| Message ID | 20181128173823.547847-1-yhs@fb.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf] tools: bpftool: fix a bitfield pretty print issue | expand |
On Wed, Nov 28, 2018 at 10:09 AM Yonghong Song <yhs@fb.com> 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 <yhs@fb.com> Acked-by: Song Liu <songliubraving@fb.com> > --- > 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 >
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 <yhs@fb.com> Applied to bpf tree. Thanks
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;
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 <yhs@fb.com> --- tools/bpf/bpftool/btf_dumper.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)