Re: [PATCH bpf-next v2 5/5] x86: use register_text_tail_vm

["Edgecombe, Rick P" <rick.p.edgecombe@intel.com>]

On Mon, 2022-11-07 at 14:39 -0800, Song Liu wrote:
> Allocate 2MB pages up to round_up(_etext, 2MB), and register memory
> [round_up(_etext, 4kb), round_up(_etext, 2MB)] with
> register_text_tail_vm
> so that we can use this part of memory for dynamic kernel text (BPF
> programs, etc.).
> 
> Here is an example:
> 
> [root@eth50-1 ~]# grep _etext /proc/kallsyms
> ffffffff82202a08 T _etext
> 
> [root@eth50-1 ~]# grep bpf_prog_ /proc/kallsyms  | tail -n 3
> ffffffff8220f920 t
> bpf_prog_cc61a5364ac11d93_handle__sched_wakeup       [bpf]
> ffffffff8220fa28 t
> bpf_prog_cc61a5364ac11d93_handle__sched_wakeup_new   [bpf]
> ffffffff8220fad4 t
> bpf_prog_3bf73fa16f5e3d92_handle__sched_switch       [bpf]
> 
> [root@eth50-1 ~]#  grep 0xffffffff82200000
> /sys/kernel/debug/page_tables/kernel
> 0xffffffff82200000-0xffffffff82400000     2M     ro   PSE         x 
> pmd
> 
> ffffffff82200000-ffffffff82400000 is a 2MB page, serving kernel text,
> and
> bpf programs.
> 
> Signed-off-by: Song Liu <song@kernel.org>

Please update Documentation/x86/x86_64/mm.txt and teach places that
check if an address is text about it.