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jit: make sure RSP is 16 byte aligned when we call into rust code #515

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Sep 19, 2023
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jit: make sure RSP is 16 byte aligned when we call into rust code #515

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21 changes: 17 additions & 4 deletions src/jit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -852,13 +852,23 @@ impl<'a, V: Verifier, C: ContextObject> JitCompiler<'a, V, C> {
for reg in saved_registers.iter() {
self.emit_ins(X86Instruction::push(*reg, None));
}


// Align RSP to 16 bytes
self.emit_ins(X86Instruction::push(RSP, None));
self.emit_ins(X86Instruction::push(RSP, Some(X86IndirectAccess::OffsetIndexShift(0, RSP, 0))));
self.emit_ins(X86Instruction::alu(OperandSize::S64, 0x81, 4, RSP, -16, None));

let stack_arguments = arguments.len().saturating_sub(ARGUMENT_REGISTERS.len()) as i64;
if stack_arguments % 2 != 0 {
// If we're going to pass an odd number of stack args we need to pad
// to preserve alignment
self.emit_ins(X86Instruction::alu(OperandSize::S64, 0x81, 5, RSP, 8, None));
}

// Pass arguments
let mut stack_arguments = 0;
for argument in arguments {
let is_stack_argument = argument.index >= ARGUMENT_REGISTERS.len();
let dst = if is_stack_argument {
stack_arguments += 1;
R11
} else {
ARGUMENT_REGISTERS[argument.index]
Expand Down Expand Up @@ -926,7 +936,10 @@ impl<'a, V: Verifier, C: ContextObject> JitCompiler<'a, V, C> {
}

// Restore registers from stack
self.emit_ins(X86Instruction::alu(OperandSize::S64, 0x81, 0, RSP, stack_arguments * 8, None));
self.emit_ins(X86Instruction::alu(OperandSize::S64, 0x81, 0, RSP,
if stack_arguments % 2 != 0 { stack_arguments + 1 } else { stack_arguments } * 8, None));
self.emit_ins(X86Instruction::load(OperandSize::S64, RSP, RSP, X86IndirectAccess::OffsetIndexShift(8, RSP, 0)));

for reg in saved_registers.iter().rev() {
self.emit_ins(X86Instruction::pop(*reg));
}
Expand Down