solana_sbpf/elf.rs
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//! This module relocates a BPF ELF
// Note: Typically ELF shared objects are loaded using the program headers and
// not the section headers. Since we are leveraging the elfkit crate its much
// easier to use the section headers. There are cases (reduced size, obfuscation)
// where the section headers may be removed from the ELF. If that happens then
// this loader will need to be re-written to use the program headers instead.
use crate::{
aligned_memory::{is_memory_aligned, AlignedMemory},
ebpf::{self, EF_SBPF_V2, HOST_ALIGN, INSN_SIZE},
elf_parser::{
consts::{
ELFCLASS64, ELFDATA2LSB, ELFOSABI_NONE, EM_BPF, EM_SBPF, ET_DYN, R_X86_64_32,
R_X86_64_64, R_X86_64_NONE, R_X86_64_RELATIVE,
},
types::{Elf64Phdr, Elf64Shdr, Elf64Word},
Elf64, ElfParserError,
},
error::EbpfError,
memory_region::MemoryRegion,
program::{BuiltinProgram, FunctionRegistry, SBPFVersion},
verifier::Verifier,
vm::{Config, ContextObject},
};
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
use crate::jit::{JitCompiler, JitProgram};
use byteorder::{ByteOrder, LittleEndian};
use std::{collections::BTreeMap, fmt::Debug, mem, ops::Range, str};
#[cfg(not(feature = "shuttle-test"))]
use std::sync::Arc;
#[cfg(feature = "shuttle-test")]
use shuttle::sync::Arc;
/// Error definitions
#[derive(Debug, thiserror::Error, PartialEq, Eq)]
pub enum ElfError {
/// Failed to parse ELF file
#[error("Failed to parse ELF file: {0}")]
FailedToParse(String),
/// Entrypoint out of bounds
#[error("Entrypoint out of bounds")]
EntrypointOutOfBounds,
/// Invalid entrypoint
#[error("Invalid entrypoint")]
InvalidEntrypoint,
/// Failed to get section
#[error("Failed to get section {0}")]
FailedToGetSection(String),
/// Unresolved symbol
#[error("Unresolved symbol ({0}) at instruction #{1:?} (ELF file offset {2:#x})")]
UnresolvedSymbol(String, usize, usize),
/// Section not found
#[error("Section not found: {0}")]
SectionNotFound(String),
/// Relative jump out of bounds
#[error("Relative jump out of bounds at instruction #{0}")]
RelativeJumpOutOfBounds(usize),
/// Symbol hash collision
#[error("Symbol hash collision {0:#x}")]
SymbolHashCollision(u32),
/// Incompatible ELF: wrong endianess
#[error("Incompatible ELF: wrong endianess")]
WrongEndianess,
/// Incompatible ELF: wrong ABI
#[error("Incompatible ELF: wrong ABI")]
WrongAbi,
/// Incompatible ELF: wrong machine
#[error("Incompatible ELF: wrong machine")]
WrongMachine,
/// Incompatible ELF: wrong class
#[error("Incompatible ELF: wrong class")]
WrongClass,
/// Not one text section
#[error("Multiple or no text sections, consider removing llc option: -function-sections")]
NotOneTextSection,
/// Read-write data not supported
#[error("Found writable section ({0}) in ELF, read-write data not supported")]
WritableSectionNotSupported(String),
/// Relocation failed, no loadable section contains virtual address
#[error("Relocation failed, no loadable section contains virtual address {0:#x}")]
AddressOutsideLoadableSection(u64),
/// Relocation failed, invalid referenced virtual address
#[error("Relocation failed, invalid referenced virtual address {0:#x}")]
InvalidVirtualAddress(u64),
/// Relocation failed, unknown type
#[error("Relocation failed, unknown type {0:?}")]
UnknownRelocation(u32),
/// Failed to read relocation info
#[error("Failed to read relocation info")]
FailedToReadRelocationInfo,
/// Incompatible ELF: wrong type
#[error("Incompatible ELF: wrong type")]
WrongType,
/// Unknown symbol
#[error("Unknown symbol with index {0}")]
UnknownSymbol(usize),
/// Offset or value is out of bounds
#[error("Offset or value is out of bounds")]
ValueOutOfBounds,
/// Detected sbpf_version required by the executable which are not enabled
#[error("Detected sbpf_version required by the executable which are not enabled")]
UnsupportedSBPFVersion,
/// Invalid program header
#[error("Invalid ELF program header")]
InvalidProgramHeader,
}
impl From<ElfParserError> for ElfError {
fn from(err: ElfParserError) -> Self {
match err {
ElfParserError::InvalidSectionHeader
| ElfParserError::InvalidString
| ElfParserError::InvalidSize
| ElfParserError::Overlap
| ElfParserError::SectionNotInOrder
| ElfParserError::NoSectionNameStringTable
| ElfParserError::InvalidDynamicSectionTable
| ElfParserError::InvalidRelocationTable
| ElfParserError::InvalidAlignment
| ElfParserError::NoStringTable
| ElfParserError::NoDynamicStringTable
| ElfParserError::InvalidFileHeader
| ElfParserError::StringTooLong(_, _) => ElfError::FailedToParse(err.to_string()),
ElfParserError::InvalidProgramHeader => ElfError::InvalidProgramHeader,
ElfParserError::OutOfBounds => ElfError::ValueOutOfBounds,
}
}
}
fn get_section(elf: &Elf64, name: &[u8]) -> Result<Elf64Shdr, ElfError> {
for section_header in elf.section_header_table() {
if elf.section_name(section_header.sh_name)? == name {
return Ok(section_header.clone());
}
}
Err(ElfError::SectionNotFound(
std::str::from_utf8(name)
.unwrap_or("UTF-8 error")
.to_string(),
))
}
// For more information on the BPF instruction set:
// https://github.com/iovisor/bpf-docs/blob/master/eBPF.md
// msb lsb
// +------------------------+----------------+----+----+--------+
// |immediate |offset |src |dst |opcode |
// +------------------------+----------------+----+----+--------+
// From least significant to most significant bit:
// 8 bit opcode
// 4 bit destination register (dst)
// 4 bit source register (src)
// 16 bit offset
// 32 bit immediate (imm)
/// Byte offset of the immediate field in the instruction
const BYTE_OFFSET_IMMEDIATE: usize = 4;
/// Byte length of the immediate field
const BYTE_LENGTH_IMMEDIATE: usize = 4;
/// BPF relocation types.
#[allow(non_camel_case_types)]
#[derive(Debug, PartialEq, Copy, Clone)]
enum BpfRelocationType {
/// No relocation, placeholder
R_Bpf_None = 0,
/// R_BPF_64_64 relocation type is used for ld_imm64 instruction.
/// The actual to-be-relocated data (0 or section offset) is
/// stored at r_offset + 4 and the read/write data bitsize is 32
/// (4 bytes). The relocation can be resolved with the symbol
/// value plus implicit addend.
R_Bpf_64_64 = 1,
/// 64 bit relocation of a ldxdw instruction. The ldxdw
/// instruction occupies two instruction slots. The 64-bit address
/// to load from is split into the 32-bit imm field of each
/// slot. The first slot's pre-relocation imm field contains the
/// virtual address (typically same as the file offset) of the
/// location to load. Relocation involves calculating the
/// post-load 64-bit physical address referenced by the imm field
/// and writing that physical address back into the imm fields of
/// the ldxdw instruction.
R_Bpf_64_Relative = 8,
/// Relocation of a call instruction. The existing imm field
/// contains either an offset of the instruction to jump to (think
/// local function call) or a special value of "-1". If -1 the
/// symbol must be looked up in the symbol table. The relocation
/// entry contains the symbol number to call. In order to support
/// both local jumps and calling external symbols a 32-bit hash is
/// computed and stored in the the call instruction's 32-bit imm
/// field. The hash is used later to look up the 64-bit address
/// to jump to. In the case of a local jump the hash is
/// calculated using the current program counter and in the case
/// of a symbol the hash is calculated using the name of the
/// symbol.
R_Bpf_64_32 = 10,
}
impl BpfRelocationType {
fn from_x86_relocation_type(from: u32) -> Option<BpfRelocationType> {
match from {
R_X86_64_NONE => Some(BpfRelocationType::R_Bpf_None),
R_X86_64_64 => Some(BpfRelocationType::R_Bpf_64_64),
R_X86_64_RELATIVE => Some(BpfRelocationType::R_Bpf_64_Relative),
R_X86_64_32 => Some(BpfRelocationType::R_Bpf_64_32),
_ => None,
}
}
}
/// ELF section
#[derive(Debug, PartialEq)]
pub enum Section {
/// Owned section data.
///
/// The first field is virtual address of the section.
/// The second field is the actual section data.
Owned(usize, Vec<u8>),
/// Borrowed section data.
///
/// The first field is virtual address of the section.
/// The second field can be used to index the input ELF buffer to
/// retrieve the section data.
Borrowed(usize, Range<usize>),
}
/// Elf loader/relocator
#[derive(Debug, PartialEq)]
pub struct Executable<C: ContextObject> {
/// Loaded and executable elf
elf_bytes: AlignedMemory<{ HOST_ALIGN }>,
/// Required SBPF capabilities
sbpf_version: SBPFVersion,
/// Read-only section
ro_section: Section,
/// Text section virtual address
text_section_vaddr: u64,
/// Text section range in `elf_bytes`
text_section_range: Range<usize>,
/// Address of the entry point
entry_pc: usize,
/// Call resolution map (hash, pc, name)
function_registry: FunctionRegistry<usize>,
/// Loader built-in program
loader: Arc<BuiltinProgram<C>>,
/// Compiled program and argument
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
compiled_program: Option<JitProgram>,
}
impl<C: ContextObject> Executable<C> {
/// Get the configuration settings
pub fn get_config(&self) -> &Config {
self.loader.get_config()
}
/// Get the executable sbpf_version
pub fn get_sbpf_version(&self) -> SBPFVersion {
self.sbpf_version
}
/// Get the .text section virtual address and bytes
pub fn get_text_bytes(&self) -> (u64, &[u8]) {
(
self.text_section_vaddr,
&self.elf_bytes.as_slice()[self.text_section_range.clone()],
)
}
/// Get the concatenated read-only sections (including the text section)
pub fn get_ro_section(&self) -> &[u8] {
match &self.ro_section {
Section::Owned(_offset, data) => data.as_slice(),
Section::Borrowed(_offset, byte_range) => {
&self.elf_bytes.as_slice()[byte_range.clone()]
}
}
}
/// Get a memory region that can be used to access the merged readonly section
pub fn get_ro_region(&self) -> MemoryRegion {
get_ro_region(&self.ro_section, self.elf_bytes.as_slice())
}
/// Get the entry point offset into the text section
pub fn get_entrypoint_instruction_offset(&self) -> usize {
self.entry_pc
}
/// Get the text section offset in the ELF file
#[cfg(feature = "debugger")]
pub fn get_text_section_offset(&self) -> u64 {
self.text_section_range.start as u64
}
/// Get the loader built-in program
pub fn get_loader(&self) -> &Arc<BuiltinProgram<C>> {
&self.loader
}
/// Get the JIT compiled program
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
pub fn get_compiled_program(&self) -> Option<&JitProgram> {
self.compiled_program.as_ref()
}
/// Verify the executable
pub fn verify<V: Verifier>(&self) -> Result<(), EbpfError> {
<V as Verifier>::verify(
self.get_text_bytes().1,
self.get_config(),
self.get_sbpf_version(),
self.get_function_registry(),
self.loader.get_function_registry(),
)?;
Ok(())
}
/// JIT compile the executable
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
pub fn jit_compile(&mut self) -> Result<(), crate::error::EbpfError> {
let jit = JitCompiler::<C>::new(self)?;
self.compiled_program = Some(jit.compile()?);
Ok(())
}
/// Get the function registry
pub fn get_function_registry(&self) -> &FunctionRegistry<usize> {
&self.function_registry
}
/// Create from raw text section bytes (list of instructions)
pub fn new_from_text_bytes(
text_bytes: &[u8],
loader: Arc<BuiltinProgram<C>>,
sbpf_version: SBPFVersion,
mut function_registry: FunctionRegistry<usize>,
) -> Result<Self, ElfError> {
let elf_bytes = AlignedMemory::from_slice(text_bytes);
let entry_pc = if let Some((_name, pc)) = function_registry.lookup_by_name(b"entrypoint") {
pc
} else {
function_registry.register_function_hashed_legacy(
&loader,
!sbpf_version.static_syscalls(),
*b"entrypoint",
0,
)?;
0
};
Ok(Self {
elf_bytes,
sbpf_version,
ro_section: Section::Borrowed(ebpf::MM_RODATA_START as usize, 0..text_bytes.len()),
text_section_vaddr: if sbpf_version.enable_lower_bytecode_vaddr() {
ebpf::MM_BYTECODE_START
} else {
ebpf::MM_RODATA_START
},
text_section_range: 0..text_bytes.len(),
entry_pc,
function_registry,
loader,
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
compiled_program: None,
})
}
/// Fully loads an ELF
pub fn load(bytes: &[u8], loader: Arc<BuiltinProgram<C>>) -> Result<Self, ElfError> {
const E_FLAGS_OFFSET: usize = 48;
let e_flags = LittleEndian::read_u32(
bytes
.get(E_FLAGS_OFFSET..E_FLAGS_OFFSET.saturating_add(std::mem::size_of::<u32>()))
.ok_or(ElfParserError::OutOfBounds)?,
);
let config = loader.get_config();
let sbpf_version = if config.enabled_sbpf_versions.end() == &SBPFVersion::V0 {
if e_flags == EF_SBPF_V2 {
SBPFVersion::Reserved
} else {
SBPFVersion::V0
}
} else {
match e_flags {
0 => SBPFVersion::V0,
1 => SBPFVersion::V1,
2 => SBPFVersion::V2,
3 => SBPFVersion::V3,
_ => SBPFVersion::Reserved,
}
};
if !config.enabled_sbpf_versions.contains(&sbpf_version) {
return Err(ElfError::UnsupportedSBPFVersion);
}
let mut executable = if sbpf_version.enable_stricter_elf_headers() {
Self::load_with_strict_parser(bytes, loader)?
} else {
Self::load_with_lenient_parser(bytes, loader)?
};
executable.sbpf_version = sbpf_version;
Ok(executable)
}
/// Loads an ELF without relocation
pub fn load_with_strict_parser(
bytes: &[u8],
loader: Arc<BuiltinProgram<C>>,
) -> Result<Self, ElfParserError> {
use crate::elf_parser::{
consts::{
ELFMAG, EV_CURRENT, PF_R, PF_W, PF_X, PT_GNU_STACK, PT_LOAD, PT_NULL, SHN_UNDEF,
STT_FUNC,
},
types::{Elf64Ehdr, Elf64Shdr, Elf64Sym},
};
let aligned_memory = AlignedMemory::<{ HOST_ALIGN }>::from_slice(bytes);
let elf_bytes = aligned_memory.as_slice();
let (file_header_range, file_header) = Elf64::parse_file_header(elf_bytes)?;
let program_header_table_range = mem::size_of::<Elf64Ehdr>()
..mem::size_of::<Elf64Phdr>()
.saturating_mul(file_header.e_phnum as usize)
.saturating_add(mem::size_of::<Elf64Ehdr>());
if file_header.e_ident.ei_mag != ELFMAG
|| file_header.e_ident.ei_class != ELFCLASS64
|| file_header.e_ident.ei_data != ELFDATA2LSB
|| file_header.e_ident.ei_version != EV_CURRENT as u8
|| file_header.e_ident.ei_osabi != ELFOSABI_NONE
|| file_header.e_ident.ei_abiversion != 0x00
|| file_header.e_ident.ei_pad != [0x00; 7]
|| file_header.e_type != ET_DYN
|| file_header.e_machine != EM_SBPF
|| file_header.e_version != EV_CURRENT
// file_header.e_entry
|| file_header.e_phoff != mem::size_of::<Elf64Ehdr>() as u64
// file_header.e_shoff
// file_header.e_flags
|| file_header.e_ehsize != mem::size_of::<Elf64Ehdr>() as u16
|| file_header.e_phentsize != mem::size_of::<Elf64Phdr>() as u16
|| file_header.e_phnum < EXPECTED_PROGRAM_HEADERS.len() as u16
|| program_header_table_range.end >= elf_bytes.len()
|| file_header.e_shentsize != mem::size_of::<Elf64Shdr>() as u16
// file_header.e_shnum
|| file_header.e_shstrndx >= file_header.e_shnum
{
return Err(ElfParserError::InvalidFileHeader);
}
const EXPECTED_PROGRAM_HEADERS: [(u32, u32, u64); 5] = [
(PT_LOAD, PF_X, ebpf::MM_BYTECODE_START), // byte code
(PT_LOAD, PF_R, ebpf::MM_RODATA_START), // read only data
(PT_GNU_STACK, PF_R | PF_W, ebpf::MM_STACK_START), // stack
(PT_LOAD, PF_R | PF_W, ebpf::MM_HEAP_START), // heap
(PT_NULL, 0, 0xFFFFFFFF00000000), // dynamic symbol table
];
let program_header_table =
Elf64::slice_from_bytes::<Elf64Phdr>(elf_bytes, program_header_table_range.clone())?;
for (program_header, (p_type, p_flags, p_vaddr)) in program_header_table
.iter()
.zip(EXPECTED_PROGRAM_HEADERS.iter())
{
let p_filesz = if (*p_flags & PF_W) != 0 {
0
} else {
program_header.p_memsz
};
if program_header.p_type != *p_type
|| program_header.p_flags != *p_flags
|| program_header.p_offset < program_header_table_range.end as u64
|| program_header.p_offset >= elf_bytes.len() as u64
|| program_header.p_offset.checked_rem(ebpf::INSN_SIZE as u64) != Some(0)
|| program_header.p_vaddr != *p_vaddr
|| program_header.p_paddr != *p_vaddr
|| program_header.p_filesz != p_filesz
|| program_header.p_filesz
> (elf_bytes.len() as u64).saturating_sub(program_header.p_offset)
|| program_header.p_memsz >= ebpf::MM_REGION_SIZE
{
return Err(ElfParserError::InvalidProgramHeader);
}
}
let config = loader.get_config();
let symbol_names_section_header = if config.enable_symbol_and_section_labels {
let (_section_header_table_range, section_header_table) =
Elf64::parse_section_header_table(
elf_bytes,
file_header_range.clone(),
file_header,
program_header_table_range.clone(),
)?;
let section_names_section_header = (file_header.e_shstrndx != SHN_UNDEF)
.then(|| {
section_header_table
.get(file_header.e_shstrndx as usize)
.ok_or(ElfParserError::OutOfBounds)
})
.transpose()?
.ok_or(ElfParserError::NoSectionNameStringTable)?;
let mut symbol_names_section_header = None;
for section_header in section_header_table.iter() {
let section_name = Elf64::get_string_in_section(
elf_bytes,
section_names_section_header,
section_header.sh_name,
64,
)?;
if section_name == b".dynstr" {
symbol_names_section_header = Some(section_header);
}
}
symbol_names_section_header
} else {
None
};
let bytecode_header = &program_header_table[0];
let rodata_header = &program_header_table[1];
let dynamic_symbol_table: &[Elf64Sym] =
Elf64::slice_from_program_header(elf_bytes, &program_header_table[4])?;
let mut function_registry = FunctionRegistry::<usize>::default();
let mut expected_symbol_address = bytecode_header.p_vaddr;
for symbol in dynamic_symbol_table {
if symbol.st_info & STT_FUNC == 0 {
continue;
}
if symbol.st_value != expected_symbol_address {
return Err(ElfParserError::OutOfBounds);
}
if symbol.st_size == 0 || symbol.st_size.checked_rem(ebpf::INSN_SIZE as u64) != Some(0)
{
return Err(ElfParserError::InvalidSize);
}
if symbol.st_size
> bytecode_header
.vm_range()
.end
.saturating_sub(symbol.st_value)
{
return Err(ElfParserError::OutOfBounds);
}
let target_pc = symbol
.st_value
.saturating_sub(bytecode_header.p_vaddr)
.checked_div(ebpf::INSN_SIZE as u64)
.unwrap_or_default() as usize;
let name = if config.enable_symbol_and_section_labels {
Elf64::get_string_in_section(
elf_bytes,
symbol_names_section_header
.as_ref()
.ok_or(ElfParserError::NoStringTable)?,
symbol.st_name as Elf64Word,
u8::MAX as usize,
)?
} else {
&[]
};
function_registry
.register_function(target_pc as u32, name, target_pc)
.unwrap();
expected_symbol_address = symbol.st_value.saturating_add(symbol.st_size);
}
if expected_symbol_address != bytecode_header.vm_range().end {
return Err(ElfParserError::OutOfBounds);
}
if !bytecode_header.vm_range().contains(&file_header.e_entry)
|| file_header.e_entry.checked_rem(ebpf::INSN_SIZE as u64) != Some(0)
{
return Err(ElfParserError::InvalidFileHeader);
}
let entry_pc = file_header
.e_entry
.saturating_sub(bytecode_header.p_vaddr)
.checked_div(ebpf::INSN_SIZE as u64)
.unwrap_or_default() as usize;
if function_registry.lookup_by_key(entry_pc as u32).is_none() {
return Err(ElfParserError::InvalidFileHeader);
}
let text_section_vaddr = bytecode_header.p_vaddr;
let text_section_range = bytecode_header.file_range().unwrap_or_default();
let ro_section = Section::Borrowed(
rodata_header.p_vaddr as usize,
rodata_header.file_range().unwrap_or_default(),
);
Ok(Self {
elf_bytes: aligned_memory,
sbpf_version: SBPFVersion::Reserved, // Is set in Self::load()
ro_section,
text_section_vaddr,
text_section_range,
entry_pc,
function_registry,
loader,
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
compiled_program: None,
})
}
/// Loads an ELF with relocation
fn load_with_lenient_parser(
bytes: &[u8],
loader: Arc<BuiltinProgram<C>>,
) -> Result<Self, ElfError> {
// We always need one memory copy to take ownership and for relocations
let aligned_memory = AlignedMemory::<{ HOST_ALIGN }>::from_slice(bytes);
let (mut elf_bytes, unrelocated_elf_bytes) =
if is_memory_aligned(bytes.as_ptr() as usize, HOST_ALIGN) {
(aligned_memory, bytes)
} else {
// We might need another memory copy to ensure alignment
(aligned_memory.clone(), aligned_memory.as_slice())
};
let elf = Elf64::parse(unrelocated_elf_bytes)?;
let config = loader.get_config();
let header = elf.file_header();
let sbpf_version = if header.e_flags == EF_SBPF_V2 {
SBPFVersion::Reserved
} else {
SBPFVersion::V0
};
Self::validate(config, &elf, elf_bytes.as_slice())?;
// calculate the text section info
let text_section = get_section(&elf, b".text")?;
let text_section_vaddr =
if sbpf_version.enable_elf_vaddr() && text_section.sh_addr >= ebpf::MM_RODATA_START {
text_section.sh_addr
} else {
text_section.sh_addr.saturating_add(ebpf::MM_RODATA_START)
};
let vaddr_end = if sbpf_version.reject_rodata_stack_overlap() {
text_section_vaddr.saturating_add(text_section.sh_size)
} else {
text_section_vaddr
};
if (config.reject_broken_elfs
&& !sbpf_version.enable_elf_vaddr()
&& text_section.sh_addr != text_section.sh_offset)
|| vaddr_end > ebpf::MM_STACK_START
{
return Err(ElfError::ValueOutOfBounds);
}
// relocate symbols
let mut function_registry = FunctionRegistry::default();
Self::relocate(
&mut function_registry,
&loader,
&elf,
elf_bytes.as_slice_mut(),
)?;
// calculate entrypoint offset into the text section
let offset = header.e_entry.saturating_sub(text_section.sh_addr);
if offset.checked_rem(ebpf::INSN_SIZE as u64) != Some(0) {
return Err(ElfError::InvalidEntrypoint);
}
let entry_pc = if let Some(entry_pc) = (offset as usize).checked_div(ebpf::INSN_SIZE) {
if !sbpf_version.static_syscalls() {
function_registry.unregister_function(ebpf::hash_symbol_name(b"entrypoint"));
}
function_registry.register_function_hashed_legacy(
&loader,
!sbpf_version.static_syscalls(),
*b"entrypoint",
entry_pc,
)?;
entry_pc
} else {
return Err(ElfError::InvalidEntrypoint);
};
let ro_section = Self::parse_ro_sections(
config,
&sbpf_version,
elf.section_header_table()
.iter()
.map(|s| (elf.section_name(s.sh_name).ok(), s)),
elf_bytes.as_slice(),
)?;
Ok(Self {
elf_bytes,
sbpf_version,
ro_section,
text_section_vaddr,
text_section_range: text_section.file_range().unwrap_or_default(),
entry_pc,
function_registry,
loader,
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
compiled_program: None,
})
}
/// Calculate the total memory size of the executable
#[rustfmt::skip]
#[allow(clippy::size_of_ref)]
pub fn mem_size(&self) -> usize {
let mut total = mem::size_of::<Self>();
total = total
// elf bytes
.saturating_add(self.elf_bytes.mem_size())
// ro section
.saturating_add(match &self.ro_section {
Section::Owned(_, data) => data.capacity(),
Section::Borrowed(_, _) => 0,
})
// bpf functions
.saturating_add(self.function_registry.mem_size());
#[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
{
// compiled programs
total = total.saturating_add(self.compiled_program.as_ref().map_or(0, |program| program.mem_size()));
}
total
}
// Functions exposed for tests
/// Validates the ELF
pub fn validate(config: &Config, elf: &Elf64, elf_bytes: &[u8]) -> Result<(), ElfError> {
let header = elf.file_header();
if header.e_ident.ei_class != ELFCLASS64 {
return Err(ElfError::WrongClass);
}
if header.e_ident.ei_data != ELFDATA2LSB {
return Err(ElfError::WrongEndianess);
}
if header.e_ident.ei_osabi != ELFOSABI_NONE {
return Err(ElfError::WrongAbi);
}
if header.e_machine != EM_BPF && header.e_machine != EM_SBPF {
return Err(ElfError::WrongMachine);
}
if header.e_type != ET_DYN {
return Err(ElfError::WrongType);
}
let sbpf_version = if header.e_flags == EF_SBPF_V2 {
SBPFVersion::Reserved
} else {
SBPFVersion::V0
};
if !config.enabled_sbpf_versions.contains(&sbpf_version) {
return Err(ElfError::UnsupportedSBPFVersion);
}
if sbpf_version.enable_elf_vaddr() {
if !config.optimize_rodata {
// When optimize_rodata=false, we allocate a vector and copy all
// rodata sections into it. In that case we can't allow virtual
// addresses or we'd potentially have to do huge allocations.
return Err(ElfError::UnsupportedSBPFVersion);
}
// The toolchain currently emits up to 4 program headers. 10 is a
// future proof nice round number.
//
// program_headers() returns an ExactSizeIterator so count doesn't
// actually iterate again.
if elf.program_header_table().iter().count() >= 10 {
return Err(ElfError::InvalidProgramHeader);
}
}
let num_text_sections =
elf.section_header_table()
.iter()
.fold(0, |count: usize, section_header| {
if let Ok(this_name) = elf.section_name(section_header.sh_name) {
if this_name == b".text" {
return count.saturating_add(1);
}
}
count
});
if 1 != num_text_sections {
return Err(ElfError::NotOneTextSection);
}
for section_header in elf.section_header_table().iter() {
if let Ok(name) = elf.section_name(section_header.sh_name) {
if name.starts_with(b".bss")
|| (section_header.is_writable()
&& (name.starts_with(b".data") && !name.starts_with(b".data.rel")))
{
return Err(ElfError::WritableSectionNotSupported(
String::from_utf8_lossy(name).to_string(),
));
}
}
}
for section_header in elf.section_header_table().iter() {
let start = section_header.sh_offset as usize;
let end = section_header
.sh_offset
.checked_add(section_header.sh_size)
.ok_or(ElfError::ValueOutOfBounds)? as usize;
let _ = elf_bytes
.get(start..end)
.ok_or(ElfError::ValueOutOfBounds)?;
}
let text_section = get_section(elf, b".text")?;
if !text_section.vm_range().contains(&header.e_entry) {
return Err(ElfError::EntrypointOutOfBounds);
}
Ok(())
}
/// Parses and concatenates the readonly data sections
pub fn parse_ro_sections<'a, S: IntoIterator<Item = (Option<&'a [u8]>, &'a Elf64Shdr)>>(
config: &Config,
sbpf_version: &SBPFVersion,
sections: S,
elf_bytes: &[u8],
) -> Result<Section, ElfError> {
// the lowest section address
let mut lowest_addr = usize::MAX;
// the highest section address
let mut highest_addr = 0;
// the aggregated section length, not including gaps between sections
let mut ro_fill_length = 0usize;
let mut invalid_offsets = false;
// when sbpf_version.enable_elf_vaddr()=true, we allow section_addr != sh_offset
// if section_addr - sh_offset is constant across all sections. That is,
// we allow sections to be translated by a fixed virtual offset.
let mut addr_file_offset = None;
// keep track of where ro sections are so we can tell whether they're
// contiguous
let mut first_ro_section = 0;
let mut last_ro_section = 0;
let mut n_ro_sections = 0usize;
let mut ro_slices = vec![];
for (i, (name, section_header)) in sections.into_iter().enumerate() {
match name {
Some(name)
if name == b".text"
|| name == b".rodata"
|| name == b".data.rel.ro"
|| name == b".eh_frame" => {}
_ => continue,
}
if n_ro_sections == 0 {
first_ro_section = i;
}
last_ro_section = i;
n_ro_sections = n_ro_sections.saturating_add(1);
let section_addr = section_header.sh_addr;
// sh_offset handling:
//
// If sbpf_version.enable_elf_vaddr()=true, we allow section_addr >
// sh_offset, if section_addr - sh_offset is constant across all
// sections. That is, we allow the linker to align rodata to a
// positive base address (MM_RODATA_START) as long as the mapping
// to sh_offset(s) stays linear.
//
// If sbpf_version.enable_elf_vaddr()=false, section_addr must match
// sh_offset for backwards compatibility
if !invalid_offsets {
if sbpf_version.enable_elf_vaddr() {
// This is enforced in validate()
debug_assert!(config.optimize_rodata);
if section_addr < section_header.sh_offset {
invalid_offsets = true;
} else {
let offset = section_addr.saturating_sub(section_header.sh_offset);
if *addr_file_offset.get_or_insert(offset) != offset {
// The sections are not all translated by the same
// constant. We won't be able to borrow, but unless
// config.reject_broken_elf=true, we're still going
// to accept this file for backwards compatibility.
invalid_offsets = true;
}
}
} else if section_addr != section_header.sh_offset {
invalid_offsets = true;
}
}
let mut vaddr_end =
if sbpf_version.enable_elf_vaddr() && section_addr >= ebpf::MM_RODATA_START {
section_addr
} else {
section_addr.saturating_add(ebpf::MM_RODATA_START)
};
if sbpf_version.reject_rodata_stack_overlap() {
vaddr_end = vaddr_end.saturating_add(section_header.sh_size);
}
if (config.reject_broken_elfs && invalid_offsets) || vaddr_end > ebpf::MM_STACK_START {
return Err(ElfError::ValueOutOfBounds);
}
let section_data = elf_bytes
.get(section_header.file_range().unwrap_or_default())
.ok_or(ElfError::ValueOutOfBounds)?;
let section_addr = section_addr as usize;
lowest_addr = lowest_addr.min(section_addr);
highest_addr = highest_addr.max(section_addr.saturating_add(section_data.len()));
ro_fill_length = ro_fill_length.saturating_add(section_data.len());
ro_slices.push((section_addr, section_data));
}
if config.reject_broken_elfs && lowest_addr.saturating_add(ro_fill_length) > highest_addr {
return Err(ElfError::ValueOutOfBounds);
}
let can_borrow = !invalid_offsets
&& last_ro_section
.saturating_add(1)
.saturating_sub(first_ro_section)
== n_ro_sections;
if sbpf_version.enable_elf_vaddr() && !can_borrow {
return Err(ElfError::ValueOutOfBounds);
}
let ro_section = if config.optimize_rodata && can_borrow {
// Read only sections are grouped together with no intermixed non-ro
// sections. We can borrow.
// When sbpf_version.enable_elf_vaddr()=true, section addresses and their
// corresponding buffer offsets can be translated by a constant
// amount. Subtract the constant to get buffer positions.
let buf_offset_start =
lowest_addr.saturating_sub(addr_file_offset.unwrap_or(0) as usize);
let buf_offset_end =
highest_addr.saturating_sub(addr_file_offset.unwrap_or(0) as usize);
let addr_offset = if lowest_addr >= ebpf::MM_RODATA_START as usize {
// The first field of Section::Borrowed is an offset from
// ebpf::MM_RODATA_START so if the linker has already put the
// sections within ebpf::MM_RODATA_START, we need to subtract
// it now.
lowest_addr
} else {
if sbpf_version.enable_elf_vaddr() {
return Err(ElfError::ValueOutOfBounds);
}
lowest_addr.saturating_add(ebpf::MM_RODATA_START as usize)
};
Section::Borrowed(addr_offset, buf_offset_start..buf_offset_end)
} else {
// Read only and other non-ro sections are mixed. Zero the non-ro
// sections and and copy the ro ones at their intended offsets.
if config.optimize_rodata {
// The rodata region starts at MM_RODATA_START + offset,
// [MM_RODATA_START, MM_RODATA_START + offset) is not
// mappable. We only need to allocate highest_addr - lowest_addr
// bytes.
highest_addr = highest_addr.saturating_sub(lowest_addr);
} else {
// For backwards compatibility, the whole [MM_RODATA_START,
// MM_RODATA_START + highest_addr) range is mappable. We need
// to allocate the whole address range.
lowest_addr = 0;
};
let buf_len = highest_addr;
if buf_len > elf_bytes.len() {
return Err(ElfError::ValueOutOfBounds);
}
let mut ro_section = vec![0; buf_len];
for (section_addr, slice) in ro_slices.iter() {
let buf_offset_start = section_addr.saturating_sub(lowest_addr);
ro_section[buf_offset_start..buf_offset_start.saturating_add(slice.len())]
.copy_from_slice(slice);
}
let addr_offset = if lowest_addr >= ebpf::MM_RODATA_START as usize {
lowest_addr
} else {
lowest_addr.saturating_add(ebpf::MM_RODATA_START as usize)
};
Section::Owned(addr_offset, ro_section)
};
Ok(ro_section)
}
/// Relocates the ELF in-place
fn relocate(
function_registry: &mut FunctionRegistry<usize>,
loader: &BuiltinProgram<C>,
elf: &Elf64,
elf_bytes: &mut [u8],
) -> Result<(), ElfError> {
let mut syscall_cache = BTreeMap::new();
let text_section = get_section(elf, b".text")?;
let sbpf_version = if elf.file_header().e_flags == EF_SBPF_V2 {
SBPFVersion::Reserved
} else {
SBPFVersion::V0
};
// Fixup all program counter relative call instructions
let config = loader.get_config();
let text_bytes = elf_bytes
.get_mut(text_section.file_range().unwrap_or_default())
.ok_or(ElfError::ValueOutOfBounds)?;
let instruction_count = text_bytes
.len()
.checked_div(ebpf::INSN_SIZE)
.ok_or(ElfError::ValueOutOfBounds)?;
for i in 0..instruction_count {
let insn = ebpf::get_insn(text_bytes, i);
if insn.opc == ebpf::CALL_IMM && insn.imm != -1 {
let target_pc = (i as isize)
.saturating_add(1)
.saturating_add(insn.imm as isize);
if target_pc < 0 || target_pc >= instruction_count as isize {
return Err(ElfError::RelativeJumpOutOfBounds(i));
}
let name = if config.enable_symbol_and_section_labels {
format!("function_{target_pc}")
} else {
String::default()
};
let key = function_registry.register_function_hashed_legacy(
loader,
!sbpf_version.static_syscalls(),
name.as_bytes(),
target_pc as usize,
)?;
if !sbpf_version.static_syscalls() {
let offset = i.saturating_mul(ebpf::INSN_SIZE).saturating_add(4);
let checked_slice = text_bytes
.get_mut(offset..offset.saturating_add(4))
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u32(checked_slice, key);
}
}
}
let mut program_header: Option<&Elf64Phdr> = None;
// Fixup all the relocations in the relocation section if exists
for relocation in elf.dynamic_relocations_table().unwrap_or_default().iter() {
let mut r_offset = relocation.r_offset as usize;
// When sbpf_version.enable_elf_vaddr()=true, we allow section.sh_addr !=
// section.sh_offset so we need to bring r_offset to the correct
// byte offset.
if sbpf_version.enable_elf_vaddr() {
match program_header {
Some(header) if header.vm_range().contains(&(r_offset as u64)) => {}
_ => {
program_header = elf
.program_header_table()
.iter()
.find(|header| header.vm_range().contains(&(r_offset as u64)))
}
}
let header = program_header.as_ref().ok_or(ElfError::ValueOutOfBounds)?;
r_offset = r_offset
.saturating_sub(header.p_vaddr as usize)
.saturating_add(header.p_offset as usize);
}
match BpfRelocationType::from_x86_relocation_type(relocation.r_type()) {
Some(BpfRelocationType::R_Bpf_64_64) => {
// Offset of the immediate field
let imm_offset = if text_section
.file_range()
.unwrap_or_default()
.contains(&r_offset)
|| sbpf_version == SBPFVersion::V0
{
r_offset.saturating_add(BYTE_OFFSET_IMMEDIATE)
} else {
r_offset
};
// Read the instruction's immediate field which contains virtual
// address to convert to physical
let checked_slice = elf_bytes
.get(imm_offset..imm_offset.saturating_add(BYTE_LENGTH_IMMEDIATE))
.ok_or(ElfError::ValueOutOfBounds)?;
let refd_addr = LittleEndian::read_u32(checked_slice) as u64;
let symbol = elf
.dynamic_symbol_table()
.and_then(|table| table.get(relocation.r_sym() as usize).cloned())
.ok_or_else(|| ElfError::UnknownSymbol(relocation.r_sym() as usize))?;
// The relocated address is relative to the address of the
// symbol at index `r_sym`
let mut addr = symbol.st_value.saturating_add(refd_addr);
// The "physical address" from the VM's perspective is rooted
// at `MM_RODATA_START`. If the linker hasn't already put
// the symbol within `MM_RODATA_START`, we need to do so
// now.
if addr < ebpf::MM_RODATA_START {
addr = ebpf::MM_RODATA_START.saturating_add(addr);
}
if text_section
.file_range()
.unwrap_or_default()
.contains(&r_offset)
|| sbpf_version == SBPFVersion::V0
{
let imm_low_offset = imm_offset;
let imm_high_offset = imm_low_offset.saturating_add(INSN_SIZE);
// Write the low side of the relocate address
let imm_slice = elf_bytes
.get_mut(
imm_low_offset
..imm_low_offset.saturating_add(BYTE_LENGTH_IMMEDIATE),
)
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u32(imm_slice, (addr & 0xFFFFFFFF) as u32);
// Write the high side of the relocate address
let imm_slice = elf_bytes
.get_mut(
imm_high_offset
..imm_high_offset.saturating_add(BYTE_LENGTH_IMMEDIATE),
)
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u32(
imm_slice,
addr.checked_shr(32).unwrap_or_default() as u32,
);
} else {
let imm_slice = elf_bytes
.get_mut(imm_offset..imm_offset.saturating_add(8))
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u64(imm_slice, addr);
}
}
Some(BpfRelocationType::R_Bpf_64_Relative) => {
// Relocation between different sections, where the target
// memory is not associated to a symbol (eg some compiler
// generated rodata that doesn't have an explicit symbol).
// Offset of the immediate field
let imm_offset = r_offset.saturating_add(BYTE_OFFSET_IMMEDIATE);
if text_section
.file_range()
.unwrap_or_default()
.contains(&r_offset)
{
// We're relocating a lddw instruction, which spans two
// instruction slots. The address to be relocated is
// split in two halves in the two imms of the
// instruction slots.
let imm_low_offset = imm_offset;
let imm_high_offset = r_offset
.saturating_add(INSN_SIZE)
.saturating_add(BYTE_OFFSET_IMMEDIATE);
// Read the low side of the address
let imm_slice = elf_bytes
.get(
imm_low_offset
..imm_low_offset.saturating_add(BYTE_LENGTH_IMMEDIATE),
)
.ok_or(ElfError::ValueOutOfBounds)?;
let va_low = LittleEndian::read_u32(imm_slice) as u64;
// Read the high side of the address
let imm_slice = elf_bytes
.get(
imm_high_offset
..imm_high_offset.saturating_add(BYTE_LENGTH_IMMEDIATE),
)
.ok_or(ElfError::ValueOutOfBounds)?;
let va_high = LittleEndian::read_u32(imm_slice) as u64;
// Put the address back together
let mut refd_addr = va_high.checked_shl(32).unwrap_or_default() | va_low;
if refd_addr == 0 {
return Err(ElfError::InvalidVirtualAddress(refd_addr));
}
if refd_addr < ebpf::MM_RODATA_START {
// The linker hasn't already placed rodata within
// MM_RODATA_START, so we do so now
refd_addr = ebpf::MM_RODATA_START.saturating_add(refd_addr);
}
// Write back the low half
let imm_slice = elf_bytes
.get_mut(
imm_low_offset
..imm_low_offset.saturating_add(BYTE_LENGTH_IMMEDIATE),
)
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u32(imm_slice, (refd_addr & 0xFFFFFFFF) as u32);
// Write back the high half
let imm_slice = elf_bytes
.get_mut(
imm_high_offset
..imm_high_offset.saturating_add(BYTE_LENGTH_IMMEDIATE),
)
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u32(
imm_slice,
refd_addr.checked_shr(32).unwrap_or_default() as u32,
);
} else {
let refd_addr = if sbpf_version != SBPFVersion::V0 {
// We're relocating an address inside a data section (eg .rodata). The
// address is encoded as a simple u64.
let addr_slice = elf_bytes
.get(r_offset..r_offset.saturating_add(mem::size_of::<u64>()))
.ok_or(ElfError::ValueOutOfBounds)?;
let mut refd_addr = LittleEndian::read_u64(addr_slice);
if refd_addr < ebpf::MM_RODATA_START {
// Not within MM_RODATA_START, do it now
refd_addr = ebpf::MM_RODATA_START.saturating_add(refd_addr);
}
refd_addr
} else {
// There used to be a bug in toolchains before
// https://github.com/solana-labs/llvm-project/pull/35 where for 64 bit
// relocations we were encoding only the low 32 bits, shifted 32 bits to
// the left. Our relocation code used to be compatible with that, so we
// need to keep supporting this case for backwards compatibility.
let addr_slice = elf_bytes
.get(imm_offset..imm_offset.saturating_add(BYTE_LENGTH_IMMEDIATE))
.ok_or(ElfError::ValueOutOfBounds)?;
let refd_addr = LittleEndian::read_u32(addr_slice) as u64;
ebpf::MM_RODATA_START.saturating_add(refd_addr)
};
let addr_slice = elf_bytes
.get_mut(r_offset..r_offset.saturating_add(mem::size_of::<u64>()))
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u64(addr_slice, refd_addr);
}
}
Some(BpfRelocationType::R_Bpf_64_32) => {
// The .text section has an unresolved call to symbol instruction
// Hash the symbol name and stick it into the call instruction's imm
// field. Later that hash will be used to look up the function location.
// Offset of the immediate field
let imm_offset = r_offset.saturating_add(BYTE_OFFSET_IMMEDIATE);
let symbol = elf
.dynamic_symbol_table()
.and_then(|table| table.get(relocation.r_sym() as usize).cloned())
.ok_or_else(|| ElfError::UnknownSymbol(relocation.r_sym() as usize))?;
let name = elf
.dynamic_symbol_name(symbol.st_name as Elf64Word)
.map_err(|_| ElfError::UnknownSymbol(symbol.st_name as usize))?;
// If the symbol is defined, this is a bpf-to-bpf call
let key = if symbol.is_function() && symbol.st_value != 0 {
if !text_section.vm_range().contains(&symbol.st_value) {
return Err(ElfError::ValueOutOfBounds);
}
let target_pc = (symbol.st_value.saturating_sub(text_section.sh_addr)
as usize)
.checked_div(ebpf::INSN_SIZE)
.unwrap_or_default();
function_registry.register_function_hashed_legacy(
loader,
!sbpf_version.static_syscalls(),
name,
target_pc,
)?
} else {
// Else it's a syscall
let hash = *syscall_cache
.entry(symbol.st_name)
.or_insert_with(|| ebpf::hash_symbol_name(name));
if config.reject_broken_elfs
&& loader.get_function_registry().lookup_by_key(hash).is_none()
{
return Err(ElfError::UnresolvedSymbol(
String::from_utf8_lossy(name).to_string(),
r_offset.checked_div(ebpf::INSN_SIZE).unwrap_or(0),
r_offset,
));
}
hash
};
let checked_slice = elf_bytes
.get_mut(imm_offset..imm_offset.saturating_add(BYTE_LENGTH_IMMEDIATE))
.ok_or(ElfError::ValueOutOfBounds)?;
LittleEndian::write_u32(checked_slice, key);
}
_ => return Err(ElfError::UnknownRelocation(relocation.r_type())),
}
}
if config.enable_symbol_and_section_labels {
// Register all known function names from the symbol table
for symbol in elf.symbol_table().ok().flatten().unwrap_or_default().iter() {
if symbol.st_info & 0xEF != 0x02 {
continue;
}
if !text_section.vm_range().contains(&symbol.st_value) {
return Err(ElfError::ValueOutOfBounds);
}
let target_pc = (symbol.st_value.saturating_sub(text_section.sh_addr) as usize)
.checked_div(ebpf::INSN_SIZE)
.unwrap_or_default();
let name = elf
.symbol_name(symbol.st_name as Elf64Word)
.map_err(|_| ElfError::UnknownSymbol(symbol.st_name as usize))?;
function_registry.register_function_hashed_legacy(
loader,
!sbpf_version.static_syscalls(),
name,
target_pc,
)?;
}
}
Ok(())
}
#[allow(dead_code)]
fn dump_data(name: &str, prog: &[u8]) {
let mut eight_bytes: Vec<u8> = Vec::new();
println!("{name}");
for i in prog.iter() {
if eight_bytes.len() >= 7 {
println!("{eight_bytes:02X?}");
eight_bytes.clear();
} else {
eight_bytes.push(*i);
}
}
}
}
/// Creates a [MemoryRegion] for the given [Section]
pub fn get_ro_region(ro_section: &Section, elf: &[u8]) -> MemoryRegion {
let (offset, ro_data) = match ro_section {
Section::Owned(offset, data) => (*offset, data.as_slice()),
Section::Borrowed(offset, byte_range) => (*offset, &elf[byte_range.clone()]),
};
// If offset > 0, the region will start at MM_RODATA_START + the offset of
// the first read only byte. [MM_RODATA_START, MM_RODATA_START + offset)
// will be unmappable, see MemoryRegion::vm_to_host.
MemoryRegion::new_readonly(ro_data, offset as u64)
}