* 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. - * + * *
* {@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). - * + * *
* 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. + *
+ * 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. diff --git a/src/main/java/net/fornwall/jelf/ElfSymbol.java b/src/main/java/net/fornwall/jelf/ElfSymbol.java index a8f8e8a..637afc3 100644 --- a/src/main/java/net/fornwall/jelf/ElfSymbol.java +++ b/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. + *
+ * In the elf.h header file the struct definitions are: + * + *
+ * 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;
+ *
*/
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);
}
diff --git a/src/test/java/net/fornwall/jelf/BasicTest.java b/src/test/java/net/fornwall/jelf/BasicTest.java
index a59f7ef..16fdc50 100644
--- a/src/test/java/net/fornwall/jelf/BasicTest.java
+++ b/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);
}
}