Debian SID kernel doesn't boot on PowerBook 3400c

[Christophe Leroy]

Le 07/08/2021 à 15:09, Stan Johnson a écrit :
> On 8/6/21 10:08 PM, Finn Thain wrote:
>>
>> On Fri, 6 Aug 2021, Stan Johnson wrote:
>>
>>> $ egrep '(CONFIG_PPC_KUAP|CONFIG_VMAP_STACK)' .config
>>> CONFIG_PPC_KUAP=y
>>> CONFIG_PPC_KUAP_DEBUG=y
>>> CONFIG_VMAP_STACK=y
>>> $ strings vmlinux | fgrep "Linux version"
>>> Linux version 5.13.0-pmac-00004-g63e3756d1bd ...
>>> $ cp vmlinux ../vmlinux-5.13.0-pmac-00004-g63e3756d1bd-1
>>>
>>> 1) PB 3400c
>>> vmlinux-5.13.0-pmac-00004-g63e3756d1bd-1
>>> Boots, no errors logging in at (text) fb console. Logging in via ssh and
>>> running "ls -Rail /usr/include" generated errors (and a hung ssh
>>> session). Once errors started, they repeated for almost every command.
>>> See pb3400c-63e3756d1bdf-1.txt.
>>>
>>> 2) Wallstreet
>>> vmlinux-5.13.0-pmac-00004-g63e3756d1bd-1
>>> X login failed, there were errors ("Oops: Kernel access of bad area",
>>> "Oops: Exception in kernel mode"). Logging in via SSH, there were no
>>> additional errors after running "ls -Rail /usr/include" -- the errors
>>> did not escalate as they did on the PB 3400.
>>> See Wallstreet-63e3756d1bdf-1.txt.
>>>
>> ...
>>> $ egrep '(CONFIG_PPC_KUAP|CONFIG_VMAP_STACK)' .config
>>> CONFIG_PPC_KUAP=y
>>> CONFIG_PPC_KUAP_DEBUG=y
>>> # CONFIG_VMAP_STACK is not set
>>> $ strings vmlinux | fgrep "Linux version"
>>> Linux version 5.13.0-pmac-00004-g63e3756d1bd ...
>>> $ cp vmlinux ../vmlinux-5.13.0-pmac-00004-g63e3756d1bd-2
>>>
>>> 3) PB 3400c
>>> vmlinux-5.13.0-pmac-00004-g63e3756d1bd-2
>>> Filesystem was corrupt from the previous test (probably from all the
>>> errors during shutdown). After fixing the filesystem:
>>> Boots, no errors logging in at (text) fb console. Logging in via ssh and
>>> running "ls -Rail /usr/include" generated a few errors. There didn't
>>> seem to be as many errors as in the previous test, there were a few
>>> errors during shutdown but the shutdown was otherwise normal.
>>> See pb3400c-63e3756d1bdf-2.txt.
>>>
>>> 4) Wallstreet
>>> vmlinux-5.13.0-pmac-00004-g63e3756d1bd-2
>>> X login worked, and there were no errors. There were no errors during
>>> ssh access.
>>> See Wallstreet-63e3756d1bdf-2.txt.
>>>
>>
>> Thanks for collecting these results, Stan. Do you think that the
>> successful result from test 4) could have been just chance?
> 
> No. I repeated Test 4 above two more times on the Wallstreet. After
> stomping on it as hard as I could, I didn't see any errors. I ran the
> following tests simultaneously, with no errors:
> 
> a) Ping flood the Wallstreet
> 862132 packets transmitted, 862117 packets received, 0.0% packet loss
> round-trip min/avg/max/stddev = 0.316/0.418/12.163/0.143 ms
> 
> b) "ls -Rail /usr" in an ssh window.
> 
> c) "find /usr/include -type f -exec sha1sum {} \;" in a second ssh window.
> 
> d) With a, b and c running, I logged in at the X console (slow but it
> worked). Load average was 7.0 as reported by uptime.
> 
> So the success seems to be repeatable (or at least the errors are so
> unlikely to happen that I'm not seeing anything).
> 
>>
>> It appears that the bug affecting the Powerbook 3400 is unaffected by
>> CONFIG_VMAP_STACK.
>>
>> Whereas the bug affecting the Powerbook G3 disappears when
>> CONFIG_VMAP_STACK is disabled (assuming the result from 4 is reliable).
>>
>> Either way, these results reiterate that "Oops: Kernel access of bad area,
>> sig: 11" was not entirely resolved by "powerpc/32s: Fix napping restore in
>> data storage interrupt (DSI)".
>>
> 
> That sounds right. Thanks for investigating this.
> 


Thanks a lot for your patience and for the tests.

I'm still having hard time understanding what the problem is.

Could you try the new change I pushed into the git repo ? It shouldn't have any effect, but I prefer 
to eliminate all possibilities. The documentation says that SRR1 upper bit are 0 on DSI and the code 
relies on that. But if the doc is wrong then that can explain the problem. So now I'm forcing it to 
0 regardless.

To get the change, you just have to do 'git pull -r' inside the directory where you checked out the 
sources and build.

Thanks again
Christophe