Date: Wed, 23 Jul 2008 09:15:06 -0700 From: Marcel Moolenaar <xcllnt@mac.com> To: Bruce Evans <brde@optusnet.com.au> Cc: Alfred Perlstein <alfred@FreeBSD.org>, freebsd-arch@FreeBSD.org Subject: Re: RFC: cross-libkvm/libthread_db/proc_service Message-ID: <71C01B9B-1E42-4D65-A3D7-F1DA14123524@mac.com> In-Reply-To: <20080723032109.W18257@delplex.bde.org> References: <34889018-8358-46AC-897E-32767FB84E14@mac.com> <200807211049.47579.jhb@freebsd.org> <Pine.GSO.4.64.0807211659450.2608@sea.ntplx.net> <20080721214104.GF76659@elvis.mu.org> <20080723025519.F18257@delplex.bde.org> <20080723032109.W18257@delplex.bde.org>
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On Jul 22, 2008, at 10:27 AM, Bruce Evans wrote: > On Wed, 23 Jul 2008, Bruce Evans wrote: > >> 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. > > Bah, I forgot the original mail which already says to use an integral > type named psaddr_t, and that, unfortunately, this seems to need being > 64 bits even on pure 32-bit systems in case you want to run an (not > quite pure) 32-bit application in compat32 mode on 64-bit system > without > recompiling. Actually, the intend is more generic (or more limited, depending on how you look at it): the ability to cross-debug any (say ia64) kernel on any other (say powerpc) machine. The integral needs to be constant and equal in width across all platforms. This means that an uint<#>_t is the best option. The largest we support is 64-bit. We can already build a cross gdb from the source tree, but without threading support (libthread_db and proc_service limitation). We can't build a cross kgdb from the source tree because of libkvm. Both I'd like to be able to do. FYI, -- Marcel Moolenaar xcllnt@mac.com
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