Date: Tue, 16 Sep 2014 21:28:49 -0700 From: Mark Millard <markmi@dsl-only.net> To: Justin Hibbits <chmeeedalf@gmail.com> Cc: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: PowerMac G5 boot hangups before Copyright notice: "Stopped at 0: illegal instruction 0" [10.1-BETA1 example] Message-ID: <6D729F43-662A-429E-9503-0148EC3250B1@dsl-only.net> In-Reply-To: <CAHSQbTBXxrgXQdNeCs=C5wJaT_bmh9FU836O6VnJDbJuqCUujw@mail.gmail.com> References: <1118046C-0FF7-49FC-82DA-DB9A7A310991@dsl-only.net> <2ED3DB50-B985-4382-8FF2-3B44E7E65453@dsl-only.net> <CAHSQbTBXxrgXQdNeCs=C5wJaT_bmh9FU836O6VnJDbJuqCUujw@mail.gmail.com>
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In part I sent directly to you because of a past exchange (July-27) = where you had written: > Nathan and I both speculate that it's > dropping into Open Firmware (we make extensive use of OFW), and then > messing something up, taking a page fault or something. The specific text that I report and its uniformity when it is produced = seems to add a little information beyond a speculated "page fault or = something" and so might eventually help a little. As I understand the = text it is reporting execution reaching address zero without any prior = un-handled exceptions or other such that would stop it. A corrupted = stack (pointer) so a bad return address or some such? I'd guess there = are no explicit jumps to address zero so I expect that indirection is = likely involved, with the content for the indirection messed up. I really wish that I had a logic analyzer configuration for this. I've = not found a way to make the failing context visible so far and the extra = way of looking at things might have helped. =3D=3D=3D Mark Millard markmi@dsl-only.net On Sep 16, 2014, at 8:28 PM, Justin Hibbits <chmeeedalf@gmail.com> = wrote: Hi mark, I see this on my G5, and I think it's due to the amount of RAM in the = machine. More than 4gb seems to confuse open firmware when called by = FreeBSD. There is some effort to remove the need of the callbacks but = thus far it's not far along. The good news is that after it boots it's = solid except when switching vtys, buy earlier this year or last year I = added a sysctl hack to disable the call into open firmware on vty switch = (don't recall offhand and not at my computer right now, but if you grep = the sysctl output for reset and ofw you can find it). -Justin On Sep 16, 2014 8:01 PM, "Mark Millard" <markmi@dsl-only.net> wrote: I've now spent time with rebooting and power-off/power-on for all 3 = PowerMac G5's (one PowerMac7,2 and two PowerMac11,2's) and all 3 get the > GDB: no debug ports present > KDB: debugger backends: DDB > KDB: current backend: DDB > [ thread pid -1 tid 1006665719 ] > Stopped at 0: illegal instruction 0 > db> when they fail just before the Copyright notice would normally be = displayed. None fail any earlier. At that spot none have failed any = other way. It is the same SSD in all 3. (Happens with other SSD's as = well.) Overall there is a mix of Radeon and NVIDIA display boards. = Besides the SSD use and RAM upgrades the rest is stock equipment. scons = used, not vt. (I've yet to try vt.) Seeing a failure after the Copyright notice as been fairly rare in all = my experiments from when I started last April or so. The ones that I've = noted had Data Storage Interrupt reported. So far no examples of the = above have been reported after the Copyright notice. So I'd guess that = they are separate issues. Of course it seems that only in the last few = days would I have seen the above sort of thing if it did happen after = the Copyright notice: The prior history does not count for judgements = about that. =3D=3D=3D Mark Millard markmi at dsl-only.net On Sep 16, 2014, at 8:15 AM, Mark Millard <markmi@dsl-only.net> wrote: Using 10.1-BETA1 I added "options DDB" and "options GDB" to powerpc64's = GENERIC64. (I also used WITH_DEBUG_FILES=3D, WITHOUT_CLANG=3D, and = WITH_DEBUG=3D in /etc/make.conf.) So buildworld, kernel was basically = just set up to have more of a debugging context around (including for = any ports builds). The result was new information about the PowerMac G5 boot hangups: The = screen is no longer blank when the G5 is hung up without there being a = Copyright notice yet. It says... > GDB: no debug ports present > KDB: debugger backends: DDB > KDB: current backend: DDB > [ thread pid -1 tid 1006665719 ] > Stopped at 0: illegal instruction 0 > db> (I had no ability to input at that point.) Normally the Copyright notice = would have displayed instead of "[...]" and what follows. (I do not = claim to have all the spacing, capitalization, and such correct above.) That text is constant from hang to hang when it hangs just before it = would normally output the Copyright notice: The numbers do not vary, = much less the other text. It has never failed until after the two KDB = messages are present. So far I've only tested one PowerMac G5, booting = over and over for a few hours. (I do not claim to be set up for remote kernel debugging. I just decided = to let GDB go along for the ride when I added DDB.) =3D=3D=3D Mark Millard markmi at dsl-only.net
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