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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 2018-04-09 01:00:01 +02:00 committed by Damien George
parent 4404dababb
commit 70f50c46cc
2 changed files with 183 additions and 0 deletions
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132
lib/utils/semihosting.c Normal file
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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2018 Ayke van Laethem
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "semihosting.h"
// Resources:
// http://embed.rs/articles/2016/semi-hosting-rust/
// https://wiki.dlang.org/Minimal_semihosted_ARM_Cortex-M_%22Hello_World%22
// https://github.com/arduino/OpenOCD/blob/master/src/target/arm_semihosting.c
#define SYS_OPEN 0x01
#define SYS_WRITEC 0x03
#define SYS_WRITE 0x05
#define SYS_READC 0x07
// Constants:
#define OPEN_MODE_READ (0) // mode "r"
#define OPEN_MODE_WRITE (4) // mode "w"
#ifndef __thumb__
#error Semihosting is only implemented for ARM microcontrollers.
#endif
static int mp_semihosting_stdout;
static uint32_t mp_semihosting_call(uint32_t num, const void *arg) {
// A semihosting call works as follows, similar to a SVCall:
// * the call is invoked by a special breakpoint: 0xAB
// * the command is placed in r0
// * a pointer to the arguments is placed in r1
// * the return value is placed in r0
// Note that because it uses the breakpoint instruction, applications
// will hang if they're not connected to a debugger. And they'll be
// stuck in a breakpoint if semihosting is not specifically enabled in
// the debugger.
// Also note that semihosting is extremely slow (sometimes >100ms per
// call).
register uint32_t num_reg __asm__ ("r0") = num;
register const void *args_reg __asm__ ("r1") = arg;
__asm__ __volatile__ (
"bkpt 0xAB\n" // invoke semihosting call
: "+r" (num_reg) // call number and result
: "r" (args_reg) // arguments
: "memory"); // make sure args aren't optimized away
return num_reg; // r0, which became the result
}
static int mp_semihosting_open_console(uint32_t mode) {
struct {
char *name;
uint32_t mode;
uint32_t name_len;
} args = {
.name = ":tt", // magic path to console
.mode = mode, // e.g. "r", "w" (see OPEN_MODE_* constants)
.name_len = 3, // strlen(":tt")
};
return mp_semihosting_call(SYS_OPEN, &args);
}
void mp_semihosting_init() {
mp_semihosting_stdout = mp_semihosting_open_console(OPEN_MODE_WRITE);
}
int mp_semihosting_rx_char() {
return mp_semihosting_call(SYS_READC, NULL);
}
static void mp_semihosting_tx_char(char c) {
mp_semihosting_call(SYS_WRITEC, &c);
}
uint32_t mp_semihosting_tx_strn(const char *str, size_t len) {
if (len == 0) {
return 0; // nothing to do
}
if (len == 1) {
mp_semihosting_tx_char(*str); // maybe faster?
return 0;
}
struct {
uint32_t fd;
const char *str;
uint32_t len;
} args = {
.fd = mp_semihosting_stdout,
.str = str,
.len = len,
};
return mp_semihosting_call(SYS_WRITE, &args);
}
uint32_t mp_semihosting_tx_strn_cooked(const char *str, size_t len) {
// Write chunks of data until (excluding) the first '\n' character,
// insert a '\r' character, and then continue with the next chunk
// (starting with '\n').
// Doing byte-by-byte writes would be easier to implement but is far
// too slow.
size_t start = 0;
for (size_t i = 0; i < len; i++) {
if (str[i] == '\n') {
mp_semihosting_tx_strn(str + start, i - start);
mp_semihosting_tx_char('\r');
start = i;
}
}
return mp_semihosting_tx_strn(str + start, len - start);
}

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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2018 Ayke van Laethem
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef MICROPY_INCLUDED_LIB_UTILS_SEMIHOSTING_H
#define MICROPY_INCLUDED_LIB_UTILS_SEMIHOSTING_H
/*
To use semi-hosting for a replacement UART:
- Add lib/semihosting/semihosting.c to the Makefile sources.
- Call mp_semihosting_init() in main(), around the time UART is initialized.
- Replace mp_hal_stdin_rx_chr and similar in mphalport.c with the semihosting equivalent.
- Include lib/semihosting/semihosting.h in the relevant files.
Then make sure the debugger is attached and enables semihosting. In OpenOCD this is
done with ARM semihosting enable followed by reset. The terminal will need further
configuration to work with MicroPython (bash: stty raw -echo).
*/
#include <stddef.h>
#include <stdint.h>
void mp_semihosting_init();
int mp_semihosting_rx_char();
uint32_t mp_semihosting_tx_strn(const char *str, size_t len);
uint32_t mp_semihosting_tx_strn_cooked(const char *str, size_t len);
#endif // MICROPY_INCLUDED_LIB_UTILS_SEMIHOSTING_H