Re: [PATCH] x86: Fix earlyprintk ttyS2/3

[Joe Perches <joe@perches.com>]

On Tue, 2015-04-07 at 22:29 +0800, Daniel J Blueman wrote:
> Quite a few platforms use ttyS2 for their serial-over-LAN, so fix early
> printk support for ttyS2 and 3, avoiding the need to hard-code the IO port.
[]
> diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
[]
> @@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
>  			else
>  				pos = e - arg;
>  		} else if (!strncmp(arg + pos, "ttyS", 4)) {
> -			static const int bases[] = { 0x3f8, 0x2f8 };
> -			int idx = 0;
> +			static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
> +			unsigned idx = 0;
>  
>  			if (!strncmp(arg + pos, "ttyS", 4))
>  				pos += 4;
>  
> -			if (arg[pos++] == '1')
> -				idx = 1;
> +			if ((arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
> +				idx = arg[pos] - '0';

This doesn't prevent negative indexing in case someone
does something like shift key typo "ttyS!" for "ttyS1".

I've done that.