uprobes: Introduce prepare_uprobe()

Preparation. Extract the copy_insn/arch_uprobe_analyze_insn code
from install_breakpoint() into the new helper, prepare_uprobe().

And move uprobe->flags defines from uprobes.h to uprobes.c, nobody
else can use them anyway.

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

2 files changed, 41 insertions, 29 deletions

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 18d839da6517..24594571c5a3 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -35,16 +35,6 @@ struct inode;
 # include <asm/uprobes.h>
 #endif
 
-/* flags that denote/change uprobes behaviour */
-
-/* Have a copy of original instruction */
-#define UPROBE_COPY_INSN        0x1
-
-/* Dont run handlers when first register/ last unregister in progress*/
-#define UPROBE_RUN_HANDLER      0x2
-/* Can skip singlestep */
-#define UPROBE_SKIP_SSTEP       0x4
-
 struct uprobe_consumer {
         int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
         /*
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c718fef28617..4f315fa94c52 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -78,6 +78,13 @@ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
  */
 static atomic_t uprobe_events = ATOMIC_INIT(0);
 
+/* Have a copy of original instruction */
+#define UPROBE_COPY_INSN        0x1
+/* Dont run handlers when first register/ last unregister in progress*/
+#define UPROBE_RUN_HANDLER      0x2
+/* Can skip singlestep */
+#define UPROBE_SKIP_SSTEP       0x4
+
 struct uprobe {
         struct rb_node          rb_node;        /* node in the rb tree */
         atomic_t                ref;
@@ -563,6 +570,37 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp)
         return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
 }
 
+static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
+                                struct mm_struct *mm, unsigned long vaddr)
+{
+        int ret = 0;
+
+        if (uprobe->flags & UPROBE_COPY_INSN)
+                return ret;
+
+        ret = copy_insn(uprobe, file);
+        if (ret)
+                goto out;
+
+        ret = -ENOTSUPP;
+        if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
+                goto out;
+
+        ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
+        if (ret)
+                goto out;
+
+        /* write_opcode() assumes we don't cross page boundary */
+        BUG_ON((uprobe->offset & ~PAGE_MASK) +
+                        UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
+
+        smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
+        uprobe->flags |= UPROBE_COPY_INSN;
+
+ out:
+        return ret;
+}
+
 static int
 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
                         struct vm_area_struct *vma, unsigned long vaddr)
@@ -580,25 +618,9 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
         if (!uprobe->consumers)
                 return 0;
 
-        if (!(uprobe->flags & UPROBE_COPY_INSN)) {
-                ret = copy_insn(uprobe, vma->vm_file);
-                if (ret)
-                        return ret;
-
-                if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
-                        return -ENOTSUPP;
-
-                ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
-                if (ret)
-                        return ret;
-
-                /* write_opcode() assumes we don't cross page boundary */
-                BUG_ON((uprobe->offset & ~PAGE_MASK) +
-                                UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
-
-                smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
-                uprobe->flags |= UPROBE_COPY_INSN;
-        }
+        ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
+        if (ret)
+                return ret;
 
         /*
          * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),