Re: [PATCH 11/11] x86/pti: leave kernel text global for !PCID

[Kees Cook]

On Fri, Apr 6, 2018 at 1:55 PM, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote:
> +/*
> + * For some configurations, map all of kernel text into the user page
> + * tables.  This reduces TLB misses, especially on non-PCID systems.
> + */
> +void pti_clone_kernel_text(void)
> +{
> +       unsigned long start = PFN_ALIGN(_text);
> +       unsigned long end = ALIGN((unsigned long)_end, PMD_PAGE_SIZE);

I think this is too much set global: _end is after data, bss, and brk,
and all kinds of other stuff that could hold secrets. I think this
should match what mark_rodata_ro() is doing and use
__end_rodata_hpage_align. (And on i386, this should be maybe _etext.)

-Kees

-- 
Kees Cook
Pixel Security