From af7312edb0c7f3815bb365c09e871ac7c1930c3b Mon Sep 17 00:00:00 2001
From: Stefan Lankes <slankes@eonerc.rwth-aachen.de>
Date: Mon, 1 May 2023 23:11:42 +0200
Subject: [PATCH] revise TLS handling
- ARM used variant 1 of the TLS handling (see
https://uclibc.org/docs/tls.pdf)
- the previous version doesn't work correctly
- using an unsized struct to implement TLS like a C kernel
---
src/arch/aarch64/kernel/scheduler.rs | 78 +++++++++++++++++++++-------
src/arch/x86_64/kernel/scheduler.rs | 4 +-
src/scheduler/task.rs | 3 +-
3 files changed, 62 insertions(+), 23 deletions(-)
diff --git a/src/arch/aarch64/kernel/scheduler.rs b/src/arch/aarch64/kernel/scheduler.rs
index 05d7b4fed..7ac05c0ac 100644
--- a/src/arch/aarch64/kernel/scheduler.rs
+++ b/src/arch/aarch64/kernel/scheduler.rs
@@ -1,10 +1,11 @@
//! Architecture dependent interface to initialize a task
+use alloc::alloc::{alloc_zeroed, Layout};
use alloc::boxed::Box;
use alloc::rc::Rc;
use core::arch::asm;
use core::cell::RefCell;
-use core::{mem, ptr};
+use core::{mem, ptr, slice};
use align_address::Align;
@@ -261,13 +262,34 @@ impl Drop for TaskStacks {
}
}
+/*
+ * https://fuchsia.dev/fuchsia-src/development/kernel/threads/tls and
+ * and https://uclibc.org/docs/tls.pdf is used to understand variant 1
+ * of the TLS implementations.
+ */
+
+#[derive(Copy, Clone)]
+#[repr(C)]
+struct DtvPointer {
+ val: *const (),
+ to_free: *const (),
+}
+
+#[repr(C)]
+union Dtv {
+ counter: usize,
+ pointer: DtvPointer,
+}
+
+#[repr(C)]
pub struct TaskTLS {
- thread_ptr: Box<*mut ()>,
- _block: Box<[u8]>,
+ dtv: mem::MaybeUninit<Box<[Dtv; 2]>>,
+ _private: usize,
+ block: [u8],
}
impl TaskTLS {
- fn from_environment() -> Option<Self> {
+ fn from_environment() -> Option<Box<Self>> {
let tls_len = env::get_tls_memsz();
if env::get_tls_memsz() == 0 {
@@ -280,28 +302,39 @@ impl TaskTLS {
let tls_init_len = env::get_tls_filesz();
// SAFETY: We will have to trust the environment here.
- unsafe { core::slice::from_raw_parts(tls_init_data, tls_init_len) }
+ unsafe { slice::from_raw_parts(tls_init_data, tls_init_len) }
};
- // Allocate TLS block
- let mut block = vec![0; tls_len].into_boxed_slice();
-
- // Initialize beginning of the TLS block with TLS initialization image
- block[..tls_init_image.len()].copy_from_slice(tls_init_image);
+ let off = core::cmp::max(16, env::get_tls_align()) - 16;
+ let block_len = env::get_tls_memsz() + off;
+ let len = block_len + mem::size_of::<Box<[Dtv; 2]>>();
+
+ let layout = Layout::from_size_align(len, 16).unwrap();
+ let mut this = unsafe {
+ let data = alloc_zeroed(layout);
+ let raw = ptr::slice_from_raw_parts_mut(data, block_len) as *mut TaskTLS;
+
+ let addr = (*raw).block.as_ptr().offset(off as isize).cast::<()>();
+ (*raw).dtv.as_mut_ptr().write(Box::new([
+ Dtv { counter: 1 },
+ Dtv {
+ pointer: DtvPointer {
+ val: addr,
+ to_free: ptr::null(),
+ },
+ },
+ ]));
+
+ Box::from_raw(raw)
+ };
- let thread_ptr = block.as_mut_ptr_range().start.cast::<()>();
- // Put thread pointer on heap, so it does not move and can be referenced in fs:0
- let thread_ptr = Box::new(thread_ptr);
+ this.block[off..off + tls_init_image.len()].copy_from_slice(tls_init_image);
- let this = Self {
- thread_ptr,
- _block: block,
- };
Some(this)
}
- fn thread_ptr(&self) -> &*mut () {
- &self.thread_ptr
+ fn thread_ptr(&self) -> *const Box<[Dtv; 2]> {
+ self.dtv.as_ptr()
}
}
@@ -309,6 +342,11 @@ extern "C" fn leave_task() -> ! {
core_scheduler().exit(0)
}
+#[cfg(not(target_os = "none"))]
+extern "C" fn task_start(_f: extern "C" fn(usize), _arg: usize, _user_stack: u64) -> ! {
+ unimplemented!()
+}
+
#[cfg(target_os = "none")]
#[naked]
extern "C" fn task_start(_f: extern "C" fn(usize), _arg: usize, _user_stack: u64) -> ! {
@@ -357,7 +395,7 @@ impl TaskFrame for Task {
ptr::write_bytes(stack.as_mut_ptr::<u8>(), 0, mem::size_of::<State>());
if let Some(tls) = &self.tls {
- (*state).tpidr_el0 = tls.thread_ptr() as *const _ as u64;
+ (*state).tpidr_el0 = tls.thread_ptr() as u64;
}
/*
diff --git a/src/arch/x86_64/kernel/scheduler.rs b/src/arch/x86_64/kernel/scheduler.rs
index cb55af6c8..ec8b3544d 100644
--- a/src/arch/x86_64/kernel/scheduler.rs
+++ b/src/arch/x86_64/kernel/scheduler.rs
@@ -236,7 +236,7 @@ pub struct TaskTLS {
}
impl TaskTLS {
- fn from_environment() -> Option<Self> {
+ fn from_environment() -> Option<Box<Self>> {
// For details on thread-local storage data structures see
//
// “ELF Handling For Thread-Local Storage†Section 3.4.6: x86-64 Specific Definitions for Run-Time Handling of TLS
@@ -287,7 +287,7 @@ impl TaskTLS {
_block: block,
thread_ptr,
};
- Some(this)
+ Some(Box::new(this))
}
fn thread_ptr(&self) -> &*mut () {
diff --git a/src/scheduler/task.rs b/src/scheduler/task.rs
index 88ad9c863..c8a6a0ac5 100644
--- a/src/scheduler/task.rs
+++ b/src/scheduler/task.rs
@@ -1,3 +1,4 @@
+use alloc::boxed::Box;
use alloc::collections::{LinkedList, VecDeque};
use alloc::rc::Rc;
use core::cell::RefCell;
@@ -372,7 +373,7 @@ pub struct Task {
/// Stack of the task
pub stacks: TaskStacks,
/// Task Thread-Local-Storage (TLS)
- pub tls: Option<TaskTLS>,
+ pub tls: Option<Box<TaskTLS>>,
/// lwIP error code for this task
#[cfg(feature = "newlib")]
pub lwip_errno: i32,
--
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