Merge branch 'master' into release

Author: adamgreig

cortex-m-rt/ci/script.sh

@@ -10,8 +10,12 @@ main() {
         minimal
         main
         override-exception
+        pre_init
         state
     )
+    local fail_examples=(
+        data_overflow
+    )
     if [ $TRAVIS_RUST_VERSION = nightly ]; then
         # linking with GNU LD
         for ex in "${examples[@]}"; do
@@ -23,6 +27,15 @@ main() {
                   -C link-arg=-nostartfiles \
                   -C link-arg=-Wl,-Tlink.x
         done
+        for ex in "${fail_examples[@]}"; do
+            ! cargo rustc --target $TARGET --example $ex -- \
+                  -C link-arg=-nostartfiles \
+                  -C link-arg=-Wl,-Tlink.x
+
+            ! cargo rustc --target $TARGET --example $ex --release -- \
+                  -C link-arg=-nostartfiles \
+                  -C link-arg=-Wl,-Tlink.x
+        done
 
         cargo rustc --target $TARGET --example device --features device -- \
               -C link-arg=-nostartfiles \
@@ -44,6 +57,17 @@ main() {
                   -Z linker-flavor=ld.lld \
                   -C link-arg=-Tlink.x
         done
+        for ex in "${fail_examples[@]}"; do
+            ! cargo rustc --target $TARGET --example $ex -- \
+                  -C linker=rust-lld \
+                  -Z linker-flavor=ld.lld \
+                  -C link-arg=-Tlink.x
+
+            ! cargo rustc --target $TARGET --example $ex --release -- \
+                  -C linker=rust-lld \
+                  -Z linker-flavor=ld.lld \
+                  -C link-arg=-Tlink.x
+        done
 
         cargo rustc --target $TARGET --example device --features device -- \
               -C linker=rust-lld \

cortex-m-rt/examples/data_overflow.rs

@@ -0,0 +1,30 @@
+//! This is not an example; this is a linker overflow detection test
+//! which should fail to link due to .data overflowing FLASH.
+
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+#[macro_use(entry)]
+extern crate cortex_m_rt as rt;
+extern crate panic_abort;
+
+use core::ptr;
+
+entry!(main);
+
+// This large static array uses most of .rodata
+static RODATA: [u8; 48*1024] = [1u8; 48*1024];
+
+// This large mutable array causes .data to use the rest of FLASH
+// without also overflowing RAM.
+static mut DATA: [u8; 16*1024] = [1u8; 16*1024];
+
+fn main() -> ! {
+    unsafe {
+        let _bigdata = ptr::read_volatile(&RODATA as *const u8);
+        let _bigdata = ptr::read_volatile(&DATA as *const u8);
+    }
+
+    loop {}
+}

cortex-m-rt/examples/pre_init.rs

@@ -0,0 +1,22 @@
+//! `cortex-m-rt` based program with a function run before RAM is initialized.
+
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+#[macro_use(entry, pre_init)]
+extern crate cortex_m_rt as rt;
+extern crate panic_semihosting;
+
+pre_init!(disable_watchdog);
+
+unsafe fn disable_watchdog() {
+    // Do what you need to disable the watchdog.
+}
+
+// the program entry point
+entry!(main);
+
+fn main() -> ! {
+    loop {}
+}

cortex-m-rt/link.x.in

@@ -51,6 +51,11 @@ PROVIDE(UserHardFault = DefaultUserHardFault);
 /* # Interrupt vectors */
 EXTERN(__INTERRUPTS); /* `static` variable similar to `__EXCEPTIONS` */
 
+/* # Pre-initialization function */
+/* If the user overrides this using the `pre_init!` macro or by creating a `__pre_init` function,
+   then the function this points to will be called before the RAM is initialized. */
+PROVIDE(__pre_init = DefaultPreInit);
+
 /* # Sections */
 SECTIONS
 {
@@ -84,24 +89,24 @@ SECTIONS
   } > FLASH
 
   /* ### .rodata */
-  .rodata :
+  .rodata : ALIGN(4)
   {
     *(.rodata .rodata.*);
 
-    /* 4-byte align the end (VMA) of this section */
-    /* WHY? To my knowledge there's no way to indicate the alignment of *LMA* so we align *this*
-    section with the goal of using its end address as the LMA of .data */
+    /* 4-byte align the end (VMA) of this section.
+       This is required by LLD to ensure the LMA of the following .data
+       section will have the correct alignment. */
     . = ALIGN(4);
   } > FLASH
 
   /* ## Sections in RAM */
   /* ### .data */
-  .data : AT(ADDR(.rodata) + SIZEOF(.rodata)) /* LMA */
+  .data : ALIGN(4)
   {
     *(.data .data.*);
 
     . = ALIGN(4); /* 4-byte align the end (VMA) of this section */
-  } > RAM
+  } > RAM AT > FLASH
 
   /* VMA of .data */
   __sdata = ADDR(.data);
@@ -111,7 +116,7 @@ SECTIONS
   __sidata = LOADADDR(.data);
 
   /* ### .bss */
-  .bss :
+  .bss : ALIGN(4)
   {
     *(.bss .bss.*);
 

cortex-m-rt/memory.x

@@ -1,8 +1,12 @@
 /* Device specific memory layout */
 
+/* This file is used to build the cortex-m-rt examples,
+   but not other applications using cortex-m-rt. */
+
 MEMORY
 {
   /* FLASH and RAM are mandatory memory regions */
+  /* Update examples/data_overflow.rs if you change these sizes. */
   FLASH : ORIGIN = 0x08000000, LENGTH = 64K
   RAM : ORIGIN = 0x20000000, LENGTH = 20K
 

cortex-m-rt/src/lib.rs

@@ -237,6 +237,11 @@
 //! have a size of 32 vectors (on ARMv6-M) or 240 vectors (on ARMv7-M). This array is located after
 //! `__EXCEPTIONS` in the `.vector_table` section.
 //!
+//! - `__pre_init`. This is a function to be run before RAM is initialized. It defaults to an empty
+//! function. The function called can be changed by calling the `pre_init!` macro. The empty
+//! function is not optimized out by default, but if an empty function is passed to `pre_init!` the
+//! function call will be optimized out.
+//!
 //! If you override any exception handler you'll find it as an unmangled symbol, e.g. `SysTick` or
 //! `SVCall`, in the output of `objdump`,
 //!
@@ -378,6 +383,14 @@
 //!     println!("cargo:rustc-link-search={}", out.display());
 //! }
 //! ```
+//!
+//! ## `pre_init!`
+//!
+//! A user-defined function can be run at the start of the reset handler, before RAM is
+//! initialized. The macro `pre_init!` can be called to set the function to be run. The function is
+//! intended to perform actions that cannot wait the time it takes for RAM to be initialized, such
+//! as disabling a watchdog. As the function is called before RAM is initialized, any access of
+//! static variables will result in undefined behavior.
 
 // # Developer notes
 //
@@ -474,8 +487,13 @@ pub unsafe extern "C" fn Reset() -> ! {
         static mut __sdata: u32;
         static mut __edata: u32;
         static __sidata: u32;
+
+        fn __pre_init();
     }
 
+    let pre_init: unsafe extern "C" fn() = __pre_init;
+    pre_init();
+
     // Initialize RAM
     r0::zero_bss(&mut __sbss, &mut __ebss);
     r0::init_data(&mut __sdata, &mut __edata, &__sidata);
@@ -531,6 +549,10 @@ pub unsafe extern "C" fn DefaultUserHardFault() {
     }
 }
 
+#[doc(hidden)]
+#[no_mangle]
+pub unsafe extern "C" fn DefaultPreInit() {}
+
 /// Macro to define the entry point of the program
 ///
 /// **NOTE** This macro must be invoked once and must be invoked from an accessible module, ideally
@@ -872,3 +894,35 @@ macro_rules! exception {
         }
     };
 }
+
+/// Macro to set the function to be called at the beginning of the reset handler.
+///
+/// The function must have the signature of `unsafe fn()`.
+///
+/// The function passed will be called before static variables are initialized. Any access of static
+/// variables will result in undefined behavior.
+///
+/// # Examples
+///
+/// ``` ignore
+/// pre_init!(foo::bar);
+///
+/// mod foo {
+///     pub unsafe fn bar() {
+///         // do something here
+///     }
+/// }
+/// ```
+#[macro_export]
+macro_rules! pre_init {
+    ($handler:path) => {
+        #[allow(unsafe_code)]
+        #[deny(private_no_mangle_fns)] // raise an error if this item is not accessible
+        #[no_mangle]
+        pub unsafe extern "C" fn __pre_init() {
+            // validate user handler
+            let f: unsafe fn() = $handler;
+            f();
+        }
+    }
+}