* Oleg Nesterov <o...@redhat.com> [2012-09-16 19:52:48]:
> valid_vma(false) ignores ->vm_flags, this is not actually right.
> We should never try to write into MAP_SHARED mapping, this can
> confuse an apllication which actually writes to ->vm_file.
Agree,
>
> With this patch valid_vma(false) ignores VM_WRITE only but checks
> other (immutable) bits checked by valid_vma(true).
Yes, checking for other immutable flags other than VM_WRITE is good.
> This can also
> speedup uprobe_munmap() and uprobe_unregister().
>
I didnt get how it speeds up uprobe_munmap() and uprobe_unregister()?
> Note: even after this patch _unregister can confuse the probed
> application if it does mprotect(PROT_WRITE) after _register and
> installs "int3", but this is hardly possible to avoid and this
> doesn't differ from gdb case.
>
Again I didnt quite understand how unregister can confuse the probed
application.
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
The changes look good.
Acked-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> ---
> kernel/events/uprobes.c | 13 ++++---------
> 1 files changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index b9b50dd..78364a2 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -100,17 +100,12 @@ struct uprobe {
> */
> static bool valid_vma(struct vm_area_struct *vma, bool is_register)
> {
> - if (!vma->vm_file)
> - return false;
> -
> - if (!is_register)
> - return true;
> + vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED;
>
> - if ((vma->vm_flags & (VM_HUGETLB | VM_WRITE | VM_MAYEXEC | VM_SHARED))
> - == VM_MAYEXEC)
> - return true;
> + if (is_register)
> + flags |= VM_WRITE;
>
> - return false;
> + return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
> }
>
> static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t
> offset)
> --
> 1.5.5.1
>
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