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

[Dmitry Safonov]

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):

--->8---
diff --git a/criu/pie/parasite-vdso.c b/criu/pie/parasite-vdso.c
index 38da766804ab..614237492f2b 100644
--- a/criu/pie/parasite-vdso.c
+++ b/criu/pie/parasite-vdso.c
@@ -292,6 +292,10 @@ int vdso_proxify(struct vdso_maps *rt, bool
*added_proxy,
                return -1;
        }

+       /* Anonymous images don't have vdso in pages*.img */
+       if (opts.anonymize)
+               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.