miri/shims/
extern_static.rs

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

miri/shims/
extern_static.rs
