To support global field arrays for bpf_rb_root, bpf_list_head, and kptr,
the nelems (number of elements) has been added to btf_field_info and
btf_field. The value of nelems is the length of a field array. Nested
arrays are flatten to get the length.
If a field is not an array, the value of nelems should be 1. In the other
word, you can not distinguish an array with only one element from a field
with the same type as array's element. However, it is not a problem with
the help of the offset and size in btf_field.
field->size will be the size of the array if it is.
The value of nelems of btf_field is always 1 to deactivate arrays for now,
but the nelems of btf_field_info has been updated as the number of elements
for data sections. A later patch will activate it.
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
include/linux/bpf.h | 1 +
kernel/bpf/btf.c | 24 +++++++++++++++++++++---
2 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5034c1b4ded7..cab479925dfd 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -226,6 +226,7 @@ struct btf_field_graph_root {
struct btf_field {
u32 offset;
u32 size;
+ u32 nelems;
enum btf_field_type type;
union {
struct btf_field_kptr kptr;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e71ea78a4db9..6fb482789f8e 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3289,6 +3289,7 @@ enum {
struct btf_field_info {
enum btf_field_type type;
u32 off;
+ u32 nelems;
union {
struct {
u32 type_id;
@@ -3548,6 +3549,7 @@ static int btf_find_struct_field(const struct btf *btf,
continue;
if (idx >= info_cnt)
return -E2BIG;
+ info[idx].nelems = 1;
++idx;
}
return idx;
@@ -3565,6 +3567,19 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
for_each_vsi(i, t, vsi) {
const struct btf_type *var = btf_type_by_id(btf, vsi->type);
const struct btf_type *var_type = btf_type_by_id(btf, var->type);
+ const struct btf_array *array;
+ u32 j, nelems = 1;
+
+ /* Walk into array types to find the element type and the
+ * number of elements in the (flattened) array.
+ */
+ for (j = 0; j < MAX_RESOLVE_DEPTH && btf_type_is_array(var_type); j++) {
+ array = btf_array(var_type);
+ nelems *= array->nelems;
+ var_type = btf_type_by_id(btf, array->type);
+ }
+ if (nelems == 0)
+ continue;
field_type = btf_get_field_type(__btf_name_by_offset(btf, var_type->name_off),
field_mask, &seen_mask, &align, &sz);
@@ -3574,7 +3589,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
return field_type;
off = vsi->offset;
- if (vsi->size != sz)
+ if (vsi->size != sz * nelems)
continue;
if (off % align)
continue;
@@ -3582,9 +3597,11 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
switch (field_type) {
case BPF_SPIN_LOCK:
case BPF_TIMER:
+ case BPF_REFCOUNT:
case BPF_LIST_NODE:
case BPF_RB_NODE:
- case BPF_REFCOUNT:
+ if (nelems != 1)
+ continue;
ret = btf_find_struct(btf, var_type, off, sz, field_type,
idx < info_cnt ? &info[idx] : &tmp);
if (ret < 0)
@@ -3615,7 +3632,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
continue;
if (idx >= info_cnt)
return -E2BIG;
- ++idx;
+ info[idx++].nelems = nelems;
}
return idx;
}
@@ -3834,6 +3851,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
rec->fields[i].offset = info_arr[i].off;
rec->fields[i].type = info_arr[i].type;
rec->fields[i].size = field_type_size;
+ rec->fields[i].nelems = 1;
switch (info_arr[i].type) {
case BPF_SPIN_LOCK:
--
2.34.1
