(2015/01/15 0:39), Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
>
> As the set_ftrace_filter affects both the function tracer as well as the
> function graph tracer, the ops that represent each have a shared
> ftrace_ops_hash structure. This allows both to be updated when the filter
> files are updated.
>
> But if function graph is enabled and the global_ops (function tracing) ops
> is not, then it is possible that the filter could be changed without the
> update happening for the function graph ops. This will cause the changes
> to not take place and may even cause a ftrace_bug to occur as it could mess
> with the trampoline accounting.
>
> The solution is to check if the ops uses the shared global_ops filter and
> if the ops itself is not enabled, to check if there's another ops that is
> enabled and also shares the global_ops filter. In that case, the
> modification still needs to be executed.
>
Looks good to me.
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Thank you,
> Cc: stable@xxxxxxxxxxxxxxx # 3.17+
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> ---
> kernel/trace/ftrace.c | 26 +++++++++++++++++++++++++-
> 1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 929a733d302e..2b35d0ba578d 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4008,8 +4008,32 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
> static void ftrace_ops_update_code(struct ftrace_ops *ops,
> struct ftrace_hash *old_hash)
> {
> - if (ops->flags & FTRACE_OPS_FL_ENABLED && ftrace_enabled)
> + struct ftrace_ops *op;
> +
> + if (!ftrace_enabled)
> + return;
> +
> + if (ops->flags & FTRACE_OPS_FL_ENABLED) {
> ftrace_run_modify_code(ops, FTRACE_UPDATE_CALLS, old_hash);
> + return;
> + }
> +
> + /*
> + * If this is the shared global_ops filter, then we need to
> + * check if there is another ops that shares it, is enabled.
> + * If so, we still need to run the modify code.
> + */
> + if (ops->func_hash != &global_ops.local_hash)
> + return;
> +
> + do_for_each_ftrace_op(op, ftrace_ops_list) {
> + if (op->func_hash == &global_ops.local_hash &&
> + op->flags & FTRACE_OPS_FL_ENABLED) {
> + ftrace_run_modify_code(op, FTRACE_UPDATE_CALLS, old_hash);
> + /* Only need to do this once */
> + return;
> + }
> + } while_for_each_ftrace_op(op);
> }
>
> static int
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
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