[PATCH] powerpc: Don't overwrite flat device tree with kdump kernel

[Haren Myneni]

Kumar Gala wrote:

>
> On Feb 4, 2006, at 8:25 PM, Haren Myneni wrote:
>
>> Kumar Gala wrote:
>>
>>> On Feb 3, 2006, at 2:05 AM, Michael Ellerman wrote:
>>>
>>>
>>>> It's possible for prom_init to allocate the flat device tree  
>>>> inside  the
>>>> kdump crash kernel region. If this happens, when we load the  
>>>> kdump  kernel we
>>>> overwrite the flattened device tree, which is bad.
>>>>
>>>> We could make prom_init try and avoid allocating inside the  crash  
>>>> kernel
>>>> region, but then we run into issues if the crash kernel region  
>>>> uses  all the
>>>> space inside the RMO. The easiest solution is to move the flat   
>>>> device tree
>>>> once we're running in the kernel.
>>>>
>>>> Signed-off-by: Michael Ellerman <michael at ellerman.id.au>
>>>>
>>>
>>> Doesn't setup_32.c need a similar change?
>>>
>> At present kdump will not be supported on ppc32.
>> In case, kdump_move_device_tree() can be called at the beginning of  
>> unflatten_device_tree() to support both ppc32 and 64 instead of  
>> making changes in setup_64.c and setup_32.c.  The extern definition  
>> can be removed from asm-powerpc/prom.h and this function can be  static.
>>
>> Michael, what do you think if we have some printk to tell the user  
>> that device_tree is moved to new location. Because, the console  
>> messages from prom_init are saying about old addresses.
>
>
> What's the issue with kdump on ppc32?  One of the reasons we merged  
> ppc32 and ppc64 was to avoid such issues going forward?

Main issue is with the user level kexec-tools which does not have the 
kdump support for PPC32. One of the changes should be some cleanup/merge 
the way it happened in the kernel. At present, normal kexec support is 
included for gamecube/ppc32. Any help is appreciated.

Thanks
Haren

>
> - k
>
>>>> ---
>>>>
>>>> arch/powerpc/kernel/prom.c     |   27 +++++++++++++++++++++++++++
>>>> arch/powerpc/kernel/setup_64.c |    3 +++
>>>> include/asm-powerpc/prom.h     |    2 ++
>>>> 3 files changed, 32 insertions(+)
>>>>
>>>> Index: kdump/arch/powerpc/kernel/prom.c
>>>> ===================================================================
>>>> --- kdump.orig/arch/powerpc/kernel/prom.c
>>>> +++ kdump/arch/powerpc/kernel/prom.c
>>>> @@ -1913,3 +1913,30 @@ int prom_update_property(struct device_n
>>>>
>>>>     return 0;
>>>> }
>>>> +
>>>> +#ifdef CONFIG_KEXEC
>>>> +/* We may have allocated the flat device tree inside the crash   
>>>> kernel region
>>>> + * in prom_init. If so we need to move it out into regular  
>>>> memory. */
>>>> +void kdump_move_device_tree(void)
>>>> +{
>>>> +    unsigned long start, end;
>>>> +    struct boot_param_header *new;
>>>> +
>>>> +    start = __pa((unsigned long)initial_boot_params);
>>>> +    end = start + initial_boot_params->totalsize;
>>>> +
>>>> +    if (end < crashk_res.start || start > crashk_res.end)
>>>> +        return;
>>>> +
>>>> +    new = (struct boot_param_header*)
>>>> +        __va(lmb_alloc(initial_boot_params->totalsize, PAGE_SIZE));
>>>> +
>>>> +    memcpy(new, initial_boot_params, initial_boot_params->totalsize);
>>>> +
>>>> +    initial_boot_params = new;
>>>> +
>>>> +    DBG("Flat device tree blob moved to %p\n", initial_boot_params);
>>>> +
>>>> +    /* XXX should we unreserve the old DT? */
>>>> +}
>>>> +#endif /* CONFIG_KEXEC */
>>>> Index: kdump/arch/powerpc/kernel/setup_64.c
>>>> ===================================================================
>>>> --- kdump.orig/arch/powerpc/kernel/setup_64.c
>>>> +++ kdump/arch/powerpc/kernel/setup_64.c
>>>> @@ -398,6 +398,9 @@ void __init setup_system(void)
>>>> {
>>>>     DBG(" -> setup_system()\n");
>>>>
>>>> +#ifdef CONFIG_KEXEC
>>>> +    kdump_move_device_tree();
>>>> +#endif
>>>>     /*
>>>>      * Unflatten the device-tree passed by prom_init or kexec
>>>>      */
>>>> Index: kdump/include/asm-powerpc/prom.h
>>>> ===================================================================
>>>> --- kdump.orig/include/asm-powerpc/prom.h
>>>> +++ kdump/include/asm-powerpc/prom.h
>>>> @@ -222,5 +222,7 @@ extern int of_address_to_resource(struct
>>>> extern int of_pci_address_to_resource(struct device_node *dev,  
>>>> int  bar,
>>>>                       struct resource *r);
>>>>
>>>> +extern void kdump_move_device_tree(void);
>>>> +
>>>> #endif /* __KERNEL__ */
>>>> #endif /* _POWERPC_PROM_H */
>>>> _______________________________________________
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>>>> Linuxppc64-dev at ozlabs.org
>>>> https://ozlabs.org/mailman/listinfo/linuxppc64-dev
>>>>
>>>
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>>>
>
>