uretprobes: Introduce uprobe_consumer->ret_handler()

Enclose return probes implementation, introduce ->ret_handler() and update
existing code to rely on ->handler() *and* ->ret_handler() for uprobe and
uretprobe respectively.

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

2 files changed, 17 insertions, 3 deletions

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 19612881399a..5c8d3290df41 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -46,6 +46,9 @@ enum uprobe_filter_ctx {
 
 struct uprobe_consumer {
         int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
+        int (*ret_handler)(struct uprobe_consumer *self,
+                                unsigned long func,
+                                struct pt_regs *regs);
         bool (*filter)(struct uprobe_consumer *self,
                                 enum uprobe_filter_ctx ctx,
                                 struct mm_struct *mm);
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 7312503caf2e..eb384e90ac92 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -838,6 +838,14 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
         struct uprobe *uprobe;
         int ret;
 
+        /* Uprobe must have at least one set consumer */
+        if (!uc->handler && !uc->ret_handler)
+                return -EINVAL;
+
+        /* TODO: Implement return probes */
+        if (uc->ret_handler)
+                return -ENOSYS;
+
         /* Racy, just to catch the obvious mistakes */
         if (offset > i_size_read(inode))
                 return -EINVAL;
@@ -1497,10 +1505,13 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
 
         down_read(&uprobe->register_rwsem);
         for (uc = uprobe->consumers; uc; uc = uc->next) {
-                int rc = uc->handler(uc, regs);
+                int rc = 0;
 
-                WARN(rc & ~UPROBE_HANDLER_MASK,
-                        "bad rc=0x%x from %pf()\n", rc, uc->handler);
+                if (uc->handler) {
+                        rc = uc->handler(uc, regs);
+                        WARN(rc & ~UPROBE_HANDLER_MASK,
+                                "bad rc=0x%x from %pf()\n", rc, uc->handler);
+                }
                 remove &= rc;
         }