[kernel-hardening] Re: [PATCH] x86/power/64: Do not refer to __PAGE_OFFSET from assembly code

[Pavel Machek <pavel@denx.de>]

On Wed 2016-08-03 01:19:26, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> When CONFIG_RANDOMIZE_MEMORY is set on x86-64, __PAGE_OFFSET becomes
> a variable and using it as a symbol in the image memory restoration
> assembly code under core_restore_code is not correct any more.

On a related note... we should really have page_offset variable in
such case, and use that -- having __FOO_BAR not being a constant is
ugly/confusing/dangerous.

> To avoid that problem, modify set_up_temporary_mappings() to compute
> the physical address of the temporary page tables and store it in
> temp_level4_pgt, so that the value of that variable is ready to be
> written into CR3.  Then, the assembly code doesn't have to worry
> about converting that value into a physical address and things work
> regardless of whether or not CONFIG_RANDOMIZE_MEMORY is set.
> 
> Reported-and-tested-by: Thomas Garnier <thgarnie@google.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Acked-by: Pavel Machek <pavel@ucw.cz>

Is similar patch needed for i386?

Best regards,
								Pavel


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