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//! Exports the [`macro@cpu_local`] macro.
#![feature(proc_macro_diagnostic, proc_macro_span, let_chains)]
mod int;
use convert_case::{Case, Casing};
use proc_macro::{Diagnostic, Level, Span, TokenStream};
use quote::{quote, ToTokens};
use syn::{
parse::{Parse, ParseStream},
parse_macro_input,
spanned::Spanned,
Attribute, Expr, Ident, LitBool, Path, Token, Type, Visibility,
};
struct CpuLocal {
attributes: Vec<Attribute>,
visibility: Visibility,
name: Ident,
ty: Type,
init: Expr,
}
impl Parse for CpuLocal {
fn parse(input: ParseStream) -> syn::Result<Self> {
let attributes = input.call(Attribute::parse_outer)?;
let visibility: Visibility = input.parse()?;
input.parse::<Token![static]>()?;
let name: Ident = input.parse()?;
input.parse::<Token![:]>()?;
let ty: Type = input.parse()?;
input.parse::<Token![=]>()?;
let init: Expr = input.parse()?;
input.parse::<Token![;]>()?;
Ok(CpuLocal {
attributes,
visibility,
name,
ty,
init,
})
}
}
struct Args {
cls_dependency: bool,
stores_guard: Option<Type>,
}
impl Parse for Args {
fn parse(input: ParseStream) -> syn::Result<Self> {
let mut cls_dependency = true;
let mut stores_guard = None;
while let Ok(name) = input.parse::<Path>() {
input.parse::<Token![=]>()?;
if name.is_ident("cls_dep") {
cls_dependency = input.parse::<LitBool>()?.value();
} else if name.is_ident("stores_guard") {
stores_guard = Some((name, input.parse::<Type>()?));
} else {
Diagnostic::spanned(
name.span().unwrap(),
Level::Error,
format!("invalid argument `{}`", name.to_token_stream()),
)
.help("valid arguments are: `cls_dep`, `stores_guard`")
.emit();
return Err(syn::Error::new(name.span(), ""));
}
let _ = input.parse::<Token![,]>();
}
if let Some((ref name, ref value)) = stores_guard && !cls_dependency {
let span = name.span().join(value.span()).unwrap().unwrap();
Diagnostic::spanned(
span,
Level::Error,
"`stores_guard` requires `cls_dep`",
)
.emit();
return Err(syn::Error::new(name.span(), ""));
}
Ok(Self {
cls_dependency,
stores_guard: stores_guard.map(|tuple| tuple.1),
})
}
}
/// A macro for declaring CPU-local variables.
///
/// Variables must be an unsigned integer, bar `u128`.
///
/// The initialisation expression has no effect; to set the initial value,
/// `per_cpu::PerCpuData::new` must be modified.
///
/// # Arguments
///
/// The macro supports additional named arguments defined after the offset (e.g.
/// `#[cpu_local(0, cls_dep = false)]`):
/// - `cls_dep`: Whether to define methods that depend on `cls` indirectly
/// adding a dependency on `preemption` and `irq_safety`. This is only really
/// useful for CPU locals defined in `preemption` to avoid a circular
/// dependency. Defaults to true.
/// - `stores_guard`: If defined, must be set to either `HeldInterrupts` or
/// `PreemptionGuard` and signifies that the CPU local has the type
/// `Option<Guard>`. This option defines special methods that use the guard
/// being switched into the CPU local, rather than an additional guard
/// parameter, as proof that the CPU local can be safely accessed.
#[proc_macro_attribute]
pub fn cpu_local(args: TokenStream, input: TokenStream) -> TokenStream {
let Args {
cls_dependency,
stores_guard,
} = match syn::parse(args) {
Ok(args) => args,
Err(error) => {
if error.to_string() == "" {
// We've already emmited an error diagnostic.
return TokenStream::new();
} else {
Diagnostic::spanned(error.span().unwrap(), Level::Error, error.to_string()).emit();
return TokenStream::new();
}
}
};
let CpuLocal {
attributes,
visibility,
name,
ty,
init,
} = parse_macro_input!(input as CpuLocal);
let attributes = attributes.iter().map(|attribute| quote! { #attribute });
let struct_name = Ident::new(
&format!("CPU_LOCAL_{name}").to_case(Case::Pascal),
Span::call_site().into(),
);
let offset_expr = cls_offset_expr(&name);
let ref_expr = quote! {
{
let offset = #offset_expr;
#[cfg(target_arch = "x86_64")]
let mut ptr = {
use cls::__private::x86_64::registers::segmentation::{GS, Segment64};
let gs = GS::read_base().as_u64();
// If this CLS section was statically linked, its `offset` will be negative on x86_64 only.
let (value, _) = gs.overflowing_add(offset);
value
};
#[cfg(target_arch = "aarch64")]
let mut ptr = {
use cls::__private::tock_registers::interfaces::Readable;
let tpidr_el1 = cls::__private::cortex_a::registers::TPIDR_EL1.get();
tpidr_el1 + offset
};
unsafe { &mut*(ptr as *mut #ty) }
}
};
let cls_dep_functions = if cls_dependency {
let guarded_functions = quote! {
#[inline]
pub fn replace_guarded<G>(&self, mut value: #ty, guard: &G) -> #ty
where
G: ::cls::CpuAtomicGuard,
{
let rref = #ref_expr;
::core::mem::swap(rref, &mut value);
value
}
#[inline]
pub fn set_guarded<G>(&self, mut value: #ty, guard: &G)
where
G: ::cls::CpuAtomicGuard,
{
self.replace_guarded(value, guard);
}
#[inline]
pub fn update_guarded<F, R, G>(&self, f: F, guard: &G) -> R
where
F: ::core::ops::FnOnce(&mut #ty) -> R,
G: ::cls::CpuAtomicGuard,
{
let rref = #ref_expr;
f(rref)
}
};
if let Some(guard_type) = stores_guard {
quote! {
#guarded_functions
#[inline]
pub fn replace(&self, guard: #guard_type) -> #ty {
// Check that the guard type matches the type of the static.
// https://github.com/rust-lang/rust/issues/20041#issuecomment-820911297
trait TyEq {}
impl<T> TyEq for (T, T) {}
fn ty_eq<A, B>()
where
(A, B): TyEq
{}
ty_eq::<::core::option::Option<#guard_type>, #ty>();
// Check that the guard type implements cls::Guard.
fn implements_guard_trait<T>()
where
T: ::cls::CpuAtomicGuard
{}
implements_guard_trait::<#guard_type>();
let rref = #ref_expr;
let mut guard = Some(guard);
::core::mem::swap(rref, &mut guard);
guard
}
#[inline]
pub fn set(&self, mut guard: #guard_type) {
self.replace(guard);
}
}
} else {
quote! {
#guarded_functions
#[inline]
pub fn replace(&self, value: #ty) -> #ty {
// TODO: Should this ever be `disable_interrupts` instead?
let guard = ::cls::__private::preemption::hold_preemption();
self.replace_guarded(value, &guard)
}
#[inline]
pub fn set(&self, value: #ty) {
// TODO: Should this ever be `disable_interrupts` instead?
let guard = ::cls::__private::preemption::hold_preemption();
self.set_guarded(value, &guard);
}
#[inline]
pub fn update<F, R>(&self, f: F) -> R
where
F: ::core::ops::FnOnce(&mut #ty) -> R,
{
// TODO: Should this ever be `disable_interrupts` instead?
let guard = ::cls::__private::preemption::hold_preemption();
self.update_guarded(f, &guard)
}
}
}
} else {
proc_macro2::TokenStream::new()
};
let int_functions = int::int_functions(&ty, &name);
quote! {
#(#attributes)*
#[thread_local]
#[link_section = ".cls"]
#[used]
#visibility static #name: #struct_name = #struct_name {
__inner: #init,
};
#[repr(transparent)]
#[doc(hidden)]
#visibility struct #struct_name {
__inner: #ty,
}
impl #struct_name {
#int_functions
#cls_dep_functions
}
}
.into()
}
fn cls_offset_expr(name: &Ident) -> proc_macro2::TokenStream {
quote! {
{
// See the crate-level docs in `cls` for an explanation of the implementation.
#[cfg(target_arch = "x86_64")]
{
extern "C" {
static __THESEUS_CLS_SIZE: u8;
static __THESEUS_TLS_SIZE: u8;
}
// TODO: Open an issue in rust repo? We aren't actually doing anything unsafe.
// SAFETY: We don't access the extern static.
let cls_size = unsafe { ::core::ptr::addr_of!(__THESEUS_CLS_SIZE) } as u64;
// SAFETY: We don't access the extern static.
let tls_size = unsafe { ::core::ptr::addr_of!(__THESEUS_TLS_SIZE) } as u64;
// On x86_64, `mod_mgmt` will set `__THESEUS_CLS_SIZE` and `__THESEUS_TLS_SIZE` to
// `usize::MAX` in order to indicate dynamic loading/linking is being used.
if cls_size == u64::MAX && tls_size == u64::MAX {
// The offset is always correct when dynamically linked (since we set it in `mod_mgmt`),
// so there is no need to modify the offset here, we can just use it directly.
let offset: u64;
unsafe {
::core::arch::asm!(
"lea {offset}, [{cls}@TPOFF]",
offset = out(reg) offset,
cls = sym #name,
options(nomem, preserves_flags, nostack),
)
};
offset
}
// Otherwise, if the CLS section/symbol was statically linked,
// we need to adjust the offset to account for the section's 4K page alignment
// and the size of the preceding static TLS sections.
// See the crate-level docs of `cls` for a detailed explanation of this.
else {
// If the statically-linked base kernel image has no TLS sections,
// the `{cls}@TPOFF` expression alone correctly gives us the offset
// from the end of the `.cls` section.
if tls_size == 0 {
let offset: u64;
unsafe {
::core::arch::asm!(
"lea {offset}, [{cls}@TPOFF]",
offset = out(reg) offset,
cls = sym #name,
options(nomem, preserves_flags, nostack),
)
};
offset
} else {
// The linker script aligns sections to page boundaries.
const ALIGNMENT: u64 = 1 << 12;
// TODO: Use `next_multiple_of(0x1000)` when stabilised.
let cls_start_to_tls_start = (cls_size + ALIGNMENT - 1) & !(ALIGNMENT - 1);
let from_cls_start: u64;
unsafe {
::core::arch::asm!(
"lea {from_cls_start}, [{cls}@TPOFF + {tls_size} + {cls_start_to_tls_start}]",
from_cls_start = lateout(reg) from_cls_start,
cls = sym #name,
tls_size = in(reg) tls_size,
cls_start_to_tls_start = in(reg) cls_start_to_tls_start,
options(nomem, preserves_flags, nostack),
)
};
let offset = (cls_size - from_cls_start).wrapping_neg();
offset
}
}
}
#[cfg(target_arch = "aarch64")]
{
extern "C" {
static __THESEUS_TLS_SIZE: u8;
}
// TODO: Open an issue in rust repo? We aren't actually doing anything unsafe.
// SAFETY: We don't access the extern static.
let tls_size = unsafe { ::core::ptr::addr_of!(__THESEUS_TLS_SIZE) } as u64;
// The linker script aligns sections to page boundaries.
const ALIGNMENT: u64 = 1 << 12;
// TODO: Use `next_multiple_of(0x1000)` when stabilised.
let tls_start_to_cls_start = (tls_size + ALIGNMENT - 1) & !(ALIGNMENT - 1);
let mut offset = 0;
unsafe {
// This will compile into something like
// ```armasm
// add {offset}, 0, #1, lsl #12
// add {offset}, {offset}, #0x10
// sub {offset}, {offset}, #1, lsl #12
// ```
// `#1, lsl #12` is `1 << 12 = 0x1000` which is the size of a single page.
//
// The first add instruction loads the upper 12 bits of the offset into
// `{offset}`, and the second add instruction loads the lower 12 bits. Then,
// since all CLS offsets on aarch64 are a page size larger than they are
// supposed to be, we subtract a page size. Realistically, we could just omit
// loading the upper 12 bits of the offset and the `sub` insntruction under the
// assumption that the CLS section will never be larger than a page. But that
// would lead to very cryptic bugs if we were to ever breach that limit and an
// extra `sub` instruction per CLS access isn't significant.
::core::arch::asm!(
"add {offset}, {offset}, #:tprel_hi12:{cls}, lsl #12",
"add {offset}, {offset}, #:tprel_lo12_nc:{cls}",
"sub {offset}, {offset}, {tls_start_to_cls_start}",
offset = inout(reg) offset,
cls = sym #name,
tls_start_to_cls_start = in(reg) tls_start_to_cls_start,
options(nomem, preserves_flags, nostack),
)
};
offset
}
}
}
}