Remove elf specific info from ELFWriter.h to Elf.h. Code cleanup and more comments added

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72982 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 186 insertions, 0 deletions

diff --git a/lib/CodeGen/ELF.h b/lib/CodeGen/ELF.h
new file mode 100644
index 0000000000..bf43622a6f
--- /dev/null
+++ b/lib/CodeGen/ELF.h
@@ -0,0 +1,186 @@
+//===-- lib/CodeGen/ELF.h - ELF constants and data structures ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header contains common, non-processor-specific data structures and
+// constants for the ELF file format.
+//
+// The details of the ELF32 bits in this file are largely based on
+// the Tool Interface Standard (TIS) Executable and Linking Format
+// (ELF) Specification Version 1.2, May 1995. The ELF64 stuff is not
+// standardized, as far as I can tell. It was largely based on information
+// I found in OpenBSD header files.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CODEGEN_ELF_H
+#define CODEGEN_ELF_H
+
+#include "llvm/Support/DataTypes.h"
+#include <cstring>
+
+namespace llvm {
+  class GlobalVariable;
+
+  // Identification Indexes
+  enum {
+    EI_MAG0 = 0,
+    EI_MAG1 = 1,
+    EI_MAG2 = 2,
+    EI_MAG3 = 3
+  };
+
+  // File types
+  enum {
+    ET_NONE   = 0,      // No file type
+    ET_REL    = 1,      // Relocatable file
+    ET_EXEC   = 2,      // Executable file
+    ET_DYN    = 3,      // Shared object file
+    ET_CORE   = 4,      // Core file
+    ET_LOPROC = 0xff00, // Beginning of processor-specific codes
+    ET_HIPROC = 0xffff  // Processor-specific
+  };
+
+  // Object file classes.
+  enum {
+    ELFCLASS32 = 1, // 32-bit object file
+    ELFCLASS64 = 2  // 64-bit object file
+  };
+
+  // Object file byte orderings.
+  enum {
+    ELFDATA2LSB = 1, // Little-endian object file
+    ELFDATA2MSB = 2  // Big-endian object file
+  };
+
+  // Versioning
+  enum {
+    EV_NONE = 0,
+    EV_CURRENT = 1
+  };
+
+  /// ELFSection - This struct contains information about each section that is
+  /// emitted to the file.  This is eventually turned into the section header
+  /// table at the end of the file.
+  struct ELFSection {
+
+    // ELF specific fields
+    std::string Name;       // Name of the section.
+    unsigned NameIdx;       // Index in .shstrtab of name, once emitted.
+    unsigned Type;
+    unsigned Flags;
+    uint64_t Addr;
+    unsigned Offset;
+    unsigned Size;
+    unsigned Link;
+    unsigned Info;
+    unsigned Align;
+    unsigned EntSize;
+
+    // Section Header Flags
+    enum {
+      SHF_WRITE            = 1 << 0, // Writable
+      SHF_ALLOC            = 1 << 1, // Mapped into the process addr space
+      SHF_EXECINSTR        = 1 << 2, // Executable
+      SHF_MERGE            = 1 << 4, // Might be merged if equal
+      SHF_STRINGS          = 1 << 5, // Contains null-terminated strings
+      SHF_INFO_LINK        = 1 << 6, // 'sh_info' contains SHT index
+      SHF_LINK_ORDER       = 1 << 7, // Preserve order after combining
+      SHF_OS_NONCONFORMING = 1 << 8, // nonstandard OS support required
+      SHF_GROUP            = 1 << 9, // Section is a member of a group
+      SHF_TLS              = 1 << 10 // Section holds thread-local data
+    };
+
+    // Section Types
+    enum {
+      SHT_NULL     = 0,  // No associated section (inactive entry).
+      SHT_PROGBITS = 1,  // Program-defined contents.
+      SHT_SYMTAB   = 2,  // Symbol table.
+      SHT_STRTAB   = 3,  // String table.
+      SHT_RELA     = 4,  // Relocation entries; explicit addends.
+      SHT_HASH     = 5,  // Symbol hash table.
+      SHT_DYNAMIC  = 6,  // Information for dynamic linking.
+      SHT_NOTE     = 7,  // Information about the file.
+      SHT_NOBITS   = 8,  // Data occupies no space in the file.
+      SHT_REL      = 9,  // Relocation entries; no explicit addends.
+      SHT_SHLIB    = 10, // Reserved.
+      SHT_DYNSYM   = 11, // Symbol table.
+      SHT_LOPROC   = 0x70000000, // Lowest processor architecture-specific type.
+      SHT_HIPROC   = 0x7fffffff, // Highest processor architecture-specific type.
+      SHT_LOUSER   = 0x80000000, // Lowest type reserved for applications.
+      SHT_HIUSER   = 0xffffffff  // Highest type reserved for applications.
+    };
+
+    // Special section indices.
+    enum {
+      SHN_UNDEF     = 0,      // Undefined, missing, irrelevant, or meaningless
+      SHN_LORESERVE = 0xff00, // Lowest reserved index
+      SHN_LOPROC    = 0xff00, // Lowest processor-specific index
+      SHN_HIPROC    = 0xff1f, // Highest processor-specific index
+      SHN_ABS       = 0xfff1, // Symbol has absolute value; does not need relocation
+      SHN_COMMON    = 0xfff2, // FORTRAN COMMON or C external global variables
+      SHN_HIRESERVE = 0xffff  // Highest reserved index
+    };
+
+    /// SectionIdx - The number of the section in the Section Table.
+    unsigned short SectionIdx;
+
+    /// SectionData - The actual data for this section which we are building
+    /// up for emission to the file.
+    std::vector<unsigned char> SectionData;
+
+    ELFSection(const std::string &name)
+      : Name(name), Type(0), Flags(0), Addr(0), Offset(0), Size(0),
+        Link(0), Info(0), Align(0), EntSize(0) {}
+  };
+
+  /// ELFSym - This struct contains information about each symbol that is
+  /// added to logical symbol table for the module.  This is eventually
+  /// turned into a real symbol table in the file.
+  struct ELFSym {
+    const GlobalValue *GV;    // The global value this corresponds to.
+
+    // ELF specific fields
+    unsigned NameIdx;         // Index in .strtab of name, once emitted.
+    uint64_t Value;
+    unsigned Size;
+    uint8_t Info;
+    uint8_t Other;
+    unsigned short SectionIdx;
+
+    enum { 
+      STB_LOCAL = 0,
+      STB_GLOBAL = 1,
+      STB_WEAK = 2 
+    };
+
+    enum { 
+      STT_NOTYPE = 0,
+      STT_OBJECT = 1,
+      STT_FUNC = 2,
+      STT_SECTION = 3,
+      STT_FILE = 4 
+    };
+
+    ELFSym(const GlobalValue *gv) : GV(gv), Value(0),
+                                    Size(0), Info(0), Other(0),
+                                    SectionIdx(ELFSection::SHN_UNDEF) {}
+
+    void SetBind(unsigned X) {
+      assert(X == (X & 0xF) && "Bind value out of range!");
+      Info = (Info & 0x0F) | (X << 4);
+    }
+    void SetType(unsigned X) {
+      assert(X == (X & 0xF) && "Type value out of range!");
+      Info = (Info & 0xF0) | X;
+    }
+  };
+
+} // end namespace llvm
+
+#endif