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Date: Wed, 23 Jul 2008 03:18:20 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Alfred Perlstein <alfred@FreeBSD.org>
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Cc: Marcel Moolenaar <xcllnt@mac.com>, freebsd-arch@FreeBSD.org
Subject: Re: RFC: cross-libkvm/libthread_db/proc_service
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On Mon, 21 Jul 2008, Alfred Perlstein wrote:

> Isn't it a bit strange to export 64bit pointers to 32 bit userspace?

Only for pointers in kernel objects, and I think the proposed change
doesn't touch that.

kvm_read() doesn't use pointers for kernel addresses.  It uses unsigned
longs.  But even uintmax_t is not enough in general, since the application
uintmax_t might be too small to represent a kernel pointer.  The type
used shouldn't be fixed-width, but typedefed in an MD way like vm_offset_t.
vm_offset_t gives the correct integral type to use for (mapped) kernel
addresses and related compat_fewer_bit[s] type[s] are needed in userland.
It would probably be too hard to support the general case which requires
the compat types to be arrays or structs.

Bruce