[CRIU] Restoring images with page-*.img anonymized

[Dmitry Safonov]

On 9/27/19 2:41 PM, Dmitry Safonov wrote:
> On 9/27/19 8:45 AM, Cyrill Gorcunov wrote:
>> On Thu, Sep 26, 2019 at 10:48:24PM +0000, Pavel Emelianov wrote:
>>> On 26.09.2019 18:37, Harshavardhan Unnibhavi wrote:
>>>> Hi,
>>>>
>>>> I am trying to restore images with pages*.img removed. When restore calls
>>>> vdso_proxify there is a problem with the ELF headers and their associated
>>>> addresses as they are not available. What should I do?
>>>
>>> Cyrill, Dima, would you please help us on this. Briefly -- we want to
>>> "emulate" the restoration from images with pages*.img files removed and
>>> we hit this:
>>>
>>> vdso: Parsing at 0x7ffca6198000 0x7ffca619a000
>>> vdso: PT_LOAD p_vaddr: 0x0
>>> vdso: DT_HASH: 0x120
>>> vdso: DT_STRTAB: 0x298
>>> vdso: DT_SYMTAB: 0x1a8
>>> vdso: DT_STRSZ: 0x5e
>>> vdso: DT_SYMENT: 0x18
>>>   vdso: nbucket 0x3 nchain 0xa bucket 0x7ffca6198128 chain 0x7ffca6198134
>>> vdso: image [vdso] 0x7ffca6198000-0x7ffca619a000 [vvar] 0x7ffca6195000-0x7ffca6198000
>>> vdso: Runtime vdso/vvar matches dumpee, remap inplace
>>> vdso: Remap rt-vdso 0x2c000 -> 0x7ffca6198000
>>> vdso: Remap rt-vvar 0x29000 -> 0x7ffca6195000
>>> vdso: Using gettimeofday() on vdso at 0x7ffca6198d40
>>>
>>> apparently, the parsed info is taken from pages images which are missing.
>>> Does this parsing affects anything beyond the memory contents, or can we
>>> just skip the whole parse code for our purposes?
>>
>> I think when you're dropping content of pages you should not modify vdso page
>> but leave it as is. Don't you?
> 
> Either this or hack it under anonimization, something like this
> (completely untested):

[..]
And a little self-correction:

--->8---

diff --git a/criu/pie/parasite-vdso.c b/criu/pie/parasite-vdso.c
index 38da766804ab..3e48013b9e63 100644
--- a/criu/pie/parasite-vdso.c
+++ b/criu/pie/parasite-vdso.c
@@ -292,6 +292,12 @@ int vdso_proxify(struct vdso_maps *rt, bool
*added_proxy,
                return -1;
        }

+       /* Anonymous images don't have vdso in pages*.img */
+       if (opts.anonymize) {
+               *added_proxy = false;
+               return remap_rt_vdso(vma_vdso, vma_vvar, rt);
+       }
+
        /*
         * vDSO mark overwrites Elf program header of proxy vDSO thus
         * it must never ever be greater in size.