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Implement support for async functions in Wasmtime #2434

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4 changes: 3 additions & 1 deletion .github/workflows/main.yml
Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ jobs:
name: Doc - build the API documentation
runs-on: ubuntu-latest
env:
RUSTDOCFLAGS: -Dbroken_intra_doc_links
RUSTDOCFLAGS: -Dbroken_intra_doc_links --cfg nightlydoc
OPENVINO_SKIP_LINKING: 1
steps:
- uses: actions/checkout@v2
Expand Down Expand Up @@ -120,6 +120,8 @@ jobs:
- run: cargo check --manifest-path crates/wasmtime/Cargo.toml --features wat
- run: cargo check --manifest-path crates/wasmtime/Cargo.toml --features lightbeam
- run: cargo check --manifest-path crates/wasmtime/Cargo.toml --features jitdump
- run: cargo check --manifest-path crates/wasmtime/Cargo.toml --features cache
- run: cargo check --manifest-path crates/wasmtime/Cargo.toml --features async

# Check some feature combinations of the `wasmtime-c-api` crate
- run: cargo check --manifest-path crates/c-api/Cargo.toml --no-default-features
Expand Down
18 changes: 18 additions & 0 deletions Cargo.lock

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30 changes: 30 additions & 0 deletions crates/fiber/Cargo.toml
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
[package]
name = "wasmtime-fiber"
version = "0.23.0"
authors = ["The Wasmtime Project Developers"]
description = "Fiber support for Wasmtime"
license = "Apache-2.0 WITH LLVM-exception"
repository = "https://github.com/bytecodealliance/wasmtime"
edition = "2018"

# We link to some native code with symbols that don't change often, so let Cargo
# know that we can't show up multiple times in a crate graph. If this is an
# issue in the future we should tweak the build script to set `#define`
# directives or similar to embed a version number of this crate in symbols.
links = "wasmtime-fiber-shims"

[target.'cfg(unix)'.dependencies]
libc = "0.2.80"

[target.'cfg(windows)'.dependencies.winapi]
version = "0.3.9"
features = [
"fibersapi",
"winbase",
]

[build-dependencies]
cc = "1.0"

[dev-dependencies]
backtrace = "0.3"
25 changes: 25 additions & 0 deletions crates/fiber/build.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
use std::env;
use std::fs;

fn main() {
let mut build = cc::Build::new();
let arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
let family = env::var("CARGO_CFG_TARGET_FAMILY").unwrap();
let os = env::var("CARGO_CFG_TARGET_OS").unwrap();

let family_file = format!("src/arch/{}.c", family);
let arch_file = format!("src/arch/{}.S", arch);
if fs::metadata(&family_file).is_ok() {
build.file(&family_file);
} else if fs::metadata(&arch_file).is_ok() {
build.file(&arch_file);
} else {
panic!(
"wasmtime doesn't support fibers on platform: {}",
env::var("TARGET").unwrap()
);
}
build.define(&format!("CFG_TARGET_OS_{}", os), None);
build.define(&format!("CFG_TARGET_ARCH_{}", arch), None);
build.compile("wasmtime-fiber");
}
122 changes: 122 additions & 0 deletions crates/fiber/src/arch/aarch64.S
Original file line number Diff line number Diff line change
@@ -0,0 +1,122 @@
// A WORD OF CAUTION
//
// This entire file basically needs to be kept in sync with itself. It's not
// really possible to modify just one bit of this file without understanding
// all the other bits. Documentation tries to reference various bits here and
// there but try to make sure to read over everything before tweaking things!
//
// Also at this time this file is heavily based off the x86_64 file, so you'll
// probably want to read that one as well.

#include "header.h"

// fn(top_of_stack(%x0): *mut u8)
HIDDEN(wasmtime_fiber_switch)
GLOBL(wasmtime_fiber_switch)
.p2align 2
TYPE(wasmtime_fiber_switch)
FUNCTION(wasmtime_fiber_switch):
// Save all callee-saved registers on the stack since we're assuming
// they're clobbered as a result of the stack switch.
stp lr, fp, [sp, -16]!
stp x20, x19, [sp, -16]!
stp x22, x21, [sp, -16]!
stp x24, x23, [sp, -16]!
stp x26, x25, [sp, -16]!
stp x28, x27, [sp, -16]!
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stp d9, d8, [sp, -16]!
stp d11, d10, [sp, -16]!
stp d13, d12, [sp, -16]!
stp d15, d14, [sp, -16]!

// Load our previously saved stack pointer to resume to, and save off our
// current stack pointer on where to come back to eventually.
ldr x8, [x0, -0x10]
mov x9, sp
str x9, [x0, -0x10]

// Switch to the new stack and restore all our callee-saved registers after
// the switch and return to our new stack.
mov sp, x8
ldp d15, d14, [sp], 16
ldp d13, d12, [sp], 16
ldp d11, d10, [sp], 16
ldp d9, d8, [sp], 16
ldp x28, x27, [sp], 16
ldp x26, x25, [sp], 16
ldp x24, x23, [sp], 16
ldp x22, x21, [sp], 16
ldp x20, x19, [sp], 16
ldp lr, fp, [sp], 16
ret
SIZE(wasmtime_fiber_switch)

// fn(
// top_of_stack(%x0): *mut u8,
// entry_point(%x1): extern fn(*mut u8, *mut u8),
// entry_arg0(%x2): *mut u8,
// )
HIDDEN(wasmtime_fiber_init)
GLOBL(wasmtime_fiber_init)
.p2align 2
TYPE(wasmtime_fiber_init)
FUNCTION(wasmtime_fiber_init):
adr x8, FUNCTION(wasmtime_fiber_start)
stp x0, x8, [x0, -0x28] // x0 => x19, x8 => lr
stp x2, x1, [x0, -0x38] // x1 => x20, x2 => x21

// `wasmtime_fiber_switch` has an 0xa0 byte stack, and we add 0x10 more for
// the original reserved 16 bytes.
add x8, x0, -0xb0
str x8, [x0, -0x10]
ret
SIZE(wasmtime_fiber_init)

.p2align 2
TYPE(wasmtime_fiber_start)
FUNCTION(wasmtime_fiber_start):
.cfi_startproc simple

// See the x86_64 file for more commentary on what these CFI directives are
// doing. Like over there note that the relative offsets to registers here
// match the frame layout in `wasmtime_fiber_switch`.
.cfi_escape 0x0f, /* DW_CFA_def_cfa_expression */ \
5, /* the byte length of this expression */ \
0x6f, /* DW_OP_reg31(%sp) */ \
0x06, /* DW_OP_deref */ \
0x23, 0xa0, 0x1 /* DW_OP_plus_uconst 0xa0 */

.cfi_rel_offset lr, -0x10
.cfi_rel_offset x19, -0x18
.cfi_rel_offset x20, -0x20
.cfi_rel_offset x21, -0x28
.cfi_rel_offset x22, -0x30
.cfi_rel_offset x23, -0x38
.cfi_rel_offset x24, -0x40
.cfi_rel_offset x25, -0x48
.cfi_rel_offset x26, -0x50
.cfi_rel_offset x27, -0x58
.cfi_rel_offset x29, -0x60

// Load our two arguments from the stack, where x1 is our start procedure
// and x0 is its first argument. This also blows away the stack space used
// by those two arguments.
mov x0, x21
mov x1, x19

// ... and then we call the function! Note that this is a function call so
// our frame stays on the stack to backtrace through.
blr x20
// .. technically we shouldn't get here, and I would like to write in an
// instruction which just aborts, but I don't know such an instruction in
// aarch64 land.
.cfi_endproc
SIZE(wasmtime_fiber_start)

// This omits the `.subsections_via_symbols` directive on macOS which means we
// can't GC specific intrinsics from this file, but it enables usage of the
// `adr` instruction above in lieu of figuring out a slightly more complicated
// way of implementing that.
#ifndef CFG_TARGET_OS_macos
FOOTER
#endif
83 changes: 83 additions & 0 deletions crates/fiber/src/arch/arm.S
Original file line number Diff line number Diff line change
@@ -0,0 +1,83 @@
// A WORD OF CAUTION
//
// This entire file basically needs to be kept in sync with itself. It's not
// really possible to modify just one bit of this file without understanding
// all the other bits. Documentation tries to reference various bits here and
// there but try to make sure to read over everything before tweaking things!
//
// Also at this time this file is heavily based off the x86_64 file, so you'll
// probably want to read that one as well.

#include "header.h"

// fn(top_of_stack(%r0): *mut u8)
HIDDEN(wasmtime_fiber_switch)
GLOBL(wasmtime_fiber_switch)
TYPE(wasmtime_fiber_switch)
FUNCTION(wasmtime_fiber_switch):
// Save callee-saved registers
push {r4-r11,lr}

// Swap stacks, recording our current stack pointer
ldr r4, [r0, #-0x08]
str sp, [r0, #-0x08]
mov sp, r4

// Restore and return
pop {r4-r11,lr}
bx lr
SIZE(wasmtime_fiber_switch)

// fn(
// top_of_stack(%r0): *mut u8,
// entry_point(%r1): extern fn(*mut u8, *mut u8),
// entry_arg0(%r2): *mut u8,
// )
HIDDEN(wasmtime_fiber_init)
GLOBL(wasmtime_fiber_init)
TYPE(wasmtime_fiber_init)
FUNCTION(wasmtime_fiber_init):
adr r3, FUNCTION(wasmtime_fiber_start)
str r3, [r0, #-0x0c] // => lr
str r0, [r0, #-0x10] // => r11
str r1, [r0, #-0x14] // => r10
str r2, [r0, #-0x18] // => r9

add r3, r0, #-0x2c
str r3, [r0, #-0x08]
bx lr
SIZE(wasmtime_fiber_init)

FUNCTION(wasmtime_fiber_start):
.cfi_startproc simple
// See the x86_64 file for more commentary on what these CFI directives are
// doing. Like over there note that the relative offsets to registers here
// match the frame layout in `wasmtime_fiber_switch`.
//
// TODO: this is only lightly tested. This gets backtraces in gdb but not
// at runtime. Perhaps the libgcc at runtime was too old? Doesn't support
// something here? Unclear. Will need investigation if someone ends up
// needing this and it still doesn't work.
.cfi_escape 0x0f, /* DW_CFA_def_cfa_expression */ \
5, /* the byte length of this expression */ \
0x7d, 0x00, /* DW_OP_breg14(%sp) + 0 */ \
0x06, /* DW_OP_deref */ \
0x23, 0x24 /* DW_OP_plus_uconst 0x24 */

.cfi_rel_offset lr, -0x04
.cfi_rel_offset r11, -0x08
.cfi_rel_offset r10, -0x0c
.cfi_rel_offset r9, -0x10
.cfi_rel_offset r8, -0x14
.cfi_rel_offset r7, -0x18
.cfi_rel_offset r6, -0x1c
.cfi_rel_offset r5, -0x20
.cfi_rel_offset r4, -0x24

mov r1, r11
mov r0, r9
blx r10
.cfi_endproc
SIZE(wasmtime_fiber_start)

FOOTER
36 changes: 36 additions & 0 deletions crates/fiber/src/arch/header.h
Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
#ifndef __wasmtime_common_h
#define __wasmtime_common_h

#if CFG_TARGET_OS_macos

.section __TEXT,__text,regular,pure_instructions

#define GLOBL(fnname) .globl _##fnname
#define HIDDEN(fnname) .private_extern _##fnname
#define TYPE(fnname)
#define FUNCTION(fnname) _##fnname
#define SIZE(fnname)

// Tells the linker it's safe to gc symbols away if not used.
#define FOOTER .subsections_via_symbols

#else

.text

#define GLOBL(fnname) .globl fnname
#define HIDDEN(fnname) .hidden fnname
#ifdef CFG_TARGET_ARCH_arm
#define TYPE(fnname) .type fnname,%function
#else
#define TYPE(fnname) .type fnname,@function
#endif
#define FUNCTION(fnname) fnname
#define SIZE(fnname) .size fnname,.-fnname

// Mark that we don't need executable stack.
#define FOOTER .section .note.GNU-stack,"",%progbits

#endif

#endif // __wasmtime_common_h
5 changes: 5 additions & 0 deletions crates/fiber/src/arch/windows.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
#include <windows.h>

LPVOID wasmtime_fiber_get_current() {
return GetCurrentFiber();
}
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