Add ARM v6 syscalls and Raspberry Pi Pico / Nano Rp2040 Connect

Makefile

@@ -194,6 +194,24 @@ flash-nrf52840:
 	LIBTOCK_PLATFORM=nrf52840 cargo run --example $(EXAMPLE) $(features) \
 		--target=thumbv7em-none-eabi $(release) -- --deploy=tockloader
 
+.PHONY: raspberrypi_pico
+raspberrypi_pico:
+	LIBTOCK_PLATFORM=raspberrypi_pico cargo run --example $(EXAMPLE) $(features) \
+		--target=thumbv6m-none-eabi $(release)
+	mkdir -p target/tbf/raspberrypi_pico
+	cp target/thumbv6m-none-eabi/release/examples/$(EXAMPLE).tab \
+		target/thumbv6m-none-eabi/release/examples/$(EXAMPLE).tbf \
+		target/tbf/raspberrypi_pico
+
+.PHONY: nano_rp2040_connect
+nano_rp2040_connect:
+	LIBTOCK_PLATFORM=nano_rp2040_connect cargo run --example $(EXAMPLE) $(features) \
+		--target=thumbv6m-none-eabi $(release)
+	mkdir -p target/tbf/nano_rp2040_connect
+	cp target/thumbv6m-none-eabi/release/examples/$(EXAMPLE).tab \
+		target/thumbv6m-none-eabi/release/examples/$(EXAMPLE).tbf \
+		target/tbf/nano_rp2040_connect
+
 .PHONY: stm32f3discovery
 stm32f3discovery:
 	LIBTOCK_PLATFORM=stm32f3discovery cargo run --example $(EXAMPLE) \

runtime/layouts/nano_rp2040_connect.ld

@@ -0,0 +1,9 @@
+/* Layout for the Raspberry Pi Pico board, used by the examples in this repository. */
+
+MEMORY {
+  FLASH (X) : ORIGIN = 0x10020000, LENGTH = 256K
+  RAM (W) : ORIGIN = 0x20004000, LENGTH = 248K
+}
+
+TBF_HEADER_SIZE = 0x48;
+INCLUDE libtock_layout.ld

runtime/layouts/raspberrypi_pico.ld

@@ -0,0 +1,9 @@
+/* Layout for the Raspberry Pi Pico board, used by the examples in this repository. */
+
+MEMORY {
+  FLASH (X) : ORIGIN = 0x10020000, LENGTH = 256K
+  RAM (W) : ORIGIN = 0x20004000, LENGTH = 248K
+}
+
+TBF_HEADER_SIZE = 0x48;
+INCLUDE libtock_layout.ld

runtime/src/startup/asm_arm.s

@@ -25,6 +25,10 @@
  *
  * We currently only use the value in r0. It is copied into r5 early on because
  * r0 is needed to invoke system calls.
+ *
+ * To be compatible with ARMv6 Thumb-1, we the cmp and beq instructions
+ * instead of cbz in two places. This increases the code size with 4 bytes,
+ * but allows us to use it on Cortex-M0+ processors.
  */
 .section .start, "ax"
 .global start
@@ -37,8 +41,8 @@ start:
 	mov r5, r0        /* Save rt_header; we use r0 for syscalls */
 	ldr r0, [r5, #0]  /* r0 = rt_header.start */
 	adds r0, #3       /* r0 = rt_header.start + 4 - 1 (for Thumb bit) */
-	cmp r0, r4
-	beq .Lset_brk     /* Skip error handling if pc correct */
+	cmp r0, r4        /* Skip error handling if pc correct */
+	beq .Lset_brk     
 	/* 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. */
 	movs r0, #8  /* LowLevelDebug driver number */
@@ -60,7 +64,8 @@ start:
 
 	/* Copy .data into place */
 	ldr r0, [r5, #12]          /* remaining = rt_header.data_size */
-	cbz r0, .Lzero_bss         /* Jump to zero_bss if remaining == 0 */
+	cmp r0, #0                 /* Jump to zero_bss if remaining == 0 */	
+	beq .Lzero_bss         
 	ldr r1, [r5, #16]          /* src = rt_header.data_flash_start */
 	ldr r2, [r5, #20]          /* dest = rt_header.data_ram_start */
 .Ldata_loop_body:
@@ -74,7 +79,8 @@ start:
 
 .Lzero_bss:
 	ldr r0, [r5, #24]          /* remaining = rt_header.bss_size */
-	cbz r0, .Lcall_rust_start  /* Jump to call_rust_start if remaining == 0 */
+	cmp r0, #0                 /* Jump to call_rust_start if remaining == 0 */
+	beq .Lcall_rust_start  
 	ldr r1, [r5, #28]          /* dest = rt_header.bss_start */
 	movs r2, #0                /* r2 = 0 */
 .Lbss_loop_body:

runtime/src/syscalls_impl_arm.rs

@@ -5,41 +5,40 @@ unsafe impl RawSyscalls for crate::TockSyscalls {
     unsafe fn yield1([Register(r0)]: [Register; 1]) {
         // Safety: This matches the invariants required by the documentation on
         // RawSyscalls::yield1
+        // the use of `clobber_abi` allows us this to run on both Thumb-1 and Thumb-2
         unsafe {
             asm!("svc 0",
                  inlateout("r0") r0 => _, // a1
-                 lateout("r1") _,         // a2
-                 lateout("r2") _,         // a3
-                 lateout("r3") _,         // a4
                  // r4-r8 are callee-saved.
                  // r9 is platform-specific. We don't use it in libtock_runtime,
                  // so it is either unused or used as a callee-saved register.
                  // r10 and r11 are callee-saved.
-                 lateout("r12") _, // ip
+
                  // r13 is the stack pointer and must be restored by the callee.
-                 lateout("r14") _, // lr
                  // r15 is the program counter.
+
+                 clobber_abi("C"), // a2, a3, a4, ip (r12), lr (r14)
             );
         }
     }
 
     unsafe fn yield2([Register(r0), Register(r1)]: [Register; 2]) {
         // Safety: This matches the invariants required by the documentation on
         // RawSyscalls::yield2
+        // the use of `clobber_abi` allows us this to run on both Thumb-1 and Thumb-2
         unsafe {
             asm!("svc 0",
                  inlateout("r0") r0 => _, // a1
                  inlateout("r1") r1 => _, // a2
-                 lateout("r2") _,         // a3
-                 lateout("r3") _,         // a4
                  // r4-r8 are callee-saved.
                  // r9 is platform-specific. We don't use it in libtock_runtime,
                  // so it is either unused or used as a callee-saved register.
                  // r10 and r11 are callee-saved.
-                 lateout("r12") _, // ip
+
                  // r13 is the stack pointer and must be restored by the callee.
-                 lateout("r14") _, // lr
                  // r15 is the program counter.
+
+                 clobber_abi("C"), // a3, a4, ip (r12), lr (r14)
             );
         }
     }