[ipxe-devel] Recaptcha

[Robin Smidsrød]

Yes, I'm aware, but to use newer recaptcha we need to upgrade the forum
software.

Michael: Is this something you can take care of?

-- Robin

On 20.04.2018 06.25, Rusty Weber wrote:
> PS.. I would use the forum.. but I cannot sign up because recapcha on
> the site is broken.
> The recaptcha directs me to tell you to go to:
> g.co/recaptcha/upgrade
> 
>  
> 
> *From:*Rusty Weber
> *Sent:* Thursday, April 19, 2018 9:59 PM
> *To:* 'ipxe-devel at lists.ipxe.org'
> *Subject:* Big endian VS little endian decided during compile time.
> 
>  
> 
> After setting some machines to re-provision themselves through ipxe, I
> noted that some of the UUID’s I gathered from the running OS () of the
> system did not match the UUID that ipxe returned.
> Furthermore, I specifically noted a pattern in which the UUID’s returned
> by ipxe differed in a very big endian to little endian way for the first
> 8 bytes of the UUID (At first I wasn’t really certain why the last half
> of the ID worked fine).  To make matters more complicated, some of the
> machines in my lab work as expected while others do not.
> 
> Example:
> (System UUID returned by installed OS) != (System UUID returned by ipxe)
> From a Dell R-730
> 44454c4c-4d00-1051-8037-b8c04f583532 != 4c4c4544-004d-5110-8037-b8c04f583532
> From an HP DL-380 gen8
> 32333536-3030-5355-4532-333343395834 == 32333536-3030-5355-4532-333343395834
> 
> 
> The first 8 bytes of the first UUID returned by ipxe in the previous
> example are wrong,  either that or the Linux and windows guys both got
> their code for reading the value wrong.  In any case, those values
> should match and my investigation started with ipxe.
> Investigating where the UUID was being generated from, “./core/uuid.c” I
> noticed that the first half of the uuid was being printed out and
> processed by a number of macros defined in “./include/byteswap.h“ named
> “be(16|32)_to_cpu”.  The names of these macros are as follows:
> 
> ```
> #if __BYTE_ORDER == __LITTLE_ENDIAN
> 
> #define __cpu_to_leNN( bits, value ) (value)
> 
> #define __cpu_to_beNN( bits, value ) __bswap_ ## bits (value)
> 
> #define __leNN_to_cpu( bits, value ) (value)
> 
> #define __beNN_to_cpu( bits, value ) __bswap_ ## bits (value)
> 
> #define __cpu_to_leNNs( bits, ptr ) do { } while ( 0 )
> 
> #define __cpu_to_beNNs( bits, ptr ) __bswap_ ## bits ## s (ptr)
> 
> #define __leNN_to_cpus( bits, ptr ) do { } while ( 0 )
> 
> #define __beNN_to_cpus( bits, ptr ) __bswap_ ## bits ## s (ptr)
> 
> #endif
> 
>  
> 
> #if __BYTE_ORDER == __BIG_ENDIAN
> 
> #define __cpu_to_leNN( bits, value ) __bswap_ ## bits (value)
> 
> #define __cpu_to_beNN( bits, value ) (value)
> 
> #define __leNN_to_cpu( bits, value ) __bswap_ ## bits (value)
> 
> #define __beNN_to_cpu( bits, value ) (value)
> 
> #define __cpu_to_leNNs( bits, ptr ) __bswap_ ## bits ## s (ptr)
> 
> #define __cpu_to_beNNs( bits, ptr ) do { } while ( 0 )
> 
> #define __leNN_to_cpus( bits, ptr ) __bswap_ ## bits ## s (ptr)
> 
> #define __beNN_to_cpus( bits, ptr ) do { } while ( 0 )
> 
> #endif
> 
> #define be16_to_cpu( value ) __beNN_to_cpu ( 16, value )
> 
> #define be32_to_cpu( value ) __beNN_to_cpu ( 32, value )
> 
> ```
> 
> From uuid.c
> ```
> const char * uuid_ntoa ( const union uuid *uuid ) {
> 
>         static char buf[37]; /* "00000000-0000-0000-0000-000000000000" */
> 
>  
> 
>         sprintf ( buf, "%08x-%04x-%04x-%04x-%02x%02x%02x%02x%02x%02x",
> 
>                   be32_to_cpu ( uuid->canonical.a ),
> 
>                   be16_to_cpu ( uuid->canonical.b ),
> 
>                   be16_to_cpu ( uuid->canonical.c ),
> 
>                   be16_to_cpu ( uuid->canonical.d ),
> 
>                   uuid->canonical.e[0], uuid->canonical.e[1],
> 
>                   uuid->canonical.e[2], uuid->canonical.e[3],
> 
>                   uuid->canonical.e[4], uuid->canonical.e[5] );
> 
>         return buf;
> ```
> 
> Here is where I get lost/ am not sure to proceed on, why does the UUID
> differ from the UUID that the OS returned?  Is it possible that there
> are difference between CPU’s where the valued in the UUID are not little
> endian?  Differences in endianness from uefi and the x86 bios images?
> 
> Russell Weber
> Software Support and Quality engineer
> 
>  
> 
> 
> 
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