Re: Deprecate the ppc405 boards in QEMU?

[Christophe Leroy]

Le 19/10/2021 à 16:56, BALATON Zoltan a écrit :
> On Tue, 19 Oct 2021, Christophe Leroy wrote:
> > Le 19/10/2021 à 15:44, Christophe Leroy a écrit :
> > > There is something:
> > >
> > > => bootm 0
> > > Wrong Image Format for bootm command
> > > ERROR: can't get kernel image!
> > >
> > > => md 0
> > > 00000000: 00000000 b497aae1 616e9207 003227a4    '..V....an...2'.
> > > 00000010: 00000000 00000000 ee36255f 05070201    .........6%_....
> > > 00000020: 4c696e75 782d352e 31352e30 2d726335    Linux-5.15.0-rc5
> > > 00000030: 2d303232 32342d67 61336330 30376164    -02224-ga3c007ad
> > > 00000040: 1f8b0800 00000000 0203ec5c 0f7013e7    ...........\.p..
> > >
> > > => mw.l 0 0x27051956
> > >
> > > => bootm 0
> > > ## Booting kernel from Legacy Image at 00000000 ...
> > >     Image Name:   Linux-5.15.0-rc5-02224-ga3c007ad
> > >     Image Type:   PowerPC Linux Kernel Image (gzip compressed)
> > >     Data Size:    3286948 Bytes = 3.1 MiB
> > >     Load Address: 00000000
> > >     Entry Point:  00000000
> > >     Verifying Checksum ... Bad Data CRC
> > > ERROR: can't get kernel image!
> > >
> > >
> > > So we have something but it seems it gets overwritten by stuff.
> > >
> > > Anyway loading a uImage at 0 is just bad because it is a gzipped 
> > > image that should get gunzipped at address 0.
> > >
> > > Or should we just copy the raw kernel at 0 and jump to the entry 
> > > point ? But then we also need a device tree somewhere.
> >
> > If I change KERNEL_LOAD_ADDR to 0x1000000, I can bootm at that 
> > address, and it seems it properly decompress the kernel:
> >
> > => bootm 0x1000000
> > ## Booting kernel from Legacy Image at 01000000 ...
> >   Image Name:   Linux-5.15.0-rc5-02224-ga3c007ad
> >   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
> >   Data Size:    3296789 Bytes = 3.1 MiB
> >   Load Address: 00000000
> >   Entry Point:  00000000
> >   Verifying Checksum ... OK
> >   Uncompressing Kernel Image ... OK
> >
> >
> > And it initialises the MMU properly.
> >
> > Then it gets stuck because there is no devicetree.
> >
> > (gdb) bt
> > #0  0xc00094cc in udelay ()
> > #1  0xc0025d34 in panic ()
> > #2  0xc06415a0 in early_init_devtree ()
> > #3  0xc0641da8 in machine_init ()
> > #4  0xc0002200 in start_here ()
>
> Maybe you need to embed a dtb in your kernel if that's possible somehow? 
> Or QEMU has a -dtb option that sets machine->dtb but you need board code 
> to do something with it. See how it's done in other boards like 
> virtex_ml507 and sam460ex. But maybe you'd be better off not using 
> -kernel option as it seems to not really working for these 405 boards 
> but load and start the kernel from u-boot. Not sure what device does 
> u-boot support but QEMU can emulate usb-storage, network, different 
> disks so something might work with u-boot if this board has any 
> peripherals. If it doesn't emulate any peripherals what do you expect to 
> do with the kernel once it boots?

I should be able to build a multi-FIT image that embeds the kernel and 
the device tree.

I don't know about the peripherals, what I need it a kernel that is able 
to boot and run some user exe. I'm working on low level functionnalities 
like VMAP_STACK, STRICT_KERNEL_RWX, Userspace protection, etc ... I want 
to be able to check that after some modifications the kernel can still 
boot on every CPU sub-family, and I need to run LKDTM tests.

For this a kernel + initrd is enough.

Thanks
Christophe