[patch] export CPU physical and virtual address sizes in sysctl oids using do_cpuid

[Sofian Brabez]

This patch uses do_cpuid function to fetch CPU Physical and Virtual address sizes
and adds 2 new sysctl machine dependant OIDs (machdep.cpu_physical_address_bits
and machdep.cpu_virtual_address_bits).

In order to retrieve the information, it calls do_cpuid by setting eax register
to 0x80000008 value like referenced in chapter 5.2.7 in the CPUID specification [1]

Apple, Inc. in xnu kernel do the same thing but they created a specific node called
'machdep.cpu' to store CPU Vendor information, the sysctls are
machdep.cpu.address_bits.virtual and machdep.cpu.address_bits.virtual.

I really would like to see this patch in our operating system because it's a
valuable information nowdays and should be provided like others.

Thus, I would like advices to see if before to be imported it needs modification
to fit like Apple (i.e using a new sysctl node) or stay like that.

Also, I profited of this changes to patch sys/modules/linprocfs in order to
display the address sizes values in the output of /usr/compat/linux/proc/cpuinfo
like it's done in Linux procfs [2].

I filled a pr referenced as amd64/178357 [3]. My kernel was rebuilt without any
problems in r250287 and it works as expected.

You could find details here [4] and patch in attachment.

Regards

[1] http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/processor-identification-cpuid-instruction-note.pdf
[2] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/cpu/proc.c#n113
[3] http://www.freebsd.org/cgi/query-pr.cgi?pr=178357
[4] http://people.freebsd.org/~sbz/cpu/

--
Sofian Brabez
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