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denoland-deno/ext/ffi/turbocall.rs

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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
use std::cmp::max;
use std::ffi::c_void;
use std::iter::once;
use deno_core::v8::fast_api;
use dynasmrt::dynasm;
use dynasmrt::DynasmApi;
use dynasmrt::ExecutableBuffer;
use crate::dlfcn::needs_unwrap;
use crate::NativeType;
use crate::Symbol;
pub(crate) fn is_compatible(sym: &Symbol) -> bool {
// TODO: Support structs by value in fast call
cfg!(any(
all(target_arch = "x86_64", target_family = "unix"),
all(target_arch = "x86_64", target_family = "windows"),
all(target_arch = "aarch64", target_vendor = "apple")
)) && !sym.can_callback
&& !matches!(sym.result_type, NativeType::Struct(_))
&& !sym
.parameter_types
.iter()
.any(|t| matches!(t, NativeType::Struct(_)))
}
pub(crate) fn compile_trampoline(sym: &Symbol) -> Trampoline {
#[cfg(all(target_arch = "x86_64", target_family = "unix"))]
return SysVAmd64::compile(sym);
#[cfg(all(target_arch = "x86_64", target_family = "windows"))]
return Win64::compile(sym);
#[cfg(all(target_arch = "aarch64", target_vendor = "apple"))]
return Aarch64Apple::compile(sym);
#[allow(unreachable_code)]
{
unimplemented!("fast API is not implemented for the current target");
}
}
pub(crate) fn make_template(sym: &Symbol, trampoline: &Trampoline) -> Template {
let mut params = once(fast_api::Type::V8Value) // Receiver
.chain(sym.parameter_types.iter().map(|t| t.into()))
.collect::<Vec<_>>();
let ret = if needs_unwrap(&sym.result_type) {
params.push(fast_api::Type::TypedArray(fast_api::CType::Int32));
fast_api::Type::Void
} else if sym.result_type == NativeType::Buffer {
// Buffer can be used as a return type and converts differently than in parameters.
fast_api::Type::Pointer
} else {
fast_api::Type::from(&sym.result_type)
};
Template {
args: params.into_boxed_slice(),
ret: (&ret).into(),
symbol_ptr: trampoline.ptr(),
}
}
/// Trampoline for fast-call FFI functions
///
/// Calls the FFI function without the first argument (the receiver)
pub(crate) struct Trampoline(ExecutableBuffer);
impl Trampoline {
fn ptr(&self) -> *const c_void {
&self.0[0] as *const u8 as *const c_void
}
}
pub(crate) struct Template {
pub args: Box<[fast_api::Type]>,
pub ret: fast_api::CType,
pub symbol_ptr: *const c_void,
}
impl fast_api::FastFunction for Template {
fn function(&self) -> *const c_void {
self.symbol_ptr
}
fn args(&self) -> &'static [fast_api::Type] {
Box::leak(self.args.clone())
}
fn return_type(&self) -> fast_api::CType {
self.ret
}
}
impl From<&NativeType> for fast_api::Type {
fn from(native_type: &NativeType) -> Self {
match native_type {
NativeType::Bool => fast_api::Type::Bool,
NativeType::U8 | NativeType::U16 | NativeType::U32 => {
fast_api::Type::Uint32
}
NativeType::I8 | NativeType::I16 | NativeType::I32 => {
fast_api::Type::Int32
}
NativeType::F32 => fast_api::Type::Float32,
NativeType::F64 => fast_api::Type::Float64,
NativeType::Void => fast_api::Type::Void,
NativeType::I64 => fast_api::Type::Int64,
NativeType::U64 => fast_api::Type::Uint64,
NativeType::ISize => fast_api::Type::Int64,
NativeType::USize => fast_api::Type::Uint64,
NativeType::Pointer | NativeType::Function => fast_api::Type::Pointer,
NativeType::Buffer => fast_api::Type::TypedArray(fast_api::CType::Uint8),
NativeType::Struct(_) => {
fast_api::Type::TypedArray(fast_api::CType::Uint8)
}
}
}
}
macro_rules! x64 {
($assembler:expr; $($tokens:tt)+) => {
dynasm!($assembler; .arch x64; $($tokens)+)
}
}
macro_rules! aarch64 {
($assembler:expr; $($tokens:tt)+) => {
dynasm!($assembler; .arch aarch64; $($tokens)+)
}
}
struct SysVAmd64 {
// Reference: https://refspecs.linuxfoundation.org/elf/x86_64-abi-0.99.pdf
assmblr: dynasmrt::x64::Assembler,
// Parameter counters
integral_params: u32,
float_params: u32,
// Stack offset accumulators
offset_trampoline: u32,
offset_callee: u32,
allocated_stack: u32,
frame_pointer: u32,
}
#[cfg_attr(
not(all(target_aarch = "x86_64", target_family = "unix")),
allow(dead_code)
)]
impl SysVAmd64 {
// Integral arguments go to the following GPR, in order: rdi, rsi, rdx, rcx, r8, r9
const INTEGRAL_REGISTERS: u32 = 6;
// SSE arguments go to the first 8 SSE registers: xmm0-xmm7
const FLOAT_REGISTERS: u32 = 8;
fn new() -> Self {
Self {
assmblr: dynasmrt::x64::Assembler::new().unwrap(),
integral_params: 0,
float_params: 0,
// Start at 8 to account for trampoline caller's return address
offset_trampoline: 8,
// default to tail-call mode. If a new stack frame is allocated this becomes 0
offset_callee: 8,
allocated_stack: 0,
frame_pointer: 0,
}
}
fn compile(sym: &Symbol) -> Trampoline {
let mut compiler = Self::new();
let must_cast_return_value =
compiler.must_cast_return_value(&sym.result_type);
let must_wrap_return_value =
compiler.must_wrap_return_value_in_typed_array(&sym.result_type);
let must_save_preserved_register = must_wrap_return_value;
let cannot_tailcall = must_cast_return_value || must_wrap_return_value;
if cannot_tailcall {
if must_save_preserved_register {
compiler.save_preserved_register_to_stack();
}
compiler.allocate_stack(&sym.parameter_types);
}
for param in sym.parameter_types.iter().cloned() {
compiler.move_left(param)
}
if !compiler.is_recv_arg_overridden() {
// the receiver object should never be expected. Avoid its unexpected or deliberate leak
compiler.zero_first_arg();
}
if must_wrap_return_value {
compiler.save_out_array_to_preserved_register();
}
if cannot_tailcall {
compiler.call(sym.ptr.as_ptr());
if must_cast_return_value {
compiler.cast_return_value(&sym.result_type);
}
if must_wrap_return_value {
compiler.wrap_return_value_in_out_array();
}
compiler.deallocate_stack();
if must_save_preserved_register {
compiler.recover_preserved_register();
}
compiler.ret();
} else {
compiler.tailcall(sym.ptr.as_ptr());
}
Trampoline(compiler.finalize())
}
fn move_left(&mut self, param: NativeType) {
// Section 3.2.3 of the SysV ABI spec, on argument classification:
// - INTEGER:
// > Arguments of types (signed and unsigned) _Bool, char, short, int,
// > long, long long, and pointers are in the INTEGER class.
// - SSE:
// > Arguments of types float, double, _Decimal32, _Decimal64 and
// > __m64 are in class SSE.
match param.into() {
Int(integral) => self.move_integral(integral),
Float(float) => self.move_float(float),
}
}
fn move_float(&mut self, param: Floating) {
// Section 3.2.3 of the SysV AMD64 ABI:
// > If the class is SSE, the next available vector register is used, the registers
// > are taken in the order from %xmm0 to %xmm7.
// [...]
// > Once registers are assigned, the arguments passed in memory are pushed on
// > the stack in reversed (right-to-left) order
let param_i = self.float_params;
let is_in_stack = param_i >= Self::FLOAT_REGISTERS;
// floats are only moved to accommodate integer movement in the stack
let stack_has_moved = self.allocated_stack > 0
|| self.integral_params >= Self::INTEGRAL_REGISTERS;
if is_in_stack && stack_has_moved {
let s = &mut self.assmblr;
let ot = self.offset_trampoline as i32;
let oc = self.offset_callee as i32;
match param {
Single => x64!(s
; movss xmm8, [rsp + ot]
; movss [rsp + oc], xmm8
),
Double => x64!(s
; movsd xmm8, [rsp + ot]
; movsd [rsp + oc], xmm8
),
}
// Section 3.2.3 of the SysV AMD64 ABI:
// > The size of each argument gets rounded up to eightbytes. [...] Therefore the stack will always be eightbyte aligned.
self.offset_trampoline += 8;
self.offset_callee += 8;
debug_assert!(
self.allocated_stack == 0 || self.offset_callee <= self.allocated_stack
);
}
self.float_params += 1;
}
fn move_integral(&mut self, arg: Integral) {
// Section 3.2.3 of the SysV AMD64 ABI:
// > If the class is INTEGER, the next available register of the sequence %rdi,
// > %rsi, %rdx, %rcx, %r8 and %r9 is used
// [...]
// > Once registers are assigned, the arguments passed in memory are pushed on
// > the stack in reversed (right-to-left) order
let s = &mut self.assmblr;
let param_i = self.integral_params;
// move each argument one position to the left. The first argument in the stack moves to the last integer register (r9).
// If the FFI function is called with a new stack frame, the arguments remaining in the stack are copied to the new stack frame.
// Otherwise, they are copied 8 bytes lower in the same frame
match (param_i, arg) {
// u8 and u16 parameters are defined as u32 parameters in the V8's fast API function. The trampoline takes care of the cast.
// Conventionally, many compilers expect 8 and 16 bit arguments to be sign/zero extended by the caller
// See https://stackoverflow.com/a/36760539/2623340
(0, U(B)) => x64!(s; movzx edi, sil),
(0, I(B)) => x64!(s; movsx edi, sil),
(0, U(W)) => x64!(s; movzx edi, si),
(0, I(W)) => x64!(s; movsx edi, si),
(0, U(DW) | I(DW)) => x64!(s; mov edi, esi),
(0, U(QW) | I(QW)) => x64!(s; mov rdi, rsi),
// The fast API expects buffer arguments passed as a pointer to a FastApiTypedArray<Uint8> struct
// Here we blindly follow the layout of https://github.com/denoland/rusty_v8/blob/main/src/fast_api.rs#L190-L200
// although that might be problematic: https://discord.com/channels/684898665143206084/956626010248478720/1009450940866252823
(0, Buffer) => x64!(s; mov rdi, [rsi + 8]),
(1, U(B)) => x64!(s; movzx esi, dl),
(1, I(B)) => x64!(s; movsx esi, dl),
(1, U(W)) => x64!(s; movzx esi, dx),
(1, I(W)) => x64!(s; movsx esi, dx),
(1, U(DW) | I(DW)) => x64!(s; mov esi, edx),
(1, U(QW) | I(QW)) => x64!(s; mov rsi, rdx),
(1, Buffer) => x64!(s; mov rsi, [rdx + 8]),
(2, U(B)) => x64!(s; movzx edx, cl),
(2, I(B)) => x64!(s; movsx edx, cl),
(2, U(W)) => x64!(s; movzx edx, cx),
(2, I(W)) => x64!(s; movsx edx, cx),
(2, U(DW) | I(DW)) => x64!(s; mov edx, ecx),
(2, U(QW) | I(QW)) => x64!(s; mov rdx, rcx),
(2, Buffer) => x64!(s; mov rdx, [rcx + 8]),
(3, U(B)) => x64!(s; movzx ecx, r8b),
(3, I(B)) => x64!(s; movsx ecx, r8b),
(3, U(W)) => x64!(s; movzx ecx, r8w),
(3, I(W)) => x64!(s; movsx ecx, r8w),
(3, U(DW) | I(DW)) => x64!(s; mov ecx, r8d),
(3, U(QW) | I(QW)) => x64!(s; mov rcx, r8),
(3, Buffer) => x64!(s; mov rcx, [r8 + 8]),
(4, U(B)) => x64!(s; movzx r8d, r9b),
(4, I(B)) => x64!(s; movsx r8d, r9b),
(4, U(W)) => x64!(s; movzx r8d, r9w),
(4, I(W)) => x64!(s; movsx r8d, r9w),
(4, U(DW) | I(DW)) => x64!(s; mov r8d, r9d),
(4, U(QW) | I(QW)) => x64!(s; mov r8, r9),
(4, Buffer) => x64!(s; mov r8, [r9 + 8]),
(5, param) => {
let ot = self.offset_trampoline as i32;
// First argument in stack goes to last register (r9)
match param {
U(B) => x64!(s; movzx r9d, BYTE [rsp + ot]),
I(B) => x64!(s; movsx r9d, BYTE [rsp + ot]),
U(W) => x64!(s; movzx r9d, WORD [rsp + ot]),
I(W) => x64!(s; movsx r9d, WORD [rsp + ot]),
U(DW) | I(DW) => x64!(s; mov r9d, [rsp + ot]),
U(QW) | I(QW) => x64!(s; mov r9, [rsp + ot]),
Buffer => x64!(s
; mov r9, [rsp + ot]
; mov r9, [r9 + 8]
),
}
// Section 3.2.3 of the SysV AMD64 ABI:
// > The size of each argument gets rounded up to eightbytes. [...] Therefore the stack will always be eightbyte aligned.
self.offset_trampoline += 8;
}
(6.., param) => {
let ot = self.offset_trampoline as i32;
let oc = self.offset_callee as i32;
match param {
U(B) => x64!(s
// TODO: optimize to [rsp] (without immediate) when offset is 0
; movzx eax, BYTE [rsp + ot]
; mov [rsp + oc], eax
),
I(B) => x64!(s
; movsx eax, BYTE [rsp + ot]
; mov [rsp + oc], eax
),
U(W) => x64!(s
; movzx eax, WORD [rsp + ot]
; mov [rsp + oc], eax
),
I(W) => x64!(s
; movsx eax, WORD [rsp + ot]
; mov [rsp + oc], eax
),
U(DW) | I(DW) => x64!(s
; mov eax, [rsp + ot]
; mov [rsp + oc], eax
),
U(QW) | I(QW) => x64!(s
; mov rax, [rsp + ot]
; mov [rsp + oc], rax
),
Buffer => x64!(s
; mov rax, [rsp + ot]
; mov rax, [rax + 8]
; mov [rsp + oc], rax
),
}
// Section 3.2.3 of the SysV AMD64 ABI:
// > The size of each argument gets rounded up to eightbytes. [...] Therefore the stack will always be eightbyte aligned.
self.offset_trampoline += 8;
self.offset_callee += 8;
debug_assert!(
self.allocated_stack == 0
|| self.offset_callee <= self.allocated_stack
);
}
}
self.integral_params += 1;
}
fn zero_first_arg(&mut self) {
debug_assert!(
self.integral_params == 0,
"the trampoline would zero the first argument after having overridden it with the second one"
);
dynasm!(self.assmblr
; .arch x64
; xor edi, edi
);
}
fn cast_return_value(&mut self, rv: &NativeType) {
let s = &mut self.assmblr;
// V8 only supports 32bit integers. We support 8 and 16 bit integers casting them to 32bits.
// In SysV-AMD64 the convention dictates that the unused bits of the return value contain garbage, so we
// need to zero/sign extend the return value explicitly
match rv {
NativeType::U8 => x64!(s; movzx eax, al),
NativeType::I8 => x64!(s; movsx eax, al),
NativeType::U16 => x64!(s; movzx eax, ax),
NativeType::I16 => x64!(s; movsx eax, ax),
_ => (),
}
}
fn save_out_array_to_preserved_register(&mut self) {
let s = &mut self.assmblr;
// functions returning 64 bit integers have the out array appended as their last parameter,
// and it is a *FastApiTypedArray<Int32>
match self.integral_params {
// Trampoline's signature is (receiver, [param0, param1, ...], *FastApiTypedArray)
// self.integral_params account only for the original params [param0, param1, ...]
// and the out array has not been moved left
0 => x64!(s; mov rbx, [rsi + 8]),
1 => x64!(s; mov rbx, [rdx + 8]),
2 => x64!(s; mov rbx, [rcx + 8]),
3 => x64!(s; mov rbx, [r8 + 8]),
4 => x64!(s; mov rbx, [r9 + 8]),
5.. => {
x64!(s
; mov rax, [rsp + self.offset_trampoline as i32]
; mov rbx, [rax + 8]
)
}
}
}
fn wrap_return_value_in_out_array(&mut self) {
x64!(self.assmblr; mov [rbx], rax);
}
fn save_preserved_register_to_stack(&mut self) {
x64!(self.assmblr; push rbx);
self.offset_trampoline += 8;
// stack pointer has been modified, and the callee stack parameters are expected at the top of the stack
self.offset_callee = 0;
self.frame_pointer += 8;
}
fn recover_preserved_register(&mut self) {
debug_assert!(
self.frame_pointer >= 8,
"the trampoline would try to pop from the stack beyond its frame pointer"
);
x64!(self.assmblr; pop rbx);
self.frame_pointer -= 8;
// parameter offsets are invalid once this method is called
}
fn allocate_stack(&mut self, params: &[NativeType]) {
let mut int_params = 0u32;
let mut float_params = 0u32;
for param in params {
match param {
NativeType::F32 | NativeType::F64 => float_params += 1,
_ => int_params += 1,
}
}
let mut stack_size = (int_params.saturating_sub(Self::INTEGRAL_REGISTERS)
+ float_params.saturating_sub(Self::FLOAT_REGISTERS))
* 8;
// Align new stack frame (accounting for the 8 byte of the trampoline caller's return address
// and any other potential addition to the stack prior to this allocation)
// Section 3.2.2 of the SysV AMD64 ABI:
// > The end of the input argument area shall be aligned on a 16 (32 or 64, if
// > __m256 or __m512 is passed on stack) byte boundary. In other words, the value
// > (%rsp + 8) is always a multiple of 16 (32 or 64) when control is transferred to
// > the function entry point. The stack pointer, %rsp, always points to the end of the
// > latest allocated stack frame.
stack_size += padding_to_align(16, self.frame_pointer + stack_size + 8);
if stack_size > 0 {
x64!(self.assmblr; sub rsp, stack_size as i32);
self.offset_trampoline += stack_size;
// stack pointer has been modified, and the callee stack parameters are expected at the top of the stack
self.offset_callee = 0;
self.allocated_stack += stack_size;
self.frame_pointer += stack_size;
}
}
fn deallocate_stack(&mut self) {
debug_assert!(
self.frame_pointer >= self.allocated_stack,
"the trampoline would try to deallocate stack beyond its frame pointer"
);
if self.allocated_stack > 0 {
x64!(self.assmblr; add rsp, self.allocated_stack as i32);
self.frame_pointer -= self.allocated_stack;
self.allocated_stack = 0;
}
}
fn call(&mut self, ptr: *const c_void) {
// the stack has been aligned during stack allocation and/or pushing of preserved registers
debug_assert!(
(8 + self.frame_pointer) % 16 == 0,
"the trampoline would call the FFI function with an unaligned stack"
);
x64!(self.assmblr
; mov rax, QWORD ptr as _
; call rax
);
}
fn tailcall(&mut self, ptr: *const c_void) {
// stack pointer is never modified and remains aligned
// return address remains the one provided by the trampoline's caller (V8)
debug_assert!(
self.allocated_stack == 0,
"the trampoline would tail call the FFI function with an outstanding stack allocation"
);
debug_assert!(
self.frame_pointer == 0,
"the trampoline would tail call the FFI function with outstanding locals in the frame"
);
x64!(self.assmblr
; mov rax, QWORD ptr as _
; jmp rax
);
}
fn ret(&mut self) {
debug_assert!(
self.allocated_stack == 0,
"the trampoline would return with an outstanding stack allocation"
);
debug_assert!(
self.frame_pointer == 0,
"the trampoline would return with outstanding locals in the frame"
);
x64!(self.assmblr; ret);
}
fn is_recv_arg_overridden(&self) -> bool {
// V8 receiver is the first parameter of the trampoline function and is a pointer
self.integral_params > 0
}
fn must_cast_return_value(&self, rv: &NativeType) -> bool {
// V8 only supports i32 and u32 return types for integers
// We support 8 and 16 bit integers by extending them to 32 bits in the trampoline before returning
matches!(
rv,
NativeType::U8 | NativeType::I8 | NativeType::U16 | NativeType::I16
)
}
fn must_wrap_return_value_in_typed_array(&self, rv: &NativeType) -> bool {
// V8 only supports i32 and u32 return types for integers
// We support 64 bit integers by wrapping them in a TypedArray out parameter
crate::dlfcn::needs_unwrap(rv)
}
fn finalize(self) -> ExecutableBuffer {
self.assmblr.finalize().unwrap()
}
}
struct Aarch64Apple {
// Reference https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst
assmblr: dynasmrt::aarch64::Assembler,
// Parameter counters
integral_params: u32,
float_params: u32,
// Stack offset accumulators
offset_trampoline: u32,
offset_callee: u32,
allocated_stack: u32,
}
#[cfg_attr(
not(all(target_aarch = "aarch64", target_vendor = "apple")),
allow(dead_code)
)]
impl Aarch64Apple {
// Integral arguments go to the first 8 GPR: x0-x7
const INTEGRAL_REGISTERS: u32 = 8;
// Floating-point arguments go to the first 8 SIMD & Floating-Point registers: v0-v1
const FLOAT_REGISTERS: u32 = 8;
fn new() -> Self {
Self {
assmblr: dynasmrt::aarch64::Assembler::new().unwrap(),
integral_params: 0,
float_params: 0,
offset_trampoline: 0,
offset_callee: 0,
allocated_stack: 0,
}
}
fn compile(sym: &Symbol) -> Trampoline {
let mut compiler = Self::new();
let must_wrap_return_value =
compiler.must_wrap_return_value_in_typed_array(&sym.result_type);
let must_save_preserved_register = must_wrap_return_value;
let cannot_tailcall = must_wrap_return_value;
if cannot_tailcall {
compiler.allocate_stack(sym);
compiler.save_frame_record();
if compiler.must_save_preserved_register_to_stack(sym) {
compiler.save_preserved_register_to_stack();
}
}
for param in sym.parameter_types.iter().cloned() {
compiler.move_left(param)
}
if !compiler.is_recv_arg_overridden() {
// the receiver object should never be expected. Avoid its unexpected or deliberate leak
compiler.zero_first_arg();
}
if compiler.must_wrap_return_value_in_typed_array(&sym.result_type) {
compiler.save_out_array_to_preserved_register();
}
if cannot_tailcall {
compiler.call(sym.ptr.as_ptr());
if must_wrap_return_value {
compiler.wrap_return_value_in_out_array();
}
if must_save_preserved_register {
compiler.recover_preserved_register();
}
compiler.recover_frame_record();
compiler.deallocate_stack();
compiler.ret();
} else {
compiler.tailcall(sym.ptr.as_ptr());
}
Trampoline(compiler.finalize())
}
fn move_left(&mut self, param: NativeType) {
// Section 6.4.2 of the Aarch64 Procedure Call Standard (PCS), on argument classification:
// - INTEGRAL or POINTER:
// > If the argument is an Integral or Pointer Type, the size of the argument is less than or equal to 8 bytes
// > and the NGRN is less than 8, the argument is copied to the least significant bits in x[NGRN].
//
// - Floating-Point or Vector:
// > If the argument is a Half-, Single-, Double- or Quad- precision Floating-point or short vector type
// > and the NSRN is less than 8, then the argument is allocated to the least significant bits of register v[NSRN]
match param.into() {
Int(integral) => self.move_integral(integral),
Float(float) => self.move_float(float),
}
}
fn move_float(&mut self, param: Floating) {
// Section 6.4.2 of the Aarch64 PCS:
// > If the argument is a Half-, Single-, Double- or Quad- precision Floating-point or short vector type and the NSRN is less than 8, then the
// > argument is allocated to the least significant bits of register v[NSRN]. The NSRN is incremented by one. The argument has now been allocated.
// > [if NSRN is equal or more than 8]
// > The argument is copied to memory at the adjusted NSAA. The NSAA is incremented by the size of the argument. The argument has now been allocated.
let param_i = self.float_params;
let is_in_stack = param_i >= Self::FLOAT_REGISTERS;
if is_in_stack {
// https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms:
// > Function arguments may consume slots on the stack that are not multiples of 8 bytes.
// (i.e. natural alignment instead of eightbyte alignment)
let padding_trampl =
(param.size() - self.offset_trampoline % param.size()) % param.size();
let padding_callee =
(param.size() - self.offset_callee % param.size()) % param.size();
// floats are only moved to accommodate integer movement in the stack
let stack_has_moved = self.integral_params >= Self::INTEGRAL_REGISTERS;
if stack_has_moved {
let s = &mut self.assmblr;
let ot = self.offset_trampoline;
let oc = self.offset_callee;
match param {
Single => aarch64!(s
// 6.1.2 Aarch64 PCS:
// > Registers v8-v15 must be preserved by a callee across subroutine calls;
// > the remaining registers (v0-v7, v16-v31) do not need to be preserved (or should be preserved by the caller).
; ldr s16, [sp, ot + padding_trampl]
; str s16, [sp, oc + padding_callee]
),
Double => aarch64!(s
; ldr d16, [sp, ot + padding_trampl]
; str d16, [sp, oc + padding_callee]
),
}
}
self.offset_trampoline += padding_trampl + param.size();
self.offset_callee += padding_callee + param.size();
debug_assert!(
self.allocated_stack == 0 || self.offset_callee <= self.allocated_stack
);
}
self.float_params += 1;
}
fn move_integral(&mut self, param: Integral) {
let s = &mut self.assmblr;
// Section 6.4.2 of the Aarch64 PCS:
// If the argument is an Integral or Pointer Type, the size of the argument is less than or
// equal to 8 bytes and the NGRN is less than 8, the argument is copied to the least
// significant bits in x[NGRN]. The NGRN is incremented by one. The argument has now been
// allocated.
// [if NGRN is equal or more than 8]
// The argument is copied to memory at the adjusted NSAA. The NSAA is incremented by the size
// of the argument. The argument has now been allocated.
let param_i = self.integral_params;
// move each argument one position to the left. The first argument in the stack moves to the last integer register (x7).
match (param_i, param) {
// From https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms:
// > The caller of a function is responsible for signing or zero-extending any argument with fewer than 32 bits.
// > The standard ABI expects the callee to sign or zero-extend those arguments.
// (this applies to register parameters, as stack parameters are not eightbyte aligned in Apple)
(0, I(B)) => aarch64!(s; sxtb w0, w1),
(0, U(B)) => aarch64!(s; and w0, w1, 0xFF),
(0, I(W)) => aarch64!(s; sxth w0, w1),
(0, U(W)) => aarch64!(s; and w0, w1, 0xFFFF),
(0, I(DW) | U(DW)) => aarch64!(s; mov w0, w1),
(0, I(QW) | U(QW)) => aarch64!(s; mov x0, x1),
// The fast API expects buffer arguments passed as a pointer to a FastApiTypedArray<Uint8> struct
// Here we blindly follow the layout of https://github.com/denoland/rusty_v8/blob/main/src/fast_api.rs#L190-L200
// although that might be problematic: https://discord.com/channels/684898665143206084/956626010248478720/1009450940866252823
(0, Buffer) => aarch64!(s; ldr x0, [x1, 8]),
(1, I(B)) => aarch64!(s; sxtb w1, w2),
(1, U(B)) => aarch64!(s; and w1, w2, 0xFF),
(1, I(W)) => aarch64!(s; sxth w1, w2),
(1, U(W)) => aarch64!(s; and w1, w2, 0xFFFF),
(1, I(DW) | U(DW)) => aarch64!(s; mov w1, w2),
(1, I(QW) | U(QW)) => aarch64!(s; mov x1, x2),
(1, Buffer) => aarch64!(s; ldr x1, [x2, 8]),
(2, I(B)) => aarch64!(s; sxtb w2, w3),
(2, U(B)) => aarch64!(s; and w2, w3, 0xFF),
(2, I(W)) => aarch64!(s; sxth w2, w3),
(2, U(W)) => aarch64!(s; and w2, w3, 0xFFFF),
(2, I(DW) | U(DW)) => aarch64!(s; mov w2, w3),
(2, I(QW) | U(QW)) => aarch64!(s; mov x2, x3),
(2, Buffer) => aarch64!(s; ldr x2, [x3, 8]),
(3, I(B)) => aarch64!(s; sxtb w3, w4),
(3, U(B)) => aarch64!(s; and w3, w4, 0xFF),
(3, I(W)) => aarch64!(s; sxth w3, w4),
(3, U(W)) => aarch64!(s; and w3, w4, 0xFFFF),
(3, I(DW) | U(DW)) => aarch64!(s; mov w3, w4),
(3, I(QW) | U(QW)) => aarch64!(s; mov x3, x4),
(3, Buffer) => aarch64!(s; ldr x3, [x4, 8]),
(4, I(B)) => aarch64!(s; sxtb w4, w5),
(4, U(B)) => aarch64!(s; and w4, w5, 0xFF),
(4, I(W)) => aarch64!(s; sxth w4, w5),
(4, U(W)) => aarch64!(s; and w4, w5, 0xFFFF),
(4, I(DW) | U(DW)) => aarch64!(s; mov w4, w5),
(4, I(QW) | U(QW)) => aarch64!(s; mov x4, x5),
(4, Buffer) => aarch64!(s; ldr x4, [x5, 8]),
(5, I(B)) => aarch64!(s; sxtb w5, w6),
(5, U(B)) => aarch64!(s; and w5, w6, 0xFF),
(5, I(W)) => aarch64!(s; sxth w5, w6),
(5, U(W)) => aarch64!(s; and w5, w6, 0xFFFF),
(5, I(DW) | U(DW)) => aarch64!(s; mov w5, w6),
(5, I(QW) | U(QW)) => aarch64!(s; mov x5, x6),
(5, Buffer) => aarch64!(s; ldr x5, [x6, 8]),
(6, I(B)) => aarch64!(s; sxtb w6, w7),
(6, U(B)) => aarch64!(s; and w6, w7, 0xFF),
(6, I(W)) => aarch64!(s; sxth w6, w7),
(6, U(W)) => aarch64!(s; and w6, w7, 0xFFFF),
(6, I(DW) | U(DW)) => aarch64!(s; mov w6, w7),
(6, I(QW) | U(QW)) => aarch64!(s; mov x6, x7),
(6, Buffer) => aarch64!(s; ldr x6, [x7, 8]),
(7, param) => {
let ot = self.offset_trampoline;
match param {
I(B) => {
aarch64!(s; ldrsb w7, [sp, ot])
}
U(B) => {
// ldrb zero-extends the byte to fill the 32bits of the register
aarch64!(s; ldrb w7, [sp, ot])
}
I(W) => {
aarch64!(s; ldrsh w7, [sp, ot])
}
U(W) => {
// ldrh zero-extends the half-word to fill the 32bits of the register
aarch64!(s; ldrh w7, [sp, ot])
}
I(DW) | U(DW) => {
aarch64!(s; ldr w7, [sp, ot])
}
I(QW) | U(QW) => {
aarch64!(s; ldr x7, [sp, ot])
}
Buffer => {
aarch64!(s
; ldr x7, [sp, ot]
; ldr x7, [x7, 8]
)
}
}
// 16 and 8 bit integers are 32 bit integers in v8
self.offset_trampoline += max(param.size(), 4);
}
(8.., param) => {
// https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms:
// > Function arguments may consume slots on the stack that are not multiples of 8 bytes.
// (i.e. natural alignment instead of eightbyte alignment)
//
// N.B. V8 does not currently follow this Apple's policy, and instead aligns all arguments to 8 Byte boundaries.
// The current implementation follows the V8 incorrect calling convention for the sake of a seamless experience
// for the Deno users. Whenever upgrading V8 we should make sure that the bug has not been amended, and revert this
// workaround once it has been. The bug is being tracked in https://bugs.chromium.org/p/v8/issues/detail?id=13171
let size_original = param.size();
// 16 and 8 bit integers are 32 bit integers in v8
// let size_trampl = max(size_original, 4); // <-- Apple alignment
let size_trampl = 8; // <-- V8 incorrect alignment
let padding_trampl =
padding_to_align(size_trampl, self.offset_trampoline);
let padding_callee =
padding_to_align(size_original, self.offset_callee);
let ot = self.offset_trampoline;
let oc = self.offset_callee;
match param {
I(B) | U(B) => aarch64!(s
; ldr w8, [sp, ot + padding_trampl]
; strb w8, [sp, oc + padding_callee]
),
I(W) | U(W) => aarch64!(s
; ldr w8, [sp, ot + padding_trampl]
; strh w8, [sp, oc + padding_callee]
),
I(DW) | U(DW) => aarch64!(s
; ldr w8, [sp, ot + padding_trampl]
; str w8, [sp, oc + padding_callee]
),
I(QW) | U(QW) => aarch64!(s
; ldr x8, [sp, ot + padding_trampl]
; str x8, [sp, oc + padding_callee]
),
Buffer => aarch64!(s
; ldr x8, [sp, ot + padding_trampl]
; ldr x8, [x8, 8]
; str x8, [sp, oc + padding_callee]
),
}
self.offset_trampoline += padding_trampl + size_trampl;
self.offset_callee += padding_callee + size_original;
debug_assert!(
self.allocated_stack == 0
|| self.offset_callee <= self.allocated_stack
);
}
};
self.integral_params += 1;
}
fn zero_first_arg(&mut self) {
debug_assert!(
self.integral_params == 0,
"the trampoline would zero the first argument after having overridden it with the second one"
);
aarch64!(self.assmblr; mov x0, xzr);
}
fn save_out_array_to_preserved_register(&mut self) {
let s = &mut self.assmblr;
// functions returning 64 bit integers have the out array appended as their last parameter,
// and it is a *FastApiTypedArray<Int32>
match self.integral_params {
// x0 is always V8's receiver
0 => aarch64!(s; ldr x19, [x1, 8]),
1 => aarch64!(s; ldr x19, [x2, 8]),
2 => aarch64!(s; ldr x19, [x3, 8]),
3 => aarch64!(s; ldr x19, [x4, 8]),
4 => aarch64!(s; ldr x19, [x5, 8]),
5 => aarch64!(s; ldr x19, [x6, 8]),
6 => aarch64!(s; ldr x19, [x7, 8]),
7.. => {
aarch64!(s
; ldr x19, [sp, self.offset_trampoline]
; ldr x19, [x19, 8]
)
}
}
}
fn wrap_return_value_in_out_array(&mut self) {
aarch64!(self.assmblr; str x0, [x19]);
}
#[allow(clippy::unnecessary_cast)]
fn save_frame_record(&mut self) {
debug_assert!(
self.allocated_stack >= 16,
"the trampoline would try to save the frame record to the stack without having allocated enough space for it"
);
aarch64!(self.assmblr
// Frame record is stored at the bottom of the stack frame
; stp x29, x30, [sp, self.allocated_stack - 16]
; add x29, sp, self.allocated_stack - 16
)
}
#[allow(clippy::unnecessary_cast)]
fn recover_frame_record(&mut self) {
// The stack cannot have been deallocated before the frame record is restored
debug_assert!(
self.allocated_stack >= 16,
"the trampoline would try to load the frame record from the stack, but it couldn't possibly contain it"
);
// Frame record is stored at the bottom of the stack frame
aarch64!(self.assmblr; ldp x29, x30, [sp, self.allocated_stack - 16])
}
fn save_preserved_register_to_stack(&mut self) {
// If a preserved register needs to be used, we must have allocated at least 32 bytes in the stack
// 16 for the frame record, 8 for the preserved register, and 8 for 16-byte alignment.
debug_assert!(
self.allocated_stack >= 32,
"the trampoline would try to save a register to the stack without having allocated enough space for it"
);
// preserved register is stored after frame record
aarch64!(self.assmblr; str x19, [sp, self.allocated_stack - 24]);
}
fn recover_preserved_register(&mut self) {
// The stack cannot have been deallocated before the preserved register is restored
// 16 for the frame record, 8 for the preserved register, and 8 for 16-byte alignment.
debug_assert!(
self.allocated_stack >= 32,
"the trampoline would try to recover the value of a register from the stack, but it couldn't possibly contain it"
);
// preserved register is stored after frame record
aarch64!(self.assmblr; ldr x19, [sp, self.allocated_stack - 24]);
}
fn allocate_stack(&mut self, symbol: &Symbol) {
// https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms:
// > Function arguments may consume slots on the stack that are not multiples of 8 bytes.
// (i.e. natural alignment instead of eightbyte alignment)
let mut int_params = 0u32;
let mut float_params = 0u32;
let mut stack_size = 0u32;
for param in symbol.parameter_types.iter().cloned() {
match param.into() {
Float(float_param) => {
float_params += 1;
if float_params > Self::FLOAT_REGISTERS {
stack_size += float_param.size();
}
}
Int(integral_param) => {
int_params += 1;
if int_params > Self::INTEGRAL_REGISTERS {
stack_size += integral_param.size();
}
}
}
}
// Section 6.2.3 of the Aarch64 PCS:
// > Each frame shall link to the frame of its caller by means of a frame record of two 64-bit values on the stack
stack_size += 16;
if self.must_save_preserved_register_to_stack(symbol) {
stack_size += 8;
}
// Section 6.2.2 of Aarch64 PCS:
// > At any point at which memory is accessed via SP, the hardware requires that
// > - SP mod 16 = 0. The stack must be quad-word aligned.
// > The stack must also conform to the following constraint at a public interface:
// > - SP mod 16 = 0. The stack must be quad-word aligned.
stack_size += padding_to_align(16, stack_size);
if stack_size > 0 {
aarch64!(self.assmblr; sub sp, sp, stack_size);
self.offset_trampoline += stack_size;
// stack pointer has been modified, and the callee stack parameters are expected at the top of the stack
self.offset_callee = 0;
self.allocated_stack += stack_size;
}
}
fn deallocate_stack(&mut self) {
if self.allocated_stack > 0 {
aarch64!(self.assmblr; add sp, sp, self.allocated_stack);
self.allocated_stack = 0;
}
}
fn call(&mut self, ptr: *const c_void) {
// the stack has been aligned during stack allocation
// Frame record has been stored in stack and frame pointer points to it
debug_assert!(
self.allocated_stack % 16 == 0,
"the trampoline would call the FFI function with an unaligned stack"
);
debug_assert!(
self.allocated_stack >= 16,
"the trampoline would call the FFI function without allocating enough stack for the frame record"
);
self.load_callee_address(ptr);
aarch64!(self.assmblr; blr x8);
}
fn tailcall(&mut self, ptr: *const c_void) {
// stack pointer is never modified and remains aligned
// frame pointer and link register remain the one provided by the trampoline's caller (V8)
debug_assert!(
self.allocated_stack == 0,
"the trampoline would tail call the FFI function with an outstanding stack allocation"
);
self.load_callee_address(ptr);
aarch64!(self.assmblr; br x8);
}
fn ret(&mut self) {
debug_assert!(
self.allocated_stack == 0,
"the trampoline would return with an outstanding stack allocation"
);
aarch64!(self.assmblr; ret);
}
fn load_callee_address(&mut self, ptr: *const c_void) {
// Like all ARM instructions, move instructions are 32bit long and can fit at most 16bit immediates.
// bigger immediates are loaded in multiple steps applying a left-shift modifier
let mut address = ptr as u64;
let mut imm16 = address & 0xFFFF;
aarch64!(self.assmblr; movz x8, imm16 as u32);
address >>= 16;
let mut shift = 16;
while address > 0 {
imm16 = address & 0xFFFF;
if imm16 != 0 {
aarch64!(self.assmblr; movk x8, imm16 as u32, lsl shift);
}
address >>= 16;
shift += 16;
}
}
fn is_recv_arg_overridden(&self) -> bool {
// V8 receiver is the first parameter of the trampoline function and is a pointer
self.integral_params > 0
}
fn must_save_preserved_register_to_stack(&mut self, symbol: &Symbol) -> bool {
self.must_wrap_return_value_in_typed_array(&symbol.result_type)
}
fn must_wrap_return_value_in_typed_array(&self, rv: &NativeType) -> bool {
// V8 only supports i32 and u32 return types for integers
// We support 64 bit integers by wrapping them in a TypedArray out parameter
crate::dlfcn::needs_unwrap(rv)
}
fn finalize(self) -> ExecutableBuffer {
self.assmblr.finalize().unwrap()
}
}
struct Win64 {
// Reference: https://github.com/MicrosoftDocs/cpp-docs/blob/main/docs/build/x64-calling-convention.md
assmblr: dynasmrt::x64::Assembler,
// Params counter (Windows does not distinguish by type with regards to parameter position)
params: u32,
// Stack offset accumulators
offset_trampoline: u32,
offset_callee: u32,
allocated_stack: u32,
frame_pointer: u32,
}
#[cfg_attr(
not(all(target_aarch = "x86_64", target_family = "windows")),
allow(dead_code)
)]
impl Win64 {
// Section "Parameter Passing" of the Windows x64 calling convention:
// > By default, the x64 calling convention passes the first four arguments to a function in registers.
const REGISTERS: u32 = 4;
fn new() -> Self {
Self {
assmblr: dynasmrt::x64::Assembler::new().unwrap(),
params: 0,
// trampoline caller's return address + trampoline's shadow space
offset_trampoline: 8 + 32,
offset_callee: 8 + 32,
allocated_stack: 0,
frame_pointer: 0,
}
}
fn compile(sym: &Symbol) -> Trampoline {
let mut compiler = Self::new();
let must_cast_return_value =
compiler.must_cast_return_value(&sym.result_type);
let must_wrap_return_value =
compiler.must_wrap_return_value_in_typed_array(&sym.result_type);
let must_save_preserved_register = must_wrap_return_value;
let cannot_tailcall = must_cast_return_value || must_wrap_return_value;
if cannot_tailcall {
if must_save_preserved_register {
compiler.save_preserved_register_to_stack();
}
compiler.allocate_stack(&sym.parameter_types);
}
for param in sym.parameter_types.iter().cloned() {
compiler.move_left(param)
}
if !compiler.is_recv_arg_overridden() {
// the receiver object should never be expected. Avoid its unexpected or deliberate leak
compiler.zero_first_arg();
}
if must_wrap_return_value {
compiler.save_out_array_to_preserved_register();
}
if cannot_tailcall {
compiler.call(sym.ptr.as_ptr());
if must_cast_return_value {
compiler.cast_return_value(&sym.result_type);
}
if must_wrap_return_value {
compiler.wrap_return_value_in_out_array();
}
compiler.deallocate_stack();
if must_save_preserved_register {
compiler.recover_preserved_register();
}
compiler.ret();
} else {
compiler.tailcall(sym.ptr.as_ptr());
}
Trampoline(compiler.finalize())
}
fn move_left(&mut self, param: NativeType) {
// Section "Parameter Passing" of the Windows x64 calling convention:
// > By default, the x64 calling convention passes the first four arguments to a function in registers.
// > The registers used for these arguments depend on the position and type of the argument.
// > Remaining arguments get pushed on the stack in right-to-left order.
// > [...]
// > Integer valued arguments in the leftmost four positions are passed in left-to-right order in RCX, RDX, R8, and R9
// > [...]
// > Any floating-point and double-precision arguments in the first four parameters are passed in XMM0 - XMM3, depending on position
let s = &mut self.assmblr;
let param_i = self.params;
// move each argument one position to the left. The first argument in the stack moves to the last register (r9 or xmm3).
// If the FFI function is called with a new stack frame, the arguments remaining in the stack are copied to the new stack frame.
// Otherwise, they are copied 8 bytes lower in the same frame
match (param_i, param.into()) {
// Section "Parameter Passing" of the Windows x64 calling convention:
// > All integer arguments in registers are right-justified, so the callee can ignore the upper bits of the register
// > and access only the portion of the register necessary.
// (i.e. unlike in SysV or Aarch64-Apple, 8/16 bit integers are not expected to be zero/sign extended)
(0, Int(U(B | W | DW) | I(B | W | DW))) => x64!(s; mov ecx, edx),
(0, Int(U(QW) | I(QW))) => x64!(s; mov rcx, rdx),
// The fast API expects buffer arguments passed as a pointer to a FastApiTypedArray<Uint8> struct
// Here we blindly follow the layout of https://github.com/denoland/rusty_v8/blob/main/src/fast_api.rs#L190-L200
// although that might be problematic: https://discord.com/channels/684898665143206084/956626010248478720/1009450940866252823
(0, Int(Buffer)) => x64!(s; mov rcx, [rdx + 8]),
// Use movaps for singles and doubles, benefits of smaller encoding outweigh those of using the correct instruction for the type,
// which for doubles should technically be movapd
(0, Float(_)) => {
x64!(s; movaps xmm0, xmm1);
self.zero_first_arg();
}
(1, Int(U(B | W | DW) | I(B | W | DW))) => x64!(s; mov edx, r8d),
(1, Int(U(QW) | I(QW))) => x64!(s; mov rdx, r8),
(1, Int(Buffer)) => x64!(s; mov rdx, [r8 + 8]),
(1, Float(_)) => x64!(s; movaps xmm1, xmm2),
(2, Int(U(B | W | DW) | I(B | W | DW))) => x64!(s; mov r8d, r9d),
(2, Int(U(QW) | I(QW))) => x64!(s; mov r8, r9),
(2, Int(Buffer)) => x64!(s; mov r8, [r9 + 8]),
(2, Float(_)) => x64!(s; movaps xmm2, xmm3),
(3, param) => {
let ot = self.offset_trampoline as i32;
match param {
Int(U(B | W | DW) | I(B | W | DW)) => {
x64!(s; mov r9d, [rsp + ot])
}
Int(U(QW) | I(QW)) => {
x64!(s; mov r9, [rsp + ot])
}
Int(Buffer) => {
x64!(s
; mov r9, [rsp + ot]
; mov r9, [r9 + 8])
}
Float(_) => {
// parameter 4 is always 16-byte aligned, so we can use movaps instead of movups
x64!(s; movaps xmm3, [rsp + ot])
}
}
// Section "x64 Aggregate and Union layout" of the windows x64 software conventions doc:
// > The alignment of the beginning of a structure or a union is the maximum alignment of any individual member
// Ref: https://github.com/MicrosoftDocs/cpp-docs/blob/main/docs/build/x64-software-conventions.md#x64-aggregate-and-union-layout
self.offset_trampoline += 8;
}
(4.., param) => {
let ot = self.offset_trampoline as i32;
let oc = self.offset_callee as i32;
match param {
Int(U(B | W | DW) | I(B | W | DW)) => {
x64!(s
; mov eax, [rsp + ot]
; mov [rsp + oc], eax
)
}
Int(U(QW) | I(QW)) => {
x64!(s
; mov rax, [rsp + ot]
; mov [rsp + oc], rax
)
}
Int(Buffer) => {
x64!(s
; mov rax, [rsp + ot]
; mov rax, [rax + 8]
; mov [rsp + oc], rax
)
}
Float(_) => {
x64!(s
; movups xmm4, [rsp + ot]
; movups [rsp + oc], xmm4
)
}
}
// Section "x64 Aggregate and Union layout" of the windows x64 software conventions doc:
// > The alignment of the beginning of a structure or a union is the maximum alignment of any individual member
// Ref: https://github.com/MicrosoftDocs/cpp-docs/blob/main/docs/build/x64-software-conventions.md#x64-aggregate-and-union-layout
self.offset_trampoline += 8;
self.offset_callee += 8;
debug_assert!(
self.allocated_stack == 0
|| self.offset_callee <= self.allocated_stack
);
}
}
self.params += 1;
}
fn zero_first_arg(&mut self) {
debug_assert!(
self.params == 0,
"the trampoline would zero the first argument after having overridden it with the second one"
);
x64!(self.assmblr; xor ecx, ecx);
}
fn cast_return_value(&mut self, rv: &NativeType) {
let s = &mut self.assmblr;
// V8 only supports 32bit integers. We support 8 and 16 bit integers casting them to 32bits.
// Section "Return Values" of the Windows x64 Calling Convention doc:
// > The state of unused bits in the value returned in RAX or XMM0 is undefined.
match rv {
NativeType::U8 => x64!(s; movzx eax, al),
NativeType::I8 => x64!(s; movsx eax, al),
NativeType::U16 => x64!(s; movzx eax, ax),
NativeType::I16 => x64!(s; movsx eax, ax),
_ => (),
}
}
fn save_out_array_to_preserved_register(&mut self) {
let s = &mut self.assmblr;
// functions returning 64 bit integers have the out array appended as their last parameter,
// and it is a *FastApiTypedArray<Int32>
match self.params {
// rcx is always V8 receiver
0 => x64!(s; mov rbx, [rdx + 8]),
1 => x64!(s; mov rbx, [r8 + 8]),
2 => x64!(s; mov rbx, [r9 + 8]),
3.. => {
x64!(s
; mov rax, [rsp + self.offset_trampoline as i32]
; mov rbx, [rax + 8]
)
}
}
}
fn wrap_return_value_in_out_array(&mut self) {
x64!(self.assmblr; mov [rbx], rax)
}
fn save_preserved_register_to_stack(&mut self) {
x64!(self.assmblr; push rbx);
self.offset_trampoline += 8;
// stack pointer has been modified, and the callee stack parameters are expected at the top of the stack
self.offset_callee = 0;
self.frame_pointer += 8;
}
fn recover_preserved_register(&mut self) {
debug_assert!(
self.frame_pointer >= 8,
"the trampoline would try to pop from the stack beyond its frame pointer"
);
x64!(self.assmblr; pop rbx);
self.frame_pointer -= 8;
// parameter offsets are invalid once this method is called
}
fn allocate_stack(&mut self, params: &[NativeType]) {
let mut stack_size = 0;
// Section "Calling Convention Defaults" of the x64-calling-convention and Section "Stack Allocation" of the stack-usage docs:
// > The x64 Application Binary Interface (ABI) uses a four-register fast-call calling convention by default.
// > Space is allocated on the call stack as a shadow store for callees to save those registers.
// > [...]
// > Any parameters beyond the first four must be stored on the stack after the shadow store before the call
// > [...]
// > Even if the called function has fewer than 4 parameters, these 4 stack locations are effectively owned by the called function,
// > and may be used by the called function for other purposes besides saving parameter register values
stack_size += max(params.len() as u32, 4) * 8;
// Align new stack frame (accounting for the 8 byte of the trampoline caller's return address
// and any other potential addition to the stack prior to this allocation)
// Section "Stack Allocation" of stack-usage docs:
// > The stack will always be maintained 16-byte aligned, except within the prolog (for example, after the return address is pushed)
stack_size += padding_to_align(16, self.frame_pointer + stack_size + 8);
x64!(self.assmblr; sub rsp, stack_size as i32);
self.offset_trampoline += stack_size;
// stack pointer has been modified, and the callee stack parameters are expected at the top of the stack right after the shadow space
self.offset_callee = 32;
self.allocated_stack += stack_size;
self.frame_pointer += stack_size;
}
fn deallocate_stack(&mut self) {
debug_assert!(
self.frame_pointer >= self.allocated_stack,
"the trampoline would try to deallocate stack beyond its frame pointer"
);
x64!(self.assmblr; add rsp, self.allocated_stack as i32);
self.frame_pointer -= self.allocated_stack;
self.allocated_stack = 0;
}
fn call(&mut self, ptr: *const c_void) {
// the stack has been aligned during stack allocation and/or pushing of preserved registers
debug_assert!(
(8 + self.frame_pointer) % 16 == 0,
"the trampoline would call the FFI function with an unaligned stack"
);
x64!(self.assmblr
; mov rax, QWORD ptr as _
; call rax
);
}
fn tailcall(&mut self, ptr: *const c_void) {
// stack pointer is never modified and remains aligned
// return address remains the one provided by the trampoline's caller (V8)
debug_assert!(
self.allocated_stack == 0,
"the trampoline would tail call the FFI function with an outstanding stack allocation"
);
debug_assert!(
self.frame_pointer == 0,
"the trampoline would tail call the FFI function with outstanding locals in the frame"
);
x64!(self.assmblr
; mov rax, QWORD ptr as _
; jmp rax
);
}
fn ret(&mut self) {
debug_assert!(
self.allocated_stack == 0,
"the trampoline would return with an outstanding stack allocation"
);
debug_assert!(
self.frame_pointer == 0,
"the trampoline would return with outstanding locals in the frame"
);
x64!(self.assmblr; ret);
}
fn is_recv_arg_overridden(&self) -> bool {
self.params > 0
}
fn must_cast_return_value(&self, rv: &NativeType) -> bool {
// V8 only supports i32 and u32 return types for integers
// We support 8 and 16 bit integers by extending them to 32 bits in the trampoline before returning
matches!(
rv,
NativeType::U8 | NativeType::I8 | NativeType::U16 | NativeType::I16
)
}
fn must_wrap_return_value_in_typed_array(&self, rv: &NativeType) -> bool {
// V8 only supports i32 and u32 return types for integers
// We support 64 bit integers by wrapping them in a TypedArray out parameter
crate::dlfcn::needs_unwrap(rv)
}
fn finalize(self) -> ExecutableBuffer {
self.assmblr.finalize().unwrap()
}
}
fn padding_to_align(alignment: u32, size: u32) -> u32 {
(alignment - size % alignment) % alignment
}
#[derive(Clone, Copy, Debug)]
enum Floating {
Single = 4,
Double = 8,
}
impl Floating {
fn size(self) -> u32 {
self as u32
}
}
use Floating::*;
#[derive(Clone, Copy, Debug)]
enum Integral {
I(Size),
U(Size),
Buffer,
}
impl Integral {
fn size(self) -> u32 {
match self {
I(size) | U(size) => size as u32,
Buffer => 8,
}
}
}
use Integral::*;
#[derive(Clone, Copy, Debug)]
enum Size {
B = 1,
W = 2,
DW = 4,
QW = 8,
}
use Size::*;
#[allow(clippy::enum_variant_names)]
#[derive(Clone, Copy, Debug)]
enum Param {
Int(Integral),
Float(Floating),
}
use Param::*;
impl From<NativeType> for Param {
fn from(native: NativeType) -> Self {
match native {
NativeType::F32 => Float(Single),
NativeType::F64 => Float(Double),
NativeType::Bool | NativeType::U8 => Int(U(B)),
NativeType::U16 => Int(U(W)),
NativeType::U32 | NativeType::Void => Int(U(DW)),
NativeType::U64
| NativeType::USize
| NativeType::Pointer
| NativeType::Function => Int(U(QW)),
NativeType::I8 => Int(I(B)),
NativeType::I16 => Int(I(W)),
NativeType::I32 => Int(I(DW)),
NativeType::I64 | NativeType::ISize => Int(I(QW)),
NativeType::Buffer => Int(Buffer),
NativeType::Struct(_) => unimplemented!(),
}
}
}
#[cfg(test)]
mod tests {
use std::ptr::null_mut;
use libffi::middle::Type;
use crate::NativeType;
use crate::Symbol;
fn symbol(parameters: Vec<NativeType>, ret: NativeType) -> Symbol {
Symbol {
cif: libffi::middle::Cif::new(vec![], Type::void()),
ptr: libffi::middle::CodePtr(null_mut()),
parameter_types: parameters,
result_type: ret,
can_callback: false,
}
}
mod sysv_amd64 {
use std::ops::Deref;
use dynasmrt::dynasm;
use dynasmrt::DynasmApi;
use super::super::SysVAmd64;
use super::symbol;
use crate::NativeType::*;
#[test]
fn tailcall() {
let trampoline = SysVAmd64::compile(&symbol(
vec![
U8, U16, I16, I8, U32, U64, Buffer, Function, I64, I32, I16, I8, F32,
F32, F32, F32, F64, F64, F64, F64, F32, F64,
],
Void,
));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/KE9x1h9xq
dynasm!(assembler
; .arch x64
; movzx edi, sil // u8
; movzx esi, dx // u16
; movsx edx, cx // i16
; movsx ecx, r8b // i8
; mov r8d, r9d // u32
; mov r9, [DWORD rsp + 8] // u64
; mov rax, [DWORD rsp + 16] // Buffer
; mov rax, [rax + 8] // ..
; mov [DWORD rsp + 8], rax // ..
; mov rax, [DWORD rsp + 24] // Function
; mov [DWORD rsp + 16], rax // ..
; mov rax, [DWORD rsp + 32] // i64
; mov [DWORD rsp + 24], rax // ..
; mov eax, [DWORD rsp + 40] // i32
; mov [DWORD rsp + 32], eax // ..
; movsx eax, WORD [DWORD rsp + 48] // i16
; mov [DWORD rsp + 40], eax // ..
; movsx eax, BYTE [DWORD rsp + 56] // i8
; mov [DWORD rsp + 48], eax // ..
; movss xmm8, [DWORD rsp + 64] // f32
; movss [DWORD rsp + 56], xmm8 // ..
; movsd xmm8, [DWORD rsp + 72] // f64
; movsd [DWORD rsp + 64], xmm8 // ..
; mov rax, QWORD 0
; jmp rax
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn integer_casting() {
let trampoline = SysVAmd64::compile(&symbol(
vec![U8, U16, I8, I16, U8, U16, I8, I16, U8, U16, I8, I16],
I8,
));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/qo59bPsfv
dynasm!(assembler
; .arch x64
; sub rsp, DWORD 56 // stack allocation
; movzx edi, sil // u8
; movzx esi, dx // u16
; movsx edx, cl // i8
; movsx ecx, r8w // i16
; movzx r8d, r9b // u8
; movzx r9d, WORD [DWORD rsp + 64] // u16
; movsx eax, BYTE [DWORD rsp + 72] // i8
; mov [DWORD rsp + 0], eax // ..
; movsx eax, WORD [DWORD rsp + 80] // i16
; mov [DWORD rsp + 8], eax // ..
; movzx eax, BYTE [DWORD rsp + 88] // u8
; mov [DWORD rsp + 16], eax // ..
; movzx eax, WORD [DWORD rsp + 96] // u16
; mov [DWORD rsp + 24], eax // ..
; movsx eax, BYTE [DWORD rsp + 104] // i8
; mov [DWORD rsp + 32], eax // ..
; movsx eax, WORD [DWORD rsp + 112] // i16
; mov [DWORD rsp + 40], eax // ..
; mov rax, QWORD 0
; call rax
; movsx eax, al // return value cast
; add rsp, DWORD 56 // stack deallocation
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn buffer_parameters() {
let trampoline = SysVAmd64::compile(&symbol(
vec![
Buffer, Buffer, Buffer, Buffer, Buffer, Buffer, Buffer, Buffer,
],
Void,
));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/hqv63M3Ko
dynasm!(assembler
; .arch x64
; mov rdi, [rsi + 8] // Buffer
; mov rsi, [rdx + 8] // Buffer
; mov rdx, [rcx + 8] // Buffer
; mov rcx, [r8 + 8] // Buffer
; mov r8, [r9 + 8] // Buffer
; mov r9, [DWORD rsp + 8] // Buffer
; mov r9, [r9 + 8] // ..
; mov rax, [DWORD rsp + 16] // Buffer
; mov rax, [rax + 8] // ..
; mov [DWORD rsp + 8], rax // ..
; mov rax, [DWORD rsp + 24] // Buffer
; mov rax, [rax + 8] // ..
; mov [DWORD rsp + 16], rax // ..
; mov rax, QWORD 0
; jmp rax
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn return_u64_in_register_typed_array() {
let trampoline = SysVAmd64::compile(&symbol(vec![], U64));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/8G7a488o7
dynasm!(assembler
; .arch x64
; push rbx
; xor edi, edi // recv
; mov rbx, [rsi + 8] // save data array pointer to non-volatile register
; mov rax, QWORD 0
; call rax
; mov [rbx], rax // copy return value to data pointer address
; pop rbx
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn return_u64_in_stack_typed_array() {
let trampoline = SysVAmd64::compile(&symbol(
vec![U64, U64, U64, U64, U64, U64, U64],
U64,
));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/cPnPYWdWq
dynasm!(assembler
; .arch x64
; push rbx
; sub rsp, DWORD 16
; mov rdi, rsi // u64
; mov rsi, rdx // u64
; mov rdx, rcx // u64
; mov rcx, r8 // u64
; mov r8, r9 // u64
; mov r9, [DWORD rsp + 32] // u64
; mov rax, [DWORD rsp + 40] // u64
; mov [DWORD rsp + 0], rax // ..
; mov rax, [DWORD rsp + 48] // save data array pointer to non-volatile register
; mov rbx, [rax + 8] // ..
; mov rax, QWORD 0
; call rax
; mov [rbx], rax // copy return value to data pointer address
; add rsp, DWORD 16
; pop rbx
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
}
mod aarch64_apple {
use std::ops::Deref;
use dynasmrt::dynasm;
use super::super::Aarch64Apple;
use super::symbol;
use crate::NativeType::*;
#[test]
fn tailcall() {
let trampoline = Aarch64Apple::compile(&symbol(
vec![
U8, U16, I16, I8, U32, U64, Buffer, Function, I64, I32, I16, I8, F32,
F32, F32, F32, F64, F64, F64, F64, F32, F64,
],
Void,
));
let mut assembler = dynasmrt::aarch64::Assembler::new().unwrap();
// See https://godbolt.org/z/oefqYWT13
dynasm!(assembler
; .arch aarch64
; and w0, w1, 0xFF // u8
; and w1, w2, 0xFFFF // u16
; sxth w2, w3 // i16
; sxtb w3, w4 // i8
; mov w4, w5 // u32
; mov x5, x6 // u64
; ldr x6, [x7, 8] // Buffer
; ldr x7, [sp] // Function
; ldr x8, [sp, 8] // i64
; str x8, [sp] // ..
; ldr w8, [sp, 16] // i32
; str w8, [sp, 8] // ..
; ldr w8, [sp, 24] // i16
; strh w8, [sp, 12] // ..
; ldr w8, [sp, 32] // i8
; strb w8, [sp, 14] // ..
; ldr s16, [sp, 40] // f32
; str s16, [sp, 16] // ..
; ldr d16, [sp, 48] // f64
; str d16, [sp, 24] // ..
; movz x8, 0
; br x8
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn integer_casting() {
let trampoline = Aarch64Apple::compile(&symbol(
vec![U8, U16, I8, I16, U8, U16, I8, I16, U8, U16, I8, I16],
I8,
));
let mut assembler = dynasmrt::aarch64::Assembler::new().unwrap();
// See https://godbolt.org/z/7qfzbzobM
dynasm!(assembler
; .arch aarch64
; and w0, w1, 0xFF // u8
; and w1, w2, 0xFFFF // u16
; sxtb w2, w3 // i8
; sxth w3, w4 // i16
; and w4, w5, 0xFF // u8
; and w5, w6, 0xFFFF // u16
; sxtb w6, w7 // i8
; ldrsh w7, [sp] // i16
; ldr w8, [sp, 8] // u8
; strb w8, [sp] // ..
; ldr w8, [sp, 16] // u16
; strh w8, [sp, 2] // ..
; ldr w8, [sp, 24] // i8
; strb w8, [sp, 4] // ..
; ldr w8, [sp, 32] // i16
; strh w8, [sp, 6] // ..
; movz x8, 0
; br x8
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn buffer_parameters() {
let trampoline = Aarch64Apple::compile(&symbol(
vec![
Buffer, Buffer, Buffer, Buffer, Buffer, Buffer, Buffer, Buffer,
Buffer, Buffer,
],
Void,
));
let mut assembler = dynasmrt::aarch64::Assembler::new().unwrap();
// See https://godbolt.org/z/obd6z6vsf
dynasm!(assembler
; .arch aarch64
; ldr x0, [x1, 8] // Buffer
; ldr x1, [x2, 8] // Buffer
; ldr x2, [x3, 8] // Buffer
; ldr x3, [x4, 8] // Buffer
; ldr x4, [x5, 8] // Buffer
; ldr x5, [x6, 8] // Buffer
; ldr x6, [x7, 8] // Buffer
; ldr x7, [sp] // Buffer
; ldr x7, [x7, 8] // ..
; ldr x8, [sp, 8] // Buffer
; ldr x8, [x8, 8] // ..
; str x8, [sp] // ..
; ldr x8, [sp, 16] // Buffer
; ldr x8, [x8, 8] // ..
; str x8, [sp, 8] // ..
; movz x8, 0
; br x8
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn return_u64_in_register_typed_array() {
let trampoline = Aarch64Apple::compile(&symbol(vec![], U64));
let mut assembler = dynasmrt::aarch64::Assembler::new().unwrap();
// See https://godbolt.org/z/47EvvYb83
dynasm!(assembler
; .arch aarch64
; sub sp, sp, 32
; stp x29, x30, [sp, 16]
; add x29, sp, 16
; str x19, [sp, 8]
; mov x0, xzr // recv
; ldr x19, [x1, 8] // save data array pointer to non-volatile register
; movz x8, 0
; blr x8
; str x0, [x19] // copy return value to data pointer address
; ldr x19, [sp, 8]
; ldp x29, x30, [sp, 16]
; add sp, sp, 32
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn return_u64_in_stack_typed_array() {
let trampoline = Aarch64Apple::compile(&symbol(
vec![U64, U64, U64, U64, U64, U64, U64, U64, U8, U8],
U64,
));
let mut assembler = dynasmrt::aarch64::Assembler::new().unwrap();
// See https://godbolt.org/z/PvYPbsE1b
dynasm!(assembler
; .arch aarch64
; sub sp, sp, 32
; stp x29, x30, [sp, 16]
; add x29, sp, 16
; str x19, [sp, 8]
; mov x0, x1 // u64
; mov x1, x2 // u64
; mov x2, x3 // u64
; mov x3, x4 // u64
; mov x4, x5 // u64
; mov x5, x6 // u64
; mov x6, x7 // u64
; ldr x7, [sp, 32] // u64
; ldr w8, [sp, 40] // u8
; strb w8, [sp] // ..
; ldr w8, [sp, 48] // u8
; strb w8, [sp, 1] // ..
; ldr x19, [sp, 56] // save data array pointer to non-volatile register
; ldr x19, [x19, 8] // ..
; movz x8, 0
; blr x8
; str x0, [x19] // copy return value to data pointer address
; ldr x19, [sp, 8]
; ldp x29, x30, [sp, 16]
; add sp, sp, 32
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
}
mod x64_windows {
use std::ops::Deref;
use dynasmrt::dynasm;
use dynasmrt::DynasmApi;
use super::super::Win64;
use super::symbol;
use crate::NativeType::*;
#[test]
fn tailcall() {
let trampoline =
Win64::compile(&symbol(vec![U8, I16, F64, F32, U32, I8, Buffer], Void));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/TYzqrf9aj
dynasm!(assembler
; .arch x64
; mov ecx, edx // u8
; mov edx, r8d // i16
; movaps xmm2, xmm3 // f64
; movaps xmm3, [DWORD rsp + 40] // f32
; mov eax, [DWORD rsp + 48] // u32
; mov [DWORD rsp + 40], eax // ..
; mov eax, [DWORD rsp + 56] // i8
; mov [DWORD rsp + 48], eax // ..
; mov rax, [DWORD rsp + 64] // Buffer
; mov rax, [rax + 8] // ..
; mov [DWORD rsp + 56], rax // ..
; mov rax, QWORD 0
; jmp rax
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn integer_casting() {
let trampoline = Win64::compile(&symbol(
vec![U8, U16, I8, I16, U8, U16, I8, I16, U8, U16, I8, I16],
I8,
));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/KMx56KGTq
dynasm!(assembler
; .arch x64
; sub rsp, DWORD 104 // stack allocation
; mov ecx, edx // u8
; mov edx, r8d // u16
; mov r8d, r9d // i8
; mov r9d, [DWORD rsp + 144] // i16
; mov eax, [DWORD rsp + 152] // u8
; mov [DWORD rsp + 32], eax // ..
; mov eax, [DWORD rsp + 160] // u16
; mov [DWORD rsp + 40], eax // u16
; mov eax, [DWORD rsp + 168] // i8
; mov [DWORD rsp + 48], eax // ..
; mov eax, [DWORD rsp + 176] // i16
; mov [DWORD rsp + 56], eax // ..
; mov eax, [DWORD rsp + 184] // u8
; mov [DWORD rsp + 64], eax // ..
; mov eax, [DWORD rsp + 192] // u16
; mov [DWORD rsp + 72], eax // ..
; mov eax, [DWORD rsp + 200] // i8
; mov [DWORD rsp + 80], eax // ..
; mov eax, [DWORD rsp + 208] // i16
; mov [DWORD rsp + 88], eax // ..
; mov rax, QWORD 0
; call rax
; movsx eax, al // return value cast
; add rsp, DWORD 104 // stack deallocation
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn buffer_parameters() {
let trampoline = Win64::compile(&symbol(
vec![Buffer, Buffer, Buffer, Buffer, Buffer, Buffer],
Void,
));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/TYzqrf9aj
dynasm!(assembler
; .arch x64
; mov rcx, [rdx + 8] // Buffer
; mov rdx, [r8 + 8] // Buffer
; mov r8, [r9 + 8] // Buffer
; mov r9, [DWORD rsp + 40] // Buffer
; mov r9, [r9 + 8] // ..
; mov rax, [DWORD rsp + 48] // Buffer
; mov rax, [rax + 8] // ..
; mov [DWORD rsp + 40], rax // ..
; mov rax, [DWORD rsp + 56] // Buffer
; mov rax, [rax + 8] // ..
; mov [DWORD rsp + 48], rax // ..
; mov rax, QWORD 0
; jmp rax
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn return_u64_in_register_typed_array() {
let trampoline = Win64::compile(&symbol(vec![], U64));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/7EnPE7o3T
dynasm!(assembler
; .arch x64
; push rbx
; sub rsp, DWORD 32
; xor ecx, ecx // recv
; mov rbx, [rdx + 8] // save data array pointer to non-volatile register
; mov rax, QWORD 0
; call rax
; mov [rbx], rax // copy return value to data pointer address
; add rsp, DWORD 32
; pop rbx
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
#[test]
fn return_u64_in_stack_typed_array() {
let trampoline =
Win64::compile(&symbol(vec![U64, U64, U64, U64, U64], U64));
let mut assembler = dynasmrt::x64::Assembler::new().unwrap();
// See https://godbolt.org/z/3966sfEex
dynasm!(assembler
; .arch x64
; push rbx
; sub rsp, DWORD 48
; mov rcx, rdx // u64
; mov rdx, r8 // u64
; mov r8, r9 // u64
; mov r9, [DWORD rsp + 96] // u64
; mov rax, [DWORD rsp + 104] // u64
; mov [DWORD rsp + 32], rax // ..
; mov rax, [DWORD rsp + 112] // save data array pointer to non-volatile register
; mov rbx, [rax + 8] // ..
; mov rax, QWORD 0
; call rax
; mov [rbx], rax // copy return value to data pointer address
; add rsp, DWORD 48
; pop rbx
; ret
);
let expected = assembler.finalize().unwrap();
assert_eq!(trampoline.0.deref(), expected.deref());
}
}
}
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