On Fri, Jan 23, 2026 at 12:43 AM Changwoo Min <[email protected]> wrote: > > Introduce bpf_in_nmi(), bpf_in_hardirq(), bpf_in_serving_softirq(), and > bpf_in_task() kfuncs to allow BPF programs to query the current execution > context. > > While BPF programs can sometimes infer context based on the attach point, > certain programs (such as those in sched_ext) may be called from multiple > contexts. These kfuncs provide a reliable way for logic to branch based on > whether the CPU is currently handling an interrupt or executing in task > context. > > For example, this is particularly useful for sched_ext schedulers that need > to differentiate between task-to-task wake-ups and interrupt-to-task > wake-ups. > > As the names imply, these helpers wrap the kernel's internal in_nmi(), > in_hardirq(), in_serving_softirq(), and in_task() macros. > > Signed-off-by: Changwoo Min <[email protected]> > --- > kernel/bpf/helpers.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 44 insertions(+) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 637677815365..cb36bc7a80c6 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -4365,6 +4365,46 @@ __bpf_kfunc int bpf_dynptr_file_discard(struct > bpf_dynptr *dynptr) > return 0; > } > > +/** > + * bpf_in_nmi - Test if the current execution context is in NMI context. > + * > + * Return: true if we are in NMI context, false otherwise. > + */ > +__bpf_kfunc bool bpf_in_nmi(void) > +{ > + return in_nmi(); > +} > + > +/** > + * bpf_in_hardirq - Test if the current execution context is in hard IRQ > context. > + * > + * Return: true if we are in hard IRQ context, false otherwise. > + */ > +__bpf_kfunc bool bpf_in_hardirq(void) > +{ > + return in_hardirq(); > +} > + > +/** > + * bpf_in_serving_softirq - Test if the current execution context is in > softirq context. > + * > + * Return: true if we are in softirq context, false otherwise. > + */ > +__bpf_kfunc bool bpf_in_serving_softirq(void) > +{ > + return in_serving_softirq(); > +} > + > +/** > + * bpf_in_task - Test if the current execution context is in task context. > + * > + * Return: true if we are in task context, false otherwise. > + */ > +__bpf_kfunc bool bpf_in_task(void) > +{ > + return in_task(); > +} > +
This functionality is already available. See bpf_in_interrupt() and get_preempt_count() in bpf_experimental.h. No need to replicate that as kfuncs. If something can be implemented as a bpf program it should stay as pure bpf code, since it's more flexible and faster this way. llvm together with JITs completely inline get_preempt_count(). pw-bot: cr
