On Thursday 30 August 2007 23:50:21 [EMAIL PROTECTED] wrote: > On Thu, 30 Aug 2007 23:41:09 +0200, Clemens Kolbitsch said: > > On Thursday 30 August 2007 23:34:52 you wrote: > > > On Thu, 30 Aug 2007, Clemens Kolbitsch wrote: > > > > is there no way to tell the kernel, that a certain mapping must not > > > > be removed, no matter what (except of course an explicit call to > > > > sys_unmap, of course)? > > > > > > I don't seem to get what is the issue here. Your mapping is not > > > removed, only the VMAs are merged together into one larger VMA if they > > > have neighbouring address ranges and compatible protection bits. See > > > vma_merge(). > > > > the thing is that they are not. the kernel chooses to REPLACE my mapping. > > > > consider the user-space code: > > > > mmap(0xaaaa0000, 0x3000, MAP_FIXED, ...); > > mmap(0xaaaa1000, 0x4000, MAP_FIXED, ...); > > > > here, the second call to mmap will shorten the first mapping to 0x1000 > > bytes and create one big vma with size 0x5000 bytes. > > > > is there a way to tell it that the second mmap MUST fail? > > There's an LSM exit point for mmap, you could perhaps do something there. > > What are you trying to achieve by forcing the second one to fail?
puh... that is a good question :-) I'm writing my master's thesis on a new model of memory protection and need to have every memory mapping in userspace duplicated. I also have kind of a second PGD/PTD that allows finding this mirrored mapping. However, as the number of original mappings grows, I suddenly have the problem that the kernel tries to allocate a new mapping and picks the address of a mirrored memory page, which it shouldn't. Honestly, I don't understand why it does so, but it simply does... so basically I want these second mappings to stay in memory as long as the original page. What do you mean exactly with > There's an LSM exit point for mmap, you could perhaps do something there. ?? By the way / @Jiri Kosina: > Which is exactly in compliance with what POSIX says about MAP_FIXED mmaps > - see http://opengroup.org/onlinepubs/007908799/xsh/mmap.html I know... I'm not even saying that this is a bug... I just wonder if there is some way to avoid this problem :-) Thanks for your help - i really appreciate that!! - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
