lib/utils: Add ARM semihosting utility functions.
This can be a replacement for a UART in custom ports.
This commit is contained in:
Ayke van Laethem
Damien George
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/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2018 Ayke van Laethem
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "semihosting.h"
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// Resources:
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// http://embed.rs/articles/2016/semi-hosting-rust/
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// https://wiki.dlang.org/Minimal_semihosted_ARM_Cortex-M_%22Hello_World%22
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// https://github.com/arduino/OpenOCD/blob/master/src/target/arm_semihosting.c
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#define SYS_OPEN 0x01
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#define SYS_WRITEC 0x03
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#define SYS_WRITE 0x05
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#define SYS_READC 0x07
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// Constants:
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#define OPEN_MODE_READ (0) // mode "r"
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#define OPEN_MODE_WRITE (4) // mode "w"
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#ifndef __thumb__
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#error Semihosting is only implemented for ARM microcontrollers.
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#endif
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static int mp_semihosting_stdout;
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static uint32_t mp_semihosting_call(uint32_t num, const void *arg) {
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// A semihosting call works as follows, similar to a SVCall:
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// * the call is invoked by a special breakpoint: 0xAB
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// * the command is placed in r0
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// * a pointer to the arguments is placed in r1
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// * the return value is placed in r0
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// Note that because it uses the breakpoint instruction, applications
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// will hang if they're not connected to a debugger. And they'll be
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// stuck in a breakpoint if semihosting is not specifically enabled in
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// the debugger.
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// Also note that semihosting is extremely slow (sometimes >100ms per
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// call).
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register uint32_t num_reg __asm__ ("r0") = num;
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register const void *args_reg __asm__ ("r1") = arg;
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__asm__ __volatile__ (
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"bkpt 0xAB\n" // invoke semihosting call
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: "+r" (num_reg) // call number and result
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: "r" (args_reg) // arguments
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: "memory"); // make sure args aren't optimized away
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return num_reg; // r0, which became the result
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}
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static int mp_semihosting_open_console(uint32_t mode) {
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struct {
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char *name;
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uint32_t mode;
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uint32_t name_len;
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} args = {
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.name = ":tt", // magic path to console
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.mode = mode, // e.g. "r", "w" (see OPEN_MODE_* constants)
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.name_len = 3, // strlen(":tt")
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};
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return mp_semihosting_call(SYS_OPEN, &args);
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}
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void mp_semihosting_init() {
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mp_semihosting_stdout = mp_semihosting_open_console(OPEN_MODE_WRITE);
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}
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int mp_semihosting_rx_char() {
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return mp_semihosting_call(SYS_READC, NULL);
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}
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static void mp_semihosting_tx_char(char c) {
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mp_semihosting_call(SYS_WRITEC, &c);
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}
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uint32_t mp_semihosting_tx_strn(const char *str, size_t len) {
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if (len == 0) {
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return 0; // nothing to do
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}
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if (len == 1) {
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mp_semihosting_tx_char(*str); // maybe faster?
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return 0;
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}
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struct {
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uint32_t fd;
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const char *str;
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uint32_t len;
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} args = {
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.fd = mp_semihosting_stdout,
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.str = str,
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.len = len,
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};
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return mp_semihosting_call(SYS_WRITE, &args);
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}
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uint32_t mp_semihosting_tx_strn_cooked(const char *str, size_t len) {
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// Write chunks of data until (excluding) the first '\n' character,
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// insert a '\r' character, and then continue with the next chunk
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// (starting with '\n').
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// Doing byte-by-byte writes would be easier to implement but is far
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// too slow.
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size_t start = 0;
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for (size_t i = 0; i < len; i++) {
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if (str[i] == '\n') {
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mp_semihosting_tx_strn(str + start, i - start);
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mp_semihosting_tx_char('\r');
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start = i;
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}
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}
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return mp_semihosting_tx_strn(str + start, len - start);
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}
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@ -0,0 +1,51 @@
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/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2018 Ayke van Laethem
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef MICROPY_INCLUDED_LIB_UTILS_SEMIHOSTING_H
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#define MICROPY_INCLUDED_LIB_UTILS_SEMIHOSTING_H
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/*
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To use semi-hosting for a replacement UART:
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- Add lib/semihosting/semihosting.c to the Makefile sources.
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- Call mp_semihosting_init() in main(), around the time UART is initialized.
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- Replace mp_hal_stdin_rx_chr and similar in mphalport.c with the semihosting equivalent.
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- Include lib/semihosting/semihosting.h in the relevant files.
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Then make sure the debugger is attached and enables semihosting. In OpenOCD this is
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done with ARM semihosting enable followed by reset. The terminal will need further
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configuration to work with MicroPython (bash: stty raw -echo).
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*/
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#include <stddef.h>
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#include <stdint.h>
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void mp_semihosting_init();
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int mp_semihosting_rx_char();
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uint32_t mp_semihosting_tx_strn(const char *str, size_t len);
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uint32_t mp_semihosting_tx_strn_cooked(const char *str, size_t len);
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#endif // MICROPY_INCLUDED_LIB_UTILS_SEMIHOSTING_H
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