blob: 7a7910ff6297cc4423453a68c4346e03da885e1b [file] [log] [blame]
/*
* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include "pico/stdio/driver.h"
#include "pico/stdio_semihosting.h"
#include "pico/binary_info.h"
static void stdio_semihosting_out_chars(const char *buf, int length) {
// must be volatile or the buffer gets put in registers & optimized away
volatile struct {
// https://developer.arm.com/documentation/dui0375/g/What-is-Semihosting-/SYS-WRITE--0x05-
// arguments, in order:
// word 0 = file handle (1 = stdout)
// word 1 = pointer to buffer
// word 2 = length of buffer
size_t fd;
const char *buf;
size_t len;
} args;
args.fd = 1; // 1 = stdout
args.buf = buf;
args.len = length;
pico_default_asm (
// r1 must contain a pointer to the arguments
"movs r1, %[args]\n"
// semihosting call number 0x05 = SYS_WRITE
"movs r0, #5\n"
// make the semihosting call: https://developer.arm.com/documentation/dui0375/g/What-is-Semihosting-/The-semihosting-interface
"bkpt 0xab\n"
:
: [args] "r" (&args)
: "r0", "r1");
}
stdio_driver_t stdio_semihosting = {
.out_chars = stdio_semihosting_out_chars,
#if PICO_STDIO_ENABLE_CRLF_SUPPORT
.crlf_enabled = PICO_STDIO_SEMIHOSTING_DEFAULT_CRLF
#endif
};
void stdio_semihosting_init() {
#if !PICO_NO_BI_STDIO_SEMIHOSTING
bi_decl_if_func_used(bi_program_feature("semihosting stdout"));
#endif
stdio_set_driver_enabled(&stdio_semihosting, true);
}