miri/shims/
extern_static.rs

1//! Provides the `extern static` that this platform expects.
2
3use rustc_symbol_mangling::mangle_internal_symbol;
4
5use crate::*;
6
7impl<'tcx> MiriMachine<'tcx> {
8    fn alloc_extern_static(
9        ecx: &mut MiriInterpCx<'tcx>,
10        name: &str,
11        val: ImmTy<'tcx>,
12    ) -> InterpResult<'tcx> {
13        let place = ecx.allocate(val.layout, MiriMemoryKind::ExternStatic.into())?;
14        ecx.write_immediate(*val, &place)?;
15        Self::add_extern_static(ecx, name, place.ptr());
16        interp_ok(())
17    }
18
19    /// Zero-initialized pointer-sized extern statics are pretty common.
20    /// Most of them are for weak symbols, which we all set to null (indicating that the
21    /// symbol is not supported, and triggering fallback code which ends up calling
22    /// some other shim that we do support).
23    fn null_ptr_extern_statics(ecx: &mut MiriInterpCx<'tcx>, names: &[&str]) -> InterpResult<'tcx> {
24        for name in names {
25            let val = ImmTy::from_int(0, ecx.machine.layouts.usize);
26            Self::alloc_extern_static(ecx, name, val)?;
27        }
28        interp_ok(())
29    }
30
31    /// Extern statics that are initialized with function pointers to the symbols of the same name.
32    fn weak_symbol_extern_statics(
33        ecx: &mut MiriInterpCx<'tcx>,
34        names: &[&str],
35    ) -> InterpResult<'tcx> {
36        for name in names {
37            assert!(ecx.is_dyn_sym(name), "{name} is not a dynamic symbol");
38            let layout = ecx.machine.layouts.const_raw_ptr;
39            let ptr = ecx.fn_ptr(FnVal::Other(DynSym::from_str(name)));
40            let val = ImmTy::from_scalar(Scalar::from_pointer(ptr, ecx), layout);
41            Self::alloc_extern_static(ecx, name, val)?;
42        }
43        interp_ok(())
44    }
45
46    /// Sets up the "extern statics" for this machine.
47    pub fn init_extern_statics(ecx: &mut MiriInterpCx<'tcx>) -> InterpResult<'tcx> {
48        // "__rust_alloc_error_handler_should_panic"
49        let val = ecx.tcx.sess.opts.unstable_opts.oom.should_panic();
50        let val = ImmTy::from_int(val, ecx.machine.layouts.u8);
51        Self::alloc_extern_static(
52            ecx,
53            &mangle_internal_symbol(*ecx.tcx, "__rust_alloc_error_handler_should_panic"),
54            val,
55        )?;
56
57        if ecx.target_os_is_unix() {
58            // "environ" is mandated by POSIX.
59            let environ = ecx.machine.env_vars.unix().environ();
60            Self::add_extern_static(ecx, "environ", environ);
61        }
62
63        match ecx.tcx.sess.target.os.as_ref() {
64            "linux" => {
65                Self::null_ptr_extern_statics(
66                    ecx,
67                    &["__cxa_thread_atexit_impl", "__clock_gettime64"],
68                )?;
69                Self::weak_symbol_extern_statics(ecx, &["getrandom", "statx"])?;
70            }
71            "freebsd" => {
72                Self::null_ptr_extern_statics(ecx, &["__cxa_thread_atexit_impl"])?;
73            }
74            "android" => {
75                Self::null_ptr_extern_statics(ecx, &["bsd_signal"])?;
76                Self::weak_symbol_extern_statics(ecx, &["signal", "getrandom"])?;
77            }
78            "windows" => {
79                // "_tls_used"
80                // This is some obscure hack that is part of the Windows TLS story. It's a `u8`.
81                let val = ImmTy::from_int(0, ecx.machine.layouts.u8);
82                Self::alloc_extern_static(ecx, "_tls_used", val)?;
83            }
84            "illumos" | "solaris" => {
85                Self::weak_symbol_extern_statics(ecx, &["pthread_setname_np"])?;
86            }
87            _ => {} // No "extern statics" supported on this target
88        }
89        interp_ok(())
90    }
91}
miri/shims/extern_static.rs

miri/shims/
extern_static.rs
