[PATCH v7 bpf-next 1/4] bpf: Export 'bpf_dynptr_get_data, bpf_dynptr_get_size' helpers

[Shmulik Ladkani <shmulik@xxxxxxxxxxxxxxxx>]

This allows kernel code dealing with dynptrs obtain dynptr's available
size and current (w. proper offset) data pointer.

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@xxxxxxxxx>

---
v5:
- fix bpf_dynptr_get_data's incorrect usage of bpf_dynptr_kern's size
  spotted by Joanne Koong <joannelkoong@xxxxxxxxx>

v6:
- Simplify bpf_dynptr_get_data's interface and make it inline
  suggested by John Fastabend <john.fastabend@xxxxxxxxx>

v7:
- Fix undefined reference to `bpf_dynptr_get_size' when CONFIG_BPF_SYSCALL
  is unset,
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
 include/linux/bpf.h  | 13 +++++++++++++
 kernel/bpf/helpers.c |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 48ae05099f36..a2f16e3cb0fa 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2631,6 +2631,19 @@ 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);
+#ifdef CONFIG_BPF_SYSCALL
+u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr);
+#else
+static inline u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
+{
+	return 0;
+}
+#endif
+
+static inline void *bpf_dynptr_get_data(struct bpf_dynptr_kern *ptr)
+{
+	return ptr->data ? ptr->data + ptr->offset : NULL;
+}
 
 #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 fc08035f14ed..824864ac82d1 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1408,7 +1408,7 @@ static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_typ
 	ptr->size |= type << DYNPTR_TYPE_SHIFT;
 }
 
-static u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
+u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
 {
 	return ptr->size & DYNPTR_SIZE_MASK;
 }
-- 
2.37.3