Steven Rostedt wrote:
On Thu, 10 Feb 2022 13:58:29 +0000
"Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxxxxxxx> wrote:
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9feb197b2daaf..68f20cf34b0c47 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1510,6 +1510,7 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
}
+#ifndef ftrace_cmp_recs
static int ftrace_cmp_recs(const void *a, const void *b)
{
const struct dyn_ftrace *key = a;
@@ -1521,6 +1522,7 @@ static int ftrace_cmp_recs(const void *a, const void *b)
return 1;
return 0;
}
+#endif
I don't really care for this part, as it seems somewhat ugly. But this
patch does appear to solve your issue, and I can't think of a prettier way
to do this.
Yes, this approach looks like it will solve a few different issues for
us. We would also like to nop-out the instruction before the branch to
_mcount(), so this helps ensure that kprobes won't also overwrite that
instruction.
So, I will reluctantly ack it.
Since we don't want to change struct dyn_ftrace, we will need to contain
changes within the architecture code, so I don't see a way to do this in
a generic manner.
The other option is to mark ftrace_cmp_recs() as a __weak function, but
I have a vague recollection of you suggesting #ifdef rather than a
__weak function in the past. I might be mis-remembering, so if you think
making this a __weak function is better, I can do that.
If anything, please add a comment above saying that architectures may need
to override this function, and when doing so, they will define their own
ftrace_cmp_recs.
Sure.
- Naveen
