Re: [Qemu-devel] sparc: crash when using initrd > 5M

[Corentin Labbe]

On Tue, Feb 05, 2019 at 04:45:16PM +0000, Mark Cave-Ayland wrote:
> On 05/02/2019 09:11, Corentin Labbe wrote:
> 
> > On Fri, Feb 01, 2019 at 02:15:15PM +0000, Mark Cave-Ayland wrote:
> >> On 18/01/2019 13:33, Mark Cave-Ayland wrote:
> >>
> >>> On 03/01/2019 15:48, Corentin Labbe wrote:
> >>>
> >>>> Hello
> >>>>
> >>>> When using an initrd > 5M, I hit the following kernel crash:
> >>>> qemu-system-sparc -kernel vmlinux -initrd rootfs.cpio.gz -nographic
> >>>> Configuration device id QEMU version 1 machine id 32
> >>>> Probing SBus slot 0 offset 0
> >>>> Probing SBus slot 1 offset 0
> >>>> Probing SBus slot 2 offset 0
> >>>> Probing SBus slot 3 offset 0
> >>>> Probing SBus slot 4 offset 0
> >>>> Probing SBus slot 5 offset 0
> >>>> Invalid FCode start byte
> >>>> CPUs: 1 x FMI,MB86904
> >>>> UUID: 00000000-0000-0000-0000-000000000000
> >>>> Welcome to OpenBIOS v1.1 built on Oct 5 2018 08:20
> >>>>   Type 'help' for detailed information
> >>>> [sparc] Kernel already loaded
> >>>> switching to new context:
> >>>> PROMLIB: obio_ranges 1
> >>>> [    0.000000] PROMLIB: Sun Boot Prom Version 3 Revision 2
> >>>> [    0.000000] Linux version 4.20.0-next-20190102+ (address@hidden) (gcc 
> >>>> version 7.3.0 (Gentoo 7.3.0-r3 p1.4)) #148 Thu Jan 3 16:17:08 CET 2019
> >>>> [    0.000000] printk: bootconsole [earlyprom0] enabled
> >>>> [    0.000000] ARCH: SUN4M
> >>>> [    0.000000] TYPE: SPARCstation 5
> >>>> [    0.000000] Ethernet address: 52:54:00:12:34:56
> >>>> [    0.000000] Unable to handle kernel NULL pointer dereference
> >>>> [    0.000000] tsk->{mm,active_mm}->context = ffffffff
> >>>> [    0.000000] tsk->{mm,active_mm}->pgd = 00000000
> >>>> [    0.000000]               \|/ ____ \|/
> >>>> [    0.000000]               "@'/ ,. \`@"
> >>>> [    0.000000]               /_| \__/ |_\
> >>>> [    0.000000]                  \__U_/
> >>>> [    0.000000] swapper(0): Oops [#1]
> >>>> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 
> >>>> 4.20.0-next-20190102+ #148
> >>>> [    0.000000] PSR: 04001fc0 PC: f0010ef0 NPC: f0010ef4 Y: 00000000    
> >>>> Not tainted
> >>>> [    0.000000] PC: <do_sparc_fault+0x158/0x404>
> >>>> [    0.000000] %G: 0000000a 000003c4  f05ece08 f05ecc00  00000000 
> >>>> 00e00000  f05d4000 00000001
> >>>> [    0.000000] %O: 00000000 00e00000  00800000 00e00000  00000000 
> >>>> 00000002  f05d5bb8 f00bba58
> >>>> [    0.000000] RPC: <memblock_reserve+0x38/0x68>
> >>>> [    0.000000] %L: 00000040 f05dfaf8  f05d5c68 00000001  0003ffff 
> >>>> 006951e0  f05ed014 f0674ab4
> >>>> [    0.000000] %I: f05d5c80 00000000  00000002 f1000000  ffffffff 
> >>>> 00000000  f05d5c20 f0007fd8
> >>>> [    0.000000] Disabling lock debugging due to kernel taint
> >>>> [    0.000000] Caller[f0007fd8]: srmmu_fault+0x58/0x68
> >>>> [    0.000000] Caller[f0618598]: memblock_alloc_try_nid+0xb8/0xc8
> >>>> [    0.000000] Caller[f0611094]: srmmu_paging_init+0x174/0xaf8
> >>>> [    0.000000] Caller[f06106a8]: paging_init+0x4/0x24
> >>>> [    0.000000] Caller[f060e4f0]: setup_arch+0x3e8/0x480
> >>>> [    0.000000] Caller[f060ab50]: start_kernel+0x48/0x460
> >>>> [    0.000000] Caller[f060a43c]: continue_boot+0x324/0x334
> >>>> [    0.000000] Caller[00000000]:   (null)
> >>>> [    0.000000] Instruction DUMP:
> >>>> [    0.000000]  c800a024 
> >>>> [    0.000000]  83286002 
> >>>> [    0.000000]  073c17b3 
> >>>> [    0.000000] <c4010001>
> >>>> [    0.000000]  c600e22c 
> >>>> [    0.000000]  8a08a003 
> >>>> [    0.000000]  80a16001 
> >>>> [    0.000000]  0280003b 
> >>>> [    0.000000]  c600c001 
> >>>> [    0.000000] 
> >>>> [    0.000000] Kernel panic - not syncing: Attempted to kill the idle 
> >>>> task!
> >>>> [    0.000000] Press Stop-A (L1-A) from sun keyboard or send break
> >>>> [    0.000000] twice on console to return to the boot prom
> >>>> [    0.000000] ---[ end Kernel panic - not syncing: Attempted to kill 
> >>>> the idle task! ]---
> >>>> qemu-system-sparc: terminating on signal 15 from pid 13043 (killall)
> >>>>
> >>>> The NULL ptr dereference is done by memset() in srmmu_nocache_init() and 
> >>>> memblock_alloc_try_nid().
> >>>> If I comment both memset, the boot pass
> >>>>
> >>>> But since nothing explain the NULL ptr deref in memset(), I suspect 
> >>>> something is overriden by the initrd
> >>>
> >>> Sorry about the delay in replying to this, I haven't been too well 
> >>> recently.
> >>>
> >>> Looking at the code I suspect the problem is that when loading a kernel 
> >>> directly,
> >>> OpenBIOS isn't adding the kernel/initrd memory ranges to the DT 
> >>> properties, and so
> >>> the kernel doesn't recreate its own mapping on boot.
> >>>
> >>> It shouldn't be too hard to make this happen, let me take and look and 
> >>> see how
> >>> difficult this would be.
> >>
> >> I think I now have a fix for this, with changes needed in both QEMU and 
> >> OpenBIOS.
> >>
> >> Firstly you'll need to apply the QEMU patch from
> >> https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg06635.html and 
> >> then you'll
> >> need an updated OpenBIOS.
> >>
> >> I've uploaded a pre-compiled openbios-sparc32 with the patches from
> >> https://mail.coreboot.org/hyperkitty/list/address@hidden/thread/E6IMJNUFRF7W6ALWSYBOOCEYLBFXXQEN/
> >> to https://www.ilande.co.uk/tmp/qemu/openbios-sparc32-initrdfix for 
> >> testing.
> >>
> >> Please can you test and let me know if this solves the issue? If so, I'll 
> >> see if I
> >> can get them merged in time for the upcoming QEMU 4.0 release.
> >>
> > 
> > Hello
> > 
> > Sorry even with the patch I still hit the issue.
> > 
> > I have added some debug and at least qemu set initrd_size correctly now.
> > 
> > I have tried to compile openbios-sparc32 for debugging but fail with
> > arch/sparc32/context.c:116:5: error: PIC register clobbered by 'l7' in 'asm'
> >      asm __volatile__ ("\n\tcall __switch_context"
> >      ^~~
> > make[1]: *** [rules.mak:219: target/arch/sparc32/context.o] Error 1
> > (gcc 7.2 and gc 6.4 with binutils 2.30)
> 
> Hmmm. One other thing I've noticed is that newer kernels tend need a minimum 
> of 256M
> RAM to start up - does it work if you add -m 256 to your command line?
> 
> 

I have already set 256M of RAM. (and tried 512)

Regards