ftrace: Fix updating FTRACE_FL_TRAMP
authorNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Thu, 26 Nov 2020 18:08:38 +0000 (23:38 +0530)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Tue, 1 Dec 2020 02:43:07 +0000 (21:43 -0500)
commit4c75b0ff4e4bf7a45b5aef9639799719c28d0073
tree13e45096d296f3e15355b12de8aeaf5cf10b3ab9
parent8fa655a3a0013a0c2a2aada6f39a93ee6fc25549
ftrace: Fix updating FTRACE_FL_TRAMP

On powerpc, kprobe-direct.tc triggered FTRACE_WARN_ON() in
ftrace_get_addr_new() followed by the below message:
  Bad trampoline accounting at: 000000004222522f (wake_up_process+0xc/0x20) (f0000001)

The set of steps leading to this involved:
- modprobe ftrace-direct-too
- enable_probe
- modprobe ftrace-direct
- rmmod ftrace-direct <-- trigger

The problem turned out to be that we were not updating flags in the
ftrace record properly. From the above message about the trampoline
accounting being bad, it can be seen that the ftrace record still has
FTRACE_FL_TRAMP set though ftrace-direct module is going away. This
happens because we are checking if any ftrace_ops has the
FTRACE_FL_TRAMP flag set _before_ updating the filter hash.

The fix for this is to look for any _other_ ftrace_ops that also needs
FTRACE_FL_TRAMP.

Link: https://lkml.kernel.org/r/56c113aa9c3e10c19144a36d9684c7882bf09af5.1606412433.git.naveen.n.rao@linux.vnet.ibm.com
Cc: stable@vger.kernel.org
Fixes: a124692b698b0 ("ftrace: Enable trampoline when rec count returns back to one")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
kernel/trace/ftrace.c