On Tue, Jul 31, 2012 at 12:21:58PM +0200, richard -rw- weinberger wrote:

On Tue, Jul 31, 2012 at 12:16 PM, Cyrill Gorcunov [off-list ref] wrote:

quoted

On Tue, Jul 31, 2012 at 12:08:22PM +0200, richard -rw- weinberger wrote:

quoted

On Tue, Jul 31, 2012 at 11:54 AM, Pavel Emelyanov [off-list ref] wrote:

quoted

quoted

Yeah, but I fear it's not that easy.
We'd have to change crtools to work without ptrace().

Well, this is hard. Using ptrace saved us from having many special-purpose
APIs for dumping various stuff (there will be an article about it). Thus I
don't know which way is simpler -- stop using ptrace or teach ptrece to allow
several tracers to attach to one task %)

Allowing multiple tracers in a safe way is IMHO even more harder.

BTW:  While reading prctl_set_mm() I noticed two things.
1.  Why isn't the return value of find_vma() verified?

prctl_set_mm
        vma = find_vma(mm, addr);
        ...
        if (!vma) {
                error = -EFAULT;
                goto out;
        }

these values are used in procfs statistics only. So I don't get
which verify you mean here.

If I do PR_SET_MM_START_BRK the if(!vma) will never be executed because
there a break in case PR_SET_MM_START_BRK.

Yes, and this is done by purpose, since we need to setup _completely_
new memory map on restore procedure.

There is a minimal check for value being sane

	if (addr >= TASK_SIZE || addr < mmap_min_addr)
		return -EINVAL;

and the address belongs to mm::start_data|end_data area. But sure,
better to add checks that at least code/data areas do exist, otherwise
the proc output will not reflect the real state of memory maps.

	Cyrill