Add initial support of ELF files

1 files changed, 328 insertions, 0 deletions

diff --git a/elf_format.h b/elf_format.h
new file mode 100644
index 0000000..b5a268a
--- /dev/null
+++ b/elf_format.h
@@ -0,0 +1,328 @@
+#pragma once
+
+/* SPDX-License-Identifier: Unlicense
+ */
+
+#include <cstddef>
+#include <cstdint>
+
+namespace ELF {
+
+constexpr size_t kIdentSize = 16;
+constexpr size_t kHeaderSize = kIdentSize + 36;
+constexpr size_t kMagicSize = 4;
+constexpr size_t kProgramHeaderSize = 32;
+
+using Address = uint32_t;
+using Offset = uint32_t;
+
+enum class FileClass : uint8_t {
+    kNone = 0,
+    k32 = 1,
+    k64 = 2,
+    kUnknown,
+};
+
+enum class DataEncoding : uint8_t {
+    kNone = 0,
+    k2LSB = 1,
+    kLE = k2LSB,
+    k2MSB = 2,
+    kBE = k2MSB,
+    kUnknown,
+};
+
+enum class Version : uint8_t {
+    kNone = 0,
+    kCurrent = 1,
+    kUnknown,
+};
+
+static constexpr inline auto ParseFileClass(const uint8_t file_class)
+{
+    switch (file_class) {
+    case static_cast<uint8_t>(FileClass::kNone): return FileClass::kNone;
+    case static_cast<uint8_t>(FileClass::k32): return FileClass::k32;
+    case static_cast<uint8_t>(FileClass::k64): return FileClass::k64;
+    }
+    return FileClass::kUnknown;
+}
+
+static constexpr inline auto ParseDataEncoding(const uint8_t data_encoding)
+{
+    switch (data_encoding) {
+    case static_cast<uint8_t>(DataEncoding::kNone): return DataEncoding::kNone;
+    case static_cast<uint8_t>(DataEncoding::k2LSB): return DataEncoding::k2LSB;
+    case static_cast<uint8_t>(DataEncoding::k2MSB): return DataEncoding::k2MSB;
+    }
+    return DataEncoding::kUnknown;
+}
+
+static constexpr inline auto ParseVersion(const uint8_t version)
+{
+    switch (version) {
+    case static_cast<uint8_t>(Version::kNone): return Version::kNone;
+    case static_cast<uint8_t>(Version::kCurrent): return Version::kCurrent;
+    }
+    return Version::kUnknown;
+}
+
+struct Ident32Raw {
+    uint8_t magic[4];
+    uint8_t file_class;
+    uint8_t data_encoding;
+    uint8_t version;
+    uint8_t os_abi;
+    uint8_t abi_version;
+    uint8_t padding[7];
+    static constexpr auto inline FromBytes(const uint8_t *data)
+    {
+        return Ident32Raw{
+            { data[0], data[1], data[2], data[3] },
+            data[4],
+            data[5],
+            data[6],
+            data[7],
+            data[8],
+            { data[9], data[10], data[11], data[12], data[13], data[14], data[15], },
+        };
+    }
+};
+
+struct Ident32 {
+    uint8_t magic[4];
+    FileClass file_class;
+    DataEncoding data_encoding;
+    Version version;
+    uint8_t os_abi;
+    uint8_t abi_version;
+    static constexpr inline auto FromBytes(const uint8_t *data)
+    {
+        return Ident32{
+            { data[0], data[1], data[2], data[3] },
+            ParseFileClass(data[4]),
+            ParseDataEncoding(data[5]),
+            ParseVersion(data[6]),
+            data[7],
+            data[8],
+        };
+    }
+    static constexpr inline auto FromIdent32Raw(const Ident32Raw raw)
+    {
+        return Ident32{
+            { raw.magic[0], raw.magic[1], raw.magic[2], raw.magic[3] },
+            ParseFileClass(raw.file_class),
+            ParseDataEncoding(raw.data_encoding),
+            ParseVersion(raw.version),
+            raw.os_abi,
+            raw.abi_version,
+        };
+    }
+};
+
+enum class ObjectType : uint16_t {
+    kNone = 0,
+    kRel = 1,
+    kExec = 2,
+    kDyn = 3,
+    kCore = 4,
+    kUnknown = 0x7fff,
+    kLoProc = 0xff00,
+    kHiProc = 0xffff,
+};
+
+enum class Machine : uint16_t {
+    kNone = 0,
+    kM32 = 1,
+    kSPARC = 2,
+    k386 = 3,
+    k68k = 4,
+    k88k = 5,
+    k860 = 7,
+    kMIPS = 8,
+    kUnknown,
+};
+
+static constexpr inline uint16_t ParseU16(const uint8_t *d, DataEncoding e)
+{
+    if (e == DataEncoding::k2MSB) {
+        return uint16_t(d[0]) << 8 | d[1];
+    }
+    return uint16_t(d[1]) << 8 | d[0];
+}
+
+static constexpr inline uint32_t ParseU32(const uint8_t *d, DataEncoding e)
+{
+    if (e == DataEncoding::k2MSB) {
+        return uint32_t(d[0]) << 24 | uint32_t(d[1]) << 16 | uint32_t(d[2]) << 8 | d[3];
+    }
+    return uint32_t(d[3]) << 24 | uint32_t(d[2]) << 16 | uint32_t(d[1]) << 8 | d[0];
+}
+
+static constexpr inline auto ParseObjectType(const uint16_t type)
+{
+    switch (type) {
+    case static_cast<uint16_t>(ObjectType::kNone): return ObjectType::kNone;
+    case static_cast<uint16_t>(ObjectType::kRel): return ObjectType::kRel;
+    case static_cast<uint16_t>(ObjectType::kExec): return ObjectType::kExec;
+    case static_cast<uint16_t>(ObjectType::kDyn): return ObjectType::kDyn;
+    case static_cast<uint16_t>(ObjectType::kCore): return ObjectType::kCore;
+    case static_cast<uint16_t>(ObjectType::kLoProc): return ObjectType::kLoProc;
+    case static_cast<uint16_t>(ObjectType::kHiProc): return ObjectType::kHiProc;
+    }
+    return ObjectType::kUnknown;
+}
+
+static constexpr inline auto ParseMachine(const uint16_t machine)
+{
+    switch (machine) {
+    case static_cast<uint16_t>(Machine::kNone): return Machine::kNone;
+    case static_cast<uint16_t>(Machine::kM32): return Machine::kM32;
+    case static_cast<uint16_t>(Machine::kSPARC): return Machine::kSPARC;
+    case static_cast<uint16_t>(Machine::k386): return Machine::k386;
+    case static_cast<uint16_t>(Machine::k68k): return Machine::k68k;
+    case static_cast<uint16_t>(Machine::k88k): return Machine::k88k;
+    case static_cast<uint16_t>(Machine::k860): return Machine::k860;
+    case static_cast<uint16_t>(Machine::kMIPS): return Machine::kMIPS;
+    }
+    return Machine::kUnknown;
+}
+
+struct Header32Raw {
+    Ident32Raw ident;
+    uint16_t type;
+    uint16_t machine;
+    uint32_t version;
+    Address entry;
+    Offset phoff;
+    Offset shoff;
+    uint32_t flags;
+    uint16_t ehsize;
+    uint16_t phentsize;
+    uint16_t phnum;
+    uint16_t shentsize;
+    uint16_t shnum;
+    uint16_t shstrndx;
+    static constexpr inline auto FromBytes(const uint8_t *data)
+    {
+        const auto ident = Ident32Raw::FromBytes(data);
+        const DataEncoding e = ParseDataEncoding(ident.data_encoding);
+        return Header32Raw{
+            /* .ident */ ident,
+            /* .type */ ParseU16(data + kIdentSize + 0, e),
+            /* .machine */ ParseU16(data + kIdentSize + 2, e),
+            /* .version */ ParseU32(data + kIdentSize + 4, e),
+            /* .entry */ ParseU32(data + kIdentSize + 8, e),
+            /* .phoff */ ParseU32(data + kIdentSize + 12, e),
+            /* .shoff */ ParseU32(data + kIdentSize + 16, e),
+            /* .flags */ ParseU32(data + kIdentSize + 20, e),
+            /* .ehsize */ ParseU16(data + kIdentSize + 24, e),
+            /* .phentsize */ ParseU16(data + kIdentSize + 26, e),
+            /* .phnum */ ParseU16(data + kIdentSize + 28, e),
+            /* .shentsize */ ParseU16(data + kIdentSize + 30, e),
+            /* .shnum */ ParseU16(data + kIdentSize + 32, e),
+            /* .shstrndx */ ParseU16(data + kIdentSize + 34, e),
+        };
+    }
+};
+
+struct Header32 {
+    Ident32 ident;
+    ObjectType type;
+    Machine machine;
+    Version version;
+    Address entry;
+    Offset phoff;
+    Offset shoff;
+    uint32_t flags;
+    uint16_t ehsize;
+    uint16_t phentsize;
+    uint16_t phnum;
+    uint16_t shentsize;
+    uint16_t shnum;
+    uint16_t shstrndx;
+    static constexpr inline auto FromBytes(const uint8_t *data)
+    {
+        const auto raw = Header32Raw::FromBytes(data);
+        return Header32{
+            Ident32::FromIdent32Raw(raw.ident),
+            ParseObjectType(raw.type),
+            ParseMachine(raw.machine),
+            ParseVersion(raw.version),
+            raw.entry,
+            raw.phoff,
+            raw.shoff,
+            raw.flags,
+            raw.ehsize,
+            raw.phentsize,
+            raw.phnum,
+            raw.shentsize,
+            raw.shnum,
+            raw.shstrndx,
+        };
+    }
+};
+
+enum class PHType : uint32_t {
+    kNull = 0,
+    kLoad = 1,
+    kDynamic = 2,
+    kInterp = 3,
+    kNote = 4,
+    kSHLIB = 5,
+    kProgramHeaderTable = 6,
+    kLoProc = 0x70000000,
+    kHiProc = 0x7fffffff,
+    kUnknown,
+};
+
+static constexpr inline auto ParsePHType(const uint32_t type)
+{
+    switch (type) {
+    case static_cast<uint32_t>(PHType::kNull): return PHType::kNull;
+    case static_cast<uint32_t>(PHType::kLoad): return PHType::kLoad;
+    case static_cast<uint32_t>(PHType::kDynamic): return PHType::kDynamic;
+    case static_cast<uint32_t>(PHType::kInterp): return PHType::kInterp;
+    case static_cast<uint32_t>(PHType::kNote): return PHType::kNote;
+    case static_cast<uint32_t>(PHType::kSHLIB): return PHType::kSHLIB;
+    case static_cast<uint32_t>(PHType::kProgramHeaderTable): return PHType::kProgramHeaderTable;
+    case static_cast<uint32_t>(PHType::kLoProc): return PHType::kLoProc;
+    case static_cast<uint32_t>(PHType::kHiProc): return PHType::kHiProc;
+    }
+    return PHType::kUnknown;
+}
+
+constexpr uint32_t kPHFlagX = 1 << 0;
+constexpr uint32_t kPHFlagW = 1 << 1;
+constexpr uint32_t kPHFlagR = 1 << 2;
+
+struct ProgramHeader32 {
+    uint32_t type;
+    Offset offset;
+    Address vaddr;
+    Address paddr;
+    uint32_t filesz;
+    uint32_t memsz;
+    uint32_t flags;
+    uint32_t align;
+    static constexpr inline auto FromBytes(const uint8_t *data, const DataEncoding e)
+    {
+        return ProgramHeader32{
+            /* type */ ParseU32(data + 0, e),
+            /* offset */ ParseU32(data + 4, e),
+            /* vaddr */ ParseU32(data + 8, e),
+            /* paddr */ ParseU32(data + 12, e),
+            /* filesz */ ParseU32(data + 16, e),
+            /* memsz */ ParseU32(data + 20, e),
+            /* flags */ ParseU32(data + 24, e),
+            /* align */ ParseU32(data + 28, e),
+        };
+    }
+};
+
+static constexpr inline bool MagicIsValid(const uint8_t *m)
+{
+    return m[0] == 0x7f && m[1] == 'E' && m[2] == 'L' && m[3] == 'F';
+}
+
+};