On Wed, 2025-06-18 at 21:39 +0100, Mykyta Yatsenko 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 | 226 ++++++++++++++++++++-----
> 1 file changed, 180 insertions(+), 46 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
> index 483442c08ecf..9942adbda411 100644
> --- a/tools/testing/selftests/bpf/veristat.c
> +++ b/tools/testing/selftests/bpf/veristat.c
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
[...]
> @@ -1670,7 +1706,7 @@ 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)) {
Out of curiosity, won't match if the pattern would remain "%s = %s %n"?
> fprintf(stderr, "Failed to parse expression '%s'\n", expr);
> return -EINVAL;
> }
> @@ -1763,17 +1799,103 @@ 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, long long *value)
> +{
> + 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 = lvalue;
> + return 0;
> + }
> + }
> + return -ESRCH;
> +}
> +
[...]
> @@ -1815,26 +1938,29 @@ const int btf_find_member(const struct btf *btf,
> static int adjust_var_secinfo(struct btf *btf, const struct btf_type *t,
> struct btf_var_secinfo *sinfo, struct var_preset *preset)
> {
> - const struct btf_type *base_type, *member_type;
> - int err, member_tid, i;
> - __u32 member_offset = 0;
> -
> - base_type = btf__type_by_id(btf, btf__resolve_type(btf, t->type));
> -
> - for (i = 1; i < preset->atom_count; ++i) {
> - err = btf_find_member(btf, base_type, 0, preset->atoms[i].name,
> - &member_tid, &member_offset);
> - if (err) {
> - fprintf(stderr, "Could not find member %s for variable %s\n",
> - preset->atoms[i].name, preset->atoms[i - 1].name);
> - return err;
> + const struct btf_type *base_type;
> + int err, i = 1, n;
> + int tid;
> +
> + tid = btf__resolve_type(btf, t->type);
> + base_type = btf__type_by_id(btf, tid);
> +
> + while (i < preset->atom_count) {
> + if (preset->atoms[i].type == ARRAY_INDEX) {
> + n = adjust_var_secinfo_array(btf, tid, preset, i, sinfo);
> + if (n < 0)
> + return n;
> + i += n;
Having a nested loop to consume all indices looks annoying.
On the other hand, there is not much one can do w/o some kind of
btf__type_physical_size.
> + } else {
> + err = btf_find_member(btf, base_type, 0, preset->atoms[i].name, sinfo);
> + if (err)
> + return err;
> + i++;
> }
> - member_type = btf__type_by_id(btf, member_tid);
> - sinfo->offset += member_offset / 8;
> - sinfo->size = member_type->size;
> - sinfo->type = member_tid;
> - base_type = member_type;
> + base_type = btf__type_by_id(btf, sinfo->type);
> + tid = sinfo->type;
> }
> +
> return 0;
> }
>
[...]
