2022-09-03 20:08:42

by Jules Irenge

Subject: [PATCH 2/2] bpf: Fix warning of incorrect type in return expression

Sparse reports a warning at bpf_array_map_seq_start()

"warning: incorrect type in return expression (different address spaces)"

The root cause is the function expect a return of type void *
but instead got a percpu value in one of the return.

To fix this a variable of type void * is created
and the complainining return value is saved into the variable and return.

Fix incorrect type in return expression

Signed-off-by: Jules Irenge <[email protected]>
---
kernel/bpf/arraymap.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 624527401d4d..b1914168c23a 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -548,6 +548,7 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos)
struct bpf_map *map = info->map;
struct bpf_array *array;
u32 index;
+ void *pptrs;

if (info->index >= map->max_entries)
return NULL;
@@ -556,8 +557,10 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos)
++*pos;
array = container_of(map, struct bpf_array, map);
index = info->index & array->index_mask;
- if (info->percpu_value_buf)
- return array->pptrs[index];
+ if (info->percpu_value_buf) {
+ pptrs = &array->pptrs[index];
+ return pptrs;
+ }
return array_map_elem_ptr(array, index);
}

--
2.35.1

2022-09-06 18:37:08

by Alexei Starovoitov

Subject: Re: [PATCH 2/2] bpf: Fix warning of incorrect type in return expression

On Sat, Sep 3, 2022 at 12:02 PM Jules Irenge <[email protected]> wrote:
>
> Sparse reports a warning at bpf_array_map_seq_start()
>
> "warning: incorrect type in return expression (different address spaces)"
>
> The root cause is the function expect a return of type void *
> but instead got a percpu value in one of the return.
>
> To fix this a variable of type void * is created
> and the complainining return value is saved into the variable and return.
>
> Fix incorrect type in return expression
>
> Signed-off-by: Jules Irenge <[email protected]>
> ---
> kernel/bpf/arraymap.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index 624527401d4d..b1914168c23a 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -548,6 +548,7 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos)
> struct bpf_map *map = info->map;
> struct bpf_array *array;
> u32 index;
> + void *pptrs;
>
> if (info->index >= map->max_entries)
> return NULL;
> @@ -556,8 +557,10 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos)
> ++*pos;
> array = container_of(map, struct bpf_array, map);
> index = info->index & array->index_mask;
> - if (info->percpu_value_buf)
> - return array->pptrs[index];
> + if (info->percpu_value_buf) {
> + pptrs = &array->pptrs[index];
> + return pptrs;
> + }

Somebody will surely send a patch to optimize above back
to original code.
Please find a different way to shut up sparse or just ignore it.