wasmtime_fiber/
stackswitch.rs

1//! ISA-specific stack-switching routines.
2
3// The bodies are defined in inline assembly in the conditionally
4// included modules below; their symbols are visible in the binary and
5// accessed via the `extern "C"` declarations below that.
6
7cfg_if::cfg_if! {
8    if #[cfg(target_arch = "aarch64")] {
9        mod aarch64;
10        pub(crate) use supported::*;
11    } else if #[cfg(target_arch = "x86_64")] {
12        mod x86_64;
13        pub(crate) use supported::*;
14    } else if #[cfg(target_arch = "x86")] {
15        mod x86;
16        pub(crate) use supported::*;
17    } else if #[cfg(target_arch = "arm")] {
18        mod arm;
19        pub(crate) use supported::*;
20    } else if #[cfg(target_arch = "s390x")] {
21        // currently `global_asm!` isn't stable on s390x so this is an external
22        // assembler file built with the `build.rs`.
23        pub(crate) use supported::*;
24    } else if #[cfg(target_arch = "riscv64")]  {
25        mod riscv64;
26        pub(crate) use supported::*;
27    } else {
28        // No support for this platform. Don't fail compilation though and
29        // instead defer the error to happen at runtime when a fiber is created.
30        // Should help keep compiles working and narrows the failure to only
31        // situations that need fibers on unsupported platforms.
32        pub(crate) use unsupported::*;
33    }
34}
35
36/// A helper module to get reeported above in each case that we actually have
37/// stack-switching routines available in in line asm. The fall-through case
38/// though reexports the `unsupported` module instead.
39#[allow(
40    dead_code,
41    reason = "expected to have dead code in some configurations"
42)]
43mod supported {
44    pub const SUPPORTED_ARCH: bool = true;
45    unsafe extern "C" {
46        #[wasmtime_versioned_export_macros::versioned_link]
47        pub(crate) fn wasmtime_fiber_init(
48            top_of_stack: *mut u8,
49            entry: extern "C" fn(*mut u8, *mut u8),
50            entry_arg0: *mut u8,
51        );
52        #[wasmtime_versioned_export_macros::versioned_link]
53        pub(crate) fn wasmtime_fiber_switch(top_of_stack: *mut u8);
54        #[wasmtime_versioned_export_macros::versioned_link]
55        pub(crate) fn wasmtime_fiber_start();
56    }
57}
58
59/// Helper module reexported in the fallback case above when the current host
60/// architecture is not supported for stack switching. The `SUPPORTED_ARCH`
61/// boolean here is set to `false` which causes `Fiber::new` to return `false`.
62#[allow(
63    dead_code,
64    reason = "expected to have dead code in some configurations"
65)]
66mod unsupported {
67    pub const SUPPORTED_ARCH: bool = false;
68
69    pub(crate) unsafe fn wasmtime_fiber_init(
70        _top_of_stack: *mut u8,
71        _entry: extern "C" fn(*mut u8, *mut u8),
72        _entry_arg0: *mut u8,
73    ) {
74        unreachable!();
75    }
76
77    pub(crate) unsafe fn wasmtime_fiber_switch(_top_of_stack: *mut u8) {
78        unreachable!();
79    }
80}
wasmtime_fiber/stackswitch.rs

wasmtime_fiber/
stackswitch.rs
