Messages in this thread | | | Date | Thu, 8 Dec 2011 11:07:24 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [rfc 3/3] prctl: Add PR_SET_MM codes to tune up mm_struct entires |
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On Wed, Dec 07, 2011 at 02:43:55PM -0800, Andrew Morton wrote: > On Wed, 7 Dec 2011 16:27:18 +0400 > Cyrill Gorcunov <gorcunov@gmail.com> wrote: > > > At process of task restoration we need a way to tune up > > a few members of mm_struct structure such as start_code, > > end_code, start_data, end_data, start_stack, start_brk, brk. > > I don't really know what "tune up" means in this context. Can we > please be more specific and detailed here? It appears that the patch > permits userspace to directly modify these fields. >
ok
> > The prctl(2) manpage will need to be updated. Please Cc Michael on all > such changes. >
you mean -- Michael Kerrisk, mtk AT man7.org, right?
... > > + > > + mm = get_task_mm(current); > > Is it necessaary to run the expensive get_task_mm() for `current'? > `current' is known to be running and you have control of it here - > nobody will be taking our mm away. Simply use current->mm? The > function actually uses current->mm later on in several places.
hmm, indeed, i'll update, thanks!
> > > + if (!mm) > > + return -ENOENT; > > + > > + down_read(&mm->mmap_sem); > > + vma = find_vma(mm, addr); > > + > > + if (opt != PR_SET_MM_START_BRK && > > + opt != PR_SET_MM_BRK) { > > 80 columns, not 40 :) > > > + /* It must be existing VMA */ > > + if (!vma || vma->vm_start > addr) > > + goto out; > > + } > > + > > + error = -EINVAL; > > + switch (opt) { > > + case PR_SET_MM_START_CODE: > > + case PR_SET_MM_END_CODE: > > + > > You're adding unneeded and unconventional newlines after the `case' > statements. >
no, I added them by a purpose -- it's a way easier to read these assignments, but fine -- I'll drop this nits.
> > This is starting to add a non-trivial amount of code. Perhaps we need > to introduce a Kconfig variable to control such things as this, to > prevent bloating up kernels which aren't require to support c/r? >
Dunno, Andrew. Actually I agreed that these snippets are mostly needed for c/r only, but the initial idea over all changes was to add levers into kernel which might be helpful not only for c/r but for someone else as well.
Cyrill
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