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bpf: Introduce css_task open-coded iterator kfuncs
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>
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@ -2560,6 +2560,9 @@ BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
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BTF_ID_FLAGS(func, bpf_iter_task_vma_new, KF_ITER_NEW | KF_RCU)
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BTF_ID_FLAGS(func, bpf_iter_task_vma_next, KF_ITER_NEXT | KF_RET_NULL)
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BTF_ID_FLAGS(func, bpf_iter_task_vma_destroy, KF_ITER_DESTROY)
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BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
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BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL)
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BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY)
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BTF_ID_FLAGS(func, bpf_dynptr_adjust)
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BTF_ID_FLAGS(func, bpf_dynptr_is_null)
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BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
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@ -894,6 +894,64 @@ __bpf_kfunc void bpf_iter_task_vma_destroy(struct bpf_iter_task_vma *it)
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__diag_pop();
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struct bpf_iter_css_task {
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__u64 __opaque[1];
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} __attribute__((aligned(8)));
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struct bpf_iter_css_task_kern {
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struct css_task_iter *css_it;
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} __attribute__((aligned(8)));
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__diag_push();
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__diag_ignore_all("-Wmissing-prototypes",
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"Global functions as their definitions will be in vmlinux BTF");
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__bpf_kfunc int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
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struct cgroup_subsys_state *css, unsigned int flags)
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{
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struct bpf_iter_css_task_kern *kit = (void *)it;
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BUILD_BUG_ON(sizeof(struct bpf_iter_css_task_kern) != sizeof(struct bpf_iter_css_task));
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BUILD_BUG_ON(__alignof__(struct bpf_iter_css_task_kern) !=
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__alignof__(struct bpf_iter_css_task));
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kit->css_it = NULL;
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switch (flags) {
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case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
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case CSS_TASK_ITER_PROCS:
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case 0:
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break;
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default:
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return -EINVAL;
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}
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kit->css_it = bpf_mem_alloc(&bpf_global_ma, sizeof(struct css_task_iter));
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if (!kit->css_it)
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return -ENOMEM;
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css_task_iter_start(css, flags, kit->css_it);
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return 0;
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}
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__bpf_kfunc struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it)
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{
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struct bpf_iter_css_task_kern *kit = (void *)it;
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if (!kit->css_it)
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return NULL;
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return css_task_iter_next(kit->css_it);
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}
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__bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it)
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{
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struct bpf_iter_css_task_kern *kit = (void *)it;
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if (!kit->css_it)
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return;
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css_task_iter_end(kit->css_it);
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bpf_mem_free(&bpf_global_ma, kit->css_it);
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}
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__diag_pop();
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DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
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static void do_mmap_read_unlock(struct irq_work *entry)
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@ -10472,6 +10472,7 @@ enum special_kfunc_type {
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KF_bpf_percpu_obj_new_impl,
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KF_bpf_percpu_obj_drop_impl,
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KF_bpf_throw,
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KF_bpf_iter_css_task_new,
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};
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BTF_SET_START(special_kfunc_set)
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@ -10495,6 +10496,7 @@ BTF_ID(func, bpf_dynptr_clone)
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BTF_ID(func, bpf_percpu_obj_new_impl)
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BTF_ID(func, bpf_percpu_obj_drop_impl)
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BTF_ID(func, bpf_throw)
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BTF_ID(func, bpf_iter_css_task_new)
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BTF_SET_END(special_kfunc_set)
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BTF_ID_LIST(special_kfunc_list)
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@ -10520,6 +10522,7 @@ BTF_ID(func, bpf_dynptr_clone)
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BTF_ID(func, bpf_percpu_obj_new_impl)
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BTF_ID(func, bpf_percpu_obj_drop_impl)
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BTF_ID(func, bpf_throw)
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BTF_ID(func, bpf_iter_css_task_new)
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static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
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{
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@ -11050,6 +11053,20 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env,
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&meta->arg_rbtree_root.field);
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}
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static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env)
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{
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enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
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switch (prog_type) {
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case BPF_PROG_TYPE_LSM:
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return true;
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case BPF_TRACE_ITER:
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return env->prog->aux->sleepable;
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default:
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return false;
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}
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}
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static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
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int insn_idx)
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{
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@ -11300,6 +11317,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
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break;
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}
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case KF_ARG_PTR_TO_ITER:
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if (meta->func_id == special_kfunc_list[KF_bpf_iter_css_task_new]) {
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if (!check_css_task_iter_allowlist(env)) {
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verbose(env, "css_task_iter is only allowed in bpf_lsm and bpf iter-s\n");
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return -EINVAL;
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}
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}
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ret = process_iter_arg(env, regno, insn_idx, meta);
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if (ret < 0)
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return ret;
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@ -458,4 +458,12 @@ extern void bpf_throw(u64 cookie) __ksym;
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__bpf_assert_op(LHS, <=, END, value, false); \
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})
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struct bpf_iter_css_task;
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struct cgroup_subsys_state;
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extern int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
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struct cgroup_subsys_state *css, unsigned int flags) __weak __ksym;
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extern struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it) __weak __ksym;
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extern void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it) __weak __ksym;
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#endif
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