Re: [PATCH] check that acpi_wakeup_address is below 1MB

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, 6 of February 2008, matthieu castet wrote:
> Hi,

Hi,

> this patch had a check that the memory allocated is in the first 1MB.
> The check is similar to the one in smp_alloc_memory.
> 
> 
> Signed-off-by: "Matthieu CASTET <castet.matthieu@free.fr>"

Please don't attach patches if possible.  It's easier to comment them if they
are in the message body.

> diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
> index 6bc815c..65ab23c 100644
> --- a/arch/x86/kernel/acpi/sleep.c
> +++ b/arch/x86/kernel/acpi/sleep.c
> @@ -65,6 +65,10 @@ void __init acpi_reserve_bootmem(void)
>  	acpi_wakeup_address = (unsigned long)alloc_bootmem_low(PAGE_SIZE*2);
>  	if (!acpi_wakeup_address)
>  		printk(KERN_ERR "ACPI: Cannot allocate lowmem, S3 disabled.\n");
> +
> +	/* check if we are in first 1MB of memory */
> +	if (__pa(acpi_wakeup_address) >= 1024*1024-PAGE_SIZE*2)
> +		BUG();

I don't like this.

First, you should use BUG_ON(something) rather that "if (something) BUG();".

Second, and more importantly, it's enough to put "acpi_wakeup_address = 0"
to disable the feature without crashing the kernel.
Of course, I'd add an error message describing what's wrong to that.

>  }

Thanks,
Rafael

 





-- 
"Premature optimization is the root of all evil." - Donald Knuth