Re: [PATCH bpf] tools: bpftool: fix a bitfield pretty print issue
On Wed, Nov 28, 2018 at 09:38:23AM -0800, Yonghong Song wrote:
> Commit b12d6ec09730 ("bpf: btf: add btf print functionality")
> added btf pretty print functionality to bpftool.
> There is a problem though in printing a bitfield whose type
> has modifiers.
>
> For example, for a type like
> typedef int ___int;
> struct tmp_t {
> int a:3;
> ___int b:3;
> };
> Suppose we have a map
> struct bpf_map_def SEC("maps") tmpmap = {
> .type = BPF_MAP_TYPE_HASH,
> .key_size = sizeof(__u32),
> .value_size = sizeof(struct tmp_t),
> .max_entries = 1,
> };
> and the hash table is populated with one element with
> key 0 and value (.a = 1 and .b = 2).
>
> In BTF, the struct member "b" will have a type "typedef" which
> points to an int type. The current implementation does not
> pass the bit offset during transition from typedef to int type,
> hence incorrectly print the value as
> $ bpftool m d id 79
> [{
> "key": 0,
> "value": {
> "a": 0x1,
> "b": 0x1
> }
> }
> ]
>
> This patch fixed the issue by carrying bit_offset along the type
> chain during bit_field print. The correct result can be printed as
> $ bpftool m d id 76
> [{
> "key": 0,
> "value": {
> "a": 0x1,
> "b": 0x2
> }
> }
> ]
>
> The kernel pretty print is implemented correctly and does not
> have this issue.
>
> Fixes: b12d6ec09730 ("bpf: btf: add btf print functionality")
> Signed-off-by: Yonghong Song
Applied to bpf tree. Thanks
Re: [PATCH bpf] tools: bpftool: fix a bitfield pretty print issue
On Wed, Nov 28, 2018 at 10:09 AM Yonghong Song wrote:
>
> Commit b12d6ec09730 ("bpf: btf: add btf print functionality")
> added btf pretty print functionality to bpftool.
> There is a problem though in printing a bitfield whose type
> has modifiers.
>
> For example, for a type like
> typedef int ___int;
> struct tmp_t {
> int a:3;
> ___int b:3;
> };
> Suppose we have a map
> struct bpf_map_def SEC("maps") tmpmap = {
> .type = BPF_MAP_TYPE_HASH,
> .key_size = sizeof(__u32),
> .value_size = sizeof(struct tmp_t),
> .max_entries = 1,
> };
> and the hash table is populated with one element with
> key 0 and value (.a = 1 and .b = 2).
>
> In BTF, the struct member "b" will have a type "typedef" which
> points to an int type. The current implementation does not
> pass the bit offset during transition from typedef to int type,
> hence incorrectly print the value as
> $ bpftool m d id 79
> [{
> "key": 0,
> "value": {
> "a": 0x1,
> "b": 0x1
> }
> }
> ]
>
> This patch fixed the issue by carrying bit_offset along the type
> chain during bit_field print. The correct result can be printed as
> $ bpftool m d id 76
> [{
> "key": 0,
> "value": {
> "a": 0x1,
> "b": 0x2
> }
> }
> ]
>
> The kernel pretty print is implemented correctly and does not
> have this issue.
>
> Fixes: b12d6ec09730 ("bpf: btf: add btf print functionality")
> Signed-off-by: Yonghong Song
Acked-by: Song Liu
> ---
> tools/bpf/bpftool/btf_dumper.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
> index 55bc512a1831..e4e6e2b3fd84 100644
> --- a/tools/bpf/bpftool/btf_dumper.c
> +++ b/tools/bpf/bpftool/btf_dumper.c
> @@ -32,7 +32,7 @@ static void btf_dumper_ptr(const void *data, json_writer_t
> *jw,
> }
>
> static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
> - const void *data)
> + __u8 bit_offset, const void *data)
> {
> int actual_type_id;
>
> @@ -40,7 +40,7 @@ static int btf_dumper_modifier(const struct btf_dumper *d,
> __u32 type_id,
> if (actual_type_id < 0)
> return actual_type_id;
>
> - return btf_dumper_do_type(d, actual_type_id, 0, data);
> + return btf_dumper_do_type(d, actual_type_id, bit_offset, data);
> }
>
> static void btf_dumper_enum(const void *data, json_writer_t *jw)
> @@ -237,7 +237,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d,
> __u32 type_id,
> case BTF_KIND_VOLATILE:
> case BTF_KIND_CONST:
> case BTF_KIND_RESTRICT:
> - return btf_dumper_modifier(d, type_id, data);
> + return btf_dumper_modifier(d, type_id, bit_offset, data);
> default:
> jsonw_printf(d->jw, "(unsupported-kind");
> return -EINVAL;
> --
> 2.17.1
>
[PATCH bpf] tools: bpftool: fix a bitfield pretty print issue
Commit b12d6ec09730 ("bpf: btf: add btf print functionality")
added btf pretty print functionality to bpftool.
There is a problem though in printing a bitfield whose type
has modifiers.
For example, for a type like
typedef int ___int;
struct tmp_t {
int a:3;
___int b:3;
};
Suppose we have a map
struct bpf_map_def SEC("maps") tmpmap = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(__u32),
.value_size = sizeof(struct tmp_t),
.max_entries = 1,
};
and the hash table is populated with one element with
key 0 and value (.a = 1 and .b = 2).
In BTF, the struct member "b" will have a type "typedef" which
points to an int type. The current implementation does not
pass the bit offset during transition from typedef to int type,
hence incorrectly print the value as
$ bpftool m d id 79
[{
"key": 0,
"value": {
"a": 0x1,
"b": 0x1
}
}
]
This patch fixed the issue by carrying bit_offset along the type
chain during bit_field print. The correct result can be printed as
$ bpftool m d id 76
[{
"key": 0,
"value": {
"a": 0x1,
"b": 0x2
}
}
]
The kernel pretty print is implemented correctly and does not
have this issue.
Fixes: b12d6ec09730 ("bpf: btf: add btf print functionality")
Signed-off-by: Yonghong Song
---
tools/bpf/bpftool/btf_dumper.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index 55bc512a1831..e4e6e2b3fd84 100644
--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c
@@ -32,7 +32,7 @@ static void btf_dumper_ptr(const void *data, json_writer_t
*jw,
}
static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
- const void *data)
+ __u8 bit_offset, const void *data)
{
int actual_type_id;
@@ -40,7 +40,7 @@ static int btf_dumper_modifier(const struct btf_dumper *d,
__u32 type_id,
if (actual_type_id < 0)
return actual_type_id;
- return btf_dumper_do_type(d, actual_type_id, 0, data);
+ return btf_dumper_do_type(d, actual_type_id, bit_offset, data);
}
static void btf_dumper_enum(const void *data, json_writer_t *jw)
@@ -237,7 +237,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d,
__u32 type_id,
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
- return btf_dumper_modifier(d, type_id, data);
+ return btf_dumper_modifier(d, type_id, bit_offset, data);
default:
jsonw_printf(d->jw, "(unsupported-kind");
return -EINVAL;
--
2.17.1
