diff options
| author | Leon Hwang <leon.hwang@linux.dev> | 2025-09-03 22:04:37 +0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2025-09-04 09:05:58 -0700 |
| commit | 4b69e31329b6ef22dc80b45d4a865f57c2346d44 (patch) | |
| tree | 516c35ec9a9c6513a74ddc2ef6f1726f8dbcfa51 /tools/testing | |
| parent | bpf, arm64: Remove duplicated bpf_flush_icache() (diff) | |
| download | linux-4b69e31329b6ef22dc80b45d4a865f57c2346d44.tar.gz linux-4b69e31329b6ef22dc80b45d4a865f57c2346d44.zip | |
selftests/bpf: Introduce experimental bpf_in_interrupt()
Filtering pid_tgid is meanlingless when the current task is preempted by
an interrupt.
To address this, introduce 'bpf_in_interrupt()' helper function, which
allows BPF programs to determine whether they are executing in interrupt
context.
'get_preempt_count()':
* On x86, '*(int *) bpf_this_cpu_ptr(&__preempt_count)'.
* On arm64, 'bpf_get_current_task_btf()->thread_info.preempt.count'.
Then 'bpf_in_interrupt()' will be:
* If !PREEMPT_RT, 'get_preempt_count() & (NMI_MASK | HARDIRQ_MASK
| SOFTIRQ_MASK)'.
* If PREEMPT_RT, '(get_preempt_count() & (NMI_MASK | HARDIRQ_MASK))
| (bpf_get_current_task_btf()->softirq_disable_cnt & SOFTIRQ_MASK)'.
As for other archs, it can be added support by updating
'get_preempt_count()'.
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20250903140438.59517-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools/testing')
| -rw-r--r-- | tools/testing/selftests/bpf/bpf_experimental.h | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h index da7e230f2781..d89eda3fd8a3 100644 --- a/tools/testing/selftests/bpf/bpf_experimental.h +++ b/tools/testing/selftests/bpf/bpf_experimental.h @@ -599,4 +599,58 @@ extern void bpf_iter_dmabuf_destroy(struct bpf_iter_dmabuf *it) __weak __ksym; extern int bpf_cgroup_read_xattr(struct cgroup *cgroup, const char *name__str, struct bpf_dynptr *value_p) __weak __ksym; +#define PREEMPT_BITS 8 +#define SOFTIRQ_BITS 8 +#define HARDIRQ_BITS 4 +#define NMI_BITS 4 + +#define PREEMPT_SHIFT 0 +#define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) +#define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) +#define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) + +#define __IRQ_MASK(x) ((1UL << (x))-1) + +#define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) +#define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) +#define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) + +extern bool CONFIG_PREEMPT_RT __kconfig __weak; +#ifdef bpf_target_x86 +extern const int __preempt_count __ksym; +#endif + +struct task_struct___preempt_rt { + int softirq_disable_cnt; +} __attribute__((preserve_access_index)); + +static inline int get_preempt_count(void) +{ +#if defined(bpf_target_x86) + return *(int *) bpf_this_cpu_ptr(&__preempt_count); +#elif defined(bpf_target_arm64) + return bpf_get_current_task_btf()->thread_info.preempt.count; +#endif + return 0; +} + +/* Description + * Report whether it is in interrupt context. Only works on the following archs: + * * x86 + * * arm64 + */ +static inline int bpf_in_interrupt(void) +{ + struct task_struct___preempt_rt *tsk; + int pcnt; + + pcnt = get_preempt_count(); + if (!CONFIG_PREEMPT_RT) + return pcnt & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_MASK); + + tsk = (void *) bpf_get_current_task_btf(); + return (pcnt & (NMI_MASK | HARDIRQ_MASK)) | + (tsk->softirq_disable_cnt & SOFTIRQ_MASK); +} + #endif |