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Change to new aarch64-unknown-none-softloat target.
Also, add safety docs where demanded by clippy.
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Diff for: ‎01_bareminimum/.cargo/config

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@@ -1,6 +1,5 @@
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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎01_bareminimum/Makefile

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@@ -22,7 +22,7 @@
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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎01_bareminimum/README.md

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@@ -26,9 +26,9 @@ much as possible, we are already setting up a Rust crate. This allows us to use
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The Raspberry Pi 3 features a processor that uses ARM's `AArch64` architecture.
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Conveniently, Rust already provides a generic target for bare-metal aarch64 code
29-
that we can leverage. It is called [aarch64-unknown-none].
29+
that we can leverage. It is called [aarch64-unknown-none-softfloat].
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[aarch64-unknown-none]: https://github.com/andre-richter/rust/blob/master/src/librustc_target/spec/aarch64_unknown_none.rs
31+
[aarch64-unknown-none-softfloat]: https://github.com/rust-lang/rust/blob/master/src/librustc_target/spec/aarch64_unknown_none_softfloat.rs
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In the `Makefile`, we select this target in various places by passing it to
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cargo using the `--target` cmdline argument.
@@ -37,28 +37,28 @@ Additionally, we provide a config file in `.cargo/config` were we make further
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specializations:
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```toml
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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]
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```
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The first line tells rustc to use our custom `link.ld` linker script. The second
49-
line instructs the compiler to not use floating point operations. This is a
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common choice when writing an operating system kernel. If floating point is not
47+
The first line tells rustc to use our custom `link.ld` linker script. The
48+
second argument specifies the exact CPU type that is used on Raspberry Pi 3, so
49+
that the compiler can optimize for it.
50+
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The target itself tells the compiler already to not use floating point
52+
operations, which is hinted by the `-softfloat` appendix. This is a common
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choice when writing an operating system kernel. If floating point is not
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explicitly disabled, it is possible that the compiler uses auto-vectorization to
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optimize, for example, operations on array data structures. This would
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implicitly result in use of floating point registers and operations. However,
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since it is very costly to save and restore floating point registers during
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context-switches, use of fp is usually disabled from the get go to save the
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cycles and optimize the kernel for fast context switching.
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Finally, the third arguments specifies the exact CPU type that is used in
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Raspberry Pi 3, so that the compiler can optimize for it.
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Since the `aarch64-unknown-none` target is not shipped with an associated
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Since the `aarch64-unknown-none-softfloat` target is not shipped with an associated
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precompiled standard library, and since we anyways modify the target via the
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`.cargo/config` file, we are using [cargo-xbuild][xbuild] to compile our own
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standard library. This way, we can ensure that our bare-metal code is optimized

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Diff for: ‎02_multicore_rust/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎02_multicore_rust/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎02_multicore_rust/raspi3_boot/src/lib.rs

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@@ -36,6 +36,10 @@ extern crate panic_abort;
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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
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///
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/// - User must ensure to provide a suitable main function for the
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/// platform.
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#[export_name = "main"]
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pub unsafe fn __main() -> ! {
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// type check the given path
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/// Reset function.
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///
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/// Initializes the bss section before calling into the user's `main()`.
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///
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/// # Safety
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///
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/// - Only a single core must be active and running this function.
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#[no_mangle]
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pub unsafe extern "C" fn reset() -> ! {
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extern "C" {

Diff for: ‎03_uart1/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎03_uart1/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎03_uart1/kernel8

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Diff for: ‎03_uart1/raspi3_boot/src/lib.rs

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@@ -36,6 +36,10 @@ extern crate panic_abort;
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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
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///
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/// - User must ensure to provide a suitable main function for the
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/// platform.
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#[export_name = "main"]
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pub unsafe fn __main() -> ! {
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// type check the given path
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/// Reset function.
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///
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/// Initializes the bss section before calling into the user's `main()`.
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///
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/// # Safety
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///
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/// - Only a single core must be active and running this function.
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#[no_mangle]
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pub unsafe extern "C" fn reset() -> ! {
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extern "C" {

Diff for: ‎04_mailboxes/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎04_mailboxes/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎04_mailboxes/raspi3_boot/src/lib.rs

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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
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///
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/// - User must ensure to provide a suitable main function for the
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/// platform.
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#[export_name = "main"]
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pub unsafe fn __main() -> ! {
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// type check the given path
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/// Reset function.
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///
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/// Initializes the bss section before calling into the user's `main()`.
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///
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/// # Safety
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///
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/// - Only a single core must be active and running this function.
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#[no_mangle]
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pub unsafe extern "C" fn reset() -> ! {
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extern "C" {

Diff for: ‎05_uart0/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎05_uart0/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎05_uart0/raspi3_boot/src/lib.rs

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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
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///
41+
/// - User must ensure to provide a suitable main function for the
42+
/// platform.
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#[export_name = "main"]
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pub unsafe fn __main() -> ! {
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// type check the given path
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/// Reset function.
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///
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/// Initializes the bss section before calling into the user's `main()`.
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///
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/// # Safety
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///
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/// - Only a single core must be active and running this function.
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#[no_mangle]
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pub unsafe extern "C" fn reset() -> ! {
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extern "C" {

Diff for: ‎06_raspbootin64/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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"-C", "relocation-model=pic",
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]

Diff for: ‎06_raspbootin64/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎06_raspbootin64/README.md

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the`.cargo/config`:
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```toml
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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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"-C", "relocation-model=pic", # <-- New
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]

Diff for: ‎06_raspbootin64/kernel8

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Diff for: ‎06_raspbootin64/raspi3_boot/src/lib.rs

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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
40+
///
41+
/// - User must ensure to provide a suitable main function for the
42+
/// platform.
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#[export_name = "main"]
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pub unsafe fn __main() -> ! {
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// type check the given path
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/// Reset function.
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///
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/// Trampolines into the user's `main()`.
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///
57+
/// # Safety
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///
59+
/// - Only a single core must be active and running this function.
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#[no_mangle]
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pub unsafe extern "C" fn reset() -> ! {
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extern "Rust" {

Diff for: ‎07_abstraction/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎07_abstraction/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎07_abstraction/README.md

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pointer is not used apart from ourselves setting it.
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```console
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ferris@box:~$ cargo objdump --target aarch64-unknown-none -- -disassemble -print-imm-hex kernel8
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ferris@box:~$ cargo objdump --target aarch64-unknown-none-softfloat -- -disassemble -print-imm-hex kernel8
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[...] (Some output omitted)
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Diff for: ‎07_abstraction/raspi3_boot/src/lib.rs

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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
39+
///
40+
/// - User must ensure to provide a suitable main function for the
41+
/// platform.
3842
#[export_name = "main"]
3943
pub unsafe fn __main() -> ! {
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// type check the given path
@@ -48,6 +52,10 @@ macro_rules! entry {
4852
/// Reset function.
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///
5054
/// Initializes the bss section before calling into the user's `main()`.
55+
///
56+
/// # Safety
57+
///
58+
/// - Only a single core must be active and running this function.
5159
unsafe fn reset() -> ! {
5260
extern "C" {
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// Boundaries of the .bss section, provided by the linker script
@@ -69,6 +77,10 @@ unsafe fn reset() -> ! {
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///
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/// Parks all cores except core0, and then jumps to the internal
7179
/// `reset()` function.
80+
///
81+
/// # Safety
82+
///
83+
/// - Linker script must ensure to place this function at `0x80_000`.
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#[link_section = ".text.boot"]
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#[no_mangle]
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pub unsafe extern "C" fn _boot_cores() -> ! {

Diff for: ‎08_random/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

Diff for: ‎08_random/Makefile

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# SOFTWARE.
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#
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TARGET = aarch64-unknown-none
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TARGET = aarch64-unknown-none-softfloat
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SOURCES = $(wildcard **/*.rs) $(wildcard **/*.S) link.ld
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Diff for: ‎08_random/raspi3_boot/src/lib.rs

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#[macro_export]
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macro_rules! entry {
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($path:path) => {
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/// # Safety
39+
///
40+
/// - User must ensure to provide a suitable main function for the
41+
/// platform.
3842
#[export_name = "main"]
3943
pub unsafe fn __main() -> ! {
4044
// type check the given path
@@ -48,6 +52,10 @@ macro_rules! entry {
4852
/// Reset function.
4953
///
5054
/// Initializes the bss section before calling into the user's `main()`.
55+
///
56+
/// # Safety
57+
///
58+
/// - Only a single core must be active and running this function.
5159
unsafe fn reset() -> ! {
5260
extern "C" {
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// Boundaries of the .bss section, provided by the linker script
@@ -69,6 +77,10 @@ unsafe fn reset() -> ! {
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///
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/// Parks all cores except core0, and then jumps to the internal
7179
/// `reset()` function.
80+
///
81+
/// # Safety
82+
///
83+
/// - Linker script must ensure to place this function at `0x80_000`.
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#[link_section = ".text.boot"]
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#[no_mangle]
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pub unsafe extern "C" fn _boot_cores() -> ! {

Diff for: ‎09_delays/.cargo/config

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[target.aarch64-unknown-none]
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[target.aarch64-unknown-none-softfloat]
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rustflags = [
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"-C", "link-arg=-Tlink.ld",
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"-C", "target-feature=-fp-armv8",
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"-C", "target-cpu=cortex-a53",
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]

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