uprobes: Simplify is_swbp_at_addr(), remove stale comments

After the previous change is_swbp_at_addr() is always called with
current->mm. Remove this check and move it close to its single caller.

Also, remove the obsolete comment about is_swbp_at_addr() and
uprobe_state.count.

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

1 files changed, 24 insertions, 49 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 9248ee76b4bb..6136854da6c6 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -282,32 +282,6 @@ put_old:
         return ret;
 }
 
-static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
-{
-        struct page *page;
-        uprobe_opcode_t opcode;
-        int result;
-
-        if (current->mm == mm) {
-                pagefault_disable();
-                result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
-                                                                sizeof(opcode));
-                pagefault_enable();
-
-                if (likely(result == 0))
-                        goto out;
-        }
-
-        result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
-        if (result < 0)
-                return result;
-
-        copy_opcode(page, vaddr, &opcode);
-        put_page(page);
- out:
-        return is_swbp_insn(&opcode);
-}
-
 /**
  * set_swbp - store breakpoint at a given address.
  * @auprobe: arch specific probepoint information.
@@ -589,29 +563,6 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp)
         return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
 }
 
-/*
- * How mm->uprobes_state.count gets updated
- * uprobe_mmap() increments the count if
- *      - it successfully adds a breakpoint.
- *      - it cannot add a breakpoint, but sees that there is a underlying
- *        breakpoint (via a is_swbp_at_addr()).
- *
- * uprobe_munmap() decrements the count if
- *      - it sees a underlying breakpoint, (via is_swbp_at_addr)
- *        (Subsequent uprobe_unregister wouldnt find the breakpoint
- *        unless a uprobe_mmap kicks in, since the old vma would be
- *        dropped just after uprobe_munmap.)
- *
- * uprobe_register increments the count if:
- *      - it successfully adds a breakpoint.
- *
- * uprobe_unregister decrements the count if:
- *      - it sees a underlying breakpoint and removes successfully.
- *        (via is_swbp_at_addr)
- *        (Subsequent uprobe_munmap wouldnt find the breakpoint
- *        since there is no underlying breakpoint after the
- *        breakpoint removal.)
- */
 static int
 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
                         struct vm_area_struct *vma, unsigned long vaddr)
@@ -1389,6 +1340,30 @@ static void mmf_recalc_uprobes(struct mm_struct *mm)
         clear_bit(MMF_HAS_UPROBES, &mm->flags);
 }
 
+static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
+{
+        struct page *page;
+        uprobe_opcode_t opcode;
+        int result;
+
+        pagefault_disable();
+        result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
+                                                        sizeof(opcode));
+        pagefault_enable();
+
+        if (likely(result == 0))
+                goto out;
+
+        result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
+        if (result < 0)
+                return result;
+
+        copy_opcode(page, vaddr, &opcode);
+        put_page(page);
+ out:
+        return is_swbp_insn(&opcode);
+}
+
 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
 {
         struct mm_struct *mm = current->mm;