[bpf-next,v2,01/13] bpf: Export bpf_dynptr_set_size()

Commit Message

Hou Tao Sept. 24, 2022, 1:36 p.m. UTC

From: Hou Tao <[e-mail]>

For map with bpf_dynptr-typed key, lookup and update procedures will use
bpf_dynptr_get_size() to get the length of key, and iteration procedure
will use bpf_dynptr_set_size() to set the length of returned key.

The implementation of bpf_dynptr_set_size() is taken from Joanne's patch
"bpf: Add bpf_dynptr_trim and bpf_dynptr_advance". Also add a const
qualifier to dynptr argument of bpf_dynptr_get_size().

Signed-off-by: Hou Tao <[e-mail]>
---
 include/linux/bpf.h  | 3 ++-
 kernel/bpf/helpers.c | 9 ++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index edd43edb27d6..66a18dc67b46 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2660,7 +2660,8 @@  void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,
 		     enum bpf_dynptr_type type, u32 offset, u32 size);
 void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr);
 int bpf_dynptr_check_size(u32 size);
-u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr);
+u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr);
+void bpf_dynptr_set_size(struct bpf_dynptr_kern *ptr, u32 new_size);
 
 #ifdef CONFIG_BPF_LSM
 void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index b069517a3da0..a9ca2de8f8cd 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1408,11 +1408,18 @@  static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_typ
 	ptr->size |= type << DYNPTR_TYPE_SHIFT;
 }
 
-u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
+u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr)
 {
 	return ptr->size & DYNPTR_SIZE_MASK;
 }
 
+void bpf_dynptr_set_size(struct bpf_dynptr_kern *ptr, u32 new_size)
+{
+	u32 metadata = ptr->size & ~DYNPTR_SIZE_MASK;
+
+	ptr->size = new_size | metadata;
+}
+
 int bpf_dynptr_check_size(u32 size)
 {
 	return size > DYNPTR_MAX_SIZE ? -E2BIG : 0;