ARMv7-M Semihosting test

main.c

#include "ch.h"
#include "hal.h"
#include <string.h>

static THD_WORKING_AREA(waThread1, 128);
static THD_FUNCTION(Thread1, arg)
{
    (void)arg;
    chRegSetThreadName("blinker");
    while (true) {
        palSetPad(GPIOD, GPIOD_LED3);       /* Orange.  */
        chThdSleepMilliseconds(500);
        palClearPad(GPIOD, GPIOD_LED3);     /* Orange.  */
        chThdSleepMilliseconds(500);
    }
}

int send_command(int command, void *message)
{
    int ret;
    asm("mov r0, %[cmd];"
       "mov r1, %[msg];"
       "bkpt #0xAB;"
       "mov %[ret], r0;"
         : [ret] "=r" (ret)
         : [cmd] "r" (command), [msg] "r" (message)
         : "r0", "r1", "memory");
    return ret;
}

// source: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471l/pge1358787045051.html
// mode number:      0   1   2   3   4   5   6   7   8   9   10  11
// ISO C fopen mode: r   rb  r+  r+b w   wb  w+  w+b a   ab  a+  a+b
#define SYS_OPEN 0x01
#define SYS_CLOSE 0x02
#define SYS_WRITE 0x05
#define SYS_READ 0x06

int main(void)
{
    halInit();
    chSysInit();

    chThdCreateStatic(waThread1, sizeof(waThread1), NORMALPRIO, Thread1, NULL);

    const char *filename = "hello.txt";
    uint32_t opencmd[] = {(uint32_t)filename, 0 /*"r"*/, strlen(filename)};
    int file = send_command(SYS_OPEN, opencmd);

    uint32_t read_len = 20;
    int res;
    static char buf[42];
    uint32_t readcmd[] = {file, (uint32_t)&buf[0], read_len};
    res = send_command(SYS_READ, readcmd);

    uint32_t closecmd[] = {file};
    res = send_command(SYS_CLOSE, closecmd);

    while (true) {
        chThdSleepMilliseconds(500);
        uint32_t m[] = {1/*stdout*/, (uint32_t)&buf[0], read_len};
        send_command(SYS_WRITE, m);
    }
}