Update the Rust toolchain to 2021-03-25.

This includes rust-lang/rust#82141, which is needed in order to add ARM support to libtock_runtime. It also allows us to use the unsafe_op_in_unsafe_fn lint.

Author: Johnathan Van Why

core/platform/src/command_return_tests.rs

@@ -130,7 +130,7 @@ fn failure_u64() {
     assert_eq!(command_return.get_failure_2_u32(), None);
     assert_eq!(
         command_return.get_failure_u64(),
-        Some((ErrorCode::Busy, 0x00001003_00001002))
+        Some((ErrorCode::Busy, 0x0000_1003_0000_1002))
     );
     assert_eq!(command_return.get_success_u32(), None);
     assert_eq!(command_return.get_success_2_u32(), None);
@@ -240,7 +240,10 @@ fn success_u64() {
     assert_eq!(command_return.get_failure_u64(), None);
     assert_eq!(command_return.get_success_u32(), None);
     assert_eq!(command_return.get_success_2_u32(), None);
-    assert_eq!(command_return.get_success_u64(), Some(0x00001002_00001001));
+    assert_eq!(
+        command_return.get_success_u64(),
+        Some(0x0000_1002_0000_1001)
+    );
     assert_eq!(command_return.get_success_3_u32(), None);
     assert_eq!(command_return.get_success_u32_u64(), None);
     assert_eq!(command_return.return_variant(), return_variant::SUCCESS_U64);
@@ -299,7 +302,7 @@ fn success_u32_u64() {
     assert_eq!(command_return.get_success_3_u32(), None);
     assert_eq!(
         command_return.get_success_u32_u64(),
-        Some((1001, 0x00001003_00001002))
+        Some((1001, 0x0000_1003_0000_1002))
     );
     assert_eq!(
         command_return.return_variant(),

core/platform/src/lib.rs

@@ -1,4 +1,5 @@
 #![no_std]
+#![warn(unsafe_op_in_unsafe_fn)]
 
 mod async_traits;
 mod command_return;

core/runtime/src/lib.rs

@@ -20,6 +20,7 @@
 
 #![feature(asm)]
 #![no_std]
+#![warn(unsafe_op_in_unsafe_fn)]
 
 mod startup;
 

core/runtime/src/syscalls_impl_riscv.rs

@@ -41,14 +41,16 @@ impl RawSyscalls for crate::TockSyscalls {
         mut r3: usize,
         class: u8,
     ) -> (u32, usize, usize, usize) {
-        asm!("ecall",
-             inlateout("a0") r0,
-             inlateout("a1") r1,
-             inlateout("a2") r2,
-             inlateout("a3") r3,
-             in("a4") class,
-             options(preserves_flags, nostack),
-        );
+        unsafe {
+            asm!("ecall",
+                 inlateout("a0") r0,
+                 inlateout("a1") r1,
+                 inlateout("a2") r2,
+                 inlateout("a3") r3,
+                 in("a4") class,
+                 options(preserves_flags, nostack),
+            );
+        }
         (r0, r1 as usize, r2, r3)
     }
 

core/src/entry_point/start_item_arm.rs

@@ -1,18 +1,12 @@
-use core::hint;
-
 /// Tock programs' entry point. Called by the kernel at program start. Sets up
 /// the stack then calls rust_start() for the remainder of setup.
 #[doc(hidden)]
 #[no_mangle]
 #[naked]
 #[link_section = ".start"]
-pub unsafe extern "C" fn _start(
-    app_start: usize,
-    mem_start: usize,
-    _memory_len: usize,
-    app_heap_break: usize,
-) -> ! {
-    llvm_asm!("
+pub unsafe extern "C" fn _start() -> ! {
+    asm!(
+        "
         // Because ROPI-RWPI support in LLVM/rustc is incomplete, Rust
         // applications must be statically linked. An offset between the
         // location the program is linked at and its actual location in flash
@@ -102,12 +96,8 @@ pub unsafe extern "C" fn _start(
         mov r2, r8
 
         // Call rust_start
-        bl rust_start"
-        :                                                              // No output operands
-        : "{r0}"(app_start), "{r1}"(mem_start), "{r3}"(app_heap_break) // Input operands
-        : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r8", "r12",
-          "cc", "memory"                                               // Clobbers
-        : "volatile"                                                   // Options
-    );
-    hint::unreachable_unchecked()
+        bl rust_start",
+        // No clobbers because we don't return.
+        options(noreturn),
+    )
 }

core/src/entry_point/start_item_riscv32.rs

@@ -1,5 +1,3 @@
-use core::hint;
-
 /// Tock programs' entry point. Called by the kernel at program start. Sets up
 /// the stack then calls rust_start() for the remainder of setup.
 #[doc(hidden)]
@@ -14,12 +12,12 @@ use core::hint;
 // Due to Rust issue: https://github.com/rust-lang/rust/issues/42779 we can't have
 // args to the function
 pub unsafe extern "C" fn _start() -> ! {
-    llvm_asm!(
-    // Compute the stack top.
-    //
-    // struct hdr* myhdr = (struct hdr*) app_start;
-    // uint32_t stacktop = (((uint32_t) mem_start + myhdr->stack_size + 7) & 0xfffffff8);
-    "lw   t0, 36(a0)         // t0 = myhdr->stack_size
+    asm!(
+        // Compute the stack top.
+        //
+        // struct hdr* myhdr = (struct hdr*) app_start;
+        // uint32_t stacktop = (((uint32_t) mem_start + myhdr->stack_size + 7) & 0xfffffff8);
+        "lw   t0, 36(a0)         // t0 = myhdr->stack_size
     addi t0, t0, 7          // t0 = myhdr->stack_size + 7
     add  t0, t0, a1         // t0 = mem_start + myhdr->stack_size + 7
     li   t1, 7              // t1 = 7
@@ -89,14 +87,10 @@ pub unsafe extern "C" fn _start() -> ! {
     mv   s0, sp             // Set the frame pointer to sp.
     mv   a1, s1             // second arg is stacktop
     mv   a2, t1             // third arg is app_heap_break that we told the kernel
-    jal  rust_start"
-    :                                                              // No output operands
-    :
-    : "memory", "x10", "x11", "x12", "x13", "x14", "x15", "x16", "x17",
-      "x5", "x6", "x7", "x28", "x29", "x30", "x31", "x1"           // Clobbers
-    : "volatile"                                                   // Options
-    );
-    hint::unreachable_unchecked();
+    jal  rust_start",
+        // No clobbers needed for a noreturn asm! block.
+        options(noreturn),
+    )
 }
 
 /// Ensure an abort symbol exists.

core/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(lang_items, llvm_asm, naked_functions)]
+#![feature(asm, lang_items, llvm_asm, naked_functions)]
 #![cfg_attr(any(target_arch = "arm", target_arch = "riscv32"), no_std)]
 #![cfg_attr(feature = "alloc", feature(alloc_error_handler))]
 

layout_generic.ld

@@ -24,9 +24,15 @@ SECTIONS {
     /* Section for just the app crt0 header.
      * This must be first so that the app can find it.
      */
-    .crt0_header :
+    /* Runtime setup logic. The crt0_header symbol is used by the entry point
+     * assembly. We have to include start here rather than .text because
+     * otherwise elf2tab fails to recognize that the process binary's flash
+     * region should start at the beginning of .start.
+     */
+    .start :
     {
         _beginning = .; /* Start of the app in flash. */
+        crt0_header = .;
         /**
          * Populate the header expected by `crt0`:
          *
@@ -68,14 +74,15 @@ SECTIONS {
          * between the header and subsequent .data section. It's unclear why,
          * but LLD is aligning sections to a multiple of 32 bytes. */
         . = ALIGN(32);
+
+        *(.start)
     } > FLASH =0xFF
 
     /* Text section, Code! */
     .text :
     {
         . = ALIGN(4);
         _text = .;
-        KEEP (*(.start))
         *(.text*)
         *(.rodata*)
         KEEP (*(.syscalls))
@@ -140,30 +147,10 @@ SECTIONS {
     {
     } > FLASH
 
-    /* ARM Exception support
-     *
-     * This contains compiler-generated support for unwinding the stack,
-     * consisting of key-value pairs of function addresses and information on
-     * how to unwind stack frames.
-     * https://wiki.linaro.org/KenWerner/Sandbox/libunwind?action=AttachFile&do=get&target=libunwind-LDS.pdf
-     *
-     * .ARM.exidx is sorted, so has to go in its own output section.
-     *
-     * __NOTE__: It's at the end because we currently don't actually serialize
-     * it to the binary in elf2tbf. If it was before the RAM sections, it would
-     * through off our calculations of the header.
-     */
-    PROVIDE_HIDDEN (__exidx_start = .);
-    .ARM.exidx :
-    {
-      /* (C++) Index entries for section unwinding */
-      *(.ARM.exidx* .gnu.linkonce.armexidx.*)
-    } > FLASH
-    PROVIDE_HIDDEN (__exidx_end = .);
-
+    /* Sections we do not need. */
     /DISCARD/ :
     {
-      *(.eh_frame)
+      *(.ARM.exidx .eh_frame)
     }
 }
 

rust-toolchain

@@ -1,7 +1,7 @@
 [toolchain]
 # See https://rust-lang.github.io/rustup-components-history/ for a list of
 # recently nightlies and what components are available for them.
-channel = "nightly-2020-08-20"
+channel = "nightly-2021-03-25"
 components = ["clippy", "miri", "rustfmt"]
 targets = ["thumbv7em-none-eabi",
            "riscv32imac-unknown-none-elf",

src/ble_composer.rs

@@ -15,7 +15,7 @@ pub struct BlePayload {
 }
 
 impl BlePayload {
-    pub fn add(&mut self, kind: u8, content: &[u8]) -> Result<(), ()> {
+    pub fn add(&mut self, kind: u8, content: &[u8]) -> Result<(), Overflow> {
         self.check_can_write_num_bytes(content.len() + 2)?;
 
         self.bytes[self.occupied] = (content.len() + 1) as u8;
@@ -26,7 +26,7 @@ impl BlePayload {
         Ok(())
     }
 
-    pub fn add_flag(&mut self, flag: u8) -> Result<(), ()> {
+    pub fn add_flag(&mut self, flag: u8) -> Result<(), Overflow> {
         self.check_can_write_num_bytes(3)?;
 
         self.bytes[self.occupied] = 2;
@@ -36,7 +36,7 @@ impl BlePayload {
         Ok(())
     }
 
-    pub fn add_service_payload(&mut self, uuid: [u8; 2], content: &[u8]) -> Result<(), ()> {
+    pub fn add_service_payload(&mut self, uuid: [u8; 2], content: &[u8]) -> Result<(), Overflow> {
         self.check_can_write_num_bytes(4 + content.len())?;
         self.bytes[self.occupied] = (content.len() + 3) as u8;
         self.bytes[self.occupied + 1] = gap_types::SERVICE_DATA;
@@ -49,11 +49,11 @@ impl BlePayload {
         Ok(())
     }
 
-    fn check_can_write_num_bytes(&self, number: usize) -> Result<(), ()> {
+    fn check_can_write_num_bytes(&self, number: usize) -> Result<(), Overflow> {
         if self.occupied + number <= self.bytes.len() {
             Ok(())
         } else {
-            Err(())
+            Err(Overflow)
         }
     }
 }
@@ -72,6 +72,10 @@ impl AsRef<[u8]> for BlePayload {
     }
 }
 
+// Error type returned when the buffer is too full to perform an operation.
+#[derive(Debug)]
+pub struct Overflow;
+
 #[cfg(test)]
 mod test {
     use super::*;