Subject: Re: [PATCH] numactl: fix libnuma on big-endian 64-bit systems

From: Lee Schermerhorn <[email-masked]>
Date: Thu, 04 Dec 2008 12:46:56 -0500

On Thu, 2008-12-04 at 18:34 +0100, Arnd Bergmann wrote:
> The read-mask function assumes that it is running in 32-bit mode,
> by addressing the bitmask as a series of int values, instead of
> longs. This is broken as can easily be reproduced by running numademo
> on a bit-endian 64-bit system.
> 
> Changing the addressing to use 'long' values fixes the problem.

Hi, Arnd:

Not sure what you mean here.  If the patch below is a proposed fix [I
don't see a 'Signed-off-by:", but maybe not needed for libnuma
patches?], the description above doesn't match the code.  Looks like
you're changing the addressing FROM 'long' values to use 'int' values so
that the size is compatible between 32- and 64-bits.  Or is that a
reverse patch/diff below?

Lee

> Reported-by: Mijo Safradin <[email-masked]>
> 
> ---
> 
> Note: the set_nodemask_size() function is broken as well, it seems
> to always set the nodemask size to "17" with the s2nbits implementation.
> The fallback path in there looks correct.
> 
> --- a/libnuma.c	2008-12-04 14:25:30.000000000 +0100
> +++ b/libnuma.c	2008-11-20 13:40:29.000000000 +0100
> @@ -392,9 +372,9 @@ read_mask(char *s, struct bitmask *bmp)
>  {
>  	char *end = s;
>  	char *prevend;
> -	unsigned long *start = bmp->maskp;
> -	unsigned long *p = start;
> -	unsigned long *q;
> +	unsigned int *start = (unsigned int *)bmp->maskp;
> +	unsigned int *p = start;
> +	unsigned int *q;
>  	unsigned int i;
>  	unsigned int n = 0;
>  
> @@ -431,14 +411,14 @@
>  	}
>  
>  	/* Poor mans fls() */
> -	for(i = sizeof(long) * 8 - 1; i >= 0; i--)
> +	for(i = 31; i >= 0; i--)
>  		if (test_bit(i, start + n))
>  			break;
>  
>  	/*
>  	 * Return the last bit set
>  	 */
> -	return ((sizeof(unsigned long)*8) * n) + i;
> +	return ((sizeof(unsigned int)*8) * n) + i;
>  }
>  
>  /*