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ftrace: Do not let direct or IPMODIFY ftrace_ops be added to module and set trampolines 

When inserting a module, we find all ftrace_ops referencing it on the
ftrace_ops_list. But FTRACE_OPS_FL_DIRECT and FTRACE_OPS_FL_IPMODIFY
flags are special, and should not be set automatically. So warn and
skip ftrace_ops that have these two flags set and adding new code.
Also check if only one ftrace_ops references the module, in which case
we can use a trampoline as an optimization.

Link: https://lkml.kernel.org/r/20200728180554.65203-2-zhouchengming@bytedance.com

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Chengming Zhou 2020-07-29 02:05:54 +08:00 committed by Steven Rostedt (VMware)
parent 8a224ffb3f
commit c5f51572a7
1 changed files with 8 additions and 0 deletions
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8
kernel/trace/ftrace.c
View File

@ -6199,9 +6199,17 @@ static int referenced_filters(struct dyn_ftrace *rec)
for (ops = ftrace_ops_list; ops != &ftrace_list_end; ops = ops->next) {
if (ops_references_rec(ops, rec)) {
if (WARN_ON_ONCE(ops->flags & FTRACE_OPS_FL_DIRECT))
continue;
if (WARN_ON_ONCE(ops->flags & FTRACE_OPS_FL_IPMODIFY))
continue;
cnt++;
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
rec->flags |= FTRACE_FL_REGS;
if (cnt == 1 && ops->trampoline)
rec->flags |= FTRACE_FL_TRAMP;
else
rec->flags &= ~FTRACE_FL_TRAMP;
}
}