Message-Id: <20220510001807.4132027-2-yosryahmed@google.com>
Date:   Tue, 10 May 2022 00:17:59 +0000
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shuah Khan <shuah@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Michal Hocko <mhocko@...nel.org>
Cc:     Stanislav Fomichev <sdf@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, cgroups@...r.kernel.org,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: [RFC PATCH bpf-next 1/9] bpf: introduce CGROUP_SUBSYS_RSTAT program type

This patch introduces a new bpf program type CGROUP_SUBSYS_RSTAT,
with new corresponding link and attach types.

The main purpose of these programs is to allow BPF programs to collect
and maintain hierarchical cgroup stats easily and efficiently by making
using of the rstat framework in the kernel.

Those programs attach to a cgroup subsystem. They typically contain logic
to aggregate per-cpu and per-cgroup stats collected by other BPF programs.

Currently, only rstat flusher programs can be attached to cgroup
subsystems, but this can be extended later if a use-case arises.

See the selftest in the final patch for a practical example.

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---
 include/linux/bpf-cgroup-subsys.h |  30 ++++++
 include/linux/bpf_types.h         |   2 +
 include/linux/cgroup-defs.h       |   4 +
 include/uapi/linux/bpf.h          |  12 +++
 kernel/bpf/Makefile               |   1 +
 kernel/bpf/cgroup_subsys.c        | 166 ++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c              |   6 ++
 kernel/cgroup/cgroup.c            |   1 +
 tools/include/uapi/linux/bpf.h    |  12 +++
 9 files changed, 234 insertions(+)
 create mode 100644 include/linux/bpf-cgroup-subsys.h
 create mode 100644 kernel/bpf/cgroup_subsys.c

diff --git a/include/linux/bpf-cgroup-subsys.h b/include/linux/bpf-cgroup-subsys.h
new file mode 100644
index 000000000000..4dcde06b5599
--- /dev/null
+++ b/include/linux/bpf-cgroup-subsys.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2022 Google LLC.
+ */
+#ifndef _BPF_CGROUP_SUBSYS_H_
+#define _BPF_CGROUP_SUBSYS_H_
+
+#include <linux/bpf.h>
+
+struct cgroup_subsys_bpf {
+	/* Head of the list of BPF rstat flushers attached to this subsystem */
+	struct list_head rstat_flushers;
+	spinlock_t flushers_lock;
+};
+
+struct bpf_subsys_rstat_flusher {
+	struct bpf_prog *prog;
+	/* List of BPF rtstat flushers, anchored at subsys->bpf */
+	struct list_head list;
+};
+
+struct bpf_cgroup_subsys_link {
+	struct bpf_link link;
+	struct cgroup_subsys *ss;
+};
+
+int cgroup_subsys_bpf_link_attach(const union bpf_attr *attr,
+				  struct bpf_prog *prog);
+
+#endif  // _BPF_CGROUP_SUBSYS_H_
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 3e24ad0c4b3c..854ee958b0e4 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -56,6 +56,8 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SYSCTL, cg_sysctl,
 	      struct bpf_sysctl, struct bpf_sysctl_kern)
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCKOPT, cg_sockopt,
 	      struct bpf_sockopt, struct bpf_sockopt_kern)
+BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT, cgroup_subsys_rstat,
+	      struct bpf_rstat_ctx, struct bpf_rstat_ctx)
 #endif
 #ifdef CONFIG_BPF_LIRC_MODE2
 BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2,
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 1bfcfb1af352..3bd6eed1fa13 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -20,6 +20,7 @@
 #include <linux/u64_stats_sync.h>
 #include <linux/workqueue.h>
 #include <linux/bpf-cgroup-defs.h>
+#include <linux/bpf-cgroup-subsys.h>
 #include <linux/psi_types.h>
 
 #ifdef CONFIG_CGROUPS
@@ -706,6 +707,9 @@ struct cgroup_subsys {
 	 * specifies the mask of subsystems that this one depends on.
 	 */
 	unsigned int depends_on;
+
+	/* used to store bpf programs.*/
+	struct cgroup_subsys_bpf bpf;
 };
 
 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index d14b10b85e51..0f4855fa85db 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -952,6 +952,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_LSM,
 	BPF_PROG_TYPE_SK_LOOKUP,
 	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
+	BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT,
 };
 
 enum bpf_attach_type {
@@ -998,6 +999,7 @@ enum bpf_attach_type {
 	BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
 	BPF_PERF_EVENT,
 	BPF_TRACE_KPROBE_MULTI,
+	BPF_CGROUP_SUBSYS_RSTAT,
 	__MAX_BPF_ATTACH_TYPE
 };
 
@@ -1013,6 +1015,7 @@ enum bpf_link_type {
 	BPF_LINK_TYPE_XDP = 6,
 	BPF_LINK_TYPE_PERF_EVENT = 7,
 	BPF_LINK_TYPE_KPROBE_MULTI = 8,
+	BPF_LINK_TYPE_CGROUP_SUBSYS = 9,
 
 	MAX_BPF_LINK_TYPE,
 };
@@ -1482,6 +1485,9 @@ union bpf_attr {
 				 */
 				__u64		bpf_cookie;
 			} perf_event;
+			struct {
+				__u64		name;
+			} cgroup_subsys;
 			struct {
 				__u32		flags;
 				__u32		cnt;
@@ -6324,6 +6330,12 @@ struct bpf_cgroup_dev_ctx {
 	__u32 minor;
 };
 
+struct bpf_rstat_ctx {
+	__u64 cgroup_id;
+	__u64 parent_cgroup_id; /* 0 if root */
+	__s32 cpu;
+};
+
 struct bpf_raw_tracepoint_args {
 	__u64 args[0];
 };
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index c1a9be6a4b9f..6caf4a61e543 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -25,6 +25,7 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
 obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
 endif
 obj-$(CONFIG_CGROUP_BPF) += cgroup.o
+obj-$(CONFIG_CGROUP_BPF) += cgroup_subsys.o
 ifeq ($(CONFIG_INET),y)
 obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
 endif
diff --git a/kernel/bpf/cgroup_subsys.c b/kernel/bpf/cgroup_subsys.c
new file mode 100644
index 000000000000..9673ce6aa84a
--- /dev/null
+++ b/kernel/bpf/cgroup_subsys.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Functions to manage eBPF programs attached to cgroup subsystems
+ *
+ * Copyright 2022 Google LLC.
+ */
+
+#include <linux/bpf-cgroup-subsys.h>
+#include <linux/filter.h>
+
+#include "../cgroup/cgroup-internal.h"
+
+
+static int cgroup_subsys_bpf_attach(struct cgroup_subsys *ss, struct bpf_prog *prog)
+{
+	struct bpf_subsys_rstat_flusher *rstat_flusher;
+
+	rstat_flusher = kmalloc(sizeof(*rstat_flusher), GFP_KERNEL);
+	if (!rstat_flusher)
+		return -ENOMEM;
+	rstat_flusher->prog = prog;
+
+	spin_lock(&ss->bpf.flushers_lock);
+	list_add(&rstat_flusher->list, &ss->bpf.rstat_flushers);
+	spin_unlock(&ss->bpf.flushers_lock);
+
+	return 0;
+}
+
+static void cgroup_subsys_bpf_detach(struct cgroup_subsys *ss, struct bpf_prog *prog)
+{
+	struct bpf_subsys_rstat_flusher *rstat_flusher = NULL;
+
+	spin_lock(&ss->bpf.flushers_lock);
+	list_for_each_entry(rstat_flusher, &ss->bpf.rstat_flushers, list)
+		if (rstat_flusher->prog == prog)
+			break;
+
+	if (rstat_flusher) {
+		list_del(&rstat_flusher->list);
+		bpf_prog_put(rstat_flusher->prog);
+		kfree(rstat_flusher);
+	}
+	spin_unlock(&ss->bpf.flushers_lock);
+}
+
+static void bpf_cgroup_subsys_link_release(struct bpf_link *link)
+{
+	struct bpf_cgroup_subsys_link *ss_link = container_of(link,
+						       struct bpf_cgroup_subsys_link,
+						       link);
+	if (ss_link->ss) {
+		cgroup_subsys_bpf_detach(ss_link->ss, ss_link->link.prog);
+		ss_link->ss = NULL;
+	}
+}
+
+static int bpf_cgroup_subsys_link_detach(struct bpf_link *link)
+{
+	bpf_cgroup_subsys_link_release(link);
+	return 0;
+}
+
+static void bpf_cgroup_subsys_link_dealloc(struct bpf_link *link)
+{
+	struct bpf_cgroup_subsys_link *ss_link = container_of(link,
+						       struct bpf_cgroup_subsys_link,
+						       link);
+	kfree(ss_link);
+}
+
+static const struct bpf_link_ops bpf_cgroup_subsys_link_lops = {
+	.detach = bpf_cgroup_subsys_link_detach,
+	.release = bpf_cgroup_subsys_link_release,
+	.dealloc = bpf_cgroup_subsys_link_dealloc,
+};
+
+int cgroup_subsys_bpf_link_attach(const union bpf_attr *attr,
+				  struct bpf_prog *prog)
+{
+	struct bpf_link_primer link_primer;
+	struct bpf_cgroup_subsys_link *link;
+	struct cgroup_subsys *ss, *attach_ss = NULL;
+	const char __user *ss_name_user;
+	char ss_name[MAX_CGROUP_TYPE_NAMELEN];
+	int ssid, err;
+
+	if (attr->link_create.target_fd || attr->link_create.flags)
+		return -EINVAL;
+
+	ss_name_user = u64_to_user_ptr(attr->link_create.cgroup_subsys.name);
+	if (strncpy_from_user(ss_name, ss_name_user, sizeof(ss_name) - 1) < 0)
+		return -EFAULT;
+
+	for_each_subsys(ss, ssid)
+		if (!strcmp(ss_name, ss->name) ||
+		    !strcmp(ss_name, ss->legacy_name))
+			attach_ss = ss;
+
+	if (!attach_ss)
+		return -EINVAL;
+
+	link = kzalloc(sizeof(*link), GFP_USER);
+	if (!link)
+		return -ENOMEM;
+
+	bpf_link_init(&link->link, BPF_LINK_TYPE_CGROUP_SUBSYS,
+		      &bpf_cgroup_subsys_link_lops,
+		      prog);
+	link->ss = attach_ss;
+
+	err = bpf_link_prime(&link->link, &link_primer);
+	if (err) {
+		kfree(link);
+		return err;
+	}
+
+	err = cgroup_subsys_bpf_attach(attach_ss, prog);
+	if (err) {
+		bpf_link_cleanup(&link_primer);
+		return err;
+	}
+
+	return bpf_link_settle(&link_primer);
+}
+
+static const struct bpf_func_proto *
+cgroup_subsys_rstat_func_proto(enum bpf_func_id func_id,
+			       const struct bpf_prog *prog)
+{
+	return bpf_base_func_proto(func_id);
+}
+
+static bool cgroup_subsys_rstat_is_valid_access(int off, int size,
+					   enum bpf_access_type type,
+					   const struct bpf_prog *prog,
+					   struct bpf_insn_access_aux *info)
+{
+	if (type == BPF_WRITE)
+		return false;
+
+	if (off < 0 || off + size > sizeof(struct bpf_rstat_ctx))
+		return false;
+	/* The verifier guarantees that size > 0 */
+	if (off % size != 0)
+		return false;
+
+	switch (off) {
+	case offsetof(struct bpf_rstat_ctx, cgroup_id):
+		return size == sizeof(__u64);
+	case offsetof(struct bpf_rstat_ctx, parent_cgroup_id):
+		return size == sizeof(__u64);
+	case offsetof(struct bpf_rstat_ctx, cpu):
+		return size == sizeof(__s32);
+	default:
+		return false;
+	}
+}
+
+const struct bpf_prog_ops cgroup_subsys_rstat_prog_ops = {
+};
+
+const struct bpf_verifier_ops cgroup_subsys_rstat_verifier_ops = {
+	.get_func_proto         = cgroup_subsys_rstat_func_proto,
+	.is_valid_access        = cgroup_subsys_rstat_is_valid_access,
+};
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index cdaa1152436a..48149c54d969 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3,6 +3,7 @@
  */
 #include <linux/bpf.h>
 #include <linux/bpf-cgroup.h>
+#include <linux/bpf-cgroup-subsys.h>
 #include <linux/bpf_trace.h>
 #include <linux/bpf_lirc.h>
 #include <linux/bpf_verifier.h>
@@ -3194,6 +3195,8 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
 		return BPF_PROG_TYPE_SK_LOOKUP;
 	case BPF_XDP:
 		return BPF_PROG_TYPE_XDP;
+	case BPF_CGROUP_SUBSYS_RSTAT:
+		return BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT;
 	default:
 		return BPF_PROG_TYPE_UNSPEC;
 	}
@@ -4341,6 +4344,9 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
 		else
 			ret = bpf_kprobe_multi_link_attach(attr, prog);
 		break;
+	case BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT:
+		ret = cgroup_subsys_bpf_link_attach(attr, prog);
+		break;
 	default:
 		ret = -EINVAL;
 	}
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index adb820e98f24..7b1448013009 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -5745,6 +5745,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
 
 	idr_init(&ss->css_idr);
 	INIT_LIST_HEAD(&ss->cfts);
+	INIT_LIST_HEAD(&ss->bpf.rstat_flushers);
 
 	/* Create the root cgroup state for this subsystem */
 	ss->root = &cgrp_dfl_root;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index d14b10b85e51..0f4855fa85db 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -952,6 +952,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_LSM,
 	BPF_PROG_TYPE_SK_LOOKUP,
 	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
+	BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT,
 };
 
 enum bpf_attach_type {
@@ -998,6 +999,7 @@ enum bpf_attach_type {
 	BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
 	BPF_PERF_EVENT,
 	BPF_TRACE_KPROBE_MULTI,
+	BPF_CGROUP_SUBSYS_RSTAT,
 	__MAX_BPF_ATTACH_TYPE
 };
 
@@ -1013,6 +1015,7 @@ enum bpf_link_type {
 	BPF_LINK_TYPE_XDP = 6,
 	BPF_LINK_TYPE_PERF_EVENT = 7,
 	BPF_LINK_TYPE_KPROBE_MULTI = 8,
+	BPF_LINK_TYPE_CGROUP_SUBSYS = 9,
 
 	MAX_BPF_LINK_TYPE,
 };
@@ -1482,6 +1485,9 @@ union bpf_attr {
 				 */
 				__u64		bpf_cookie;
 			} perf_event;
+			struct {
+				__u64		name;
+			} cgroup_subsys;
 			struct {
 				__u32		flags;
 				__u32		cnt;
@@ -6324,6 +6330,12 @@ struct bpf_cgroup_dev_ctx {
 	__u32 minor;
 };
 
+struct bpf_rstat_ctx {
+	__u64 cgroup_id;
+	__u64 parent_cgroup_id; /* 0 if root */
+	__s32 cpu;
+};
+
 struct bpf_raw_tracepoint_args {
 	__u64 args[0];
 };
-- 
2.36.0.512.ge40c2bad7a-goog

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