[PATCH v2 2/2] jump_label: Warn on failed jump_label patch

[Josh Poimboeuf]

When the jump label code encounters an address which isn't recognized by
kernel_text_address(), it just silently fails.

This can be dangerous because jump labels are used in a variety of
places, and are generally expected to work.  Convert the silent failure
to a warning.

This won't warn about attempted writes to tracepoints in __init code
after initmem has been freed, as those are already guarded by the
entry->code check.

Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
 kernel/jump_label.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 96274c6d3511..08a02ae54997 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -367,12 +367,15 @@ static void __jump_label_update(struct static_key *key,
 {
        for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
                /*
-                * entry->code set to 0 invalidates module init text sections
-                * kernel_text_address() verifies we are not in core kernel
-                * init code, see jump_label_invalidate_module_init().
+                * An entry->code of 0 indicates an entry which has been
+                * disabled because it was in an init text area.
                 */
-               if (entry->code && kernel_text_address(entry->code))
-                       arch_jump_label_transform(entry, 
jump_label_type(entry));
+               if (entry->code) {
+                       if (kernel_text_address(entry->code))
+                               arch_jump_label_transform(entry, 
jump_label_type(entry));
+                       else
+                               WARN_ONCE(1, "can't patch jump_label at %pS", 
(void *)entry->code);
+               }
        }
 }
 
-- 
2.14.3