Mach ports continued + support aarch64-apple unwinding

cranelift/codegen/src/isa/aarch64/abi.rs

@@ -475,6 +475,15 @@ impl ABIMachineSpec for AArch64MachineDeps {
 
     fn gen_prologue_frame_setup(flags: &settings::Flags) -> SmallInstVec<Inst> {
         let mut insts = SmallVec::new();
+
+        if flags.unwind_info() {
+            insts.push(Inst::Unwind {
+                inst: UnwindInst::Aarch64SetPointerAuth {
+                    return_addresses: false,
+                },
+            });
+        }
+
         // stp fp (x29), lr (x30), [sp, #-16]!
         insts.push(Inst::StoreP64 {
             rt: fp_reg(),

cranelift/codegen/src/isa/unwind.rs

@@ -69,6 +69,11 @@ pub mod input {
         RememberState,
         /// Restores the state.
         RestoreState,
+        /// On aarch64 ARMv8.3+ devices, enables or disables pointer authentication.
+        Aarch64SetPointerAuth {
+            /// Whether return addresses (hold in LR) contain a pointer-authentication code.
+            return_addresses: bool,
+        },
     }
 
     /// Unwind information as generated by a backend.
@@ -234,4 +239,10 @@ pub enum UnwindInst {
         /// The saved register.
         reg: RealReg,
     },
+    /// Defines if the aarch64-specific pointer authentication available for ARM v8.3+ devices
+    /// is enabled for certain pointers or not.
+    Aarch64SetPointerAuth {
+        /// Whether return addresses (hold in LR) contain a pointer-authentication code.
+        return_addresses: bool,
+    },
 }

cranelift/codegen/src/isa/unwind/systemv.rs

@@ -44,6 +44,11 @@ pub(crate) enum CallFrameInstruction {
     RememberState,
     RestoreState,
     ArgsSize(u32),
+    /// Enables or disables pointer authentication on aarch64 platforms post ARMv8.3.  This
+    /// particular item maps to gimli::ValExpression(RA_SIGN_STATE, lit0/lit1).
+    Aarch64SetPointerAuth {
+        return_addresses: bool,
+    },
 }
 
 impl From<gimli::write::CallFrameInstruction> for CallFrameInstruction {
@@ -75,7 +80,7 @@ impl From<gimli::write::CallFrameInstruction> for CallFrameInstruction {
 
 impl Into<gimli::write::CallFrameInstruction> for CallFrameInstruction {
     fn into(self) -> gimli::write::CallFrameInstruction {
-        use gimli::{write::CallFrameInstruction, Register};
+        use gimli::{write::CallFrameInstruction, write::Expression, Register};
 
         match self {
             Self::Cfa(reg, offset) => CallFrameInstruction::Cfa(Register(reg), offset),
@@ -92,6 +97,21 @@ impl Into<gimli::write::CallFrameInstruction> for CallFrameInstruction {
             Self::RememberState => CallFrameInstruction::RememberState,
             Self::RestoreState => CallFrameInstruction::RestoreState,
             Self::ArgsSize(size) => CallFrameInstruction::ArgsSize(size),
+            Self::Aarch64SetPointerAuth { return_addresses } => {
+                // To enable pointer authentication for return addresses in dwarf directives, we
+                // use a small dwarf expression that sets the value of the pseudo-register
+                // RA_SIGN_STATE (RA stands for return address) to 0 or 1. This behavior is
+                // documented in
+                // https://github.com/ARM-software/abi-aa/blob/master/aadwarf64/aadwarf64.rst#41dwarf-register-names.
+                let mut expr = Expression::new();
+                expr.op(if return_addresses {
+                    gimli::DW_OP_lit1
+                } else {
+                    gimli::DW_OP_lit0
+                });
+                const RA_SIGN_STATE: Register = Register(34);
+                CallFrameInstruction::ValExpression(RA_SIGN_STATE, expr)
+            }
         }
     }
 }
@@ -187,6 +207,12 @@ pub(crate) fn create_unwind_info_from_insts<MR: RegisterMapper<regalloc::Reg>>(
                 let off = (clobber_offset as i32) - (clobber_offset_to_cfa as i32);
                 instructions.push((instruction_offset, CallFrameInstruction::Offset(reg, off)));
             }
+            &UnwindInst::Aarch64SetPointerAuth { return_addresses } => {
+                instructions.push((
+                    instruction_offset,
+                    CallFrameInstruction::Aarch64SetPointerAuth { return_addresses },
+                ));
+            }
         }
     }
 
@@ -245,6 +271,9 @@ impl UnwindInfo {
                 UnwindCode::RestoreState => {
                     builder.restore_state(*offset);
                 }
+                UnwindCode::Aarch64SetPointerAuth { return_addresses } => {
+                    builder.set_aarch64_pauth(*offset, *return_addresses);
+                }
             }
         }
 
@@ -399,4 +428,11 @@ impl<'a, Reg: PartialEq + Copy> InstructionBuilder<'a, Reg> {
         self.instructions
             .push((offset, CallFrameInstruction::RestoreState));
     }
+
+    fn set_aarch64_pauth(&mut self, offset: u32, return_addresses: bool) {
+        self.instructions.push((
+            offset,
+            CallFrameInstruction::Aarch64SetPointerAuth { return_addresses },
+        ));
+    }
 }

cranelift/codegen/src/isa/unwind/winx64.rs

@@ -379,6 +379,9 @@ pub(crate) fn create_unwind_info_from_insts<MR: RegisterMapper<regalloc::Reg>>(
                     });
                 }
             },
+            &UnwindInst::Aarch64SetPointerAuth { .. } => {
+                unreachable!("no aarch64 on x64");
+            }
         }
         max_unwind_offset = instruction_offset;
     }

crates/fiber/src/arch/aarch64.S

@@ -107,9 +107,9 @@ FUNCTION(wasmtime_fiber_start):
     // ... 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.
+    // Unreachable, here for safety. This should help catch unexpected behaviors.
+    // Use a noticeable payload so one can grep for it in the codebase.
+    brk 0xf1b3
     .cfi_endproc
 SIZE(wasmtime_fiber_start)
 

crates/runtime/Cargo.toml

@@ -27,6 +27,9 @@ psm = "0.1.11"
 rand = "0.7.3"
 anyhow = "1.0.38"
 
+[target.'cfg(target_os = "macos")'.dependencies]
+mach = "0.3.2"
+
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = { version = "0.3.7", features = ["winbase", "memoryapi", "errhandlingapi"] }