Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 21 Mar 2023 09:47:17 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH 1/7] ftrace: Let unregister_ftrace_direct_multi() call ftrace_free_filter() |
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On Thu, Mar 16, 2023 at 06:38:05PM +0100, Florent Revest wrote: > A common pattern when using the ftrace_direct_multi API is to unregister > the ops and also immediately free its filter. We've noticed it's very > easy for users to miss calling ftrace_free_filter(). > > This adds a "free_filters" argument to unregister_ftrace_direct_multi() > to both remind the user they should free filters and also to make their > life easier. > > Suggested-by: Steven Rostedt <rostedt@goodmis.org> > Signed-off-by: Florent Revest <revest@chromium.org> > --- > include/linux/ftrace.h | 6 ++++-- > kernel/bpf/trampoline.c | 2 +- > kernel/trace/ftrace.c | 6 +++++- > samples/ftrace/ftrace-direct-multi-modify.c | 3 +-- > samples/ftrace/ftrace-direct-multi.c | 3 +-- > 5 files changed, 12 insertions(+), 8 deletions(-)
This looks good to me; I see that the BPF code frees the filter in bpf_trampoline_put(), so it not doing so via unregister_ftrace_direct_multi() looks fine. FWIW:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Mark.
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index 366c730beaa3..5b68ee874bc1 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -407,7 +407,8 @@ int ftrace_modify_direct_caller(struct ftrace_func_entry *entry, > unsigned long new_addr); > unsigned long ftrace_find_rec_direct(unsigned long ip); > int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr); > -int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr); > +int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr, > + bool free_filters); > int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr); > int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr); > > @@ -446,7 +447,8 @@ static inline int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned > { > return -ENODEV; > } > -static inline int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) > +static inline int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr, > + bool free_filters) > { > return -ENODEV; > } > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c > index d0ed7d6f5eec..88bc23f1e10a 100644 > --- a/kernel/bpf/trampoline.c > +++ b/kernel/bpf/trampoline.c > @@ -198,7 +198,7 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr) > int ret; > > if (tr->func.ftrace_managed) > - ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr); > + ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr, false); > else > ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL); > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 29baa97d0d53..fa379cf91fdb 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -5804,7 +5804,8 @@ EXPORT_SYMBOL_GPL(register_ftrace_direct_multi); > * 0 on success > * -EINVAL - The @ops object was not properly registered. > */ > -int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) > +int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr, > + bool free_filters) > { > struct ftrace_hash *hash = ops->func_hash->filter_hash; > int err; > @@ -5822,6 +5823,9 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) > /* cleanup for possible another register call */ > ops->func = NULL; > ops->trampoline = 0; > + > + if (free_filters) > + ftrace_free_filter(ops); > return err; > } > EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi); > diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c > index b58c594efb51..196b43971cb5 100644 > --- a/samples/ftrace/ftrace-direct-multi-modify.c > +++ b/samples/ftrace/ftrace-direct-multi-modify.c > @@ -151,8 +151,7 @@ static int __init ftrace_direct_multi_init(void) > static void __exit ftrace_direct_multi_exit(void) > { > kthread_stop(simple_tsk); > - unregister_ftrace_direct_multi(&direct, my_tramp); > - ftrace_free_filter(&direct); > + unregister_ftrace_direct_multi(&direct, my_tramp, true); > } > > module_init(ftrace_direct_multi_init); > diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c > index c27cf130c319..ea0e88ee5e43 100644 > --- a/samples/ftrace/ftrace-direct-multi.c > +++ b/samples/ftrace/ftrace-direct-multi.c > @@ -78,8 +78,7 @@ static int __init ftrace_direct_multi_init(void) > > static void __exit ftrace_direct_multi_exit(void) > { > - unregister_ftrace_direct_multi(&direct, (unsigned long) my_tramp); > - ftrace_free_filter(&direct); > + unregister_ftrace_direct_multi(&direct, (unsigned long) my_tramp, true); > } > > module_init(ftrace_direct_multi_init); > -- > 2.40.0.rc2.332.ga46443480c-goog >
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