b/c/particle-mesh: Support particle bootloader

Closes: https://github.com/RIOT-OS/RIOT/issues/12320

boards/common/particle-mesh/Makefile.include

@@ -9,18 +9,36 @@ PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.SLAB_USBtoUART*)))
 # add the common header files to the include path
 INCLUDES += -I$(RIOTBOARD)/common/particle-mesh/include
 
-# This board uses a DAP-Link programmer
-# Flashing support is provided through pyocd (default) and openocd.
-# For openocd, a version built against the development branch and containing
-# the support for nrf52 cpu is required.
-PROGRAMMER ?= pyocd
-ifeq (pyocd,$(PROGRAMMER))
-  # The board is not recognized automatically by pyocd, so the CPU target
-  # option is passed explicitly
-  FLASH_TARGET_TYPE ?= -t nrf52840
-  include $(RIOTMAKE)/tools/pyocd.inc.mk
-else ifeq (openocd,$(PROGRAMMER))
-  DEBUG_ADAPTER ?= dap
+ifeq (1,$(PARTICLE_MONOFIRMWARE))
+  CFLAGS += -DPARTICLE_MONOFIRMWARE
+  ROM_OFFSET = 0x30000
+  FW_ROM_LEN = 0xc4000
+  FLASHFILE = $(BINFILE)-checksummed
+  # Setting DFU_ARGS won't work as the implied --reset causes errors.
+  FFLAGS = -d 0x2B04:0xD00E -a 0 -s 0x30000:leave -D $(FLASHFILE)
+  PROGRAMMER = dfu-util
+  include $(RIOTMAKE)/tools/dfu.inc.mk
+else
+  # This board uses a DAP-Link programmer
+  # Flashing support is provided through pyocd (default) and openocd.
+  # For openocd, a version built against the development branch and containing
+  # the support for nrf52 cpu is required.
+  PROGRAMMER ?= pyocd
+  ifeq (pyocd,$(PROGRAMMER))
+    # The board is not recognized automatically by pyocd, so the CPU target
+    # option is passed explicitly
+    FLASH_TARGET_TYPE ?= -t nrf52840
+    include $(RIOTMAKE)/tools/pyocd.inc.mk
+  else ifeq (openocd,$(PROGRAMMER))
+    DEBUG_ADAPTER ?= dap
+  endif
 endif
 
+MONOFIRMWARETOOL = ${RIOTBOARD}/common/particle-mesh/monofirmware-tool.py
+
+# Rule (variations) for building a monofirmware populated with the right
+# (lengths and) checksum in it; only used iuf PARTICLE_MONOFIRMWARE=1
+%.bin-checksummed: %.bin %.elf ${MONOFIRMWARETOOL}
+	${MONOFIRMWARETOOL} $*.elf $< $@
+
 include $(RIOTBOARD)/common/nrf52/Makefile.include

boards/common/particle-mesh/board.c

@@ -45,6 +45,31 @@ void board_nrfantenna_select(enum board_nrfantenna_selection choice)
 
 void board_init(void)
 {
+#ifdef PARTICLE_MONOFIRMWARE
+    /* For comparison with MicroPython's hook into this bootloader, they'd set
+     * SCB->VTOR here. That is necessary because while the particle bootloader
+     * largely mimics the ARM bootup by requiring a VTOR at the start of the
+     * writable firmware, it does not set the VTOR to the loaded data.
+     *
+     * That step is not executed *right* here as cpu_init will do it a few
+     * lines down anyway. */
+
+    /* Force keeping the metadata -- the __attribute__((used)) in their macro
+     * expansions and the KEEP on the section in the linker only almost do
+     * that: at least *something* from the object file needs to be referenced
+     * to pull them all in. */
+    extern uint32_t particle_monofirmware_padding;
+    uint32_t x;
+    x = (uint32_t)&particle_monofirmware_padding;
+    (void)x;
+
+    /* Clear out POWER_CLOCK and GPIOTE interrupts set by the bootloader. (If
+     * actual RIOT code enables them, it'll do so after the board_init call).
+     * */
+    NVIC_DisableIRQ(0);
+    NVIC_DisableIRQ(6);
+#endif
+
     /* initialize the boards LEDs */
     gpio_init(LED0_PIN, GPIO_OUT);
     gpio_set(LED0_PIN);

boards/common/particle-mesh/bootloader.c

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2014-2016 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @author  Christian Amsüss <chrysn@fsfe.org>
+ */
+
+#ifdef PARTICLE_MONOFIRMWARE
+#include <stdint.h>
+#include "vectors_cortexm.h"
+
+extern const void *_isr_vectors;
+
+/* As described in Particle's dynalib/inc/module_info.h (there under LGPL-3
+ * terms; detailed license compatibility discussion skipped for not crossing
+ * any threshold of originality) */
+typedef struct module_info_t {
+    const void* module_start_address;
+    const void* module_end_address;
+    uint8_t reserved;
+    uint8_t flags;
+    uint16_t module_version;
+    uint16_t platform_id;
+    uint8_t  module_function;
+    uint8_t  module_index;
+    uint32_t dependency; /* was module_dependency_t; kept in here to ensure it's blank */
+    uint32_t dependency2; /* was module_dependency_t */
+} module_info_t;
+
+/* 64 words is the distance between the known ISR table and the fixed-position
+ * module_info at 0x200. If the ISR length is changed for any reason, this must
+ * be adapted until particle_monofirmware_module_info is precisely at 0x30200.
+ * (monofirmware-tool.py will complain if it isn't).
+ *
+ * This is not `static` as *something* from this module needs to be visible to
+ * the outside for the __attribute__((used)) and the KEEP on the section in the
+ * linker script to work; see also the reference to it in board.c. */
+ISR_VECTOR(50) const uint32_t particle_monofirmware_padding[64] = {0, };
+
+#ifdef PARTICLE_MONOFIRMWARE_CHECKSUMLIMIT
+/* Watch the ISR vector sequence here: This is placed *after* the module_info
+ * in the flash (52 > 51), but placed before it in the code to be referencable
+ * from there.
+ *
+ * The actual value is replaced by monofirmware-tool.py.
+ * */
+ISR_VECTOR(52) static const uint8_t particle_monofirmware_checksum[4] = {0, 0, 0, 0};
+#endif
+
+ISR_VECTOR(51) static const struct module_info_t particle_monofirmware_module_info = {
+    .module_start_address = &_isr_vectors,
+#ifdef PARTICLE_MONOFIRMWARE_CHECKSUMLIMIT
+    .module_end_address = &particle_monofirmware_checksum,
+    /* else, it is set by the monofirmware-tool.
+     *
+     * For that (more common) case where we check the full firmware, we would
+     * want to set set
+     *
+     * .module_end_address = &_etext + (&_erelocate - &_srelocate),
+     *
+     * but that can not be determined at compile time. Instead, this will be
+     * populated by monofirmware-tool.py, which needs to write in here anyway
+     * for the checksum. */
+#endif
+    .module_version = 0x138, /* module version that micropython uses */
+
+    .platform_id = PARTICLE_PLATFORM_ID,
+
+    .module_index = 3, /* MOD_FUNC_MONO_FIRMWARE from dynalib/inc/module_info.h */
+};
+
+#else
+typedef int dont_be_pedantic;
+#endif
+
+/** @} */

boards/common/particle-mesh/doc.txt

@@ -35,6 +35,38 @@ To flash the board with OpenOCD, use the `PROGRAMMER` variable:
     PROGRAMMER=openocd make BOARD=<board name> -C examples/hello-world flash
 ```
 
+#### Alternative flashing procedure: Particle bootloader and DFU-Util
+
+As an alternative to using the Particle Mesh debugger,
+the USB DFU mode bootloader shipped with Particle Mesh devices can be used.
+That mode can be entered by keeping the SETUP/MODE button pressed after power-up or reset
+until the RGB LED **blinks yellow fast**.
+
+In this mode, the bootloader and Soft Device are kept in place,
+reducing the available flash memory to 784kB,
+but in turn, devices can easily be switched back to using Particle software.
+
+In order to use this mode, set `PARTICLE_MONOFIRMWARE=1` wherever you set the `BOARD`.
+This will trigger the use of the appropriate linker script,
+and switch in [`dfu-util`](http://dfu-util.sourceforge.net/) as the default programmer,
+which needs to be installed.
+<!-- Using PARTICLE_MONOFIRMWARE=1 images with an external programmer is untested but might just work once checksums are static. -->
+
+On Linux hosts, devices for the DFU mode are frequently only accessible to root,
+causing error messages like
+
+    dfu-util: Cannot open DFU device 2b04:d00e
+    dfu-util: No DFU capable USB device available
+
+To make Particle devices writable for all users,
+follow [Particle's instructions](https://docs.particle.io/support/particle-tools-faq/installing-dfu-util/)
+on setting up dfu-util.
+
+The Particle bootloader checks the firmware's checksum at startup time.
+As these checks would be frustrated by flash writes inside RIOT (typically using the @ref drivers_periph_flashpage),
+the CFLAG @ref PARTICLE_MONOFIRMWARE_CHECKSUMLIMIT "-DPARTICLE_MONOFIRMWARE_CHECKSUMLIMIT" can be set.
+Then, the checksum is only calculated over the memory region that contains the interrupt vector and the bootloader manifest.
+
 ### Reset the board
 
 The on-board reset button doesn't work, so to trigger a reset of the board, use

boards/common/particle-mesh/include/board.h

@@ -26,6 +26,61 @@
 extern "C" {
 #endif
 
+/**
+ *
+ * @name    Bootloader configuration options
+ * @{
+ */
+
+/** @brief Build a firmware suitable for the Particle bootloader
+ *
+ * If this is defined, additional metadata about the firmware is included in
+ * the firmware (called the module_info in Particle), and additional code is
+ * inserted in board setup.
+ *
+ * Do not define this manually; instead, set `PARTICLE_MONOFIRMWARE=1` as an
+ * variable in the build scripts like `BOARD` is defined, and the particle
+ * common make file defines it and configures suitable postprocessing of the
+ * binary.
+ *
+ * @see @ref boards_common_particle-mesh
+ *
+ */
+#ifdef DOXYGEN
+#define PARTICLE_MONOFIRMWARE
+#endif
+
+/** @brief Limit Particle bootloader checksumming to the binary start
+ *
+ * If this define is set in the Makefile, the binary size announced to the
+ * bootloader is limited to the reset vector and the firmware metadata, and
+ * only that part is checksummed.
+ *
+ * This is useful when @ref drivers_periph_flashpage is used, as otherwise the
+ * firmware's writes on itself would invalidate its checksum.
+ *
+ * @see @ref boards_common_particle-mesh
+ */
+#ifdef DOXYGEN
+#define PARTICLE_MONOFIRMWARE_CHECKSUMLIMIT
+#endif
+
+/** @brief Platform ID of the board for the Particle bootloader
+ *
+ * This is set by the individual board's build configuration, and gets used
+ * when building with @ref PARTICLE_MONOFIRMWARE; then, it is put into the
+ * module information for the board bootloader to verify that the firmware was
+ * built for the right device.
+ *
+ * The individual values are documented in the Particle DeviceOS source code in
+ * `build/platform-id.mk`.
+ */
+#ifdef DOXYGEN
+#define PARTICLE_PLATFORM_ID
+#endif
+
+/** @} */
+
 /**
  * @name    LED pin configuration
  * @{

boards/common/particle-mesh/monofirmware-tool.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+
+"""Verify that a pair of .bin/.elf has the particle_monofirmware_module_info at
+the right place. If there is a particle_monofirmware_checksum symbol, verify
+that the module_info says the firmware ends at it, and populate the
+checksum. Otherwise, append the checksum and set the end-of-firmware field
+accordingly."""
+
+import os
+import sys
+import zlib
+import subprocess
+import argparse
+
+expected_romstart = 0x30000
+expected_moduleinfo_position = expected_romstart + 0x200
+expected_moduleinfo_size = 0x18
+# offsetof(module_end_address, module_info_t)
+end_field_offset = 4
+end_field_start = expected_moduleinfo_position - expected_romstart + end_field_offset
+end_field_end = end_field_start + 4
+
+
+def check(condition, message):
+    if not condition:
+        print(message, file=sys.stderr)
+        sys.exit(1)
+
+
+p = argparse.ArgumentParser(description=__doc__)
+p.add_argument("elf_in", help="Program in ELF form")
+p.add_argument("bin_in", help="objdump'd ROM binary of elf_in")
+p.add_argument("bin_out", help="File to write the modified bin to")
+args = p.parse_args()
+
+symbols = subprocess.check_output([
+    os.environ.get('NM', 'nm'),
+    "--format=posix",
+    "--print-size",
+    "--defined-only",
+    args.elf_in,
+    ])
+symbols = [line.split(' ') for line in symbols.decode('ascii').split('\n') if line]
+position = {s[0]: int(s[2], 16) for s in symbols}
+size = {s[0]: int(s[3], 16) for s in symbols if s[3]}
+symtype = {s[0]: s[1] for s in symbols}
+
+romstart = min(pos for (name, pos) in position.items() if symtype[name] not in '?A')
+
+check(romstart == expected_romstart, "Defined symbols do not start at %#x" % expected_romstart)
+
+check(position.get('particle_monofirmware_module_info') == expected_moduleinfo_position,
+      """Struct particle_monofirmware_module_info not found at %#x but on %#x,
+      adjust the size of particle_monofirmware_padding to match""" %
+      (expected_moduleinfo_position, position.get('particle_monofirmware_module_info')))
+check(size.get('particle_monofirmware_module_info') == expected_moduleinfo_size,
+      "Struct particle_monofirmware_module_info not of expected size %d" % expected_moduleinfo_size)
+
+binary = bytearray(open(args.bin_in, 'rb').read())
+
+indicated_start = int.from_bytes(binary[expected_moduleinfo_position - romstart:][:4], 'little')
+check(romstart == indicated_start,
+      "particle_monofirmware_module_info.module_start does not point to the module start")
+
+if 'particle_monofirmware_checksum' in position:
+    print("monifirmware-tool: Checksum symbol found, populating it.")
+    check(size.get('particle_monofirmware_checksum') == 4, "Checksum not of expected size 4")
+
+    checksum_until = position['particle_monofirmware_checksum'] - romstart
+
+    indicated_end = int.from_bytes(binary[end_field_start:end_field_end], 'little')
+    check(indicated_end == position['particle_monofirmware_checksum'],
+          "particle_monofirmware_module_info.module_end does not point to particle_monofirmware_checksum")
+else:
+    print("monifirmware-tool: No checksum symbol found, appending the checksum to the binary.")
+    checksum_until = len(binary)
+
+    # Populating the length: When the whole binary (including the rom
+    # initialization block) is checksummed, the end address can't be populated
+    # from C because that would require evaluating `&_etext + (&_erelocate -
+    # &_srelocate)` in advance
+    binary[end_field_start:end_field_end] = (checksum_until + romstart).to_bytes(4, 'little')
+
+checksum = zlib.crc32(binary[:checksum_until]).to_bytes(4, 'big')
+binary[checksum_until:checksum_until + 4] = checksum
+
+with open(args.bin_out, "wb") as o:
+    o.write(binary)

boards/particle-argon/Makefile.include

@@ -1 +1,2 @@
+CFLAGS += "-DPARTICLE_PLATFORM_ID=12"
 include $(RIOTBOARD)/common/particle-mesh/Makefile.include

boards/particle-boron/Makefile.include

@@ -1 +1,2 @@
+CFLAGS += "-DPARTICLE_PLATFORM_ID=13"
 include $(RIOTBOARD)/common/particle-mesh/Makefile.include

boards/particle-xenon/Makefile.include

@@ -1 +1,2 @@
+CFLAGS += "-DPARTICLE_PLATFORM_ID=14"
 include $(RIOTBOARD)/common/particle-mesh/Makefile.include