miri/shims/
global_ctor.rs

1//! Implement global constructors.
2
3use std::task::Poll;
4
5use rustc_abi::ExternAbi;
6use rustc_span::Span;
7use rustc_target::spec::BinaryFormat;
8
9use crate::*;
10
11#[derive(Debug, Default)]
12pub struct GlobalCtorState<'tcx>(GlobalCtorStatePriv<'tcx>);
13
14#[derive(Debug, Default)]
15enum GlobalCtorStatePriv<'tcx> {
16    #[default]
17    Init,
18    /// The list of constructor functions that we still have to call.
19    Ctors(Vec<(ImmTy<'tcx>, Span)>),
20    Done,
21}
22
23impl<'tcx> GlobalCtorState<'tcx> {
24    pub fn on_stack_empty(
25        &mut self,
26        this: &mut MiriInterpCx<'tcx>,
27    ) -> InterpResult<'tcx, Poll<()>> {
28        use GlobalCtorStatePriv::*;
29        let new_state = 'new_state: {
30            match &mut self.0 {
31                Init => {
32                    let this = this.eval_context_mut();
33
34                    // Lookup constructors from the relevant magic link section.
35                    let ctors = match this.tcx.sess.target.binary_format {
36                        // Read the CRT library section on Windows.
37                        BinaryFormat::Coff =>
38                            this.lookup_link_section(|section| section == ".CRT$XCU")?,
39
40                        // Read the `__mod_init_func` section on macOS.
41                        BinaryFormat::MachO =>
42                            this.lookup_link_section(|section| {
43                                let mut parts = section.splitn(3, ',');
44                                let (segment_name, section_name, section_type) =
45                                    (parts.next(), parts.next(), parts.next());
46
47                                segment_name == Some("__DATA")
48                                    && section_name == Some("__mod_init_func")
49                                    // The `mod_init_funcs` directive ensures that the
50                                    // `S_MOD_INIT_FUNC_POINTERS` flag is set on the section. LLVM
51                                    // adds this automatically so we currently do not require it.
52                                    // FIXME: is this guaranteed LLVM behavior? If not, we shouldn't
53                                    // implicitly add it here. Also see
54                                    // <https://github.com/rust-lang/miri/pull/4459#discussion_r2200115629>.
55                                    && matches!(section_type, None | Some("mod_init_funcs"))
56                            })?,
57
58                        // Read the standard `.init_array` section on platforms that use ELF, or WASM,
59                        // which supports the same linker directive.
60                        // FIXME: Add support for `.init_array.N` and `.ctors`?
61                        BinaryFormat::Elf | BinaryFormat::Wasm =>
62                            this.lookup_link_section(|section| section == ".init_array")?,
63
64                        // Other platforms have no global ctor support.
65                        _ => break 'new_state Done,
66                    };
67
68                    break 'new_state Ctors(ctors);
69                }
70                Ctors(ctors) => {
71                    if let Some((ctor, span)) = ctors.pop() {
72                        let this = this.eval_context_mut();
73
74                        let ctor = ctor.to_scalar().to_pointer(this)?;
75                        let thread_callback = this.get_ptr_fn(ctor)?.as_instance()?;
76
77                        // The signature of this function is `unsafe extern "C" fn()`.
78                        this.call_thread_root_function(
79                            thread_callback,
80                            ExternAbi::C { unwind: false },
81                            &[],
82                            None,
83                            span,
84                        )?;
85
86                        return interp_ok(Poll::Pending); // we stay in this state (but `ctors` got shorter)
87                    }
88
89                    // No more constructors to run.
90                    break 'new_state Done;
91                }
92                Done => return interp_ok(Poll::Ready(())),
93            }
94        };
95
96        self.0 = new_state;
97        interp_ok(Poll::Pending)
98    }
99}
miri/shims/global_ctor.rs

miri/shims/
global_ctor.rs
