diff --git a/Cargo.lock b/Cargo.lock
index eb30c4b..5946d97 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -149,9 +149,9 @@ dependencies = [
 
 [[package]]
 name = "cortex-a"
-version = "7.5.0"
+version = "8.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bdecfbb28672ad3664e71ae05a398a52df430d86d660691501b28968cc4467e6"
+checksum = "0cd4524931a4e0ec50ae91f0d55f571f31ffe11dd9ce2f9905b8343c018c25bb"
 dependencies = [
  "tock-registers",
 ]
@@ -336,15 +336,15 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.132"
+version = "0.2.134"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8371e4e5341c3a96db127eb2465ac681ced4c433e01dd0e938adbef26ba93ba5"
+checksum = "329c933548736bc49fd575ee68c89e8be4d260064184389a5b77517cddd99ffb"
 
 [[package]]
 name = "lock_api"
-version = "0.4.8"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9f80bf5aacaf25cbfc8210d1cfb718f2bf3b11c4c54e5afe36c236853a8ec390"
+checksum = "435011366fe56583b16cf956f9df0095b405b82d76425bc8981c0e22e60ec4df"
 dependencies = [
  "autocfg",
  "scopeguard",
@@ -474,9 +474,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.14.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2f7254b99e31cad77da24b08ebf628882739a608578bb1bcdfc1f9c21260d7c0"
+checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
 
 [[package]]
 name = "os_str_bytes"
@@ -521,9 +521,9 @@ checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.43"
+version = "1.0.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0a2ca2c61bc9f3d74d2886294ab7b9853abd9c1ad903a3ac7815c58989bb7bab"
+checksum = "94e2ef8dbfc347b10c094890f778ee2e36ca9bb4262e86dc99cd217e35f3470b"
 dependencies = [
  "unicode-ident",
 ]
@@ -681,9 +681,9 @@ checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
 [[package]]
 name = "syn"
-version = "1.0.99"
+version = "1.0.101"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "58dbef6ec655055e20b86b15a8cc6d439cca19b667537ac6a1369572d151ab13"
+checksum = "e90cde112c4b9690b8cbe810cba9ddd8bc1d7472e2cae317b69e9438c1cba7d2"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -707,15 +707,15 @@ checksum = "949517c0cf1bf4ee812e2e07e08ab448e3ae0d23472aee8a06c985f0c8815b16"
 
 [[package]]
 name = "tock-registers"
-version = "0.7.0"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4ee8fba06c1f4d0b396ef61a54530bb6b28f0dc61c38bc8bc5a5a48161e6282e"
+checksum = "696941a0aee7e276a165a978b37918fd5d22c55c3d6bda197813070ca9c0f21c"
 
 [[package]]
 name = "tokio"
-version = "1.21.1"
+version = "1.21.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0020c875007ad96677dcc890298f4b942882c5d4eb7cc8f439fc3bf813dc9c95"
+checksum = "a9e03c497dc955702ba729190dc4aac6f2a0ce97f913e5b1b5912fc5039d9099"
 dependencies = [
  "autocfg",
  "bytes",
@@ -723,7 +723,6 @@ dependencies = [
  "memchr",
  "mio",
  "num_cpus",
- "once_cell",
  "parking_lot",
  "pin-project-lite",
  "signal-hook-registry",
diff --git a/bin/chainboot/Cargo.toml b/bin/chainboot/Cargo.toml
index 1f5ac4c..ee6bbac 100644
--- a/bin/chainboot/Cargo.toml
+++ b/bin/chainboot/Cargo.toml
@@ -27,8 +27,8 @@ rpi4 = ["machine/rpi4"]
 
 [dependencies]
 machine = { path = "../../machine" }
-cortex-a = "7.5"
-tock-registers = "0.7"
+cortex-a = "8.0"
+tock-registers = "0.8.1"
 ux = { version = "0.1", default-features = false }
 usize_conversions = "0.2"
 bit_field = "0.10"
diff --git a/bin/chainboot/src/main.rs b/bin/chainboot/src/main.rs
index acc9af4..4ef586f 100644
--- a/bin/chainboot/src/main.rs
+++ b/bin/chainboot/src/main.rs
@@ -139,7 +139,7 @@ fn kernel_main(max_kernel_size: u64) -> ! {
     let kernel: fn() -> ! = unsafe { core::mem::transmute(kernel_addr) };
 
     // Force everything to complete before we jump.
-    unsafe { barrier::isb(barrier::SY) };
+    barrier::isb(barrier::SY);
 
     // Jump to loaded kernel!
     kernel()
diff --git a/machine/Cargo.toml b/machine/Cargo.toml
index b11ac62..22e5d23 100644
--- a/machine/Cargo.toml
+++ b/machine/Cargo.toml
@@ -29,8 +29,8 @@ rpi4 = []
 
 [dependencies]
 qemu-exit = "3.0"
-cortex-a = "7.5"
-tock-registers = "0.7"
+cortex-a = "8.0"
+tock-registers = "0.8.1"
 ux = { version = "0.1", default-features = false }
 usize_conversions = "0.2"
 bit_field = "0.10"
diff --git a/machine/src/platform/rpi3/mailbox.rs b/machine/src/platform/rpi3/mailbox.rs
index 116d5b9..470b68e 100644
--- a/machine/src/platform/rpi3/mailbox.rs
+++ b/machine/src/platform/rpi3/mailbox.rs
@@ -565,9 +565,7 @@ impl<const N_SLOTS: usize, Storage: MailboxStorage + MailboxStorageRef> Mailbox<
                 return Err(MailboxError::Timeout);
             }
         }
-        unsafe {
-            barrier::dmb(barrier::SY);
-        }
+        barrier::dmb(barrier::SY);
         self.registers
             .WRITE
             .set((buf_ptr & !CHANNEL_MASK) | (channel & CHANNEL_MASK));
diff --git a/nucleus/Cargo.toml b/nucleus/Cargo.toml
index bdb637b..bc738f7 100644
--- a/nucleus/Cargo.toml
+++ b/nucleus/Cargo.toml
@@ -28,8 +28,8 @@ rpi4 = ["machine/rpi4"]
 
 [dependencies]
 machine = { path = "../machine" }
-cortex-a = "7.5"
-tock-registers = "0.7"
+cortex-a = "8.0"
+tock-registers = "0.8.1"
 ux = { version = "0.1", default-features = false }
 usize_conversions = "0.2"
 bit_field = "0.10"