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From: Kenny Yu <kennyyu@fb.com>
To: <kennyyu@fb.com>
Cc: <andrii@kernel.org>, <ast@kernel.org>, <bpf@vger.kernel.org>,
	<daniel@iogearbox.net>, <yhs@fb.com>,
	<alexei.starovoitov@gmail.com>, <andrii.nakryiko@gmail.com>,
	<phoenix1987@gmail.com>
Subject: [PATCH v6 bpf-next 1/3] bpf: Add bpf_copy_from_user_task() helper
Date: Fri, 21 Jan 2022 11:30:45 -0800	[thread overview]
Message-ID: <20220121193047.3225019-2-kennyyu@fb.com> (raw)
In-Reply-To: <20220121193047.3225019-1-kennyyu@fb.com>

This adds a helper for bpf programs to read the memory of other
tasks. This also adds the ability for bpf iterator programs to
be sleepable.

This changes `bpf_iter_run_prog` to use the appropriate synchronization for
sleepable bpf programs. With sleepable bpf iterator programs, we can no
longer use `rcu_read_lock()` and must use `rcu_read_lock_trace()` instead
to protect the bpf program.

As an example use case at Meta, we are using a bpf task iterator program
and this new helper to print C++ async stack traces for all threads of
a given process.

Signed-off-by: Kenny Yu <kennyyu@fb.com>
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       | 10 ++++++++++
 kernel/bpf/bpf_iter.c          | 20 ++++++++++++++-----
 kernel/bpf/helpers.c           | 35 ++++++++++++++++++++++++++++++++++
 kernel/trace/bpf_trace.c       |  2 ++
 tools/include/uapi/linux/bpf.h | 10 ++++++++++
 6 files changed, 73 insertions(+), 5 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 80e3387ea3af..5917883e528b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2229,6 +2229,7 @@ extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;
 extern const struct bpf_func_proto bpf_find_vma_proto;
 extern const struct bpf_func_proto bpf_loop_proto;
 extern const struct bpf_func_proto bpf_strncmp_proto;
+extern const struct bpf_func_proto bpf_copy_from_user_task_proto;
 
 const struct bpf_func_proto *tracing_prog_func_proto(
   enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index fe2272defcd9..d82d9423874d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5049,6 +5049,15 @@ union bpf_attr {
  *		This helper is currently supported by cgroup programs only.
  *	Return
  *		0 on success, or a negative error in case of failure.
+ *
+ * long bpf_copy_from_user_task(void *dst, u32 size, const void *user_ptr, struct task_struct *tsk, u64 flags)
+ *	Description
+ *		Read *size* bytes from user space address *user_ptr* in *tsk*'s
+ *		address space, and stores the data in *dst*. *flags* is not
+ *		used yet and is provided for future extensibility. This helper
+ *		can only be used by sleepable programs.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5239,6 +5248,7 @@ union bpf_attr {
 	FN(get_func_arg_cnt),		\
 	FN(get_retval),			\
 	FN(set_retval),			\
+	FN(copy_from_user_task),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index b7aef5b3416d..110029ede71e 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -5,6 +5,7 @@
 #include <linux/anon_inodes.h>
 #include <linux/filter.h>
 #include <linux/bpf.h>
+#include <linux/rcupdate_trace.h>
 
 struct bpf_iter_target_info {
 	struct list_head list;
@@ -684,11 +685,20 @@ int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
 {
 	int ret;
 
-	rcu_read_lock();
-	migrate_disable();
-	ret = bpf_prog_run(prog, ctx);
-	migrate_enable();
-	rcu_read_unlock();
+	if (prog->aux->sleepable) {
+		rcu_read_lock_trace();
+		migrate_disable();
+		might_fault();
+		ret = bpf_prog_run(prog, ctx);
+		migrate_enable();
+		rcu_read_unlock_trace();
+	} else {
+		rcu_read_lock();
+		migrate_disable();
+		ret = bpf_prog_run(prog, ctx);
+		migrate_enable();
+		rcu_read_unlock();
+	}
 
 	/* bpf program can only return 0 or 1:
 	 *  0 : okay
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 01cfdf40c838..3bc37016fad0 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -16,6 +16,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/proc_ns.h>
 #include <linux/security.h>
+#include <linux/btf_ids.h>
 
 #include "../../lib/kstrtox.h"
 
@@ -671,6 +672,40 @@ const struct bpf_func_proto bpf_copy_from_user_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_5(bpf_copy_from_user_task, void *, dst, u32, size,
+	   const void __user *, user_ptr, struct task_struct *, tsk, u64, flags)
+{
+	int ret;
+
+	/* flags is not used yet */
+	if (flags)
+		return -EINVAL;
+
+	ret = access_process_vm(tsk, (unsigned long)user_ptr, dst, size, 0);
+	if (ret >= 0) {
+		if (ret == size)
+			ret = 0;
+		else {
+			/* If partial read, clear all bytes and return error */
+			memset(dst, 0, size);
+			ret = -EFAULT;
+		}
+	}
+	return ret;
+}
+
+const struct bpf_func_proto bpf_copy_from_user_task_proto = {
+	.func		= bpf_copy_from_user_task,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_BTF_ID,
+	.arg4_btf_id	= &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
+	.arg5_type	= ARG_ANYTHING
+};
+
 BPF_CALL_2(bpf_per_cpu_ptr, const void *, ptr, u32, cpu)
 {
 	if (cpu >= nr_cpu_ids)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 21aa30644219..d07f568646cb 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1235,6 +1235,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_task_stack_proto;
 	case BPF_FUNC_copy_from_user:
 		return prog->aux->sleepable ? &bpf_copy_from_user_proto : NULL;
+	case BPF_FUNC_copy_from_user_task:
+		return prog->aux->sleepable ? &bpf_copy_from_user_task_proto : NULL;
 	case BPF_FUNC_snprintf_btf:
 		return &bpf_snprintf_btf_proto;
 	case BPF_FUNC_per_cpu_ptr:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index fe2272defcd9..d82d9423874d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5049,6 +5049,15 @@ union bpf_attr {
  *		This helper is currently supported by cgroup programs only.
  *	Return
  *		0 on success, or a negative error in case of failure.
+ *
+ * long bpf_copy_from_user_task(void *dst, u32 size, const void *user_ptr, struct task_struct *tsk, u64 flags)
+ *	Description
+ *		Read *size* bytes from user space address *user_ptr* in *tsk*'s
+ *		address space, and stores the data in *dst*. *flags* is not
+ *		used yet and is provided for future extensibility. This helper
+ *		can only be used by sleepable programs.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5239,6 +5248,7 @@ union bpf_attr {
 	FN(get_func_arg_cnt),		\
 	FN(get_retval),			\
 	FN(set_retval),			\
+	FN(copy_from_user_task),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.30.2


  reply	other threads:[~2022-01-21 19:31 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-13 23:31 [PATCH bpf-next 0/3] Add bpf_access_process_vm helper and sleepable bpf iterator programs Kenny Yu
2022-01-13 23:31 ` [PATCH bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-13 23:31 ` [PATCH bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-13 23:31 ` [PATCH bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-14  0:48 ` [PATCH v2 bpf-next 0/4] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-14  0:48   ` [PATCH v2 bpf-next 1/4] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-14  0:48   ` [PATCH v2 bpf-next 2/4] bpf: Add support for sleepable programs in bpf_iter_run_prog Kenny Yu
2022-01-14  2:50     ` Alexei Starovoitov
2022-01-14 23:15       ` Kenny Yu
2022-01-14  0:48   ` [PATCH v2 bpf-next 3/4] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-14  0:49   ` [PATCH v2 bpf-next 4/4] selftests/bpf: Add test " Kenny Yu
2022-01-14  2:39     ` Alexei Starovoitov
2022-01-14 23:14       ` Kenny Yu
2022-01-15  1:38         ` Andrii Nakryiko
2022-01-15  4:30           ` Kenny Yu
2022-01-15 16:27           ` Gabriele
2022-01-19 16:56             ` Kenny Yu
2022-01-19 18:02 ` [PATCH v3 bpf-next 0/3] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-19 18:02   ` [PATCH v3 bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-19 20:16     ` Alexei Starovoitov
2022-01-19 22:51       ` Kenny Yu
2022-01-19 18:02   ` [PATCH v3 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-19 18:02   ` [PATCH v3 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-19 22:59 ` [PATCH v4 bpf-next 0/3] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-19 22:59   ` [PATCH v4 bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-20  3:45     ` Yonghong Song
2022-01-20 17:11       ` Kenny Yu
2022-01-19 22:59   ` [PATCH v4 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-19 22:59   ` [PATCH v4 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-20 17:29 ` [PATCH v5 bpf-next 0/3] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-20 17:29   ` [PATCH v5 bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-20 22:45     ` Andrii Nakryiko
2022-01-21  2:27       ` Alexei Starovoitov
2022-01-21 17:20         ` Andrii Nakryiko
2022-01-21 17:41           ` Kenny Yu
2022-01-21 17:47             ` Alexei Starovoitov
2022-01-21 18:30               ` Kenny Yu
2022-01-20 17:29   ` [PATCH v5 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-20 17:29   ` [PATCH v5 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-20 22:48     ` Andrii Nakryiko
2022-01-21 19:30 ` [PATCH v6 bpf-next 0/3] Add bpf_copy_from_user_task helper and " Kenny Yu
2022-01-21 19:30   ` Kenny Yu [this message]
2022-01-21 19:53     ` [PATCH v6 bpf-next 1/3] bpf: Add bpf_copy_from_user_task() helper Andrii Nakryiko
2022-01-21 20:04       ` Yonghong Song
2022-01-21 20:07         ` Andrii Nakryiko
2022-01-21 21:15           ` Yonghong Song
2022-01-24 17:30             ` Kenny Yu
2022-01-22  9:58       ` Gabriele
2022-01-22 10:08         ` Gabriele
2022-01-21 19:30   ` [PATCH v6 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-21 19:54     ` Andrii Nakryiko
2022-01-21 19:30   ` [PATCH v6 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-21 19:55     ` Andrii Nakryiko
2022-01-24 18:53 ` [PATCH v7 bpf-next 0/4] Add bpf_copy_from_user_task helper and " Kenny Yu
2022-01-24 18:54   ` [PATCH v7 bpf-next 1/4] bpf: Add support for bpf iterator programs to use sleepable helpers Kenny Yu
2022-01-24 22:19     ` Andrii Nakryiko
2022-01-24 18:54   ` [PATCH v7 bpf-next 2/4] bpf: Add bpf_copy_from_user_task() helper Kenny Yu
2022-01-24 22:18     ` Andrii Nakryiko
2022-01-25  4:06       ` Alexei Starovoitov
2022-01-24 18:54   ` [PATCH v7 bpf-next 3/4] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-24 18:54   ` [PATCH v7 bpf-next 4/4] selftests/bpf: Add test " Kenny Yu
2022-01-25  4:10   ` [PATCH v7 bpf-next 0/4] Add bpf_copy_from_user_task helper and " patchwork-bot+netdevbpf

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