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bpf: Introduce task open coded iterator kfuncs

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This patch adds kfuncs bpf_iter_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_task in open-coded iterator
style. BPF programs can use these kfuncs or through bpf_for_each macro to
iterate all processes in the system.

The API design keep consistent with SEC("iter/task"). bpf_iter_task_new()
accepts a specific task and iterating type which allows:

1. iterating all process in the system (BPF_TASK_ITER_ALL_PROCS)

2. iterating all threads in the system (BPF_TASK_ITER_ALL_THREADS)

3. iterating all threads of a specific task (BPF_TASK_ITER_PROC_THREADS)

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Link: https://lore.kernel.org/r/20231018061746.111364-4-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Chuyi Zhou
2023-10-18 14:17:41 +08:00
committed by Alexei Starovoitov
parent 9c66dc94b6
commit c68a78ffe2
3 changed files with 98 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
kernel/bpf/helpers.c
View File

@ -2563,6 +2563,9 @@ BTF_ID_FLAGS(func, bpf_iter_task_vma_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_iter_task_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_task_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_dynptr_adjust)
BTF_ID_FLAGS(func, bpf_dynptr_is_null)
BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)

90
kernel/bpf/task_iter.c
View File

@ -952,6 +952,96 @@ __bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it)
__diag_pop();
struct bpf_iter_task {
__u64 __opaque[3];
} __attribute__((aligned(8)));
struct bpf_iter_task_kern {
struct task_struct *task;
struct task_struct *pos;
unsigned int flags;
} __attribute__((aligned(8)));
enum {
/* all process in the system */
BPF_TASK_ITER_ALL_PROCS,
/* all threads in the system */
BPF_TASK_ITER_ALL_THREADS,
/* all threads of a specific process */
BPF_TASK_ITER_PROC_THREADS
};
__diag_push();
__diag_ignore_all("-Wmissing-prototypes",
"Global functions as their definitions will be in vmlinux BTF");
__bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it,
struct task_struct *task, unsigned int flags)
{
struct bpf_iter_task_kern *kit = (void *)it;
BUILD_BUG_ON(sizeof(struct bpf_iter_task_kern) > sizeof(struct bpf_iter_task));
BUILD_BUG_ON(__alignof__(struct bpf_iter_task_kern) !=
__alignof__(struct bpf_iter_task));
kit->task = kit->pos = NULL;
switch (flags) {
case BPF_TASK_ITER_ALL_THREADS:
case BPF_TASK_ITER_ALL_PROCS:
case BPF_TASK_ITER_PROC_THREADS:
break;
default:
return -EINVAL;
}
if (flags == BPF_TASK_ITER_PROC_THREADS)
kit->task = task;
else
kit->task = &init_task;
kit->pos = kit->task;
kit->flags = flags;
return 0;
}
__bpf_kfunc struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it)
{
struct bpf_iter_task_kern *kit = (void *)it;
struct task_struct *pos;
unsigned int flags;
flags = kit->flags;
pos = kit->pos;
if (!pos)
return pos;
if (flags == BPF_TASK_ITER_ALL_PROCS)
goto get_next_task;
kit->pos = next_thread(kit->pos);
if (kit->pos == kit->task) {
if (flags == BPF_TASK_ITER_PROC_THREADS) {
kit->pos = NULL;
return pos;
}
} else
return pos;
get_next_task:
kit->pos = next_task(kit->pos);
kit->task = kit->pos;
if (kit->pos == &init_task)
kit->pos = NULL;
return pos;
}
__bpf_kfunc void bpf_iter_task_destroy(struct bpf_iter_task *it)
{
}
__diag_pop();
DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
static void do_mmap_read_unlock(struct irq_work *entry)

5
tools/testing/selftests/bpf/bpf_experimental.h
View File

@ -465,5 +465,10 @@ extern int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
extern struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it) __weak __ksym;
extern void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it) __weak __ksym;
struct bpf_iter_task;
extern int bpf_iter_task_new(struct bpf_iter_task *it,
struct task_struct *task, unsigned int flags) __weak __ksym;
extern struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it) __weak __ksym;
extern void bpf_iter_task_destroy(struct bpf_iter_task *it) __weak __ksym;
#endif