netdev - [PATCH bpf-next 1/3] bpf: introduce helper bpf_get_task_stack

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Date:   Tue, 23 Jun 2020 00:08:00 -0700
From:   Song Liu <songliubraving@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     <ast@...nel.org>, <daniel@...earbox.net>, <kernel-team@...com>,
        <john.fastabend@...il.com>, <kpsingh@...omium.org>,
        Song Liu <songliubraving@...com>
Subject: [PATCH bpf-next 1/3] bpf: introduce helper bpf_get_task_stack_trace()

This helper can be used with bpf_iter__task to dump all /proc/*/stack to
a seq_file.

Signed-off-by: Song Liu <songliubraving@...com>
---
 include/uapi/linux/bpf.h       | 10 +++++++++-
 kernel/trace/bpf_trace.c       | 21 +++++++++++++++++++++
 scripts/bpf_helpers_doc.py     |  2 ++
 tools/include/uapi/linux/bpf.h | 10 +++++++++-
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 19684813faaed..a30416b822fe3 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3252,6 +3252,13 @@ union bpf_attr {
  * 		case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level
  * 		is returned or the error code -EACCES in case the skb is not
  * 		subject to CHECKSUM_UNNECESSARY.
+ *
+ * int bpf_get_task_stack_trace(struct task_struct *task, void *entries, u32 size)
+ *	Description
+ *		Save a task stack trace into array *entries*. This is a wrapper
+ *		over stack_trace_save_tsk().
+ *	Return
+ *		Number of trace entries stored.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3389,7 +3396,8 @@ union bpf_attr {
 	FN(ringbuf_submit),		\
 	FN(ringbuf_discard),		\
 	FN(ringbuf_query),		\
-	FN(csum_level),
+	FN(csum_level),			\
+	FN(get_task_stack_trace),

 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e729c9e587a07..2c13bcb5c2bce 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1488,6 +1488,23 @@ static const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {
 	.arg4_type	= ARG_ANYTHING,
 };

+BPF_CALL_3(bpf_get_task_stack_trace, struct task_struct *, task,
+	   void *, entries, u32, size)
+{
+	return stack_trace_save_tsk(task, (unsigned long *)entries, size, 0);
+}
+
+static int bpf_get_task_stack_trace_btf_ids[5];
+static const struct bpf_func_proto bpf_get_task_stack_trace_proto = {
+	.func		= bpf_get_task_stack_trace,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
+	.btf_id		= bpf_get_task_stack_trace_btf_ids,
+};
+
 static const struct bpf_func_proto *
 raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1521,6 +1538,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return prog->expected_attach_type == BPF_TRACE_ITER ?
 		       &bpf_seq_write_proto :
 		       NULL;
+	case BPF_FUNC_get_task_stack_trace:
+		return prog->expected_attach_type == BPF_TRACE_ITER ?
+			&bpf_get_task_stack_trace_proto :
+			NULL;
 	default:
 		return raw_tp_prog_func_proto(func_id, prog);
 	}
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 91fa668fa8602..a8783d668c5b7 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -421,6 +421,7 @@ class PrinterHelpers(Printer):
             'struct sockaddr',
             'struct tcphdr',
             'struct seq_file',
+            'struct task_struct',

             'struct __sk_buff',
             'struct sk_msg_md',
@@ -458,6 +459,7 @@ class PrinterHelpers(Printer):
             'struct sockaddr',
             'struct tcphdr',
             'struct seq_file',
+            'struct task_struct',
     }
     mapped_types = {
             'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 19684813faaed..a30416b822fe3 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3252,6 +3252,13 @@ union bpf_attr {
  * 		case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level
  * 		is returned or the error code -EACCES in case the skb is not
  * 		subject to CHECKSUM_UNNECESSARY.
+ *
+ * int bpf_get_task_stack_trace(struct task_struct *task, void *entries, u32 size)
+ *	Description
+ *		Save a task stack trace into array *entries*. This is a wrapper
+ *		over stack_trace_save_tsk().
+ *	Return
+ *		Number of trace entries stored.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3389,7 +3396,8 @@ union bpf_attr {
 	FN(ringbuf_submit),		\
 	FN(ringbuf_discard),		\
 	FN(ringbuf_query),		\
-	FN(csum_level),
+	FN(csum_level),			\
+	FN(get_task_stack_trace),

 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
--
2.24.1