Struct ElfLayout 

pub struct ElfLayout {
    pub position_independent: bool,
    pub interpreter: bool,
    pub phdr: u64,
    pub end: u64,
    pub text: Option<(u64, u64)>,
    pub data_span: u64,
    pub page: u64,
}

What decides where Linux starts a process’s program break after it execs an ELF image (load_elf_binary, fs/binfmt_elf.c), from the image’s file header and program headers.

Fields

position_independent: bool

Whether the image is ET_DYN (position-independent) rather than ET_EXEC.

interpreter: bool

Whether the image names a program interpreter (PT_INTERP).

phdr: u64

The virtual address of the image’s program headers before the load bias, as Linux finds it for AT_PHDR (since Linux 5.18): e_phoff in the last PT_LOAD segment whose file range holds it, or 0 where none does (AT_PHDR is then the bias itself).

end: u64

The end of the highest PT_LOAD segment in memory, p_vaddr + p_memsz, before the load bias: the end of its bss.

text: Option<(u64, u64)>

The first executable PT_LOAD segment’s file offset and virtual address, each page-aligned down: where its text mapping starts in the file and, before the load bias, in memory. None without one.

data_span: u64

mm->end_data - mm->start_data as Linux sets them: the highest segment end in the file (p_vaddr + p_filesz) less the highest segment start, which RLIMIT_DATA counts with the heap (check_data_rlimit).

page: u64

The page size Linux maps the segments with and aligns the program break to: ELF_MIN_ALIGN, the larger of ELF_EXEC_PAGESIZE and PAGE_SIZE (fs/binfmt_elf.c), which is the host’s page size, since ELF_EXEC_PAGESIZE is PAGE_SIZE on arm64 and 4096 on x86_64.

Implementations

impl ElfLayout

pub fn read(path: &Path) -> Option<Self>

The layout of the ELF64 image at path (ET_EXEC or ET_DYN), or None for any other file, one without a loadable segment, and one the caller cannot read.

pub fn read_file(file: &RawFd) -> Option<Self>

Self::read of an open file, read with raw syscalls: in-guest Detcore must not call libc’s wrappers (crate::util::raw_syscall).

pub fn start_brk(&self, at_phdr: u64) -> Result<u64, &'static str>

Where Linux starts the program break of a process that exec’d this image, given the AT_PHDR its exec reported, with address randomization off: the end of the highest loaded segment at the load bias, page-aligned up (mm->start_brk = mm->brk = ELF_PAGEALIGN(elf_brk)), or why there is no answer.

pub fn start_brk_at_bias(&self, bias: u64) -> Result<u64, &'static str>

Self::start_brk for an image loaded at load bias bias.

Trait Implementations

impl Clone for ElfLayout

fn clone(&self) -> ElfLayout

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for ElfLayout

impl Debug for ElfLayout

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for ElfLayout

impl PartialEq for ElfLayout

fn eq(&self, other: &ElfLayout) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for ElfLayout