70ce288dc7
* Wasmtime: Add a pointer to `VMRuntimeLimits` in component contexts * Save exit Wasm FP and PC in component-to-host trampolines Fixes #4535 * Add comment about why we deref the trampoline's FP * Update some tests to use new `vmruntime_limits_*` methods
136 lines
4.3 KiB
Rust
136 lines
4.3 KiB
Rust
use wasmtime_asm_macros::asm_func;
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// Helper macros for getting the first and second arguments according to the
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// system calling convention, as well as some callee-saved scratch registers we
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// can safely use in the trampolines.
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cfg_if::cfg_if! {
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if #[cfg(windows)] {
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macro_rules! arg0 { () => ("rcx") }
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macro_rules! arg1 { () => ("rdx") }
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macro_rules! scratch0 { () => ("r10") }
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macro_rules! scratch1 { () => ("r11") }
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} else if #[cfg(unix)] {
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macro_rules! arg0 { () => ("rdi") }
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macro_rules! arg1 { () => ("rsi") }
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macro_rules! scratch0 { () => ("r10") }
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macro_rules! scratch1 { () => ("r11") }
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} else {
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compile_error!("platform not supported");
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}
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}
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#[rustfmt::skip]
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asm_func!(
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"host_to_wasm_trampoline",
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"
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.cfi_startproc simple
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.cfi_def_cfa_offset 0
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// Load the pointer to `VMRuntimeLimits` in `scratch0`.
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mov ", scratch0!(), ", 8[", arg1!(), "]
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// Check to see if this is a core `VMContext` (MAGIC == 'core').
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cmp DWORD PTR [", arg0!(), "], 0x65726f63
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// Store the last Wasm SP into the `last_wasm_entry_sp` in the limits, if this
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// was core Wasm, otherwise store an invalid sentinal value.
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mov ", scratch1!(), ", -1
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cmove ", scratch1!(), ", rsp
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mov 40[", scratch0!(), "], ", scratch1!(), "
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// Tail call to the callee function pointer in the vmctx.
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jmp 16[", arg1!(), "]
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.cfi_endproc
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",
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);
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#[cfg(test)]
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mod host_to_wasm_trampoline_offsets_tests {
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use wasmtime_environ::{Module, PtrSize, VMOffsets};
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#[test]
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fn test() {
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let module = Module::new();
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let offsets = VMOffsets::new(std::mem::size_of::<*mut u8>() as u8, &module);
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assert_eq!(8, offsets.vmctx_runtime_limits());
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assert_eq!(40, offsets.ptr.vmruntime_limits_last_wasm_entry_sp());
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assert_eq!(16, offsets.vmctx_callee());
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assert_eq!(0x65726f63, u32::from_le_bytes(*b"core"));
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}
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}
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#[rustfmt::skip]
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asm_func!(
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"wasm_to_host_trampoline",
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"
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.cfi_startproc simple
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.cfi_def_cfa_offset 0
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// Load the pointer to `VMRuntimeLimits` in `scratch0`.
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mov ", scratch0!(), ", 8[", arg1!(), "]
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// Store the last Wasm FP into the `last_wasm_exit_fp` in the limits.
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mov 24[", scratch0!(), "], rbp
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// Store the last Wasm PC into the `last_wasm_exit_pc` in the limits.
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mov ", scratch1!(), ", [rsp]
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mov 32[", scratch0!(), "], ", scratch1!(), "
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// Tail call to the actual host function.
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//
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// This *must* be a tail call so that we do not push to the stack and mess
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// up the offsets of stack arguments (if any).
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jmp 8[", arg0!(), "]
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.cfi_endproc
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",
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);
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#[cfg(test)]
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mod wasm_to_host_trampoline_offsets_tests {
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use crate::VMHostFuncContext;
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use memoffset::offset_of;
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use wasmtime_environ::{Module, PtrSize, VMOffsets};
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#[test]
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fn test() {
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let module = Module::new();
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let offsets = VMOffsets::new(std::mem::size_of::<*mut u8>() as u8, &module);
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assert_eq!(8, offsets.vmctx_runtime_limits());
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assert_eq!(24, offsets.ptr.vmruntime_limits_last_wasm_exit_fp());
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assert_eq!(32, offsets.ptr.vmruntime_limits_last_wasm_exit_pc());
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assert_eq!(8, offset_of!(VMHostFuncContext, host_func));
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}
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}
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#[rustfmt::skip]
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macro_rules! wasm_to_libcall_trampoline {
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($libcall:ident ; $libcall_impl:ident) => {
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wasmtime_asm_macros::asm_func!(
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stringify!($libcall),
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"
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.cfi_startproc simple
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.cfi_def_cfa_offset 0
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// Load the pointer to `VMRuntimeLimits` in `", scratch0!(), "`.
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mov ", scratch0!(), ", 8[", arg0!(), "]
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// Store the last Wasm FP into the `last_wasm_exit_fp` in the limits.
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mov 24[", scratch0!(), "], rbp
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// Store the last Wasm PC into the `last_wasm_exit_pc` in the limits.
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mov ", scratch1!(), ", [rsp]
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mov 32[", scratch0!(), "], ", scratch1!(), "
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// Tail call to the actual implementation of this libcall.
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jmp ", wasmtime_asm_macros::asm_sym!(stringify!($libcall_impl)), "
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.cfi_endproc
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",
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);
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};
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}
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