From 1b6a04ca5504955c571d1c97504fb45ea0befee4 Mon Sep 17 00:00:00 2001
From: Valentin Popov <valentin@popov.link>
Date: Mon, 8 Jan 2024 01:21:28 +0400
Subject: Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>
---
 vendor/rustix/src/backend/linux_raw/runtime/tls.rs | 98 ++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 vendor/rustix/src/backend/linux_raw/runtime/tls.rs

(limited to 'vendor/rustix/src/backend/linux_raw/runtime/tls.rs')

diff --git a/vendor/rustix/src/backend/linux_raw/runtime/tls.rs b/vendor/rustix/src/backend/linux_raw/runtime/tls.rs
new file mode 100644
index 0000000..69bd5ce
--- /dev/null
+++ b/vendor/rustix/src/backend/linux_raw/runtime/tls.rs
@@ -0,0 +1,98 @@
+//! 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::param::auxv::exe_phdrs;
+use core::arch::global_asm;
+use core::ptr::{null, NonNull};
+use linux_raw_sys::elf::*;
+
+/// 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 (first_phdr, phent, phnum) = exe_phdrs();
+    let mut current_phdr = first_phdr.cast::<Elf_Phdr>();
+
+    // The dynamic address of the dynamic section, which we can compare with
+    // the `PT_DYNAMIC` header's static address, if present.
+    let dynamic_addr: *const c::c_void = unsafe { &_DYNAMIC };
+
+    // SAFETY: We assume the phdr array pointer and length the kernel provided
+    // to the process describe a valid phdr array.
+    unsafe {
+        let phdrs_end = current_phdr.cast::<u8>().add(phnum * phent).cast();
+        while current_phdr != phdrs_end {
+            let phdr = &*current_phdr;
+            current_phdr = current_phdr.cast::<u8>().add(phent).cast();
+
+            match phdr.p_type {
+                // Compute the offset from the static virtual addresses
+                // in the `p_vaddr` fields to the dynamic addresses. We don't
+                // always get a `PT_PHDR` or `PT_DYNAMIC` header, so use
+                // whichever one we get.
+                PT_PHDR => base = first_phdr.cast::<u8>().wrapping_sub(phdr.p_vaddr),
+                PT_DYNAMIC => base = dynamic_addr.cast::<u8>().wrapping_sub(phdr.p_vaddr),
+
+                PT_TLS => tls_phdr = phdr,
+                PT_GNU_STACK => stack_size = phdr.p_memsz,
+                _ => {}
+            }
+        }
+
+        if tls_phdr.is_null() {
+            StartupTlsInfo {
+                addr: NonNull::dangling().as_ptr(),
+                mem_size: 0,
+                file_size: 0,
+                align: 1,
+                stack_size: 0,
+            }
+        } else {
+            StartupTlsInfo {
+                addr: base.cast::<u8>().wrapping_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,
+            }
+        }
+    }
+}
+
+extern "C" {
+    /// Declare the `_DYNAMIC` symbol so that we can compare its address with
+    /// the static address in the `PT_DYNAMIC` header to learn our offset. Use
+    /// a weak symbol because `_DYNAMIC` is not always present.
+    static _DYNAMIC: c::c_void;
+}
+// Rust has `extern_weak` but it isn't stable, so use a `global_asm`.
+global_asm!(".weak _DYNAMIC");
+
+/// 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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