Messages in this thread | | | Date | Wed, 23 Nov 2022 13:25:04 +0000 | Subject | Re: [PATCH hid v12 03/15] HID: initial BPF implementation | From | Jon Hunter <> |
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On 03/11/2022 15:57, Benjamin Tissoires wrote: > Declare an entry point that can use fmod_ret BPF programs, and > also an API to access and change the incoming data. > > A simpler implementation would consist in just calling > hid_bpf_device_event() for any incoming event and let users deal > with the fact that they will be called for any event of any device. > > The goal of HID-BPF is to partially replace drivers, so this situation > can be problematic because we might have programs which will step on > each other toes. > > For that, we add a new API hid_bpf_attach_prog() that can be called > from a syscall and we manually deal with a jump table in hid-bpf. > > Whenever we add a program to the jump table (in other words, when we > attach a program to a HID device), we keep the number of time we added > this program in the jump table so we can release it whenever there are > no other users. > > HID devices have an RCU protected list of available programs in the > jump table, and those programs are called one after the other thanks > to bpf_tail_call(). > > To achieve the detection of users losing their fds on the programs we > attached, we add 2 tracing facilities on bpf_prog_release() (for when > a fd is closed) and bpf_free_inode() (for when a pinned program gets > unpinned). > > Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
...
> +static int __init hid_bpf_init(void) > +{ > + int err; > + > + /* Note: if we exit with an error any time here, we would entirely break HID, which > + * is probably not something we want. So we log an error and return success. > + * > + * This is not a big deal: the syscall allowing to attach a BPF program to a HID device > + * will not be available, so nobody will be able to use the functionality. > + */ > + > + err = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &hid_bpf_kfunc_set); > + if (err) { > + pr_warn("error while setting HID BPF tracing kfuncs: %d", err); > + return 0; > + } > + > + err = hid_bpf_preload_skel(); > + if (err) { > + pr_warn("error while preloading HID BPF dispatcher: %d", err); > + return 0; > + } > + > + /* register syscalls after we are sure we can load our preloaded bpf program */ > + err = register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &hid_bpf_syscall_kfunc_set); > + if (err) { > + pr_warn("error while setting HID BPF syscall kfuncs: %d", err); > + return 0; > + } > + > + return 0; > +}
We have a kernel test that checks for new warning and error messages on boot and with this change I am now seeing the following error message on our Tegra platforms ...
WARNING KERN hid_bpf: error while preloading HID BPF dispatcher: -13
I have a quick look at the code, but I can't say I am familiar with this. So I wanted to ask if a way to fix this or avoid this? I see the code returns 0, so one option would be to make this an informational or debug print.
Thanks Jon
-- nvpublic
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