* Laurent Dufour <lduf...@linux.vnet.ibm.com> wrote: > > I argue we should use the right condition to clear vdso_base: if > > the vDSO gets at least partially unmapped. Otherwise there's > > little point in the whole patch: either correctly track whether > > the vDSO is OK, or don't ... > > That's a good option, but it may be hard to achieve in the case the > vDSO area has been splitted in multiple pieces. > > Not sure there is a right way to handle that, here this is a best > effort, allowing a process to unmap its vDSO and having the > sigreturn call done through the stack area (it has to make it > executable). > > Anyway I'll dig into that, assuming that the vdso_base pointer > should be clear if a part of the vDSO is moved or unmapped. The > patch will be larger since I'll have to get the vDSO size which is > private to the vdso.c file.
At least for munmap() I don't think that's a worry: once unmapped (even if just partially), vdso_base becomes zero and won't ever be set again. So no need to track the zillion pieces, should there be any: Humpty Dumpty won't be whole again, right? > > There's also the question of mprotect(): can users mprotect() the > > vDSO on PowerPC? > > Yes, mprotect() the vDSO is allowed on PowerPC, as it is on x86, and > certainly all the other architectures. Furthermore, if it is done on > a partial part of the vDSO it is splitting the vma... btw., CRIU's main purpose here is to reconstruct a vDSO that was originally randomized, but whose address must now be reproduced as-is, right? In that sense detecting the 'good' mremap() as your patch does should do the trick and is certainly not objectionable IMHO - I was just wondering whether we could make a perfect job very simply. Thanks, Ingo ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user