linux-kernel - Re: [RFC][Patch] IBM Real-Time "SMI Free" mode driver

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Date:	Wed, 11 Feb 2009 10:05:57 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Keith Mannthey <kmannth@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	John Stultz <johnstul@...ibm.com>
Subject: Re: [RFC][Patch] IBM Real-Time "SMI Free" mode driver

> +	/*get the address for the RTL table from the EBDA */
> +	ebda_addr = *(unsigned short *)phys_to_virt(0x40E);
> +	ebda_addr <<= 4;
> +	ebda_size = 64*1024;

Second problem - you'll crash some systems with the assumptions here

> +	for (i = 0 ; i < ebda_size/4; i++) {
> +		unsigned int *tmp = (unsigned int *) data++;
> +		if (*tmp == RTL_MAGIC_IDENT) {
> +			table_addr = ebda_addr + i;
> +			ret = rtl_setup_sysfs();
> +			goto exit;
> +		}
> +	}

Some machines place the EBDA in the top pages of the low 640K. Your 64K
walk will continue into ISA MMIO space which isn't safe to blindly read.

Alan
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