miri/shims/
global_ctor.rs

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

miri/shims/
global_ctor.rs
