bpf: Refactor BPF_PROG_RUN_ARRAY family of macros into functions

Similar to BPF_PROG_RUN, turn BPF_PROG_RUN_ARRAY macros into proper functions
with all the same readability and maintainability benefits. Making them into
functions required shuffling around bpf_set_run_ctx/bpf_reset_run_ctx
functions. Also, explicitly specifying the type of the BPF prog run callback
required adjusting __bpf_prog_run_save_cb() to accept const void *, casted
internally to const struct sk_buff.

Further, split out a cgroup-specific BPF_PROG_RUN_ARRAY_CG and
BPF_PROG_RUN_ARRAY_CG_FLAGS from the more generic BPF_PROG_RUN_ARRAY due to
the differences in bpf_run_ctx used for those two different use cases.

I think BPF_PROG_RUN_ARRAY_CG would benefit from further refactoring to accept
struct cgroup and enum bpf_attach_type instead of bpf_prog_array, fetching
cgrp->bpf.effective[type] and RCU-dereferencing it internally. But that
required including include/linux/cgroup-defs.h, which I wasn't sure is ok with
everyone.

The remaining generic BPF_PROG_RUN_ARRAY function will be extended to
pass-through user-provided context value in the next patch.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210815070609.987780-3-andrii@kernel.org

include/linux/bpf.h

@@ -1146,67 +1146,116 @@ struct bpf_run_ctx {};
 
 struct bpf_cg_run_ctx {
 	struct bpf_run_ctx run_ctx;
-	struct bpf_prog_array_item *prog_item;
+	const struct bpf_prog_array_item *prog_item;
 };
 
+static inline struct bpf_run_ctx *bpf_set_run_ctx(struct bpf_run_ctx *new_ctx)
+{
+	struct bpf_run_ctx *old_ctx = NULL;
+
+#ifdef CONFIG_BPF_SYSCALL
+	old_ctx = current->bpf_ctx;
+	current->bpf_ctx = new_ctx;
+#endif
+	return old_ctx;
+}
+
+static inline void bpf_reset_run_ctx(struct bpf_run_ctx *old_ctx)
+{
+#ifdef CONFIG_BPF_SYSCALL
+	current->bpf_ctx = old_ctx;
+#endif
+}
+
 /* BPF program asks to bypass CAP_NET_BIND_SERVICE in bind. */
 #define BPF_RET_BIND_NO_CAP_NET_BIND_SERVICE			(1 << 0)
 /* BPF program asks to set CN on the packet. */
 #define BPF_RET_SET_CN						(1 << 0)
 
-#define BPF_PROG_RUN_ARRAY_FLAGS(array, ctx, func, ret_flags)		\
-	({								\
-		struct bpf_prog_array_item *_item;			\
-		struct bpf_prog *_prog;					\
-		struct bpf_prog_array *_array;				\
-		struct bpf_run_ctx *old_run_ctx;			\
-		struct bpf_cg_run_ctx run_ctx;				\
-		u32 _ret = 1;						\
-		u32 func_ret;						\
-		migrate_disable();					\
-		rcu_read_lock();					\
-		_array = rcu_dereference(array);			\
-		_item = &_array->items[0];				\
-		old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);	\
-		while ((_prog = READ_ONCE(_item->prog))) {		\
-			run_ctx.prog_item = _item;			\
-			func_ret = func(_prog, ctx);			\
-			_ret &= (func_ret & 1);				\
-			*(ret_flags) |= (func_ret >> 1);		\
-			_item++;					\
-		}							\
-		bpf_reset_run_ctx(old_run_ctx);				\
-		rcu_read_unlock();					\
-		migrate_enable();					\
-		_ret;							\
-	 })
+typedef u32 (*bpf_prog_run_fn)(const struct bpf_prog *prog, const void *ctx);
 
-#define __BPF_PROG_RUN_ARRAY(array, ctx, func, check_non_null, set_cg_storage)	\
-	({						\
-		struct bpf_prog_array_item *_item;	\
-		struct bpf_prog *_prog;			\
-		struct bpf_prog_array *_array;		\
-		struct bpf_run_ctx *old_run_ctx;	\
-		struct bpf_cg_run_ctx run_ctx;		\
-		u32 _ret = 1;				\
-		migrate_disable();			\
-		rcu_read_lock();			\
-		_array = rcu_dereference(array);	\
-		if (unlikely(check_non_null && !_array))\
-			goto _out;			\
-		_item = &_array->items[0];		\
-		old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);\
-		while ((_prog = READ_ONCE(_item->prog))) {	\
-			run_ctx.prog_item = _item;	\
-			_ret &= func(_prog, ctx);	\
-			_item++;			\
-		}					\
-		bpf_reset_run_ctx(old_run_ctx);		\
-_out:							\
-		rcu_read_unlock();			\
-		migrate_enable();			\
-		_ret;					\
-	 })
+static __always_inline u32
+BPF_PROG_RUN_ARRAY_CG_FLAGS(const struct bpf_prog_array __rcu *array_rcu,
+			    const void *ctx, bpf_prog_run_fn run_prog,
+			    u32 *ret_flags)
+{
+	const struct bpf_prog_array_item *item;
+	const struct bpf_prog *prog;
+	const struct bpf_prog_array *array;
+	struct bpf_run_ctx *old_run_ctx;
+	struct bpf_cg_run_ctx run_ctx;
+	u32 ret = 1;
+	u32 func_ret;
+
+	migrate_disable();
+	rcu_read_lock();
+	array = rcu_dereference(array_rcu);
+	item = &array->items[0];
+	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
+	while ((prog = READ_ONCE(item->prog))) {
+		run_ctx.prog_item = item;
+		func_ret = run_prog(prog, ctx);
+		ret &= (func_ret & 1);
+		*(ret_flags) |= (func_ret >> 1);
+		item++;
+	}
+	bpf_reset_run_ctx(old_run_ctx);
+	rcu_read_unlock();
+	migrate_enable();
+	return ret;
+}
+
+static __always_inline u32
+BPF_PROG_RUN_ARRAY_CG(const struct bpf_prog_array __rcu *array_rcu,
+		      const void *ctx, bpf_prog_run_fn run_prog)
+{
+	const struct bpf_prog_array_item *item;
+	const struct bpf_prog *prog;
+	const struct bpf_prog_array *array;
+	struct bpf_run_ctx *old_run_ctx;
+	struct bpf_cg_run_ctx run_ctx;
+	u32 ret = 1;
+
+	migrate_disable();
+	rcu_read_lock();
+	array = rcu_dereference(array_rcu);
+	item = &array->items[0];
+	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
+	while ((prog = READ_ONCE(item->prog))) {
+		run_ctx.prog_item = item;
+		ret &= run_prog(prog, ctx);
+		item++;
+	}
+	bpf_reset_run_ctx(old_run_ctx);
+	rcu_read_unlock();
+	migrate_enable();
+	return ret;
+}
+
+static __always_inline u32
+BPF_PROG_RUN_ARRAY(const struct bpf_prog_array __rcu *array_rcu,
+		   const void *ctx, bpf_prog_run_fn run_prog)
+{
+	const struct bpf_prog_array_item *item;
+	const struct bpf_prog *prog;
+	const struct bpf_prog_array *array;
+	u32 ret = 1;
+
+	migrate_disable();
+	rcu_read_lock();
+	array = rcu_dereference(array_rcu);
+	if (unlikely(!array))
+		goto out;
+	item = &array->items[0];
+	while ((prog = READ_ONCE(item->prog))) {
+		ret &= run_prog(prog, ctx);
+		item++;
+	}
+out:
+	rcu_read_unlock();
+	migrate_enable();
+	return ret;
+}
 
 /* To be used by __cgroup_bpf_run_filter_skb for EGRESS BPF progs
  * so BPF programs can request cwr for TCP packets.
@@ -1235,7 +1284,7 @@ _out:							\
 		u32 _flags = 0;				\
 		bool _cn;				\
 		u32 _ret;				\
-		_ret = BPF_PROG_RUN_ARRAY_FLAGS(array, ctx, func, &_flags); \
+		_ret = BPF_PROG_RUN_ARRAY_CG_FLAGS(array, ctx, func, &_flags); \
 		_cn = _flags & BPF_RET_SET_CN;		\
 		if (_ret)				\
 			_ret = (_cn ? NET_XMIT_CN : NET_XMIT_SUCCESS);	\
@@ -1244,12 +1293,6 @@ _out:							\
 		_ret;					\
 	})
 
-#define BPF_PROG_RUN_ARRAY(array, ctx, func)		\
-	__BPF_PROG_RUN_ARRAY(array, ctx, func, false, true)
-
-#define BPF_PROG_RUN_ARRAY_CHECK(array, ctx, func)	\
-	__BPF_PROG_RUN_ARRAY(array, ctx, func, true, false)
-
 #ifdef CONFIG_BPF_SYSCALL
 DECLARE_PER_CPU(int, bpf_prog_active);
 extern struct mutex bpf_stats_enabled_mutex;
@@ -1284,20 +1327,6 @@ static inline void bpf_enable_instrumentation(void)
 	migrate_enable();
 }
 
-static inline struct bpf_run_ctx *bpf_set_run_ctx(struct bpf_run_ctx *new_ctx)
-{
-	struct bpf_run_ctx *old_ctx;
-
-	old_ctx = current->bpf_ctx;
-	current->bpf_ctx = new_ctx;
-	return old_ctx;
-}
-
-static inline void bpf_reset_run_ctx(struct bpf_run_ctx *old_ctx)
-{
-	current->bpf_ctx = old_ctx;
-}
-
 extern const struct file_operations bpf_map_fops;
 extern const struct file_operations bpf_prog_fops;
 extern const struct file_operations bpf_iter_fops;

include/linux/filter.h

@@ -723,7 +723,7 @@ static inline void bpf_restore_data_end(
 	cb->data_end = saved_data_end;
 }
 
-static inline u8 *bpf_skb_cb(struct sk_buff *skb)
+static inline u8 *bpf_skb_cb(const struct sk_buff *skb)
 {
 	/* eBPF programs may read/write skb->cb[] area to transfer meta
 	 * data between tail calls. Since this also needs to work with
@@ -744,8 +744,9 @@ static inline u8 *bpf_skb_cb(struct sk_buff *skb)
 
 /* Must be invoked with migration disabled */
 static inline u32 __bpf_prog_run_save_cb(const struct bpf_prog *prog,
-					 struct sk_buff *skb)
+					 const void *ctx)
 {
+	const struct sk_buff *skb = ctx;
 	u8 *cb_data = bpf_skb_cb(skb);
 	u8 cb_saved[BPF_SKB_CB_LEN];
 	u32 res;

kernel/bpf/cgroup.c

@@ -1012,7 +1012,7 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
 		ret = BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY(
 			cgrp->bpf.effective[type], skb, __bpf_prog_run_save_cb);
 	} else {
-		ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], skb,
+		ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[type], skb,
 					    __bpf_prog_run_save_cb);
 		ret = (ret == 1 ? 0 : -EPERM);
 	}
@@ -1043,7 +1043,7 @@ int __cgroup_bpf_run_filter_sk(struct sock *sk,
 	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
 	int ret;
 
-	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], sk, bpf_prog_run);
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[type], sk, bpf_prog_run);
 	return ret == 1 ? 0 : -EPERM;
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
@@ -1090,7 +1090,7 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
 	}
 
 	cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
-	ret = BPF_PROG_RUN_ARRAY_FLAGS(cgrp->bpf.effective[type], &ctx,
+	ret = BPF_PROG_RUN_ARRAY_CG_FLAGS(cgrp->bpf.effective[type], &ctx,
 				          bpf_prog_run, flags);
 
 	return ret == 1 ? 0 : -EPERM;
@@ -1120,7 +1120,7 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
 	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
 	int ret;
 
-	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], sock_ops,
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[type], sock_ops,
 				    bpf_prog_run);
 	return ret == 1 ? 0 : -EPERM;
 }
@@ -1139,7 +1139,7 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
 
 	rcu_read_lock();
 	cgrp = task_dfl_cgroup(current);
-	allow = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx,
+	allow = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[type], &ctx,
 				      bpf_prog_run);
 	rcu_read_unlock();
 
@@ -1271,7 +1271,7 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
 
 	rcu_read_lock();
 	cgrp = task_dfl_cgroup(current);
-	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, bpf_prog_run);
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[type], &ctx, bpf_prog_run);
 	rcu_read_unlock();
 
 	kfree(ctx.cur_val);
@@ -1385,7 +1385,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 	}
 
 	lock_sock(sk);
-	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[BPF_CGROUP_SETSOCKOPT],
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[BPF_CGROUP_SETSOCKOPT],
 				    &ctx, bpf_prog_run);
 	release_sock(sk);
 
@@ -1495,7 +1495,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 	}
 
 	lock_sock(sk);
-	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT],
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT],
 				    &ctx, bpf_prog_run);
 	release_sock(sk);
 
@@ -1556,7 +1556,7 @@ int __cgroup_bpf_run_filter_getsockopt_kern(struct sock *sk, int level,
 	 * be called if that data shouldn't be "exported".
 	 */
 
-	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT],
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT],
 				    &ctx, bpf_prog_run);
 	if (!ret)
 		return -EPERM;

kernel/trace/bpf_trace.c

@@ -124,7 +124,7 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 	 * out of events when it was updated in between this and the
 	 * rcu_dereference() which is accepted risk.
 	 */
-	ret = BPF_PROG_RUN_ARRAY_CHECK(call->prog_array, ctx, bpf_prog_run);
+	ret = BPF_PROG_RUN_ARRAY(call->prog_array, ctx, bpf_prog_run);
 
  out:
 	__this_cpu_dec(bpf_prog_active);