Debian SID kernel doesn't boot on PowerBook 3400c

[Finn Thain]

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?

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)".