Re: [RFC][PATCH 00/24] x86/pti: Defer CR3 switch to C code

[Dave Hansen <dave.hansen@intel.com>]

On 11/9/20 6:44 AM, Alexandre Chartre wrote:
>  - map more syscall, interrupt and exception entry code into the user
>    page-table (map all noinstr code);

This seems like the thing we'd want to tag explicitly rather than make
it implicit with 'noinstr' code.  Worst-case, shouldn't this be:

#define __entry_func	noinstr

or something?

I'd also like to see a lot more discussion about what the rules are for
the C code and the compiler.  We can't, for instance, do a normal
printk() in this entry functions.  Should we stick them in a special
section and have objtool look for suspect patterns or references?

I'm most worried about things like this:

	if (something_weird)
		pr_warn("this will oops the kernel\n");