This is to track dynamic amount of stack growth for aarch64, so it is
possible to print out offensive functions that may consume too much stack.
For example,

0xffff2000084d1270 try_to_unmap_one [vmlinux]:		Dynamic (0xcf0)
0xffff200008538358 migrate_page_move_mapping [vmlinux]:	Dynamic (0xc60)
0xffff2000081276c8 copy_process.isra.2 [vmlinux]:	Dynamic (0xb20)
0xffff200008424958 show_free_areas [vmlinux]:		Dynamic (0xb40)
0xffff200008545178 __split_huge_pmd_locked [vmlinux]:	Dynamic (0xb30)
0xffff200008555120 collapse_shmem [vmlinux]:		Dynamic (0xbc0)
0xffff20000862e0d0 do_direct_IO [vmlinux]:		Dynamic (0xb70)
0xffff200008cc0aa0 md_do_sync [vmlinux]:		Dynamic (0xb90)

Link: http://lkml.kernel.org/r/20181208025143.39363-1-cai@lca.pwSigned-off-by: Qian Cai <cai@lca.pw>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>