Merge #95

95: [RFC] remove build dependency on arm-none-eabi-gcc (binary blob alternative) r=japaric a=japaric

Before this commit we used gcc to assemble external assembly files into object
files that we linked into our Rust program.

This commit drops the dependency on gcc by shipping the already assembled object
files with this crate source code.

---

This is an alternative to RFC #91 that doesn't require a breaking change or
adding a new Cargo feature and can be implemented right now.

See #91 for the rationale of dropping the dependency on gcc.

This approach can be applied to other Cortex-M crates like cortex-m-semihosting
and cortex-m (would subsume RFC rust-embedded/cortex-m#107).

This seems like an overall better approach to me, but before I go opening more
PRs I want to hear your thoughts, @rust-embedded/cortex-m

closes #91

Co-authored-by: Jorge Aparicio <jorge@japaric.io>

.gitignore

@@ -1,3 +1,6 @@
 **/*.rs.bk
 Cargo.lock
+bin/*.after
+bin/*.before
+bin/*.o
 target/

.travis.yml

@@ -3,40 +3,25 @@ language: rust
 matrix:
   include:
     - env: TARGET=x86_64-unknown-linux-gnu
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
-    - env: TARGET=thumbv6m-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv6m-none-eabi CC=clang
+    - env: TARGET=thumbv6m-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
     - env: TARGET=thumbv7m-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv7m-none-eabi CC=clang
-      rust: stable
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
     - env: TARGET=thumbv7em-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv7em-none-eabi CC=clang
-      rust: stable
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
     - env: TARGET=thumbv7em-none-eabihf
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv7em-none-eabihf CC=clang
-      rust: stable
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
     - env: TARGET=thumbv6m-none-eabi
       rust: nightly
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)

Cargo.toml

@@ -10,9 +10,6 @@ name = "cortex-m-rt"
 repository = "https://github.com/japaric/cortex-m-rt"
 version = "0.5.2"
 
-[build-dependencies]
-cc = "1.0.10"
-
 [dependencies]
 r0 = "0.2.1"
 

asm.s

@@ -1,3 +1,4 @@
+  .section .text.HardFault
   .global HardFault
   .thumb_func
 HardFault:

assemble.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+# cflags taken from cc 1.0.22
+
+crate=cortex-m-rt
+
+arm-none-eabi-as -march=armv6s-m asm.s -o bin/$crate.o
+ar crs bin/thumbv6m-none-eabi.a bin/$crate.o
+
+arm-none-eabi-as -march=armv7-m asm.s -o bin/$crate.o
+ar crs bin/thumbv7m-none-eabi.a bin/$crate.o
+
+arm-none-eabi-as -march=armv7e-m asm.s -o bin/$crate.o
+ar crs bin/thumbv7em-none-eabi.a bin/$crate.o
+ar crs bin/thumbv7em-none-eabihf.a bin/$crate.o
+
+rm bin/$crate.o

build.rs

@@ -1,18 +1,21 @@
-extern crate cc;
-
 use std::env;
-use std::fs::File;
+use std::fs::{self, File};
 use std::io::Write;
 use std::path::PathBuf;
 
 fn main() {
     let target = env::var("TARGET").unwrap();
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
 
     has_fpu(&target);
     let is_armv6m = is_armv6m(&target);
 
     if target.starts_with("thumbv") {
-        cc::Build::new().file("asm.s").compile("asm");
+        fs::copy(
+            format!("bin/{}.a", target),
+            out_dir.join("libcortex-m-rt.a"),
+        ).unwrap();
+        println!("cargo:rustc-link-lib=static=cortex-m-rt");
     }
 
     // Put the linker script somewhere the linker can find it

check-blobs.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+# Checks that the blobs are up to date with the committed assembly files
+
+set -euxo pipefail
+
+for lib in $(ls bin/*.a); do
+    filename=$(basename $lib)
+    arm-none-eabi-objdump -Cd $lib > bin/${filename%.a}.before
+done
+
+./assemble.sh
+
+for lib in $(ls bin/*.a); do
+    filename=$(basename $lib)
+    arm-none-eabi-objdump -Cd $lib > bin/${filename%.a}.after
+done
+
+for cksum in $(ls bin/*.after); do
+    diff -u $cksum ${cksum%.after}.before
+done

ci/install.sh

@@ -3,13 +3,11 @@ set -euxo pipefail
 main() {
     if [ $TARGET != x86_64-unknown-linux-gnu ]; then
         rustup target add $TARGET
+    fi
 
-        if [ ${CC:-gcc} = gcc ]; then
-            mkdir gcc
+    mkdir gcc
 
-            curl -L https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2?revision=bc2c96c0-14b5-4bb4-9f18-bceb4050fee7?product=GNU%20Arm%20Embedded%20Toolchain,64-bit,,Linux,7-2018-q2-update | tar --strip-components=1 -C gcc -xj
-        fi
-    fi
+    curl -L https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2?revision=bc2c96c0-14b5-4bb4-9f18-bceb4050fee7?product=GNU%20Arm%20Embedded%20Toolchain,64-bit,,Linux,7-2018-q2-update | tar --strip-components=1 -C gcc -xj
 }
 
 main

ci/script.sh

@@ -20,65 +20,63 @@ main() {
         # linking with GNU LD
         for ex in "${examples[@]}"; do
             cargo rustc --target $TARGET --example $ex -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
 
             cargo rustc --target $TARGET --example $ex --release -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
         done
         for ex in "${fail_examples[@]}"; do
             ! cargo rustc --target $TARGET --example $ex -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
 
             ! cargo rustc --target $TARGET --example $ex --release -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
         done
 
         cargo rustc --target $TARGET --example device --features device -- \
-              -C link-arg=-nostartfiles \
-              -C link-arg=-Wl,-Tlink.x
+              -C linker=arm-none-eabi-ld \
+              -C link-arg=-Tlink.x
 
         cargo rustc --target $TARGET --example device --features device --release -- \
-              -C link-arg=-nostartfiles \
-              -C link-arg=-Wl,-Tlink.x
+              -C linker=arm-none-eabi-ld \
+              -C link-arg=-Tlink.x
 
         # linking with rustc's LLD
         for ex in "${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 $ex --release -- \
                   -C linker=rust-lld \
-                  -Z linker-flavor=ld.lld \
                   -C link-arg=-Tlink.x
         done
         for ex in "${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 \
-              -Z linker-flavor=ld.lld \
               -C link-arg=-Tlink.x
 
         cargo rustc --target $TARGET --example device --features device --release -- \
               -C linker=rust-lld \
-              -Z linker-flavor=ld.lld \
               -C link-arg=-Tlink.x
     fi
+
+    if [ $TARGET = x86_64-unknown-linux-gnu ]; then
+        ./check-blobs.sh
+    fi
 }
 
 main