Migrate the ARM entry point to global_asm!.

.github/workflows/artifacts.yml

@@ -12,7 +12,6 @@ jobs:
 
       - name: Install dependencies
         run: |
-          sudo apt-get install binutils-arm-none-eabi
           cargo install elf2tab
 
       - name: Build LEDs

.github/workflows/ci.yml

@@ -42,7 +42,7 @@ jobs:
       # relocation.
       - name: Build and Test
         run: |
-          sudo apt-get install binutils-arm-none-eabi ninja-build
+          sudo apt-get install ninja-build
           cd "${GITHUB_WORKSPACE}"
           echo "[target.'cfg(all())']" >> .cargo/config
           echo 'rustflags = ["-D", "warnings"]' >> .cargo/config

.github/workflows/mac-os.yml

@@ -16,11 +16,6 @@ jobs:
       - name: Clone repository
         uses: actions/checkout@v2
 
-      - name: Install arm-none-eabi-gcc
-        uses: fiam/arm-none-eabi-gcc@v1
-        with:
-          release: '10-2020-q4'
-
       - name: Build and Test
         run: |
           cd "${GITHUB_WORKSPACE}"

.github/workflows/size-diff.yml

@@ -39,7 +39,6 @@ jobs:
       # master.
       - name: Compute sizes
         run: |
-          sudo apt-get install binutils-arm-none-eabi
           UPSTREAM_REMOTE_NAME="${UPSTREAM_REMOTE_NAME:-origin}"
           GITHUB_BASE_REF="${GITHUB_BASE_REF:-master}"
           cd "${GITHUB_WORKSPACE}"

runtime/build.rs

@@ -1,11 +1,9 @@
-mod extern_asm;
-
 // auto_layout() identifies the correct linker scripts to use based on the
 // LIBTOCK_PLATFORM environment variable, and copies the linker scripts into
 // OUT_DIR. The cargo invocation must pass -C link-arg=-Tlayout.ld to rustc
 // (using the rustflags cargo config).
 #[cfg(not(feature = "no_auto_layout"))]
-fn auto_layout(out_dir: &str) {
+fn auto_layout() {
     use std::fs::copy;
     use std::path::PathBuf;
 
@@ -18,6 +16,16 @@ fn auto_layout(out_dir: &str) {
 
     // Read configuration from environment variables.
 
+    // Note: cargo fails if run in a path that is not valid Unicode, so this
+    // script doesn't need to handle non-Unicode paths. Also, OUT_DIR cannot be
+    // in a location with a newline in it, or we have no way to pass
+    // rustc-link-search to cargo.
+    let out_dir = &std::env::var("OUT_DIR").expect("Unable to read OUT_DIR");
+    assert!(
+        !out_dir.contains('\n'),
+        "Build path contains a newline, which is unsupported"
+    );
+
     // Read the platform environment variable as a String (our platform names
     // should all be valid UTF-8).
     let platform = std::env::var(PLATFORM_CFG_VAR).expect("Please specify LIBTOCK_PLATFORM");
@@ -35,25 +43,12 @@ fn auto_layout(out_dir: &str) {
     println!("cargo:rerun-if-changed={}", LAYOUT_GENERIC_FILENAME);
     copy(LAYOUT_GENERIC_FILENAME, out_layout_generic)
         .expect("Unable to copy layout_generic.ld into OUT_DIR");
+
+    // Tell rustc where to search for the layout file.
+    println!("cargo:rustc-link-search={}", out_dir);
 }
 
 fn main() {
-    // Note: cargo fails if run in a path that is not valid Unicode, so this
-    // script doesn't need to handle non-Unicode paths. Also, OUT_DIR cannot be
-    // in a location with a newline in it, or we have no way to pass
-    // rustc-link-search to cargo.
-    let out_dir = &std::env::var("OUT_DIR").expect("Unable to read OUT_DIR");
-    assert!(
-        !out_dir.contains('\n'),
-        "Build path contains a newline, which is unsupported"
-    );
-
     #[cfg(not(feature = "no_auto_layout"))]
-    auto_layout(out_dir);
-
-    extern_asm::build_and_link(out_dir);
-
-    // This link search path is used by both auto_layout() and
-    // extern_asm::build_and_link().
-    println!("cargo:rustc-link-search={}", out_dir);
+    auto_layout();
 }

runtime/asm/asm_arm.S → runtime/src/startup/asm_arm.s

@@ -36,21 +36,21 @@ start:
 	mov r4, pc        /* r4 = address of .start + 4 (Thumb bit unset) */
 	mov r5, r0        /* Save rt_header; we use r0 for syscalls */
 	ldr r0, [r5, #0]  /* r0 = rt_header.start */
-	add r0, #3        /* r0 = rt_header.start + 4 - 1 (for Thumb bit) */
+	adds r0, #3       /* r0 = rt_header.start + 4 - 1 (for Thumb bit) */
 	cmp r0, r4
 	beq .Lset_brk     /* Skip error handling if pc correct */
 	/* If the beq on the previous line did not jump, then the binary is not at
 	 * the correct location. Report the error via LowLevelDebug then exit. */
-	mov r0, #8  /* LowLevelDebug driver number */
-	mov r1, #1  /* Command: print alert code */
-	mov r2, #2  /* Alert code 2 (incorrect location */
-	svc 2       /* Execute `command` */
-	mov r0, #0  /* Operation: exit-terminate */
-	svc 6       /* Execute `exit` */
+	movs r0, #8  /* LowLevelDebug driver number */
+	movs r1, #1  /* Command: print alert code */
+	movs r2, #2  /* Alert code 2 (incorrect location */
+	svc 2        /* Execute `command` */
+	movs r0, #0  /* Operation: exit-terminate */
+	svc 6        /* Execute `exit` */
 
 .Lset_brk:
 	/* memop(): set brk to rt_header's initial break value */
-	mov r0, #0        /* operation: set break */
+	movs r0, #0       /* operation: set break */
 	ldr r1, [r5, #4]  /* rt_header`s initial process break */
 	svc 5             /* call `memop` */
 
@@ -66,21 +66,21 @@ start:
 .Ldata_loop_body:
 	ldr r3, [r1]               /* r3 = *src */
 	str r3, [r2]               /* *(dest) = r3 */
-	sub r0, #4                 /* remaining -= 4 */
-	add r1, #4                 /* src += 4 */
-	add r2, #4                 /* dest += 4 */
+	subs r0, #4                /* remaining -= 4 */
+	adds r1, #4                /* src += 4 */
+	adds r2, #4                /* dest += 4 */
 	cmp r0, #0
 	bne .Ldata_loop_body       /* Iterate again if remaining != 0 */
 
 .Lzero_bss:
 	ldr r0, [r5, #24]          /* remaining = rt_header.bss_size */
 	cbz r0, .Lcall_rust_start  /* Jump to call_rust_start if remaining == 0 */
 	ldr r1, [r5, #28]          /* dest = rt_header.bss_start */
-	mov r2, #0                 /* r2 = 0 */
+	movs r2, #0                /* r2 = 0 */
 .Lbss_loop_body:
 	strb r2, [r1]              /* *(dest) = r2 = 0 */
-	sub r0, #1                 /* remaining -= 1 */
-	add r1, #1                 /* dest += 1 */
+	subs r0, #1                /* remaining -= 1 */
+	adds r1, #1                /* dest += 1 */
 	cmp r0, #0
 	bne .Lbss_loop_body        /* Iterate again if remaining != 0 */
 

runtime/src/startup/mod.rs

@@ -2,7 +2,8 @@
 
 // Include the correct `start` symbol (the program entry point) for the
 // architecture.
-// TODO: Migrate ARM to global_asm! and delete extern_asm.rs.
+#[cfg(target_arch = "arm")]
+core::arch::global_asm!(include_str!("asm_arm.s"));
 #[cfg(target_arch = "riscv32")]
 core::arch::global_asm!(include_str!("asm_riscv32.s"));