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//! TLS utilities.
//!
//! # Safety
//!
//! This file contains code that reads the raw phdr array pointed to by the
//! kernel-provided AUXV values.
#![allow(unsafe_code)]
use crate::backend::c;
use crate::backend::elf::*;
use crate::backend::param::auxv::exe_phdrs_slice;
use core::ptr::null;
/// For use with [`set_thread_area`].
///
/// [`set_thread_area`]: crate::runtime::set_thread_area
#[cfg(target_arch = "x86")]
pub type UserDesc = linux_raw_sys::general::user_desc;
pub(crate) fn startup_tls_info() -> StartupTlsInfo {
let mut base = null();
let mut tls_phdr = null();
let mut stack_size = 0;
let phdrs = exe_phdrs_slice();
// SAFETY: We assume the phdr array pointer and length the kernel provided
// to the process describe a valid phdr array.
unsafe {
for phdr in phdrs {
match phdr.p_type {
PT_PHDR => base = phdrs.as_ptr().cast::<u8>().sub(phdr.p_vaddr),
PT_TLS => tls_phdr = phdr,
PT_GNU_STACK => stack_size = phdr.p_memsz,
_ => {}
}
}
StartupTlsInfo {
addr: base.cast::<u8>().add((*tls_phdr).p_vaddr).cast(),
mem_size: (*tls_phdr).p_memsz,
file_size: (*tls_phdr).p_filesz,
align: (*tls_phdr).p_align,
stack_size,
}
}
}
/// The values returned from [`startup_tls_info`].
///
/// [`startup_tls_info`]: crate::runtime::startup_tls_info
pub struct StartupTlsInfo {
/// The base address of the TLS segment.
pub addr: *const c::c_void,
/// The size of the memory region.
pub mem_size: usize,
/// The size beyond which all memory is zero-initialized.
pub file_size: usize,
/// The required alignment for the TLS segment.
pub align: usize,
/// The requested minimum size for stacks.
pub stack_size: usize,
}
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