diff mbox series

[HID,for-next,v3,3/5] HID: bpf: enforce HID_BPF dependencies

Message ID 20221206145936.922196-4-benjamin.tissoires@redhat.com
State New
Headers
Series HID: bpf: remove the need for ALLOW_ERROR_INJECTION and Kconfig fixes |

Commit Message

Benjamin Tissoires Dec. 6, 2022, 2:59 p.m. UTC 
  As mentioned in the link below, having JIT and BPF is not enough to
have fentry/fexit/fmod_ret APIs. This resolves the error that
happens on a system without tracing enabled when hid-bpf tries to
load itself.

Link: https://lore.kernel.org/r/CABRcYmKyRchQhabi1Vd9RcMQFCcb=EtWyEbFDFRTc-L-U8WhgA@mail.gmail.com
Fixes: f5c27da4e3c8 ("HID: initial BPF implementation")
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---

no changes in v3

changes in v2:
- dropped ALLOW_ERROR_INJECTION requirement
---
 drivers/hid/bpf/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Benjamin Tissoires Dec. 7, 2022, 2:58 p.m. UTC | #1 
On Tue, Dec 6, 2022 at 3:59 PM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> As mentioned in the link below, having JIT and BPF is not enough to
> have fentry/fexit/fmod_ret APIs. This resolves the error that
> happens on a system without tracing enabled when hid-bpf tries to
> load itself.
>
> Link: https://lore.kernel.org/r/CABRcYmKyRchQhabi1Vd9RcMQFCcb=EtWyEbFDFRTc-L-U8WhgA@mail.gmail.com
> Fixes: f5c27da4e3c8 ("HID: initial BPF implementation")
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
>
> ---
>
> no changes in v3
>
> changes in v2:
> - dropped ALLOW_ERROR_INJECTION requirement

Florent, can I keep your reviewed-by on this patch?

Jon, may I ask you to do one more testing with the full v3 applied on
top of for-next?

Cheers,
Benjamin

> ---
>  drivers/hid/bpf/Kconfig | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/bpf/Kconfig b/drivers/hid/bpf/Kconfig
> index 298634fc3335..03f52145b83b 100644
> --- a/drivers/hid/bpf/Kconfig
> +++ b/drivers/hid/bpf/Kconfig
> @@ -4,7 +4,8 @@ menu "HID-BPF support"
>  config HID_BPF
>         bool "HID-BPF support"
>         default HID_SUPPORT
> -       depends on BPF && BPF_SYSCALL
> +       depends on BPF && BPF_SYSCALL && \
> +                  DYNAMIC_FTRACE_WITH_DIRECT_CALLS
>         help
>         This option allows to support eBPF programs on the HID subsystem.
>         eBPF programs can fix HID devices in a lighter way than a full
> --
> 2.38.1
>
Florent Revest Dec. 7, 2022, 3:11 p.m. UTC | #2 
On Wed, Dec 7, 2022 at 3:58 PM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> On Tue, Dec 6, 2022 at 3:59 PM Benjamin Tissoires
> <benjamin.tissoires@redhat.com> wrote:
> >
> > As mentioned in the link below, having JIT and BPF is not enough to
> > have fentry/fexit/fmod_ret APIs. This resolves the error that
> > happens on a system without tracing enabled when hid-bpf tries to
> > load itself.
> >
> > Link: https://lore.kernel.org/r/CABRcYmKyRchQhabi1Vd9RcMQFCcb=EtWyEbFDFRTc-L-U8WhgA@mail.gmail.com
> > Fixes: f5c27da4e3c8 ("HID: initial BPF implementation")
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> >
> > ---
> >
> > no changes in v3
> >
> > changes in v2:
> > - dropped ALLOW_ERROR_INJECTION requirement
>
> Florent, can I keep your reviewed-by on this patch?

Yes! :)
Reviewed-by: Florent Revest <revest@chromium.org>

Thank you for the updated series, I think it's cleaner than relying on
error injection indeed.

I still believe that, in the future, BPF should offer a proxy config
to expose if BPF tracing is supported because 1- the implementation of
BPF tracing could someday change 2- to be exactly correct, ftrace
direct call isn't _really_ a sufficient condition either: the BPF JIT
also needs to implement the arch_prepare_bpf_trampoline function.
Currently, there is no config to check if that feature is available.
But as agreed in a previous thread, that consolidation can be done
separately. For now your patch looks good enough to me already.
diff mbox series

Patch

diff --git a/drivers/hid/bpf/Kconfig b/drivers/hid/bpf/Kconfig
index 298634fc3335..03f52145b83b 100644
--- a/drivers/hid/bpf/Kconfig
+++ b/drivers/hid/bpf/Kconfig
@@ -4,7 +4,8 @@  menu "HID-BPF support"
 config HID_BPF
 	bool "HID-BPF support"
 	default HID_SUPPORT
-	depends on BPF && BPF_SYSCALL
+	depends on BPF && BPF_SYSCALL && \
+		   DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 	help
 	This option allows to support eBPF programs on the HID subsystem.
 	eBPF programs can fix HID devices in a lighter way than a full