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

[Kumar Gala]

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?

- 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 */
>>> _______________________________________________
>>> Linuxppc64-dev mailing list
>>> Linuxppc64-dev at ozlabs.org
>>> https://ozlabs.org/mailman/listinfo/linuxppc64-dev
>>>
>>
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