minidumps: Always use 64-bit physical addresses for dump_avail[]

[markj]

Summary

We recently started including dump_avail[] in minidumps. This is an
array of vm_paddr_t ranges. libkvm walks the array assuming that
sizeof(vm_paddr_t) is equal to the platform "word size", but that's not
correct on a couple of platforms, namely i386 and mips (sometimes).

Fix the problem by always dumping 64-bit addresses. On platforms where
vm_paddr_t is 32 bits wide, namely arm and mips (sometimes), translate
dump_avail[] to an array of uint64_t ranges. With this change, "word
size" is unused, so we can simplify libkvm ever so slightly.

This is a no-op on 64-bit platforms. I noticed it when trying to open
an i386 minidump.

Test Plan

This lets me open i386 minidumps. Before kgdb would crash with an assertion failure.

[kib]

sys/mips/mips/minidump_machdep.c

260 ↗

(On Diff #79148)

But then why not use uint64_t for dump_avail[] itself, on all arches ? For i386 it is required due to PAE, and for ppc I suspect we might have grow support for similar feature recently. So this leaves out arm and 32bit mips but it should be fine for them.

[markj]

sys/mips/mips/minidump_machdep.c

260 ↗

(On Diff #79148)

dump_avail[] is initialized from phys_avail[] so it feels a bit strange to use different types for them. I don't think there's any real problem with that though.

OTOH, this hack is fairly localized and only required on somewhat "legacy" platforms. Note that the problem could be fixed entirely in libkvm, it just seemed preferable to avoid the extra complexity.

[markj]

sys/mips/mips/minidump_machdep.c

260 ↗

(On Diff #79148)

Do you still think that dump_avail[] should use uint64_t, rather than converting the array on the fly? If so I'll rework the patch.

[alc]

sys/mips/mips/minidump_machdep.c

262–265 ↗

(On Diff #79148)

Is this really supposed to be using phys_avail[]? I would have expected to see dump_avail[] here.

[markj]

sys/mips/mips/minidump_machdep.c

262–265 ↗

(On Diff #79148)

Indeed, I'm not sure how I made that mistake. :(

[markj]

Fix mips minidump.