OpenBSD/sgi on octane2 - cpu1デバッグ用のcom1向け簡易printfの実装

調子にのってprintfも実装した。

#define	COM_NPORTS	8
#define	COM_FREQ	1843200	/* 16-bit baud rate divisor */
#define COMBBUF_SIZE 2048
int	combfreq = 22000000 / 3;
int	combrate = TTYDEF_SPEED;
bus_addr_t combaddr = 0x500000 + IOC3_UARTB_BASE;
bus_space_tag_t combiot = &sys_config.console_io;
bus_space_handle_t combioh;
char combbuf[COMBBUF_SIZE] = {0};

void
cominit(bus_space_tag_t iot, bus_space_handle_t ioh, int rate, int frequency);

static void
combinit(void)
{
	if (bus_space_map(combiot, combaddr, COM_NPORTS, 0, &combioh))
		panic("comcninit: mapping failed");

	if (combfreq == 0)
		combfreq = COM_FREQ;

	cominit(combiot, combioh, combrate, combfreq);
}

static void
combputc(int c)
{
	com_common_putc(combiot, combioh, c);
}

static int
combprintf(const char *fmt, ...)
{
	int i;
	va_list ap;

	va_start(ap, fmt);
	vsnprintf(combbuf, COMBBUF_SIZE, fmt, ap);
	va_end(ap);
	for(i = 0; i < COMBBUF_SIZE; i++)
		if(combbuf[i] == '\0')
			break;
		else
			combputc(combbuf[i]);
	
	return 0;
}

こんなテケトーなコードでいいのかよ。＜こまけぇことはいいんだよ！
これで走らせてみたら、なんかこんな感じに出力が乱れた。あれ、なぜ？

comb initialized by cpu1
                        ci:0xffffffffc00fe800
                                             gp:0xa8000000205c0c10
                                                                  sp:0xa800000020630eb0
            [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:357]
                                                                        [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:365]
                                                         [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:373]
                                          [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:375]
                           [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:382]
            [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:385]
                                                                        [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:387]
                                                         [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:389]
                                          [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:393]
                           [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:399]
            [../../../../arch/sgi/sgi/ip30_machdep.c:prom_cpu_hatch:404]