Re: [tip:x86/boot] x86/mm: Enable KASLR for physical mapping memory regions

[Ingo Molnar]

* Borislav Petkov <bp@xxxxxxxxx> wrote:

> On Tue, Aug 16, 2016 at 08:31:28PM -0400, Brian Gerst wrote:
> > These fixes work for my system.
> 
> Thanks Brian.
> 
> Ingo, please queue this into x86/urgent.
> 
> Thanks!
> 
> ---
> From: Borislav Petkov <bp@xxxxxxx>
> Date: Wed, 17 Aug 2016 08:23:29 +0200
> Subject: [PATCH] x86/microcode/AMD: Fix initrd loading with CONFIG_RANDOMIZE_MEMORY=y
> 
> Similar to
> 
>   efaad554b4ff ("x86/microcode/intel: Fix initrd loading with CONFIG_RANDOMIZE_MEMORY=y")
> 
> fix microcode loading from the initrd on AMD by adding the randomization
> offset to the microcode patch container within the initrd.
> 
> Reported-and-tested-by: Brian Gerst <brgerst@xxxxxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/microcode/amd.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
> index 27a0228c9cae..f43b774d0684 100644
> --- a/arch/x86/kernel/cpu/microcode/amd.c
> +++ b/arch/x86/kernel/cpu/microcode/amd.c
> @@ -355,6 +355,7 @@ void load_ucode_amd_ap(void)
>  	unsigned int cpu = smp_processor_id();
>  	struct equiv_cpu_entry *eq;
>  	struct microcode_amd *mc;
> +	u8 *cont;
>  	u32 rev, eax;
>  	u16 eq_id;
>  
> @@ -371,8 +372,14 @@ void load_ucode_amd_ap(void)
>  	if (check_current_patch_level(&rev, false))
>  		return;
>  
> +	cont = container;
> +
> +#ifdef CONFIG_RANDOMIZE_MEMORY
> +	cont += PAGE_OFFSET - __PAGE_OFFSET_BASE;
> +#endif
> +
>  	eax = cpuid_eax(0x00000001);
> -	eq  = (struct equiv_cpu_entry *)(container + CONTAINER_HDR_SZ);
> +	eq  = (struct equiv_cpu_entry *)(cont + CONTAINER_HDR_SZ);
>  
>  	eq_id = find_equiv_id(eq, eax);
>  	if (!eq_id)
> @@ -434,6 +441,10 @@ int __init save_microcode_in_initrd_amd(void)
>  	else
>  		container = cont_va;
>  
> +#ifdef CONFIG_RANDOMIZE_MEMORY
> +	container += PAGE_OFFSET - __PAGE_OFFSET_BASE;
> +#endif
> +
>  	eax   = cpuid_eax(0x00000001);
>  	eax   = ((eax >> 8) & 0xf) + ((eax >> 20) & 0xff);

So I really hate this pattern, and we already have it in 
arch/x86/kernel/cpu/microcode/intel.c as well:

                start += PAGE_OFFSET - __PAGE_OFFSET_BASE;

and note that it's not #ifdefed there - I think it's safe to leave out the #ifdef?

Thanks,

	Ingo