Re: [PATCH v10 1/5] kasan: support backing vmalloc space with real shadow memory
From: Uladzislau Rezki <urezki@gmail.com>
Date: 2019-10-30 14:30:04
Also in:
linux-mm, lkml
Hello, Daniel
quoted hunk ↗ jump to hunk
@@ -1294,14 +1299,19 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) spin_lock(&free_vmap_area_lock); llist_for_each_entry_safe(va, n_va, valist, purge_list) { unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT; + unsigned long orig_start = va->va_start; + unsigned long orig_end = va->va_end; /* * Finally insert or merge lazily-freed area. It is * detached and there is no need to "unlink" it from * anything. */ - merge_or_add_vmap_area(va, - &free_vmap_area_root, &free_vmap_area_list); + va = merge_or_add_vmap_area(va, &free_vmap_area_root, + &free_vmap_area_list); + + kasan_release_vmalloc(orig_start, orig_end, + va->va_start, va->va_end);
I have some questions here. I have not analyzed kasan_releace_vmalloc()
logic in detail, sorry for that if i miss something. __purge_vmap_area_lazy()
deals with big address space, so not only vmalloc addresses it frees here,
basically it can be any, starting from 1 until ULONG_MAX, whereas vmalloc
space spans from VMALLOC_START - VMALLOC_END:
1) Should it be checked that vmalloc only address is freed or you handle
it somewhere else?
if (is_vmalloc_addr(va->va_start))
kasan_release_vmalloc(...)
2) Have you run any bencmarking just to see how much overhead it adds?
I am asking, because probably it make sense to add those figures to the
backlog(commit message). For example you can run:
<snip>
sudo ./test_vmalloc.sh performance
and
sudo ./test_vmalloc.sh sequential_test_order=1
<snip>
Thanks!
--
Vlad Rezki