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Insert trampolines to preserve callee-saved registers for backends without register save area information.

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This commit is contained in:
losfair
2019-08-15 19:10:24 -07:00
parent 0a54213d4f
commit 6a24485999
4 changed files with 68 additions and 15 deletions
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36
lib/singlepass-backend/src/codegen_x64.rs
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@ -32,6 +32,7 @@ use wasmer_runtime_core::{
TableIndex, Type,
},
vm::{self, LocalGlobal, LocalTable, INTERNALS_SIZE},
fault::raw::register_preservation_trampoline,
};
use wasmparser::{Operator, Type as WpType, TypeOrFuncType as WpTypeOrFuncType};
@ -220,24 +221,34 @@ impl RunnableModule for X64ExecutionContext {
}
unsafe fn patch_local_function(&self, idx: usize, target_address: usize) -> bool {
// movabsq ?, %rax;
// jmpq *%rax;
/*
0: 48 b8 42 42 42 42 42 42 42 42 movabsq $4774451407313060418, %rax
a: 49 bb 43 43 43 43 43 43 43 43 movabsq $4846791580151137091, %r11
14: 41 ff e3 jmpq *%r11
*/
#[repr(packed)]
struct Trampoline {
movabsq: [u8; 2],
addr: u64,
jmpq: [u8; 2],
movabsq_rax: [u8; 2],
addr_rax: u64,
movabsq_r11: [u8; 2],
addr_r11: u64,
jmpq_r11: [u8; 3],
}
self.code.make_writable();
let trampoline = &mut *(self.function_pointers[self.func_import_count + idx].0
as *const Trampoline as *mut Trampoline);
trampoline.movabsq[0] = 0x48;
trampoline.movabsq[1] = 0xb8;
trampoline.addr = target_address as u64;
trampoline.jmpq[0] = 0xff;
trampoline.jmpq[1] = 0xe0;
trampoline.movabsq_rax[0] = 0x48;
trampoline.movabsq_rax[1] = 0xb8;
trampoline.addr_rax = target_address as u64;
trampoline.movabsq_r11[0] = 0x49;
trampoline.movabsq_r11[1] = 0xbb;
trampoline.addr_r11 = register_preservation_trampoline as unsafe extern "C" fn() as usize as u64;
trampoline.jmpq_r11[0] = 0x41;
trampoline.jmpq_r11[1] = 0xff;
trampoline.jmpq_r11[2] = 0xe3;
self.code.make_executable();
true
@ -1677,9 +1688,10 @@ impl FunctionCodeGenerator<CodegenError> for X64FunctionCode {
fn begin_body(&mut self, _module_info: &ModuleInfo) -> Result<(), CodegenError> {
let a = self.assembler.as_mut().unwrap();
let start_label = a.get_label();
// skip the patchpoint during normal execution
a.emit_jmp(Condition::None, start_label);
// patchpoint of 16 bytes
for _ in 0..16 {
// patchpoint of 32 bytes
for _ in 0..32 {
a.emit_nop();
}
a.emit_label(start_label);