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bpf: Introduce css_task open-coded iterator kfuncs

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This patch adds kfuncs bpf_iter_css_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_css_task in open-coded
iterator style. These kfuncs actually wrapps css_task_iter_{start,next,
end}. BPF programs can use these kfuncs through bpf_for_each macro for
iteration of all tasks under a css.

css_task_iter_*() would try to get the global spin-lock *css_set_lock*, so
the bpf side has to be careful in where it allows to use this iter.
Currently we only allow it in bpf_lsm and bpf iter-s.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-3-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Chuyi Zhou 2023-10-18 14:17:40 +08:00 committed by Alexei Starovoitov
parent 6da8830681
commit 9c66dc94b6
4 changed files with 92 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
kernel/bpf/helpers.c
View file

@ -2560,6 +2560,9 @@ BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_task_vma_new, KF_ITER_NEW | KF_RCU)
BTF_ID_FLAGS(func, bpf_iter_task_vma_next, KF_ITER_NEXT | KF_RET_NULL)
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_dynptr_adjust)
BTF_ID_FLAGS(func, bpf_dynptr_is_null)
BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)

58
kernel/bpf/task_iter.c
View file

@ -894,6 +894,64 @@ __bpf_kfunc void bpf_iter_task_vma_destroy(struct bpf_iter_task_vma *it)
__diag_pop();
struct bpf_iter_css_task {
__u64 __opaque[1];
} __attribute__((aligned(8)));
struct bpf_iter_css_task_kern {
struct css_task_iter *css_it;
} __attribute__((aligned(8)));
__diag_push();
__diag_ignore_all("-Wmissing-prototypes",
"Global functions as their definitions will be in vmlinux BTF");
__bpf_kfunc int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
struct cgroup_subsys_state *css, unsigned int flags)
{
struct bpf_iter_css_task_kern *kit = (void *)it;
BUILD_BUG_ON(sizeof(struct bpf_iter_css_task_kern) != sizeof(struct bpf_iter_css_task));
BUILD_BUG_ON(__alignof__(struct bpf_iter_css_task_kern) !=
__alignof__(struct bpf_iter_css_task));
kit->css_it = NULL;
switch (flags) {
case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
case CSS_TASK_ITER_PROCS:
case 0:
break;
default:
return -EINVAL;
}
kit->css_it = bpf_mem_alloc(&bpf_global_ma, sizeof(struct css_task_iter));
if (!kit->css_it)
return -ENOMEM;
css_task_iter_start(css, flags, kit->css_it);
return 0;
}
__bpf_kfunc struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it)
{
struct bpf_iter_css_task_kern *kit = (void *)it;
if (!kit->css_it)
return NULL;
return css_task_iter_next(kit->css_it);
}
__bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it)
{
struct bpf_iter_css_task_kern *kit = (void *)it;
if (!kit->css_it)
return;
css_task_iter_end(kit->css_it);
bpf_mem_free(&bpf_global_ma, kit->css_it);
}
__diag_pop();
DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
static void do_mmap_read_unlock(struct irq_work *entry)

23
kernel/bpf/verifier.c
View file

@ -10472,6 +10472,7 @@ enum special_kfunc_type {
KF_bpf_percpu_obj_new_impl,
KF_bpf_percpu_obj_drop_impl,
KF_bpf_throw,
KF_bpf_iter_css_task_new,
};
BTF_SET_START(special_kfunc_set)
@ -10495,6 +10496,7 @@ BTF_ID(func, bpf_dynptr_clone)
BTF_ID(func, bpf_percpu_obj_new_impl)
BTF_ID(func, bpf_percpu_obj_drop_impl)
BTF_ID(func, bpf_throw)
BTF_ID(func, bpf_iter_css_task_new)
BTF_SET_END(special_kfunc_set)
BTF_ID_LIST(special_kfunc_list)
@ -10520,6 +10522,7 @@ BTF_ID(func, bpf_dynptr_clone)
BTF_ID(func, bpf_percpu_obj_new_impl)
BTF_ID(func, bpf_percpu_obj_drop_impl)
BTF_ID(func, bpf_throw)
BTF_ID(func, bpf_iter_css_task_new)
static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
{
@ -11050,6 +11053,20 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env,
&meta->arg_rbtree_root.field);
}
static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env)
{
enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
switch (prog_type) {
case BPF_PROG_TYPE_LSM:
return true;
case BPF_TRACE_ITER:
return env->prog->aux->sleepable;
default:
return false;
}
}
static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
int insn_idx)
{
@ -11300,6 +11317,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
break;
}
case KF_ARG_PTR_TO_ITER:
if (meta->func_id == special_kfunc_list[KF_bpf_iter_css_task_new]) {
if (!check_css_task_iter_allowlist(env)) {
verbose(env, "css_task_iter is only allowed in bpf_lsm and bpf iter-s\n");
return -EINVAL;
}
}
ret = process_iter_arg(env, regno, insn_idx, meta);
if (ret < 0)
return ret;

8
tools/testing/selftests/bpf/bpf_experimental.h
View file

@ -458,4 +458,12 @@ extern void bpf_throw(u64 cookie) __ksym;
__bpf_assert_op(LHS, <=, END, value, false); \
})
struct bpf_iter_css_task;
struct cgroup_subsys_state;
extern int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
struct cgroup_subsys_state *css, unsigned int flags) __weak __ksym;
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;
#endif