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//! Parsing symbol table sections: `.symtab`, `.dynsym`
use crate::abi;
use crate::endian::EndianParse;
use crate::file::Class;
use crate::parse::{ParseAt, ParseError, ParsingTable};
pub type SymbolTable<'data, E> = ParsingTable<'data, E, Symbol>;
/// C-style 32-bit ELF Symbol definition
///
/// These C-style definitions are for users who want to implement their own ELF manipulation logic.
#[derive(Debug)]
#[repr(C)]
pub struct Elf32_Sym {
pub st_name: u32,
pub st_value: u32,
pub st_size: u32,
pub st_info: u8,
pub st_other: u8,
pub st_shndx: u32,
}
/// C-style 64-bit ELF Symbol definition
///
/// These C-style definitions are for users who want to implement their own ELF manipulation logic.
#[derive(Debug)]
#[repr(C)]
pub struct Elf64_Sym {
pub st_name: u32,
pub st_info: u8,
pub st_other: u8,
pub st_shndx: u16,
pub st_value: u64,
pub st_size: u64,
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Symbol {
/// This member holds an index into the symbol table's string table,
/// which holds the character representations of the symbol names. If the
/// value is non-zero, it represents a string table index that gives the
/// symbol name. Otherwise, the symbol table entry has no name.
pub st_name: u32,
/// Every symbol table entry is defined in relation to some section. This
/// member holds the relevant section header table index. As the sh_link and
/// sh_info interpretation table and the related text describe, some section
/// indexes indicate special meanings.
///
/// If this member contains SHN_XINDEX, then the actual section header index
/// is too large to fit in this field. The actual value is contained in the
/// associated section of type SHT_SYMTAB_SHNDX.
pub st_shndx: u16,
/// This member specifies the symbol's type and binding attributes.
pub st_info: u8,
/// This member currently specifies a symbol's visibility.
pub st_other: u8,
/// This member gives the value of the associated symbol. Depending on the
/// context, this may be an absolute value, an address, and so on.
///
/// * In relocatable files, st_value holds alignment constraints for a
/// symbol whose section index is SHN_COMMON.
/// * In relocatable files, st_value holds a section offset for a defined
/// symbol. st_value is an offset from the beginning of the section that
/// st_shndx identifies.
/// * In executable and shared object files, st_value holds a virtual
/// address. To make these files' symbols more useful for the dynamic
/// linker, the section offset (file interpretation) gives way to a
/// virtual address (memory interpretation) for which the section number
/// is irrelevant.
pub st_value: u64,
/// This member gives the symbol's size.
/// For example, a data object's size is the number of bytes contained in
/// the object. This member holds 0 if the symbol has no size or an unknown
/// size.
pub st_size: u64,
}
impl Symbol {
/// Returns true if a symbol is undefined in this ELF object.
///
/// When linking and loading, undefined symbols in this object get linked to
/// a defined symbol in another object.
pub fn is_undefined(&self) -> bool {
self.st_shndx == abi::SHN_UNDEF
}
pub fn st_symtype(&self) -> u8 {
self.st_info & 0xf
}
pub fn st_bind(&self) -> u8 {
self.st_info >> 4
}
pub fn st_vis(&self) -> u8 {
self.st_other & 0x3
}
}
impl ParseAt for Symbol {
fn parse_at<E: EndianParse>(
endian: E,
class: Class,
offset: &mut usize,
data: &[u8],
) -> Result<Self, ParseError> {
let st_name: u32;
let st_value: u64;
let st_size: u64;
let st_shndx: u16;
let st_info: u8;
let st_other: u8;
if class == Class::ELF32 {
st_name = endian.parse_u32_at(offset, data)?;
st_value = endian.parse_u32_at(offset, data)? as u64;
st_size = endian.parse_u32_at(offset, data)? as u64;
st_info = endian.parse_u8_at(offset, data)?;
st_other = endian.parse_u8_at(offset, data)?;
st_shndx = endian.parse_u16_at(offset, data)?;
} else {
st_name = endian.parse_u32_at(offset, data)?;
st_info = endian.parse_u8_at(offset, data)?;
st_other = endian.parse_u8_at(offset, data)?;
st_shndx = endian.parse_u16_at(offset, data)?;
st_value = endian.parse_u64_at(offset, data)?;
st_size = endian.parse_u64_at(offset, data)?;
}
Ok(Symbol {
st_name,
st_value,
st_size,
st_shndx,
st_info,
st_other,
})
}
#[inline]
fn size_for(class: Class) -> usize {
match class {
Class::ELF32 => 16,
Class::ELF64 => 24,
}
}
}
#[cfg(test)]
mod symbol_tests {
use super::*;
#[test]
fn symbol_undefined() {
let undef_sym = Symbol {
st_name: 0,
st_value: 0,
st_size: 0,
st_shndx: 0,
st_info: 0,
st_other: 0,
};
assert!(undef_sym.is_undefined());
let def_sym = Symbol {
st_name: 0,
st_value: 0,
st_size: 0,
st_shndx: 42,
st_info: 0,
st_other: 0,
};
assert!(!def_sym.is_undefined());
}
}
#[cfg(test)]
mod parse_tests {
use super::*;
use crate::endian::{BigEndian, LittleEndian};
use crate::parse::{test_parse_for, test_parse_fuzz_too_short};
#[test]
fn parse_sym32_lsb() {
test_parse_for(
LittleEndian,
Class::ELF32,
Symbol {
st_name: 0x03020100,
st_value: 0x07060504,
st_size: 0x0B0A0908,
st_shndx: 0x0F0E,
st_info: 0x0C,
st_other: 0x0D,
},
);
}
#[test]
fn parse_sym32_msb() {
test_parse_for(
BigEndian,
Class::ELF32,
Symbol {
st_name: 0x00010203,
st_value: 0x04050607,
st_size: 0x08090A0B,
st_shndx: 0x0E0F,
st_info: 0x0C,
st_other: 0x0D,
},
);
}
#[test]
fn parse_sym64_lsb() {
test_parse_for(
LittleEndian,
Class::ELF64,
Symbol {
st_name: 0x03020100,
st_value: 0x0F0E0D0C0B0A0908,
st_size: 0x1716151413121110,
st_shndx: 0x0706,
st_info: 0x04,
st_other: 0x05,
},
);
}
#[test]
fn parse_sym64_msb() {
test_parse_for(
BigEndian,
Class::ELF64,
Symbol {
st_name: 0x00010203,
st_value: 0x08090A0B0C0D0E0F,
st_size: 0x1011121314151617,
st_shndx: 0x0607,
st_info: 0x04,
st_other: 0x05,
},
);
}
#[test]
fn parse_sym32_lsb_fuzz_too_short() {
test_parse_fuzz_too_short::<_, Symbol>(LittleEndian, Class::ELF32);
}
#[test]
fn parse_sym32_msb_fuzz_too_short() {
test_parse_fuzz_too_short::<_, Symbol>(BigEndian, Class::ELF32);
}
#[test]
fn parse_sym64_lsb_fuzz_too_short() {
test_parse_fuzz_too_short::<_, Symbol>(LittleEndian, Class::ELF64);
}
#[test]
fn parse_sym64_msb_fuzz_too_short() {
test_parse_fuzz_too_short::<_, Symbol>(BigEndian, Class::ELF64);
}
}