1 /*
2 * This file is part of the MicroPython project, http://micropython.org/
3 *
4 * The MIT License (MIT)
5 *
6 * Copyright (c) 2018 Ayke van Laethem
7 *
8 * Permission is hereby granted, free of charge, to any person obtaining a copy
9 * of this software and associated documentation files (the "Software"), to deal
10 * in the Software without restriction, including without limitation the rights
11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 * copies of the Software, and to permit persons to whom the Software is
13 * furnished to do so, subject to the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be included in
16 * all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
24 * THE SOFTWARE.
25 */
26
27 #include "semihosting.h"
28
29 // Resources:
30 // http://embed.rs/articles/2016/semi-hosting-rust/
31 // https://wiki.dlang.org/Minimal_semihosted_ARM_Cortex-M_%22Hello_World%22
32 // https://github.com/arduino/OpenOCD/blob/master/src/target/arm_semihosting.c
33
34 #define SYS_OPEN 0x01
35 #define SYS_WRITEC 0x03
36 #define SYS_WRITE 0x05
37 #define SYS_READC 0x07
38
39 // Constants:
40 #define OPEN_MODE_READ (0) // mode "r"
41 #define OPEN_MODE_WRITE (4) // mode "w"
42
43 #ifndef __thumb__
44 #error Semihosting is only implemented for ARM microcontrollers.
45 #endif
46
47 static int mp_semihosting_stdout;
48
mp_semihosting_call(uint32_t num,const void * arg)49 static uint32_t mp_semihosting_call(uint32_t num, const void *arg) {
50 // A semihosting call works as follows, similar to a SVCall:
51 // * the call is invoked by a special breakpoint: 0xAB
52 // * the command is placed in r0
53 // * a pointer to the arguments is placed in r1
54 // * the return value is placed in r0
55 // Note that because it uses the breakpoint instruction, applications
56 // will hang if they're not connected to a debugger. And they'll be
57 // stuck in a breakpoint if semihosting is not specifically enabled in
58 // the debugger.
59 // Also note that semihosting is extremely slow (sometimes >100ms per
60 // call).
61 register uint32_t num_reg __asm__ ("r0") = num;
62 register const void *args_reg __asm__ ("r1") = arg;
63 __asm__ __volatile__ (
64 "bkpt 0xAB\n" // invoke semihosting call
65 : "+r" (num_reg) // call number and result
66 : "r" (args_reg) // arguments
67 : "memory"); // make sure args aren't optimized away
68 return num_reg; // r0, which became the result
69 }
70
mp_semihosting_open_console(uint32_t mode)71 static int mp_semihosting_open_console(uint32_t mode) {
72 struct {
73 char *name;
74 uint32_t mode;
75 uint32_t name_len;
76 } args = {
77 .name = ":tt", // magic path to console
78 .mode = mode, // e.g. "r", "w" (see OPEN_MODE_* constants)
79 .name_len = 3, // strlen(":tt")
80 };
81 return mp_semihosting_call(SYS_OPEN, &args);
82 }
83
mp_semihosting_init()84 void mp_semihosting_init() {
85 mp_semihosting_stdout = mp_semihosting_open_console(OPEN_MODE_WRITE);
86 }
87
mp_semihosting_rx_char()88 int mp_semihosting_rx_char() {
89 return mp_semihosting_call(SYS_READC, NULL);
90 }
91
mp_semihosting_tx_char(char c)92 static void mp_semihosting_tx_char(char c) {
93 mp_semihosting_call(SYS_WRITEC, &c);
94 }
95
mp_semihosting_tx_strn(const char * str,size_t len)96 uint32_t mp_semihosting_tx_strn(const char *str, size_t len) {
97 if (len == 0) {
98 return 0; // nothing to do
99 }
100 if (len == 1) {
101 mp_semihosting_tx_char(*str); // maybe faster?
102 return 0;
103 }
104
105 struct {
106 uint32_t fd;
107 const char *str;
108 uint32_t len;
109 } args = {
110 .fd = mp_semihosting_stdout,
111 .str = str,
112 .len = len,
113 };
114 return mp_semihosting_call(SYS_WRITE, &args);
115 }
116
mp_semihosting_tx_strn_cooked(const char * str,size_t len)117 uint32_t mp_semihosting_tx_strn_cooked(const char *str, size_t len) {
118 // Write chunks of data until (excluding) the first '\n' character,
119 // insert a '\r' character, and then continue with the next chunk
120 // (starting with '\n').
121 // Doing byte-by-byte writes would be easier to implement but is far
122 // too slow.
123 size_t start = 0;
124 for (size_t i = 0; i < len; i++) {
125 if (str[i] == '\n') {
126 mp_semihosting_tx_strn(str + start, i - start);
127 mp_semihosting_tx_char('\r');
128 start = i;
129 }
130 }
131 return mp_semihosting_tx_strn(str + start, len - start);
132 }
133