On Wed, Dec 11, 2024 at 1:29 PM Juntong Deng <juntong.deng@xxxxxxxxxxx> wrote: > > On 2024/12/10 18:58, Alexei Starovoitov wrote: > > On Tue, Dec 10, 2024 at 6:43 AM Christian Brauner <brauner@xxxxxxxxxx> wrote: > >> > >> On Tue, Dec 10, 2024 at 02:03:53PM +0000, Juntong Deng wrote: > >>> Currently fs kfuncs are only available for LSM program type, but fs > >>> kfuncs are generic and useful for scenarios other than LSM. > >>> > >>> This patch makes fs kfuncs available for SYSCALL and TRACING > >>> program types. > >> > >> I would like a detailed explanation from the maintainers what it means > >> to make this available to SYSCALL program types, please. > > > > Sigh. > > This is obviously not safe from tracing progs. > > > > From BPF_PROG_TYPE_SYSCALL these kfuncs should be safe to use, > > since those progs are not attached to anything. > > Such progs can only be executed via sys_bpf syscall prog_run command. > > They're sleepable, preemptable, faultable, in task ctx. > > > > But I'm not sure what's the value of enabling these kfuncs for > > BPF_PROG_TYPE_SYSCALL. > > Thanks for your reply. > > Song said here that we need some of these kfuncs to be available for > tracing functions [0]. > > If Song saw this email, could you please join the discussion? > > [0]: > https://lore.kernel.org/bpf/CAPhsuW6ud21v2xz8iSXf=CiDL+R_zpQ+p8isSTMTw=EiJQtRSw@xxxxxxxxxxxxxx/ > > For BPF_PROG_TYPE_SYSCALL, I think BPF_PROG_TYPE_SYSCALL has now > exceeded its original designed purpose and has become a more general > program type. > > Currently BPF_PROG_TYPE_SYSCALL is widely used in HID drivers, and there > are some use cases in sched-ext (CRIB is also a use case, although still > in infancy). hid switched to use struct_ops prog type. I believe syscall prog type in hid is a legacy code. Those still present might be leftovers for older kernels. sched-ext is struct_ops only. No syscall progs there. > As BPF_PROG_TYPE_SYSCALL becomes more general, it would be valuable to > make more kfuncs available for BPF_PROG_TYPE_SYSCALL. Maybe. I still don't understand how it helps CRIB goal.
