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

[Dave Hansen]

On 04/18/2018 05:11 PM, Kees Cook wrote:
> 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.)

Sounds reasonable to me.  This does assume that there are no secrets
built into the kernel image, right?