABI.
+             */
+            return RVC_DOUBLE_FLOAT_ABI;
+        } else {
+            throw new IllegalStateException("should not reach here");
+        }
+    }
 }
 
 enum ELFX86_64Relocation implements ELFRelocationMethod {
@@ -360,3 +407,72 @@ public long toLong() {
         return code;
     }
 }
+
+enum ELFRISCV64Relocation implements ELFRelocationMethod {
+    R_RISCV_NONE(0),
+    R_RISCV_32(1),
+    R_RISCV_64(2),
+    R_RISCV_RELATIVE(3),
+    R_RISCV_COPY(4),
+    R_RISCV_JUMP_SLOT(5),
+    R_RISCV_TLS_DTPMOD32(6),
+    R_RISCV_TLS_DTPMOD64(7),
+    R_RISCV_TLS_DTPREL32(8),
+    R_RISCV_TLS_DTPREL64(9),
+    R_RISCV_TLS_TPREL32(10),
+    R_RISCV_TLS_TPREL64(11),
+    R_RISCV_BRANCH(16),
+    R_RISCV_JAL(17),
+    R_RISCV_CALL(18),
+    R_RISCV_CALL_PLT(19),
+    R_RISCV_GOT_HI20(20),
+    R_RISCV_TLS_GOT_HI20(21),
+    R_RISCV_TLS_GD_HI20(22),
+    R_RISCV_PCREL_HI20(23),
+    R_RISCV_PCREL_LO12_I(24),
+    R_RISCV_PCREL_LO12_S(25),
+    R_RISCV_HI20(26),
+    R_RISCV_LO12_I(27),
+    R_RISCV_LO12_S(28),
+    R_RISCV_TPREL_HI20(29),
+    R_RISCV_TPREL_LO12_I(30),
+    R_RISCV_TPREL_LO12_S(31),
+    R_RISCV_TPREL_ADD(32),
+    R_RISCV_ADD8(33),
+    R_RISCV_ADD16(34),
+    R_RISCV_ADD32(35),
+    R_RISCV_ADD64(36),
+    R_RISCV_SUB8(37),
+    R_RISCV_SUB16(38),
+    R_RISCV_SUB32(39),
+    R_RISCV_SUB64(40),
+    R_RISCV_GNU_VTINHERIT(41),
+    R_RISCV_GNU_VTENTRY(42),
+    R_RISCV_ALIGN(43),
+    R_RISCV_RVC_BRANCH(44),
+    R_RISCV_RVC_JUMP(45),
+    R_RISCV_RVC_LUI(46),
+    R_RISCV_GPREL_I(47),
+    R_RISCV_GPREL_S(48),
+    R_RISCV_TPREL_I(49),
+    R_RISCV_TPREL_S(50),
+    R_RISCV_RELAX(51),
+    R_RISCV_SUB6(52),
+    R_RISCV_SET6(53),
+    R_RISCV_SET8(54),
+    R_RISCV_SET16(55),
+    R_RISCV_SET32(56),
+    R_RISCV_32_PCREL(57),
+    R_RISCV_NUM(58);
+
+    private final long code;
+
+    ELFRISCV64Relocation(long code) {
+        this.code = code;
+    }
+
+    @Override
+    public long toLong() {
+        return code;
+    }
+}

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/elf/ELFObjectFile.java

@@ -81,15 +81,15 @@ public class ELFObjectFile extends ObjectFile {
     private char abiVersion;
     private ELFClass fileClass = ELFClass.getSystemNativeValue();
     private ELFMachine machine;
-    private long processorSpecificFlags; // FIXME: to encapsulate (EF_* in elf.h)
+    private long processorFlags; // FIXME: to encapsulate (EF_* in elf.h)
     private final boolean runtimeDebugInfoGeneration;
 
     private ELFObjectFile(int pageSize, ELFMachine machine, boolean runtimeDebugInfoGeneration) {
         super(pageSize);
         this.runtimeDebugInfoGeneration = runtimeDebugInfoGeneration;
         // Create the elements of an empty ELF file:
         // 1. create header
-        header = new ELFHeader("ELFHeader");
+        header = new ELFHeader("ELFHeader", machine.flags());
         this.machine = machine;
         // 2. create shstrtab
         shstrtab = new SectionHeaderStrtab();
@@ -584,9 +584,13 @@ public int getWrittenSize() {
         }
 
         public ELFHeader(String name) { // create an "empty" default ELF header
+            this(name, 0);
+        }
+
+        public ELFHeader(String name, int processorFlags) { // create an "empty" default ELF header
             super(name);
             ELFObjectFile.this.version = 1;
-            ELFObjectFile.this.processorSpecificFlags = 0;
+            ELFObjectFile.this.processorFlags = processorFlags;
         }
 
         @Override
@@ -1129,7 +1133,7 @@ public void setMachine(ELFMachine machine) {
     }
 
     public long getFlags() {
-        return processorSpecificFlags;
+        return processorFlags;
     }
 
     @SuppressWarnings("unused")