uprobes: Kill dup_mmap()->uprobe_mmap(), simplify uprobe_mmap/munmap

1. Kill dup_mmap()->uprobe_mmap(), it was only needed to calculate
   new_mm->uprobes_state.count removed by the previous patch.

   If the forking process has a pending uprobe (int3) in vma, it will
   be copied by copy_page_range(), note that it checks vma->anon_vma
   so "Don't copy ptes" is not possible after install_breakpoint()
   which does anon_vma_prepare().

2. Remove is_swbp_at_addr() and "int count" in uprobe_mmap(). Again,
   this was needed for uprobes_state.count.

   As a side effect this fixes the bug pointed out by Srikar,
   this code lacked the necessary put_uprobe().

3. uprobe_munmap() becomes a nop after the previous patch. Remove the
   meaningless code but do not remove the helper, we will need it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

1 files changed, 0 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 2c8857e12855..912b6f6fe5b8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -454,9 +454,6 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 
                 if (retval)
                         goto out;
-
-                if (file)
-                        uprobe_mmap(tmp);
         }
         /* a new mm has just been created */
         arch_dup_mmap(oldmm, mm);