uprobes: Document xol_area and arch_uprobe->insn/ixol

Document xol_area and arch_uprobe.

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

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 51a7f53..b886a5e 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -73,6 +73,17 @@ struct uprobe {
        struct inode            *inode;         /* Also hold a ref to inode */
        loff_t                  offset;
        unsigned long           flags;
+
+       /*
+        * The generic code assumes that it has two members of unknown type
+        * owned by the arch-specific code:
+        *
+        *      insn -  copy_insn() saves the original instruction here for
+        *              arch_uprobe_analyze_insn().
+        *
+        *      ixol -  potentially modified instruction to execute out of
+        *              line, copied to xol_area by xol_get_insn_slot().
+        */
        struct arch_uprobe      arch;
 };
 
@@ -86,6 +97,10 @@ struct return_instance {
 };
 
 /*
+ * Execute out of line area: anonymous executable mapping installed
+ * by the probed task to execute the copy of the original instruction
+ * mangled by set_swbp().
+ *
  * On a breakpoint hit, thread contests for a slot.  It frees the
  * slot after singlestep. Currently a fixed number of slots are
  * allocated.