Add firstSectionByType() and firstSectionByName()

src/main/java/net/fornwall/jelf/ElfFile.java

@@ -137,50 +137,55 @@ public ElfStringTable getSectionNameStringTable() throws ElfException, IOExcepti
 
 	/** Returns the string table associated with this ELF file. */
 	public ElfStringTable getStringTable() throws ElfException, IOException {
-		return findStringTableWithName(ElfSection.STRING_TABLE_NAME);
+		return findStringTableWithName(ElfSection.NAME_STRTAB);
 	}
 
 	/**
 	 * Returns the dynamic symbol table associated with this ELF file, or null if one does not exist.
 	 */
 	public ElfStringTable getDynamicStringTable() throws ElfException, IOException {
-		return findStringTableWithName(ElfSection.DYNAMIC_STRING_TABLE_NAME);
+		return findStringTableWithName(ElfSection.NAME_DYNSTR);
 	}
 
 	private ElfStringTable findStringTableWithName(String tableName) throws ElfException, IOException {
 		// Loop through the section header and look for a section
 		// header with the name "tableName". We can ignore entry 0
 		// since it is defined as being undefined.
-		for (int i = 1; i < num_sh; i++) {
-			ElfSection sh = getSection(i);
-			if (tableName.equals(sh.getName())) return sh.getStringTable();
-		}
-		return null;
+		ElfSection section = firstSectionByName(tableName);
+		return section == null ? null : section.getStringTable();
 	}
 
 	/** The {@link ElfSection#SHT_SYMTAB} section (of which there may be only one), if any. */
-	public ElfSection getSymbolTableSection() throws ElfException, IOException {
-		return (symbolTableSection != null) ? symbolTableSection : (symbolTableSection = getSymbolTableSection(ElfSection.SHT_SYMTAB));
+	public ElfSection firstSectionByType() throws ElfException, IOException {
+		return (symbolTableSection != null) ? symbolTableSection : (symbolTableSection = firstSectionByType(ElfSection.SHT_SYMTAB));
 	}
 
 	/** The {@link ElfSection#SHT_DYNSYM} section (of which there may be only one), if any. */
 	public ElfSection getDynamicSymbolTableSection() throws ElfException, IOException {
-		return (dynamicSymbolTableSection != null) ? dynamicSymbolTableSection : (dynamicSymbolTableSection = getSymbolTableSection(ElfSection.SHT_DYNSYM));
+		return (dynamicSymbolTableSection != null) ? dynamicSymbolTableSection : (dynamicSymbolTableSection = firstSectionByType(ElfSection.SHT_DYNSYM));
 	}
 
 	/** The {@link ElfSection#SHT_DYNAMIC} section (of which there may be only one). Named ".dynamic". */
 	public ElfSection getDynamicLinkSection() throws IOException {
-		return (dynamicLinkSection != null) ? dynamicLinkSection : (dynamicLinkSection = getSymbolTableSection(ElfSection.SHT_DYNAMIC));
+		return (dynamicLinkSection != null) ? dynamicLinkSection : (dynamicLinkSection = firstSectionByType(ElfSection.SHT_DYNAMIC));
 	}
 
-	private ElfSection getSymbolTableSection(int type) throws ElfException, IOException {
+	public ElfSection firstSectionByType(int type) throws ElfException, IOException {
 		for (int i = 1; i < num_sh; i++) {
 			ElfSection sh = getSection(i);
 			if (sh.type == type) return sh;
 		}
 		return null;
 	}
 
+	public ElfSection firstSectionByName(String sectionName) throws ElfException, IOException {
+		for (int i = 1; i < num_sh; i++) {
+			ElfSection sh = getSection(i);
+			if (sectionName.equals(sh.getName())) return sh;
+		}
+		return null;
+	}
+
 	/** Returns the elf symbol with the specified name or null if one is not found. */
 	public ElfSymbol getELFSymbol(String symbolName) throws ElfException, IOException {
 		if (symbolName == null) return null;
@@ -200,7 +205,7 @@ public ElfSymbol getELFSymbol(String symbolName) throws ElfException, IOExceptio
 		}
 
 		// Check symbol table for symbol name.
-		sh = getSymbolTableSection();
+		sh = firstSectionByType();
 		if (sh != null) {
 			int numSymbols = sh.getNumberOfSymbols();
 			for (int i = 0; i < Math.ceil(numSymbols / 2); i++) {
@@ -229,19 +234,19 @@ public ElfSymbol getELFSymbol(long address) throws ElfException, IOException {
 			int numSymbols = sh.getNumberOfSymbols();
 			for (int i = 0; i < numSymbols; i++) {
 				symbol = sh.getELFSymbol(i);
-				value = symbol.value;
-				if (address >= value && address < value + symbol.size) return symbol;
+				value = symbol.st_value;
+				if (address >= value && address < value + symbol.st_size) return symbol;
 			}
 		}
 
 		// Check symbol table for symbol name.
-		sh = getSymbolTableSection();
+		sh = firstSectionByType();
 		if (sh != null) {
 			int numSymbols = sh.getNumberOfSymbols();
 			for (int i = 0; i < numSymbols; i++) {
 				symbol = sh.getELFSymbol(i);
-				value = symbol.value;
-				if (address >= value && address < value + symbol.size) return symbol;
+				value = symbol.st_value;
+				if (address >= value && address < value + symbol.st_size) return symbol;
 			}
 		}
 		return null;

src/main/java/net/fornwall/jelf/ElfSection.java

@@ -4,19 +4,19 @@
 
 /**
  * Class corresponding to the Elf32_Shdr/Elf64_Shdr struct.
- * 
+ *
  * <p>
  * An object file's section header table lets one locate all the file's sections. The section header table is an array
  * of Elf32_Shdr or Elf64_Shdr structures. A section header table index is a subscript into this array. The ELF header's
  * {@link ElfFile#sh_offset e_shoff member} gives the byte offset from the beginning of the file to the section header
  * table with each section header entry being {@link ElfFile#sh_entry_size e_shentsize} bytes big.
- * 
+ *
  * <p>
  * {@link ElfFile#num_sh e_shnum} normally tells how many entries the section header table contains, but if the number
  * of sections is greater than or equal to SHN_LORESERVE (0xff00), e_shnum has the value SHN_UNDEF (0) and the actual
  * number of section header table entries is contained in the sh_size field of the section header at index 0 (otherwise,
  * the sh_size member of the initial entry contains 0).
- * 
+ *
  * <p>
  * Some section header table indexes are reserved in contexts where index size is restricted, for example, the st_shndx
  * member of a symbol table entry and the e_shnum and e_shstrndx members of the ELF header. In such contexts, the
@@ -91,10 +91,21 @@ public final class ElfSection {
 	/** Flag informing that all the bits in the mask are reserved for processor specific semantics. */
 	public static final int FLAG_MASK = 0xf0000000;
 
-	/** Section header name identifying the section as a string table. */
-	public static final String STRING_TABLE_NAME = ".strtab";
-	/** Section header name identifying the section as a dynamic string table. */
-	public static final String DYNAMIC_STRING_TABLE_NAME = ".dynstr";
+	/**
+	 * Name for the section containing the string table.
+	 * <p>
+	 * This section contains a string table which contains names for symbol structures
+	 * by being indexed by the {@link ElfSymbol#st_name} field.
+	 */
+	public static final String NAME_STRTAB = ".strtab";
+	/**
+	 * Name for the section containing the dynamic string table.
+	 */
+	public static final String NAME_DYNSTR = ".dynstr";
+	/**
+	 * Name for the section containing read-only initialized data.
+	 */
+	public static final String NAME_RODATA = ".rodata";
 
 	/** Index into the section header string table which gives the name of the section. */
 	public final int name_ndx; // Elf32_Word or Elf64_Word - 4 bytes in both.

src/main/java/net/fornwall/jelf/ElfSymbol.java

@@ -3,7 +3,29 @@
 import java.io.IOException;
 
 /**
- * Class corresponding to the Elf32_Sym/Elf64_Sym struct.
+ * An entry in the symbol table, which holds information needed to locate and relocate a program's symbolic definitions and references.
+ * <p>
+ * In the elf.h header file the struct definitions are:
+ *
+ * <pre>
+ * typedef struct {
+ *     uint32_t      st_name;
+ *     Elf32_Addr    st_value;
+ *     uint32_t      st_size;
+ *     unsigned char st_info;
+ *     unsigned char st_other;
+ *     uint16_t      st_shndx;
+ * } Elf32_Sym;
+ *
+ * typedef struct {
+ *     uint32_t      st_name;
+ *     unsigned char st_info;
+ *     unsigned char st_other;
+ *     uint16_t      st_shndx;
+ *     Elf64_Addr    st_value;
+ *     uint64_t      st_size;
+ * } Elf64_Sym;
+ * </pre>
  */
 public final class ElfSymbol {
 
@@ -49,22 +71,22 @@ public final class ElfSymbol {
 	 * Index into the symbol string table that holds the character representation of the symbols. 0 means the symbol has
 	 * no character name.
 	 */
-	private final int name_ndx; // Elf32_Word
-	/** Value of the associated symbol. This may be a relativa address for .so or absolute address for other ELFs. */
-	public final long value; // Elf32_Addr
+	public final int st_name; // Elf32_Word
+	/** Value of the associated symbol. This may be a relative address for .so or absolute address for other ELFs. */
+	public final long st_value; // Elf32_Addr
 	/** Size of the symbol. 0 if the symbol has no size or the size is unknown. */
-	public final long size; // Elf32_Word
+	public final long st_size; // Elf32_Word
 	/** Specifies the symbol type and binding attributes. */
-	private final short info; // unsigned char
+	public final short st_info; // unsigned char
 	/** Currently holds the value of 0 and has no meaning. */
-	public final short other; // unsigned char
+	public final short st_other; // unsigned char
 	/**
 	 * Index to the associated section header. This value will need to be read as an unsigned short if we compare it to
 	 * ELFSectionHeader.NDX_LORESERVE and ELFSectionHeader.NDX_HIRESERVE.
 	 */
-	public final short section_header_ndx; // Elf32_Half
+	public final short st_shndx; // Elf32_Half
 
-	private final int section_type;
+	public final int section_type;
 
 	/** Offset from the beginning of the file to this symbol. */
 	public final long offset;
@@ -76,19 +98,19 @@ public final class ElfSymbol {
 		parser.seek(offset);
 		this.offset = offset;
 		if (parser.elfFile.objectSize == ElfFile.CLASS_32) {
-			name_ndx = parser.readInt();
-			value = parser.readInt();
-			size = parser.readInt();
-			info = parser.readUnsignedByte();
-			other = parser.readUnsignedByte();
-			section_header_ndx = parser.readShort();
+			st_name = parser.readInt();
+			st_value = parser.readInt();
+			st_size = parser.readInt();
+			st_info = parser.readUnsignedByte();
+			st_other = parser.readUnsignedByte();
+			st_shndx = parser.readShort();
 		} else {
-			name_ndx = parser.readInt();
-			info = parser.readUnsignedByte();
-			other = parser.readUnsignedByte();
-			section_header_ndx = parser.readShort();
-			value = parser.readLong();
-			size = parser.readLong();
+			st_name = parser.readInt();
+			st_info = parser.readUnsignedByte();
+			st_other = parser.readUnsignedByte();
+			st_shndx = parser.readShort();
+			st_value = parser.readLong();
+			st_size = parser.readLong();
 		}
 
 		this.section_type = section_type;
@@ -115,25 +137,25 @@ public final class ElfSymbol {
 
 	/** Returns the binding for this symbol. */
 	public int getBinding() {
-		return info >> 4;
+		return st_info >> 4;
 	}
 
 	/** Returns the symbol type. */
 	public int getType() {
-		return info & 0x0F;
+		return st_info & 0x0F;
 	}
 
 	/** Returns the name of the symbol or null if the symbol has no name. */
 	public String getName() throws ElfException, IOException {
 		// Check to make sure this symbol has a name.
-		if (name_ndx == 0) return null;
+		if (st_name == 0) return null;
 
 		// Retrieve the name of the symbol from the correct string table.
 		String symbol_name = null;
 		if (section_type == ElfSection.SHT_SYMTAB) {
-			symbol_name = elfHeader.getStringTable().get(name_ndx);
+			symbol_name = elfHeader.getStringTable().get(st_name);
 		} else if (section_type == ElfSection.SHT_DYNSYM) {
-			symbol_name = elfHeader.getDynamicStringTable().get(name_ndx);
+			symbol_name = elfHeader.getDynamicStringTable().get(st_name);
 		}
 		return symbol_name;
 	}
@@ -169,7 +191,7 @@ public String toString() {
 		}
 
 		try {
-			return "ElfSymbol[name=" + getName() + ", type=" + typeString + ", size=" + size + "]";
+			return "ElfSymbol[name=" + getName() + ", type=" + typeString + ", size=" + st_size + "]";
 		} catch (IOException e) {
 			throw new RuntimeException(e);
 		}

src/test/java/net/fornwall/jelf/BasicTest.java

@@ -124,6 +124,10 @@ public void testLinxAmd64BinDash() throws ElfException, FileNotFoundException, I
 		Assert.assertEquals(Collections.singletonList("libc.so.6"), ds.getNeededLibraries());
 
 		Assert.assertEquals("/lib64/ld-linux-x86-64.so.2", file.getInterpreter());
+
+		ElfSection rodata = file.firstSectionByName(ElfSection.NAME_RODATA);
+		Assert.assertNotNull(rodata);
+		Assert.assertEquals(ElfSection.SHT_PROGBITS, rodata.type);
 	}
 
 }