| Message ID | 170126066201.398836.837498688669005979.stgit@devnote2 (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] rethook: Use __rcu pointer for rethook::handler | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Wed, Nov 29, 2023 at 09:24:22PM +0900, Masami Hiramatsu (Google) wrote: > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > Since the rethook::handler is an RCU-maganged pointer so that it will > notice readers the rethook is stopped (unregistered) or not, it should > be an __rcu pointer and use appropriate functions to be accessed. This > will use appropriate memory barrier when accessing it. OTOH, > rethook::data is never changed, so we don't need to check it in > get_kretprobe(). > > NOTE: To avoid sparse warning, rethook::handler is defined by a raw > function pointer type with __rcu instead of rethook_handler_t. > > Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook") > Reported-by: kernel test robot <lkp@intel.com> > Closes: https://lore.kernel.org/oe-kbuild-all/202311241808.rv9ceuAh-lkp@intel.com/ > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > --- > include/linux/kprobes.h | 6 ++---- > include/linux/rethook.h | 7 ++++++- > kernel/trace/rethook.c | 23 ++++++++++++++--------- > 3 files changed, 22 insertions(+), 14 deletions(-) > > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h > index 64672bace560..0ff44d6633e3 100644 > --- a/include/linux/kprobes.h > +++ b/include/linux/kprobes.h > @@ -197,10 +197,8 @@ extern int arch_trampoline_kprobe(struct kprobe *p); > #ifdef CONFIG_KRETPROBE_ON_RETHOOK > static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri) > { > - RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(), > - "Kretprobe is accessed from instance under preemptive context"); > - > - return (struct kretprobe *)READ_ONCE(ri->node.rethook->data); > + /* rethook::data is non-changed field, so that you can access it freely. */ > + return (struct kretprobe *)ri->node.rethook->data; > } > static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri) > { > diff --git a/include/linux/rethook.h b/include/linux/rethook.h > index ce69b2b7bc35..ba60962805f6 100644 > --- a/include/linux/rethook.h > +++ b/include/linux/rethook.h > @@ -28,7 +28,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, > */ > struct rethook { > void *data; > - rethook_handler_t handler; > + /* > + * To avoid sparse warnings, this uses a raw function pointer with > + * __rcu, instead of rethook_handler_t. But this must be same as > + * rethook_handler_t. > + */ > + void (__rcu *handler) (struct rethook_node *, void *, unsigned long, struct pt_regs *); > struct objpool_head pool; > struct rcu_head rcu; > }; > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c > index 6fd7d4ecbbc6..fa03094e9e69 100644 > --- a/kernel/trace/rethook.c > +++ b/kernel/trace/rethook.c > @@ -48,7 +48,7 @@ static void rethook_free_rcu(struct rcu_head *head) > */ > void rethook_stop(struct rethook *rh) > { > - WRITE_ONCE(rh->handler, NULL); > + rcu_assign_pointer(rh->handler, NULL); > } > > /** > @@ -63,7 +63,7 @@ void rethook_stop(struct rethook *rh) > */ > void rethook_free(struct rethook *rh) > { > - WRITE_ONCE(rh->handler, NULL); > + rethook_stop(rh); > > call_rcu(&rh->rcu, rethook_free_rcu); > } > @@ -82,6 +82,12 @@ static int rethook_fini_pool(struct objpool_head *head, void *context) > return 0; > } > > +static inline rethook_handler_t rethook_get_handler(struct rethook *rh) > +{ > + return (rethook_handler_t)rcu_dereference_check(rh->handler, > + rcu_read_lock_any_held()); > +} > + > /** > * rethook_alloc() - Allocate struct rethook. > * @data: a data to pass the @handler when hooking the return. > @@ -107,7 +113,7 @@ struct rethook *rethook_alloc(void *data, rethook_handler_t handler, > return ERR_PTR(-ENOMEM); > > rh->data = data; > - rh->handler = handler; > + rcu_assign_pointer(rh->handler, handler); > > /* initialize the objpool for rethook nodes */ > if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh, > @@ -135,9 +141,10 @@ static void free_rethook_node_rcu(struct rcu_head *head) > */ > void rethook_recycle(struct rethook_node *node) > { > - lockdep_assert_preemption_disabled(); > + rethook_handler_t handler; > > - if (likely(READ_ONCE(node->rethook->handler))) > + handler = rethook_get_handler(node->rethook); > + if (likely(handler)) > objpool_push(node, &node->rethook->pool); > else > call_rcu(&node->rcu, free_rethook_node_rcu); > @@ -153,9 +160,7 @@ NOKPROBE_SYMBOL(rethook_recycle); > */ > struct rethook_node *rethook_try_get(struct rethook *rh) > { > - rethook_handler_t handler = READ_ONCE(rh->handler); > - > - lockdep_assert_preemption_disabled(); > + rethook_handler_t handler = rethook_get_handler(rh); > > /* Check whether @rh is going to be freed. */ > if (unlikely(!handler)) > @@ -300,7 +305,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs, > rhn = container_of(first, struct rethook_node, llist); > if (WARN_ON_ONCE(rhn->frame != frame)) > break; > - handler = READ_ONCE(rhn->rethook->handler); > + handler = rethook_get_handler(rhn->rethook); > if (handler) > handler(rhn, rhn->rethook->data, > correct_ret_addr, regs); > I applied and tested this patch locally on an x86_64 machine and can confirm there are no RCU-related sparse warnings. Also, kprobe tests within the ftrace selftest suite succeed just the same as before applying the patch. Tested-by: JP Kobryn <inwardvessel@gmail.com>
On Thu, 30 Nov 2023 13:44:55 -0800 JP Kobryn <inwardvessel@gmail.com> wrote: > On Wed, Nov 29, 2023 at 09:24:22PM +0900, Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > > > Since the rethook::handler is an RCU-maganged pointer so that it will > > notice readers the rethook is stopped (unregistered) or not, it should > > be an __rcu pointer and use appropriate functions to be accessed. This > > will use appropriate memory barrier when accessing it. OTOH, > > rethook::data is never changed, so we don't need to check it in > > get_kretprobe(). > > > > NOTE: To avoid sparse warning, rethook::handler is defined by a raw > > function pointer type with __rcu instead of rethook_handler_t. > > > > Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook") > > Reported-by: kernel test robot <lkp@intel.com> > > Closes: https://lore.kernel.org/oe-kbuild-all/202311241808.rv9ceuAh-lkp@intel.com/ > > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > --- > > include/linux/kprobes.h | 6 ++---- > > include/linux/rethook.h | 7 ++++++- > > kernel/trace/rethook.c | 23 ++++++++++++++--------- > > 3 files changed, 22 insertions(+), 14 deletions(-) > > > > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h > > index 64672bace560..0ff44d6633e3 100644 > > --- a/include/linux/kprobes.h > > +++ b/include/linux/kprobes.h > > @@ -197,10 +197,8 @@ extern int arch_trampoline_kprobe(struct kprobe *p); > > #ifdef CONFIG_KRETPROBE_ON_RETHOOK > > static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri) > > { > > - RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(), > > - "Kretprobe is accessed from instance under preemptive context"); > > - > > - return (struct kretprobe *)READ_ONCE(ri->node.rethook->data); > > + /* rethook::data is non-changed field, so that you can access it freely. */ > > + return (struct kretprobe *)ri->node.rethook->data; > > } > > static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri) > > { > > diff --git a/include/linux/rethook.h b/include/linux/rethook.h > > index ce69b2b7bc35..ba60962805f6 100644 > > --- a/include/linux/rethook.h > > +++ b/include/linux/rethook.h > > @@ -28,7 +28,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, > > */ > > struct rethook { > > void *data; > > - rethook_handler_t handler; > > + /* > > + * To avoid sparse warnings, this uses a raw function pointer with > > + * __rcu, instead of rethook_handler_t. But this must be same as > > + * rethook_handler_t. > > + */ > > + void (__rcu *handler) (struct rethook_node *, void *, unsigned long, struct pt_regs *); > > struct objpool_head pool; > > struct rcu_head rcu; > > }; > > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c > > index 6fd7d4ecbbc6..fa03094e9e69 100644 > > --- a/kernel/trace/rethook.c > > +++ b/kernel/trace/rethook.c > > @@ -48,7 +48,7 @@ static void rethook_free_rcu(struct rcu_head *head) > > */ > > void rethook_stop(struct rethook *rh) > > { > > - WRITE_ONCE(rh->handler, NULL); > > + rcu_assign_pointer(rh->handler, NULL); > > } > > > > /** > > @@ -63,7 +63,7 @@ void rethook_stop(struct rethook *rh) > > */ > > void rethook_free(struct rethook *rh) > > { > > - WRITE_ONCE(rh->handler, NULL); > > + rethook_stop(rh); > > > > call_rcu(&rh->rcu, rethook_free_rcu); > > } > > @@ -82,6 +82,12 @@ static int rethook_fini_pool(struct objpool_head *head, void *context) > > return 0; > > } > > > > +static inline rethook_handler_t rethook_get_handler(struct rethook *rh) > > +{ > > + return (rethook_handler_t)rcu_dereference_check(rh->handler, > > + rcu_read_lock_any_held()); > > +} > > + > > /** > > * rethook_alloc() - Allocate struct rethook. > > * @data: a data to pass the @handler when hooking the return. > > @@ -107,7 +113,7 @@ struct rethook *rethook_alloc(void *data, rethook_handler_t handler, > > return ERR_PTR(-ENOMEM); > > > > rh->data = data; > > - rh->handler = handler; > > + rcu_assign_pointer(rh->handler, handler); > > > > /* initialize the objpool for rethook nodes */ > > if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh, > > @@ -135,9 +141,10 @@ static void free_rethook_node_rcu(struct rcu_head *head) > > */ > > void rethook_recycle(struct rethook_node *node) > > { > > - lockdep_assert_preemption_disabled(); > > + rethook_handler_t handler; > > > > - if (likely(READ_ONCE(node->rethook->handler))) > > + handler = rethook_get_handler(node->rethook); > > + if (likely(handler)) > > objpool_push(node, &node->rethook->pool); > > else > > call_rcu(&node->rcu, free_rethook_node_rcu); > > @@ -153,9 +160,7 @@ NOKPROBE_SYMBOL(rethook_recycle); > > */ > > struct rethook_node *rethook_try_get(struct rethook *rh) > > { > > - rethook_handler_t handler = READ_ONCE(rh->handler); > > - > > - lockdep_assert_preemption_disabled(); > > + rethook_handler_t handler = rethook_get_handler(rh); > > > > /* Check whether @rh is going to be freed. */ > > if (unlikely(!handler)) > > @@ -300,7 +305,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs, > > rhn = container_of(first, struct rethook_node, llist); > > if (WARN_ON_ONCE(rhn->frame != frame)) > > break; > > - handler = READ_ONCE(rhn->rethook->handler); > > + handler = rethook_get_handler(rhn->rethook); > > if (handler) > > handler(rhn, rhn->rethook->data, > > correct_ret_addr, regs); > > > > I applied and tested this patch locally on an x86_64 machine and can > confirm there are no RCU-related sparse warnings. Also, kprobe tests > within the ftrace selftest suite succeed just the same as before > applying the patch. > > Tested-by: JP Kobryn <inwardvessel@gmail.com> Thank you for testing! Let me push it with your fix.
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index 64672bace560..0ff44d6633e3 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -197,10 +197,8 @@ extern int arch_trampoline_kprobe(struct kprobe *p); #ifdef CONFIG_KRETPROBE_ON_RETHOOK static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri) { - RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(), - "Kretprobe is accessed from instance under preemptive context"); - - return (struct kretprobe *)READ_ONCE(ri->node.rethook->data); + /* rethook::data is non-changed field, so that you can access it freely. */ + return (struct kretprobe *)ri->node.rethook->data; } static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri) { diff --git a/include/linux/rethook.h b/include/linux/rethook.h index ce69b2b7bc35..ba60962805f6 100644 --- a/include/linux/rethook.h +++ b/include/linux/rethook.h @@ -28,7 +28,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, */ struct rethook { void *data; - rethook_handler_t handler; + /* + * To avoid sparse warnings, this uses a raw function pointer with + * __rcu, instead of rethook_handler_t. But this must be same as + * rethook_handler_t. + */ + void (__rcu *handler) (struct rethook_node *, void *, unsigned long, struct pt_regs *); struct objpool_head pool; struct rcu_head rcu; }; diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 6fd7d4ecbbc6..fa03094e9e69 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -48,7 +48,7 @@ static void rethook_free_rcu(struct rcu_head *head) */ void rethook_stop(struct rethook *rh) { - WRITE_ONCE(rh->handler, NULL); + rcu_assign_pointer(rh->handler, NULL); } /** @@ -63,7 +63,7 @@ void rethook_stop(struct rethook *rh) */ void rethook_free(struct rethook *rh) { - WRITE_ONCE(rh->handler, NULL); + rethook_stop(rh); call_rcu(&rh->rcu, rethook_free_rcu); } @@ -82,6 +82,12 @@ static int rethook_fini_pool(struct objpool_head *head, void *context) return 0; } +static inline rethook_handler_t rethook_get_handler(struct rethook *rh) +{ + return (rethook_handler_t)rcu_dereference_check(rh->handler, + rcu_read_lock_any_held()); +} + /** * rethook_alloc() - Allocate struct rethook. * @data: a data to pass the @handler when hooking the return. @@ -107,7 +113,7 @@ struct rethook *rethook_alloc(void *data, rethook_handler_t handler, return ERR_PTR(-ENOMEM); rh->data = data; - rh->handler = handler; + rcu_assign_pointer(rh->handler, handler); /* initialize the objpool for rethook nodes */ if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh, @@ -135,9 +141,10 @@ static void free_rethook_node_rcu(struct rcu_head *head) */ void rethook_recycle(struct rethook_node *node) { - lockdep_assert_preemption_disabled(); + rethook_handler_t handler; - if (likely(READ_ONCE(node->rethook->handler))) + handler = rethook_get_handler(node->rethook); + if (likely(handler)) objpool_push(node, &node->rethook->pool); else call_rcu(&node->rcu, free_rethook_node_rcu); @@ -153,9 +160,7 @@ NOKPROBE_SYMBOL(rethook_recycle); */ struct rethook_node *rethook_try_get(struct rethook *rh) { - rethook_handler_t handler = READ_ONCE(rh->handler); - - lockdep_assert_preemption_disabled(); + rethook_handler_t handler = rethook_get_handler(rh); /* Check whether @rh is going to be freed. */ if (unlikely(!handler)) @@ -300,7 +305,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs, rhn = container_of(first, struct rethook_node, llist); if (WARN_ON_ONCE(rhn->frame != frame)) break; - handler = READ_ONCE(rhn->rethook->handler); + handler = rethook_get_handler(rhn->rethook); if (handler) handler(rhn, rhn->rethook->data, correct_ret_addr, regs);