[bpf-next,v13,14/14] bpf: pass btf object id in bpf_map_info.

Commit Message

Kui-Feng Lee Dec. 9, 2023, 12:27 a.m. UTC

From: Kui-Feng Lee <[e-mail]>

Include btf object id (btf_obj_id) in bpf_map_info so that tools (ex:
bpftools struct_ops dump) know the correct btf from the kernel to look up
type information of struct_ops types.

Since struct_ops types can be defined and registered in a module. The
type information of a struct_ops type are defined in the btf of the
module defining it.  The userspace tools need to know which btf is for
the module defining a struct_ops type.

Signed-off-by: Kui-Feng Lee <[e-mail]>
---
 include/linux/bpf.h            | 1 +
 include/uapi/linux/bpf.h       | 2 +-
 kernel/bpf/bpf_struct_ops.c    | 7 +++++++
 kernel/bpf/syscall.c           | 2 ++
 tools/include/uapi/linux/bpf.h | 2 +-
 5 files changed, 12 insertions(+), 2 deletions(-)

Comments

Martin KaFai Lau Dec. 15, 2023, 7:46 a.m. UTC | #1

On 12/8/23 4:27 PM, [e-mail] wrote:
> From: Kui-Feng Lee <[e-mail]>
> 
> Include btf object id (btf_obj_id) in bpf_map_info so that tools (ex:
> bpftools struct_ops dump) know the correct btf from the kernel to look up
> type information of struct_ops types.
> 
> Since struct_ops types can be defined and registered in a module. The
> type information of a struct_ops type are defined in the btf of the
> module defining it.  The userspace tools need to know which btf is for
> the module defining a struct_ops type.
> 
> Signed-off-by: Kui-Feng Lee <[e-mail]>
> ---
>   include/linux/bpf.h            | 1 +
>   include/uapi/linux/bpf.h       | 2 +-
>   kernel/bpf/bpf_struct_ops.c    | 7 +++++++
>   kernel/bpf/syscall.c           | 2 ++
>   tools/include/uapi/linux/bpf.h | 2 +-
>   5 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index c881befa35f5..26103d8a4374 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -3350,5 +3350,6 @@ struct bpf_struct_ops_##_name {					\
>   int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
>   			     struct btf *btf,
>   			     struct bpf_verifier_log *log);
> +void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map);

This needs to be in the CONFIG_BPF_JIT guard also.

>   
>   #endif /* _LINUX_BPF_H */
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 5c3838a97554..716c6b28764d 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6534,7 +6534,7 @@ struct bpf_map_info {
>   	__u32 btf_id;
>   	__u32 btf_key_type_id;
>   	__u32 btf_value_type_id;
> -	__u32 :32;	/* alignment pad */
> +	__u32 btf_obj_id;

may be "btf_vmlinux_id" to make it clear it is a kernel btf and should be used 
with map_info->btf_vmlinux_value_type_id.

>   	__u64 map_extra;
>   } __attribute__((aligned(8)));
>   
> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
> index fd26716fa0f9..51c0de75aa85 100644
> --- a/kernel/bpf/bpf_struct_ops.c
> +++ b/kernel/bpf/bpf_struct_ops.c
> @@ -979,3 +979,10 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
>   	kfree(link);
>   	return err;
>   }
> +
> +void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map)
> +{
> +	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
> +
> +	info->btf_obj_id = btf_obj_id(st_map->btf);
> +}
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 4aced7e58904..3cab56cd02ff 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -4715,6 +4715,8 @@ static int bpf_map_get_info_by_fd(struct file *file,
>   		info.btf_value_type_id = map->btf_value_type_id;
>   	}
>   	info.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
> +	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS)
> +		bpf_map_struct_ops_info_fill(&info, map);

This patch should be moved earlier in the set instead of after the selftest 
patch 13. May be after patch 5 where st_map->btf is added.

and where is the test for this?

>   
>   	if (bpf_map_is_offloaded(map)) {
>   		err = bpf_map_offload_info_fill(&info, map);
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 5c3838a97554..716c6b28764d 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -6534,7 +6534,7 @@ struct bpf_map_info {
>   	__u32 btf_id;
>   	__u32 btf_key_type_id;
>   	__u32 btf_value_type_id;
> -	__u32 :32;	/* alignment pad */
> +	__u32 btf_obj_id;
>   	__u64 map_extra;
>   } __attribute__((aligned(8)));
>

Kui-Feng Lee Dec. 17, 2023, 7:35 a.m. UTC | #2

On 12/14/23 23:46, Martin KaFai Lau wrote:
> On 12/8/23 4:27 PM, [e-mail] wrote:
>> From: Kui-Feng Lee <[e-mail]>
>>
>> Include btf object id (btf_obj_id) in bpf_map_info so that tools (ex:
>> bpftools struct_ops dump) know the correct btf from the kernel to look up
>> type information of struct_ops types.
>>
>> Since struct_ops types can be defined and registered in a module. The
>> type information of a struct_ops type are defined in the btf of the
>> module defining it.  The userspace tools need to know which btf is for
>> the module defining a struct_ops type.
>>
>> Signed-off-by: Kui-Feng Lee <[e-mail]>
>> ---
>>   include/linux/bpf.h            | 1 +
>>   include/uapi/linux/bpf.h       | 2 +-
>>   kernel/bpf/bpf_struct_ops.c    | 7 +++++++
>>   kernel/bpf/syscall.c           | 2 ++
>>   tools/include/uapi/linux/bpf.h | 2 +-
>>   5 files changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index c881befa35f5..26103d8a4374 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -3350,5 +3350,6 @@ struct bpf_struct_ops_##_name 
>> {                    \
>>   int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
>>                    struct btf *btf,
>>                    struct bpf_verifier_log *log);
>> +void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct 
>> bpf_map *map);
> 
> This needs to be in the CONFIG_BPF_JIT guard also.

Got it!
> 
>>   #endif /* _LINUX_BPF_H */
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 5c3838a97554..716c6b28764d 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -6534,7 +6534,7 @@ struct bpf_map_info {
>>       __u32 btf_id;
>>       __u32 btf_key_type_id;
>>       __u32 btf_value_type_id;
>> -    __u32 :32;    /* alignment pad */
>> +    __u32 btf_obj_id;
> 
> may be "btf_vmlinux_id" to make it clear it is a kernel btf and should 
> be used with map_info->btf_vmlinux_value_type_id.

Sure!

> 
>>       __u64 map_extra;
>>   } __attribute__((aligned(8)));
>> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
>> index fd26716fa0f9..51c0de75aa85 100644
>> --- a/kernel/bpf/bpf_struct_ops.c
>> +++ b/kernel/bpf/bpf_struct_ops.c
>> @@ -979,3 +979,10 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
>>       kfree(link);
>>       return err;
>>   }
>> +
>> +void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct 
>> bpf_map *map)
>> +{
>> +    struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map 
>> *)map;
>> +
>> +    info->btf_obj_id = btf_obj_id(st_map->btf);
>> +}
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index 4aced7e58904..3cab56cd02ff 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>> @@ -4715,6 +4715,8 @@ static int bpf_map_get_info_by_fd(struct file 
>> *file,
>>           info.btf_value_type_id = map->btf_value_type_id;
>>       }
>>       info.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
>> +    if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS)
>> +        bpf_map_struct_ops_info_fill(&info, map);
> 
> This patch should be moved earlier in the set instead of after the 
> selftest patch 13. May be after patch 5 where st_map->btf is added.

No problem

> 
> and where is the test for this?

I use bpf_map_info as a part of calling bpf_map_create() while
testmod.ko is unloaded. It check if this change work as well.

> 
>>       if (bpf_map_is_offloaded(map)) {
>>           err = bpf_map_offload_info_fill(&info, map);
>> diff --git a/tools/include/uapi/linux/bpf.h 
>> b/tools/include/uapi/linux/bpf.h
>> index 5c3838a97554..716c6b28764d 100644
>> --- a/tools/include/uapi/linux/bpf.h
>> +++ b/tools/include/uapi/linux/bpf.h
>> @@ -6534,7 +6534,7 @@ struct bpf_map_info {
>>       __u32 btf_id;
>>       __u32 btf_key_type_id;
>>       __u32 btf_value_type_id;
>> -    __u32 :32;    /* alignment pad */
>> +    __u32 btf_obj_id;
>>       __u64 map_extra;
>>   } __attribute__((aligned(8)));
>

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c881befa35f5..26103d8a4374 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3350,5 +3350,6 @@  struct bpf_struct_ops_##_name {					\
 int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
 			     struct btf *btf,
 			     struct bpf_verifier_log *log);
+void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map);
 
 #endif /* _LINUX_BPF_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 5c3838a97554..716c6b28764d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6534,7 +6534,7 @@  struct bpf_map_info {
 	__u32 btf_id;
 	__u32 btf_key_type_id;
 	__u32 btf_value_type_id;
-	__u32 :32;	/* alignment pad */
+	__u32 btf_obj_id;
 	__u64 map_extra;
 } __attribute__((aligned(8)));
 
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index fd26716fa0f9..51c0de75aa85 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -979,3 +979,10 @@  int bpf_struct_ops_link_create(union bpf_attr *attr)
 	kfree(link);
 	return err;
 }
+
+void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map)
+{
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
+
+	info->btf_obj_id = btf_obj_id(st_map->btf);
+}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4aced7e58904..3cab56cd02ff 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4715,6 +4715,8 @@  static int bpf_map_get_info_by_fd(struct file *file,
 		info.btf_value_type_id = map->btf_value_type_id;
 	}
 	info.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
+	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS)
+		bpf_map_struct_ops_info_fill(&info, map);
 
 	if (bpf_map_is_offloaded(map)) {
 		err = bpf_map_offload_info_fill(&info, map);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 5c3838a97554..716c6b28764d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6534,7 +6534,7 @@  struct bpf_map_info {
 	__u32 btf_id;
 	__u32 btf_key_type_id;
 	__u32 btf_value_type_id;
-	__u32 :32;	/* alignment pad */
+	__u32 btf_obj_id;
 	__u64 map_extra;
 } __attribute__((aligned(8)));