feat(ld_so/dso): TLSDESC
The dynamic linker now works on aarch64. You can also try it on Linux by setting `TEST_RUNNER` to `qemu-aarch64` when running `make test TARGET=aarch64-unknown-linux-gnu` Co-authored-by: @willnode Signed-off-by: Anhad Singh <andypython@protonmail.com>
This commit is contained in:
Anhad Singh
Vendored
+2
-1
@@ -1,3 +1,4 @@
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{
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"cmake.ignoreCMakeListsMissing": true
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"cmake.ignoreCMakeListsMissing": true,
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"editor.formatOnSave": true
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}
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+142
-8
@@ -13,20 +13,21 @@ use object::{
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use super::{
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debug::{_r_debug, RTLDDebug},
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linker::{__plt_resolve_trampoline, GLOBAL_SCOPE, Resolve, Scope, Symbol},
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tcb::Master,
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tcb::{Master, Tcb},
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};
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use crate::{
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header::sys_mman,
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header::{dl_tls::__tls_get_addr, sys_mman},
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platform::{Pal, Sys, types::c_void},
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};
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use alloc::{
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boxed::Box,
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string::{String, ToString},
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sync::Arc,
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vec::Vec,
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};
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use core::{
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ffi::c_char,
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mem::size_of,
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mem::{offset_of, size_of},
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ptr::{self, NonNull},
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slice,
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};
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@@ -208,7 +209,7 @@ impl From<&Rel> for Relocation {
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// This is matched up to REL_* constants used by musl for ease of comparison
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#[allow(dead_code)]
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#[derive(Clone, Copy, Debug)]
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#[derive(Clone, Copy, Debug, PartialEq)]
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pub enum RelocationKind {
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COPY,
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DTPMOD,
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@@ -817,6 +818,47 @@ impl DSO {
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))
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}
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/// `TLSDESC` relocation being an extension to the original TLS ABI spec can
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/// be present in either `.rela.plt` (handled in [`Self::static_relocate`])
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/// or `.rela.dyn` (handled in [`Self::lazy_relocate`]) due to the lack of a
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/// standard unfortunately.
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///
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/// # Panics
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///
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/// Panics if `reloc.kind` is not `RelocationKind::TLSDESC`.
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fn do_tlsdesc_reloc(&self, reloc: Relocation, ptr: *mut usize, global_scope: &Scope) {
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assert!(reloc.kind == RelocationKind::TLSDESC);
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let (sym, tls_module_id, tls_offset) = if reloc.sym != SymbolIndex(0) {
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let sym_name = self.dynamic.symbol_name(reloc.sym).unwrap();
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let (sym, _, obj) = resolve_sym(sym_name, &[global_scope, self.scope()]).unwrap();
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(sym.value, obj.tls_module_id, obj.tls_offset)
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} else {
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(0, self.tls_module_id, self.tls_offset)
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};
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let resolver = unsafe { &mut *ptr };
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let descriptor = unsafe { &mut *ptr.add(1) };
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if self.dlopened {
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let mut tls_index = crate::header::dl_tls::dl_tls_index {
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ti_module: tls_module_id,
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ti_offset: reloc.addend.unwrap_or_default(),
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};
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// Ensure the DTV entry is initialised.
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unsafe { __tls_get_addr(&mut tls_index) };
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*resolver = __tlsdesc_dynamic as *const () as usize;
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*descriptor = Box::into_raw(Box::new(TlsDescriptor {
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module_id: tls_module_id - 1,
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addend: sym + reloc.addend.unwrap_or_default(),
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})) as usize;
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} else {
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*resolver = __tlsdesc_static as *const () as usize;
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*descriptor = sym + tls_offset + reloc.addend.unwrap_or_default();
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}
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}
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fn static_relocate(&self, global_scope: &Scope, reloc: Relocation) -> object::Result<()> {
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let b = self.mmap.as_ptr() as usize;
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@@ -841,7 +883,7 @@ impl DSO {
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let (s, t, tls_id) = sym
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.as_ref()
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.map(|(sym, obj)| (sym.as_ptr() as usize, obj.tls_offset, obj.tls_module_id))
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//TODO: is self.tls_module_id the right fallback?
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// TODO: is self.tls_module_id the right fallback?
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.unwrap_or((0, 0, self.tls_module_id));
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let ptr = if self.pie {
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@@ -858,14 +900,14 @@ impl DSO {
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},
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};
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//TODO: support different sizes?
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// TODO: support different sizes?
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let set_usize = |value| unsafe {
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*(ptr as *mut usize) = value;
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};
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match reloc.kind {
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RelocationKind::DTPMOD => set_usize(tls_id),
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//TODO: Subtract DTP_OFFSET, which is 0x800 on riscv64, 0 on x86?
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// TODO: Subtract DTP_OFFSET, which is 0x800 on riscv64, 0 on x86?
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RelocationKind::DTPOFF => {
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if reloc.sym.0 > 0 {
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let (sym, _) = sym
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@@ -909,6 +951,9 @@ impl DSO {
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// SAFETY: Both the source and destination have the same size.
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ptr::copy_nonoverlapping(sym.as_ptr() as *const u8, ptr, sym.size);
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},
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RelocationKind::TLSDESC => {
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self.do_tlsdesc_reloc(reloc, ptr.cast::<usize>(), global_scope)
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}
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_ => unimplemented!("relocation type {:?}", reloc.kind),
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}
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@@ -927,7 +972,8 @@ impl DSO {
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unsafe {
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got.add(1).write(core::ptr::addr_of!(*self) as usize);
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got.add(2).write(__plt_resolve_trampoline as usize);
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got.add(2)
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.write(__plt_resolve_trampoline as *const () as usize);
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}
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let relsz = if self.dynamic.explicit_addend {
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@@ -975,6 +1021,13 @@ impl DSO {
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}
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}
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(RelocationKind::TLSDESC, Resolve::Now) => {
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self.do_tlsdesc_reloc(reloc, ptr, global_scope);
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}
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(RelocationKind::TLSDESC, Resolve::Lazy) => {
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unreachable!("TLSDESC cannot be lazily resolved")
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}
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_ => {
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unimplemented!(
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"relocation type {:?} with resolve {:?}",
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@@ -1092,3 +1145,84 @@ pub fn resolve_sym<'a>(
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) -> Option<(Symbol<'a>, SymbolBinding, Arc<DSO>)> {
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scopes.iter().find_map(|scope| scope.get_sym(name))
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}
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#[repr(C)]
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struct TlsDescriptor {
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module_id: usize,
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addend: usize,
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}
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#[cfg(target_arch = "aarch64")]
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#[unsafe(naked)]
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unsafe extern "C" fn __tlsdesc_static() {
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core::arch::naked_asm!("ldr x0, [x0, #8]", "ret")
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}
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#[cfg(target_arch = "x86_64")]
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#[unsafe(naked)]
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unsafe extern "C" fn __tlsdesc_static() {
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core::arch::naked_asm!("mov rax, [rax + 8]", "ret")
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}
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unsafe extern "C" {
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fn __tlsdesc_dynamic();
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}
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#[cfg(target_arch = "x86_64")]
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core::arch::global_asm!(
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"
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.global __tlsdesc_dynamic
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.hidden __tlsdesc_dynamic
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__tlsdesc_dynamic:
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push rbx
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push rcx
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mov rax, [rax + 8] // TLS descriptor
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mov rbx, [rax + {TLS_DESCRIPTOR_MODULE_ID_OFF}] // tls_descriptor.module_id
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mov rcx, [rax + {TLS_DESCRIPTOR_ADDEND_OFF}] // tls_descriptor.addend
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mov rax, qword ptr fs:[{DTV_PTR_OFF}] // tcb.dtv_ptr
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// tcb.dtv_ptr[tls_descriptor.module_id] + tls_descriptor.addend
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mov rax, [rax + rbx * 8]
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add rax, rcx
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sub rax, qword ptr fs:[{TCB_SELF_PTR_OFF}]
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pop rcx
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pop rbx
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ret
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",
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TLS_DESCRIPTOR_MODULE_ID_OFF = const offset_of!(TlsDescriptor, module_id),
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TLS_DESCRIPTOR_ADDEND_OFF = const offset_of!(TlsDescriptor, addend),
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DTV_PTR_OFF = const offset_of!(Tcb, dtv_ptr),
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TCB_SELF_PTR_OFF = const offset_of!(Tcb, generic.tcb_ptr),
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);
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#[cfg(target_arch = "aarch64")]
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core::arch::global_asm!(
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"
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.global __tlsdesc_dynamic
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.hidden __tlsdesc_dynamic
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__tlsdesc_dynamic:
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stp x1, x2, [sp, #-16]!
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ldr x0, [x0, #8] // TLS descriptor
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// x0 := tls_descriptor.module_id
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// x1 := tls_descriptor.addend
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ldp x0, x1, [x0]
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mrs x2, tpidr_el0 // ABI ptr
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ldr x2, [x2] // TCB ptr
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sub x1, x1, x2 // tls_descriptor.addend -= tcb
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ldr x2, [x2, {DTV_PTR_OFF}] // tcb.dtv_ptr
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ldr x2, [x2, x0, lsl #3] // tcb.dtv_ptr[tls_descriptor.module_id]
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add x0, x2, x1 // tcb.dtv_ptr[tls_descriptor.module_id] + tls_descriptor.addend
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ldp x1, x2, [sp], #16
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ret
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",
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DTV_PTR_OFF = const offset_of!(Tcb, dtv_ptr),
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);
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