| Message ID | 20240719095117.3482509-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Jiri Kosina |
| Headers | show |
| Series | hid: bpf: avoid building struct ops without JIT | expand |
On Jul 19 2024, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > The module does not do anything when the JIT is disabled, but instead > causes a warning: > > In file included from include/linux/bpf_verifier.h:7, > from drivers/hid/bpf/hid_bpf_struct_ops.c:10: > drivers/hid/bpf/hid_bpf_struct_ops.c: In function 'hid_bpf_struct_ops_init': > include/linux/bpf.h:1853:50: error: statement with no effect [-Werror=unused-value] > 1853 | #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; }) > | ^~~~~~~~~~~~~~~~ > drivers/hid/bpf/hid_bpf_struct_ops.c:305:16: note: in expansion of macro 'register_bpf_struct_ops' > 305 | return register_bpf_struct_ops(&bpf_hid_bpf_ops, hid_bpf_ops); > | ^~~~~~~~~~~~~~~~~~~~~~~ > > This could be avoided by making HID-BPF just depend on JIT, but that > is probably not what we want here. Checking the other users of struct_ops, > I see that those just leave out the struct_ops usage, so do the same here. Actually, if we make the struct_ops part only depend on JIT HID-BPF is kind of moot. All we could do is use HID-BPF to communicate with the device, without getting any feedback, so nothing much more than what hidraw provides. The only "interesting" bit we could do is inject a new event on a device as if it were originated from the device itself, but I really do not see the point without the struct_ops hooks. So I think struct_ops is now the base for HID-BPF, and if it's not available, we should not have HID-BPF at all. > > Fixes: ebc0d8093e8c ("HID: bpf: implement HID-BPF through bpf_struct_ops") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/hid/bpf/Makefile | 3 ++- > drivers/hid/bpf/hid_bpf_dispatch.h | 6 ++++++ > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/hid/bpf/Makefile b/drivers/hid/bpf/Makefile > index d1f2b81788ca..7566be8eefba 100644 > --- a/drivers/hid/bpf/Makefile > +++ b/drivers/hid/bpf/Makefile > @@ -8,4 +8,5 @@ LIBBPF_INCLUDE = $(srctree)/tools/lib > obj-$(CONFIG_HID_BPF) += hid_bpf.o > CFLAGS_hid_bpf_dispatch.o += -I$(LIBBPF_INCLUDE) > CFLAGS_hid_bpf_jmp_table.o += -I$(LIBBPF_INCLUDE) Unrelated to your patch, but looks like I forgot to remove that entry from the Makefile now that hid_bpf_jmp_table.c is not available :) Cheers, Benjamin > -hid_bpf-objs += hid_bpf_dispatch.o hid_bpf_struct_ops.o > +hid_bpf-y += hid_bpf_dispatch.o > +hid_bpf-$(CONFIG_BPF_JIT) += hid_bpf_struct_ops.o > diff --git a/drivers/hid/bpf/hid_bpf_dispatch.h b/drivers/hid/bpf/hid_bpf_dispatch.h > index 44c6ea22233f..577572f41454 100644 > --- a/drivers/hid/bpf/hid_bpf_dispatch.h > +++ b/drivers/hid/bpf/hid_bpf_dispatch.h > @@ -14,7 +14,13 @@ struct hid_bpf_ctx_kern { > struct hid_device *hid_get_device(unsigned int hid_id); > void hid_put_device(struct hid_device *hid); > int hid_bpf_allocate_event_data(struct hid_device *hdev); > +#ifdef CONFIG_BPF_JIT > void __hid_bpf_ops_destroy_device(struct hid_device *hdev); > +#else > +static inline void __hid_bpf_ops_destroy_device(struct hid_device *hdev) > +{ > +} > +#endif > int hid_bpf_reconnect(struct hid_device *hdev); > > struct bpf_prog; > -- > 2.39.2 >
On Fri, Jul 19, 2024, at 15:52, Benjamin Tissoires wrote: > On Jul 19 2024, Arnd Bergmann wrote: >> >> This could be avoided by making HID-BPF just depend on JIT, but that >> is probably not what we want here. Checking the other users of struct_ops, >> I see that those just leave out the struct_ops usage, so do the same here. > > Actually, if we make the struct_ops part only depend on JIT HID-BPF is > kind of moot. All we could do is use HID-BPF to communicate with the > device, without getting any feedback, so nothing much more than what > hidraw provides. > > The only "interesting" bit we could do is inject a new event on a device > as if it were originated from the device itself, but I really do not see > the point without the struct_ops hooks. > > So I think struct_ops is now the base for HID-BPF, and if it's not > available, we should not have HID-BPF at all. > Ok, got it. So my original patch was correct after all. I had tried this version and then discarded it. Arnd 8<------ Subject: [PATCH] hid: bpf: add BPF_JIT dependency The module does not do anything when the JIT is disabled, but instead causes a warning: In file included from include/linux/bpf_verifier.h:7, from drivers/hid/bpf/hid_bpf_struct_ops.c:10: drivers/hid/bpf/hid_bpf_struct_ops.c: In function 'hid_bpf_struct_ops_init': include/linux/bpf.h:1853:50: error: statement with no effect [-Werror=unused-value] 1853 | #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; }) | ^~~~~~~~~~~~~~~~ drivers/hid/bpf/hid_bpf_struct_ops.c:305:16: note: in expansion of macro 'register_bpf_struct_ops' 305 | return register_bpf_struct_ops(&bpf_hid_bpf_ops, hid_bpf_ops); | ^~~~~~~~~~~~~~~~~~~~~~~ Add a Kconfig dependency to only allow building the HID-BPF support when a JIT is enabled. Fixes: ebc0d8093e8c ("HID: bpf: implement HID-BPF through bpf_struct_ops") Signed-off-by: Arnd Bergmann <arnd@arndb.de> ---- diff --git a/drivers/hid/bpf/Kconfig b/drivers/hid/bpf/Kconfig index 83214bae6768..d65482e02a6c 100644 --- a/drivers/hid/bpf/Kconfig +++ b/drivers/hid/bpf/Kconfig @@ -3,7 +3,7 @@ menu "HID-BPF support" config HID_BPF bool "HID-BPF support" - depends on BPF + depends on BPF_JIT depends on BPF_SYSCALL depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS help
On Jul 19 2024, Arnd Bergmann wrote: > On Fri, Jul 19, 2024, at 15:52, Benjamin Tissoires wrote: > > On Jul 19 2024, Arnd Bergmann wrote: > >> > >> This could be avoided by making HID-BPF just depend on JIT, but that > >> is probably not what we want here. Checking the other users of struct_ops, > >> I see that those just leave out the struct_ops usage, so do the same here. > > > > Actually, if we make the struct_ops part only depend on JIT HID-BPF is > > kind of moot. All we could do is use HID-BPF to communicate with the > > device, without getting any feedback, so nothing much more than what > > hidraw provides. > > > > The only "interesting" bit we could do is inject a new event on a device > > as if it were originated from the device itself, but I really do not see > > the point without the struct_ops hooks. > > > > So I think struct_ops is now the base for HID-BPF, and if it's not > > available, we should not have HID-BPF at all. > > > > Ok, got it. So my original patch was correct after all. > I had tried this version and then discarded it. > > Arnd > > 8<------ > Subject: [PATCH] hid: bpf: add BPF_JIT dependency > > The module does not do anything when the JIT is disabled, but instead > causes a warning: > > In file included from include/linux/bpf_verifier.h:7, > from drivers/hid/bpf/hid_bpf_struct_ops.c:10: > drivers/hid/bpf/hid_bpf_struct_ops.c: In function 'hid_bpf_struct_ops_init': > include/linux/bpf.h:1853:50: error: statement with no effect [-Werror=unused-value] > 1853 | #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; }) > | ^~~~~~~~~~~~~~~~ > drivers/hid/bpf/hid_bpf_struct_ops.c:305:16: note: in expansion of macro 'register_bpf_struct_ops' > 305 | return register_bpf_struct_ops(&bpf_hid_bpf_ops, hid_bpf_ops); > | ^~~~~~~~~~~~~~~~~~~~~~~ > > Add a Kconfig dependency to only allow building the HID-BPF support > when a JIT is enabled. > > Fixes: ebc0d8093e8c ("HID: bpf: implement HID-BPF through bpf_struct_ops") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > ---- > diff --git a/drivers/hid/bpf/Kconfig b/drivers/hid/bpf/Kconfig > index 83214bae6768..d65482e02a6c 100644 > --- a/drivers/hid/bpf/Kconfig > +++ b/drivers/hid/bpf/Kconfig > @@ -3,7 +3,7 @@ menu "HID-BPF support" > > config HID_BPF > bool "HID-BPF support" > - depends on BPF > + depends on BPF_JIT > depends on BPF_SYSCALL > depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS > help Thanks. I've applied this patch to for-6.11/upstream-fixes in the HID tree. Cheers, Benjamin
diff --git a/drivers/hid/bpf/Makefile b/drivers/hid/bpf/Makefile index d1f2b81788ca..7566be8eefba 100644 --- a/drivers/hid/bpf/Makefile +++ b/drivers/hid/bpf/Makefile @@ -8,4 +8,5 @@ LIBBPF_INCLUDE = $(srctree)/tools/lib obj-$(CONFIG_HID_BPF) += hid_bpf.o CFLAGS_hid_bpf_dispatch.o += -I$(LIBBPF_INCLUDE) CFLAGS_hid_bpf_jmp_table.o += -I$(LIBBPF_INCLUDE) -hid_bpf-objs += hid_bpf_dispatch.o hid_bpf_struct_ops.o +hid_bpf-y += hid_bpf_dispatch.o +hid_bpf-$(CONFIG_BPF_JIT) += hid_bpf_struct_ops.o diff --git a/drivers/hid/bpf/hid_bpf_dispatch.h b/drivers/hid/bpf/hid_bpf_dispatch.h index 44c6ea22233f..577572f41454 100644 --- a/drivers/hid/bpf/hid_bpf_dispatch.h +++ b/drivers/hid/bpf/hid_bpf_dispatch.h @@ -14,7 +14,13 @@ struct hid_bpf_ctx_kern { struct hid_device *hid_get_device(unsigned int hid_id); void hid_put_device(struct hid_device *hid); int hid_bpf_allocate_event_data(struct hid_device *hdev); +#ifdef CONFIG_BPF_JIT void __hid_bpf_ops_destroy_device(struct hid_device *hdev); +#else +static inline void __hid_bpf_ops_destroy_device(struct hid_device *hdev) +{ +} +#endif int hid_bpf_reconnect(struct hid_device *hdev); struct bpf_prog;