Introduce bpf_in_nmi(), bpf_in_hardirq(), bpf_in_serving_softirq(), and bpf_in_task() inline helpers in bpf_experimental.h. These allow BPF programs to query the current execution context with higher granularity than the existing bpf_in_interrupt() helper.
While BPF programs can often infer their context from attachment points, subsystems like sched_ext may call the same BPF logic from multiple contexts (e.g., task-to-task wake-ups vs. interrupt-to-task wake-ups). These helpers provide a reliable way for logic to branch based on the current CPU execution state. Implementing these as BPF-native inline helpers wrapping get_preempt_count() allows the compiler and JIT to inline the logic. The implementation accounts for differences in preempt_count layout between standard and PREEMPT_RT kernels. Signed-off-by: Changwoo Min <[email protected]> --- .../testing/selftests/bpf/bpf_experimental.h | 38 +++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h index 68a49b1f77ae..30abdc08366f 100644 --- a/tools/testing/selftests/bpf/bpf_experimental.h +++ b/tools/testing/selftests/bpf/bpf_experimental.h @@ -610,6 +610,8 @@ extern int bpf_cgroup_read_xattr(struct cgroup *cgroup, const char *name__str, #define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) #define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) +#define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) + extern bool CONFIG_PREEMPT_RT __kconfig __weak; #ifdef bpf_target_x86 extern const int __preempt_count __ksym; @@ -648,4 +650,40 @@ static inline int bpf_in_interrupt(void) (tsk->softirq_disable_cnt & SOFTIRQ_MASK); } +static inline int bpf_in_nmi(void) +{ + return get_preempt_count() & NMI_MASK; +} + +static inline int bpf_in_hardirq(void) +{ + return get_preempt_count() & HARDIRQ_MASK; +} + +static inline int bpf_in_serving_softirq(void) +{ + struct task_struct___preempt_rt *tsk; + int pcnt; + + pcnt = get_preempt_count(); + if (!CONFIG_PREEMPT_RT) + return (pcnt & SOFTIRQ_MASK) & SOFTIRQ_OFFSET; + + tsk = (void *) bpf_get_current_task_btf(); + return (tsk->softirq_disable_cnt & SOFTIRQ_MASK) & SOFTIRQ_OFFSET; +} + +static inline int bpf_in_task(void) +{ + struct task_struct___preempt_rt *tsk; + int pcnt; + + pcnt = get_preempt_count(); + if (!CONFIG_PREEMPT_RT) + return !(pcnt & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)); + + tsk = (void *) bpf_get_current_task_btf(); + return !((pcnt & (NMI_MASK | HARDIRQ_MASK)) | + ((tsk->softirq_disable_cnt & SOFTIRQ_MASK) & SOFTIRQ_OFFSET)); +} #endif -- 2.52.0
