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[v2,bpf-next,2/6] bpf: Add bpf_dynptr_is_null and bpf_dynptr_is_rdonly

Message ID 20221207205537.860248-3-joannelkoong@gmail.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series Dynptr convenience helpers | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/apply fail Patch does not apply to bpf-next
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Commit Message

Joanne Koong Dec. 7, 2022, 8:55 p.m. UTC 
Add two new helper functions: bpf_dynptr_is_null and
bpf_dynptr_is_rdonly.

bpf_dynptr_is_null returns true if the dynptr is null / invalid
(determined by whether ptr->data is NULL), else false if
the dynptr is a valid dynptr.

bpf_dynptr_is_rdonly returns true if the dynptr is read-only,
else false if the dynptr is read-writable.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/uapi/linux/bpf.h       | 20 ++++++++++++++++++
 kernel/bpf/helpers.c           | 37 +++++++++++++++++++++++++++++++---
 scripts/bpf_doc.py             |  3 +++
 tools/include/uapi/linux/bpf.h | 20 ++++++++++++++++++
 4 files changed, 77 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c2d915601484..80582bc00bf4 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5553,6 +5553,24 @@  union bpf_attr {
  *	Return
  *		0 on success, -EINVAL if the dynptr is invalid, -ERANGE if
  *		trying to trim more bytes than the size of the dynptr.
+ *
+ * bool bpf_dynptr_is_null(struct bpf_dynptr *ptr)
+ *	Description
+ *		Determine whether a dynptr is null / invalid.
+ *
+ *		*ptr* must be an initialized dynptr.
+ *	Return
+ *		True if the dynptr is null, else false.
+ *
+ * bool bpf_dynptr_is_rdonly(struct bpf_dynptr *ptr)
+ *	Description
+ *		Determine whether a dynptr is read-only.
+ *
+ *		*ptr* must be an initialized dynptr. If *ptr*
+ *		is a null dynptr, this will return false.
+ *	Return
+ *		True if the dynptr is read-only and a valid dynptr,
+ *		else false.
  */
 #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
 	FN(unspec, 0, ##ctx)				\
@@ -5771,6 +5789,8 @@  union bpf_attr {
 	FN(dynptr_from_xdp, 213, ##ctx)			\
 	FN(dynptr_advance, 214, ##ctx)			\
 	FN(dynptr_trim, 215, ##ctx)			\
+	FN(dynptr_is_null, 216, ##ctx)			\
+	FN(dynptr_is_rdonly, 217, ##ctx)		\
 	/* */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index fa3989047ff6..cd9e1a2972fe 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1404,7 +1404,7 @@  static const struct bpf_func_proto bpf_kptr_xchg_proto = {
 #define DYNPTR_SIZE_MASK	0xFFFFFF
 #define DYNPTR_RDONLY_BIT	BIT(31)
 
-static bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr)
+static bool __bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr)
 {
 	return ptr->size & DYNPTR_RDONLY_BIT;
 }
@@ -1547,7 +1547,7 @@  BPF_CALL_5(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, void *,
 	enum bpf_dynptr_type type;
 	int err;
 
-	if (!dst->data || bpf_dynptr_is_rdonly(dst))
+	if (!dst->data || __bpf_dynptr_is_rdonly(dst))
 		return -EINVAL;
 
 	err = bpf_dynptr_check_off_len(dst, offset, len);
@@ -1605,7 +1605,7 @@  BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern *, ptr, u32, offset, u32, len
 	switch (type) {
 	case BPF_DYNPTR_TYPE_LOCAL:
 	case BPF_DYNPTR_TYPE_RINGBUF:
-		if (bpf_dynptr_is_rdonly(ptr))
+		if (__bpf_dynptr_is_rdonly(ptr))
 			return 0;
 
 		data = ptr->data;
@@ -1703,6 +1703,33 @@  static const struct bpf_func_proto bpf_dynptr_trim_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_1(bpf_dynptr_is_null, struct bpf_dynptr_kern *, ptr)
+{
+	return !ptr->data;
+}
+
+static const struct bpf_func_proto bpf_dynptr_is_null_proto = {
+	.func		= bpf_dynptr_is_null,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_DYNPTR,
+};
+
+BPF_CALL_1(bpf_dynptr_is_rdonly, struct bpf_dynptr_kern *, ptr)
+{
+	if (!ptr->data)
+		return false;
+
+	return __bpf_dynptr_is_rdonly(ptr);
+}
+
+static const struct bpf_func_proto bpf_dynptr_is_rdonly_proto = {
+	.func		= bpf_dynptr_is_rdonly,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_DYNPTR,
+};
+
 const struct bpf_func_proto bpf_get_current_task_proto __weak;
 const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;
 const struct bpf_func_proto bpf_probe_read_user_proto __weak;
@@ -1811,6 +1838,10 @@  bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_dynptr_advance_proto;
 	case BPF_FUNC_dynptr_trim:
 		return &bpf_dynptr_trim_proto;
+	case BPF_FUNC_dynptr_is_null:
+		return &bpf_dynptr_is_null_proto;
+	case BPF_FUNC_dynptr_is_rdonly:
+		return &bpf_dynptr_is_rdonly_proto;
 #ifdef CONFIG_CGROUPS
 	case BPF_FUNC_cgrp_storage_get:
 		return &bpf_cgrp_storage_get_proto;
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index fdb0aff8cb5a..c20cf141e787 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -710,6 +710,7 @@  class PrinterHelpers(Printer):
             'int',
             'long',
             'unsigned long',
+            'bool',
 
             '__be16',
             '__be32',
@@ -781,6 +782,8 @@  class PrinterHelpers(Printer):
         header = '''\
 /* This is auto-generated file. See bpf_doc.py for details. */
 
+#include <stdbool.h>
+
 /* Forward declarations of BPF structs */'''
 
         print(header)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c2d915601484..80582bc00bf4 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5553,6 +5553,24 @@  union bpf_attr {
  *	Return
  *		0 on success, -EINVAL if the dynptr is invalid, -ERANGE if
  *		trying to trim more bytes than the size of the dynptr.
+ *
+ * bool bpf_dynptr_is_null(struct bpf_dynptr *ptr)
+ *	Description
+ *		Determine whether a dynptr is null / invalid.
+ *
+ *		*ptr* must be an initialized dynptr.
+ *	Return
+ *		True if the dynptr is null, else false.
+ *
+ * bool bpf_dynptr_is_rdonly(struct bpf_dynptr *ptr)
+ *	Description
+ *		Determine whether a dynptr is read-only.
+ *
+ *		*ptr* must be an initialized dynptr. If *ptr*
+ *		is a null dynptr, this will return false.
+ *	Return
+ *		True if the dynptr is read-only and a valid dynptr,
+ *		else false.
  */
 #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
 	FN(unspec, 0, ##ctx)				\
@@ -5771,6 +5789,8 @@  union bpf_attr {
 	FN(dynptr_from_xdp, 213, ##ctx)			\
 	FN(dynptr_advance, 214, ##ctx)			\
 	FN(dynptr_trim, 215, ##ctx)			\
+	FN(dynptr_is_null, 216, ##ctx)			\
+	FN(dynptr_is_rdonly, 217, ##ctx)		\
 	/* */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't