bpf: Add "bool swap_uptrs" arg to bpf_local_storage_update() and bpf_selem_alloc()

In a later patch, the task local storage will only accept uptr
from the syscall update_elem and will not accept uptr from
the bpf prog. The reason is the bpf prog does not have a way
to provide a valid user space address.

bpf_local_storage_update() and bpf_selem_alloc() are used by
both bpf prog bpf_task_storage_get(BPF_LOCAL_STORAGE_GET_F_CREATE)
and bpf syscall update_elem. "bool swap_uptrs" arg is added
to bpf_local_storage_update() and bpf_selem_alloc() to tell if
it is called by the bpf prog or by the bpf syscall. When
swap_uptrs==true, it is called by the syscall.

The arg is named (swap_)uptrs because the later patch will swap
the uptrs between the newly allocated selem and the user space
provided map_value. It will make error handling easier in case
map->ops->map_update_elem() fails and the caller can decide
if it needs to unpin the uptr in the user space provided
map_value or the bpf_local_storage_update() has already
taken the uptr ownership and will take care of unpinning it also.

Only swap_uptrs==false is passed now. The logic to handle
the true case will be added in a later patch.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20241023234759.860539-4-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index dcddb0aef7d8..0c7216c065d5 100644
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -181,7 +181,7 @@ void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 
 struct bpf_local_storage_elem *
 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, void *value,
-		bool charge_mem, gfp_t gfp_flags);
+		bool charge_mem, bool swap_uptrs, gfp_t gfp_flags);
 
 void bpf_selem_free(struct bpf_local_storage_elem *selem,
 		    struct bpf_local_storage_map *smap,
@@ -195,7 +195,7 @@ bpf_local_storage_alloc(void *owner,
 
 struct bpf_local_storage_data *
 bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
-			 void *value, u64 map_flags, gfp_t gfp_flags);
+			 void *value, u64 map_flags, bool swap_uptrs, gfp_t gfp_flags);
 
 u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map);