github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-06-03 20:14:06 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

selftests/bpf: Introduce experimental bpf_in_interrupt()

Browse Source 
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>
This commit is contained in:
Leon Hwang 2025-09-03 22:04:37 +08:00 committed by Alexei Starovoitov
parent 929adf8838
commit 4b69e31329
1 changed files with 54 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
tools/testing/selftests/bpf/bpf_experimental.h
View File

@ -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