On Thu, Jun 5, 2025 at 11:36 AM Mykyta Yatsenko
<mykyta.yatsenko5@xxxxxxxxx> wrote:
>
> From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
>
> Implement support for presetting values for array elements in veristat.
> For example:
> ```
> sudo ./veristat set_global_vars.bpf.o -G "arr[3] = 1"
> ```
> Arrays of structures and structure of arrays work, but each individual
> scalar value has to be set separately: `foo[1].bar[2] = value`.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> ---
> tools/testing/selftests/bpf/veristat.c | 145 +++++++++++++++++++++----
> 1 file changed, 126 insertions(+), 19 deletions(-)
>
[...]
> @@ -1440,7 +1458,7 @@ static int append_var_preset(struct var_preset **presets, int *cnt, const char *
> memset(cur, 0, sizeof(*cur));
> (*cnt)++;
>
> - if (sscanf(expr, "%s = %s %n", var, val, &n) != 2 || n != strlen(expr)) {
> + if (sscanf(expr, "%[][a-zA-Z0-9_.] = %s %n", var, val, &n) != 2 || n != strlen(expr)) {
> fprintf(stderr, "Failed to parse expression '%s'\n", expr);
> return -EINVAL;
> }
> @@ -1533,6 +1551,74 @@ static bool is_preset_supported(const struct btf_type *t)
> return btf_is_int(t) || btf_is_enum(t) || btf_is_enum64(t);
> }
>
> +static int find_enum_value(const struct btf *btf, const char *name, int *value)
shouldn't value be long long or u64?
> +{
> + const struct btf_type *t;
> + int cnt, i;
> + long long lvalue;
> +
> + cnt = btf__type_cnt(btf);
> + for (i = 1; i != cnt; ++i) {
> + t = btf__type_by_id(btf, i);
> +
> + if (!btf_is_any_enum(t))
> + continue;
> +
> + if (enum_value_from_name(btf, t, name, &lvalue) == 0) {
> + *value = (int)lvalue;
why truncating here?
> + return 0;
> + }
> + }
> + return -ESRCH;
> +}
> +
> +static int adjust_array_secinfo(const struct btf *btf, const struct btf_type *t,
> + const struct var_preset_atom *var_atom,
> + struct btf_var_secinfo *sinfo)
> +{
> + struct btf_array *barr;
> + const struct btf_type *type;
> + int tid, index;
> +
> + if (!btf_is_array(t))
> + return -EINVAL;
> +
> + barr = btf_array(t);
> + tid = btf__resolve_type(btf, barr->type);
> + type = btf__type_by_id(btf, tid);
> + if (!btf_is_int(type) && !btf_is_any_enum(type) && !btf_is_composite(type)) {
> + fprintf(stderr,
> + "Unsupported array type for variable %s. Only int, enum, struct, union are supported\n",
array element type?
> + var_atom->name);
> + return -EINVAL;
> + }
> + switch (var_atom->index.type) {
> + case INTEGRAL:
> + index = var_atom->index.ivalue;
> + break;
> + case ENUMERATOR:
> + if (find_enum_value(btf, var_atom->index.svalue, &index) != 0) {
> + fprintf(stderr, "Could not find array index as enum value %s",
nit: maybe "Can't resolve %s enum as an array index"?
> + var_atom->index.svalue);
> + return -EINVAL;
> + }
> + break;
> + case NONE:
> + fprintf(stderr, "Array index is expected for %s\n", var_atom->name);
> + return -EINVAL;
> + }
> +
> + if (index < 0 || index >= barr->nelems) {
> + fprintf(stderr, "Preset index %d is invalid or out of bounds [0, %d]\n",
nelems is u32, so %u
> + index, barr->nelems);
> + return -EINVAL;
> + }
> + sinfo->size = type->size;
> + sinfo->type = tid;
> + sinfo->offset += index * type->size;
> + return 0;
> +}
> +
> const int btf_find_member(const struct btf *btf,
> const struct btf_type *parent_type,
> __u32 parent_offset,
> @@ -1540,7 +1626,7 @@ const int btf_find_member(const struct btf *btf,
> int *member_tid,
> __u32 *member_offset)
> {
> - int i;
> + int i, err;
>
> if (!btf_is_composite(parent_type))
> return -EINVAL;
> @@ -1559,16 +1645,27 @@ const int btf_find_member(const struct btf *btf,
> if (member->name_off) {
> const char *name = btf__name_by_offset(btf, member->name_off);
>
> - if (strcmp(var_atom->name, name) == 0) {
> - if (btf_member_bitfield_size(parent_type, i) != 0) {
> - fprintf(stderr, "Bitfield presets are not supported %s\n",
> - name);
> - return -EINVAL;
> - }
> - *member_offset = parent_offset + member->offset;
> - *member_tid = tid;
> - return 0;
> + if (strcmp(var_atom->name, name) != 0)
> + continue;
> +
> + if (btf_member_bitfield_size(parent_type, i) != 0) {
> + fprintf(stderr, "Bitfield presets are not supported %s\n",
> + name);
> + return -EINVAL;
> + }
> + *member_offset = parent_offset + member->offset;
> + *member_tid = tid;
> + if (btf_is_array(member_type)) {
> + struct btf_var_secinfo sinfo = {.offset = 0};
> +
> + err = adjust_array_secinfo(btf, member_type,
> + var_atom, &sinfo);
> + if (err)
> + return err;
> + *member_tid = sinfo.type;
> + *member_offset += sinfo.offset * 8;
> }
> + return 0;
> } else if (btf_is_composite(member_type)) {
> int err;
error message if array index is specified for non-array type?
please check again my comments around this functions from [0]
[0] https://lore.kernel.org/bpf/CAEf4Bzb3=brMXMBZ-AGj8xdr80XEs2Og0XeZ1zuiHnFNWWPJJQ@xxxxxxxxxxxxxx/
>
> @@ -1579,7 +1676,7 @@ const int btf_find_member(const struct btf *btf,
> }
> }
>
> - return -EINVAL;
> + return -ESRCH;
> }
>
> static int adjust_var_secinfo(struct btf *btf, const struct btf_type *t,
> @@ -1590,6 +1687,12 @@ static int adjust_var_secinfo(struct btf *btf, const struct btf_type *t,
> __u32 member_offset = 0;
>
> base_type = btf__type_by_id(btf, btf__resolve_type(btf, t->type));
> + if (btf_is_array(base_type)) {
> + err = adjust_array_secinfo(btf, base_type, &preset->atoms[0], sinfo);
> + if (err)
> + return err;
> + base_type = btf__type_by_id(btf, sinfo->type);
> + }
>
> for (i = 1; i < preset->atom_count; ++i) {
> err = btf_find_member(btf, base_type, 0, &preset->atoms[i],
> @@ -1739,8 +1842,9 @@ static int set_global_vars(struct bpf_object *obj, struct var_preset *presets, i
> }
> for (i = 0; i < npresets; ++i) {
> if (!presets[i].applied) {
> - fprintf(stderr, "Global variable preset %s has not been applied\n",
> - presets[i].full_name);
> + fprintf(stderr, "Global variable preset %s has not been applied %s\n",
is this a debugging leftover? not sure why logging both full name and
just first atom?..
> + presets[i].full_name, presets[i].atoms[0].name);
> + err = -EINVAL;
> }
> presets[i].applied = false;
> }
> @@ -2928,8 +3032,11 @@ int main(int argc, char **argv)
> free(env.deny_filters);
> for (i = 0; i < env.npresets; ++i) {
> free(env.presets[i].full_name);
> - for (j = 0; j < env.presets[i].atom_count; ++j)
> + for (j = 0; j < env.presets[i].atom_count; ++j) {
> free(env.presets[i].atoms[j].name);
> + if (env.presets[i].atoms[j].index.type == ENUMERATOR)
> + free(env.presets[i].atoms[j].index.svalue);
> + }
> free(env.presets[i].atoms);
> if (env.presets[i].value.type == ENUMERATOR)
> free(env.presets[i].value.svalue);
> --
> 2.49.0
>
