Subject: Re: KASAN debug kernel fails to boot at early stage when CONFIG_SMP=y is set (kernel 6.5-rc5, PowerMac G4 3,6)

From: Michael Ellerman <[email-masked]>
Date: Fri, 18 Aug 2023 09:13:21 +1000

Erhard Furtner <[email-masked]> writes:
> On Wed, 16 Aug 2023 15:56:26 +0000
> Christophe Leroy <[email-masked]> wrote:
>
>> Not sure this is the reason of the crash. Just that it disables bootx 
>> console here and doesn't re-enable any console before the crash.
>> 
>> Could you move the call to btext_unmap() after the call to 
>> memblock_set_current_limit(lowmem_end_addr); at the end of function 
>> MMU_init()
>> 
>> And redo the test, still with my patch applied for the additional pr_infos.
>
> I moved btext_unmap() as you suggested and the order of functions displayed changed accordingly. Now the freeze happens later but still after the 1st call to btext_unmap():
>
> [    0.000000] printk: bootconsole [udbg0] enabled
> [    0.000000] Total memory = 2048MB; using 4096kB for hash table
> [    0.000000] mapin_ram:125
> [    0.000000] mmu_mapin_ram:169 0 30000000 1400000 2000000
> [    0.000000] __mmu_mapin_ram:146 0 1400000
> [    0.000000] __mmu_mapin_ram:155 1400000
> [    0.000000] __mmu_mapin_ram:146 1400000 30000000
> [    0.000000] __mmu_mapin_ram:155 20000000
> [    0.000000] __mapin_ram_chunk:107 20000000 30000000
> [    0.000000] __mapin_ram_chunk:117
> [    0.000000] mapin_ram:134
> [    0.000000] kasan_mmu_init:129
> [    0.000000] kasan_mmu_init:132 0
> [    0.000000] kasan_mmu_init:137
> [    0.000000] setup_kuap:23
> [    0.000000] setup_kuap:25
> [    0.000000] setup_kuap:30
> [    0.000000] setup_kuap:35
> [    0.000000] Activating Kernel Userspace Access Protection
> [    0.000000] setup_kuap:40
> [    0.000000] Activating Kernel Userspace Execution Prevention
> [    0.000000] btext_unmap:129

Try just removing the call to btext_unmap() entirely and see how far it goes?

cheers