Subject: Re: [PATCH] powerpc: fix xmon disassembler for little-endian

From: Philippe Bergheaud <[email-masked]>
Date: Thu, 05 Dec 2013 09:50:23 +0100

Benjamin Herrenschmidt wrote:
> On Wed, 2013-12-04 at 14:45 +0100, Philippe Bergheaud wrote:
> 
> 
>>>>+#ifdef __LITTLE_ENDIAN__
>>>>+#define GETWORD(v)	(((v)[3] << 24) + ((v)[2] << 16) + ((v)[1] << 8) + (v)[0])
>>>>+#else
>>>>#define GETWORD(v)	(((v)[0] << 24) + ((v)[1] << 16) + ((v)[2] << 8) + (v)[3])
>>>>+#endif
>>>>
>>>>#define isxdigit(c)	(('0' <= (c) && (c) <= '9') \
>>>>			 || ('a' <= (c) && (c) <= 'f') \
>>>>
>>>
>>>
>>>Philippe:  Wouldn't it be better to just do a 32-bit load and let the endianness be worked out
>>>by the hardware?  i.e.
>>>
>>>#define GETWORD(v) (*(u32 *)v)
>>
>>Yes, your alternative is better.
>>Wouldn't it narrow the scope of the macro to aligned words on POWER7?
>>I think that all references to GETWORD operate on aligned words anyway.
> 
> 
> Well, xmon has to be robust ... as long as you are *certain* that even
> with crap entry state it won't try to access unaligned boundaries then
> go for it but we aren't looking at performance here.
Thank you Tom and Ben.  We are definitely not looking at performance here.
I prefer to stay on the safe side, and leave the original patch untouched.

Philippe