Re: [PATCH 1/5] x86_64: fix kasan shadow region page tables

Ingo Molnar
2015-07-01T09:08:18Z

* Andrey Ryabinin <a.ryabinin@samsung.com> wrote:

> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 5a46681..f129a9a 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -161,11 +161,12 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
> /* Kill off the identity-map trampoline */
> reset_early_page_tables();
>
> - kasan_map_early_shadow(early_level4_pgt);
> -
> - /* clear bss before set_intr_gate with early_idt_handler */
> clear_bss();
>
> + clear_page(init_level4_pgt);
> +
> + kasan_early_init();
> +
> for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
> set_intr_gate(i, early_idt_handler_array[i]);
> load_idt((const struct desc_ptr *)&idt_descr);
> @@ -177,12 +178,9 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
> */
> load_ucode_bsp();
>
> - clear_page(init_level4_pgt);
> /* set init_level4_pgt kernel high mapping*/
> init_level4_pgt[511] = early_level4_pgt[511];
>
> - kasan_map_early_shadow(init_level4_pgt);
> -
> x86_64_start_reservations(real_mode_data);
> }
>

So this changes generic code (moves the clear_page(init_level4_pgt) call), but the
changelog claims it's a KASAN-specific change.

Please split this into two patches: the first one does the generic change, the
second one the KASAN specific one.

That way if anything breaks in the generic code due to this change we have a
simple commit to bisect to.

Thanks,

Ingo