circuitpython/shared/runtime/semihosting.c

133 lines
4.5 KiB
C

/*
* 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);
}