On Tue, 2025-06-10 at 20:08 +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>
> ---
A few nits regarding error reporting:
./veristat -q -G ptr_arr[10]=0 set_global_vars.bpf.o
Unsupported array element type for variable ptr_arr. Only int, enum, struct, union are supported
^^^
missing dot
./veristat -G arr[[10]]=0 set_global_vars.bpf.o
Could not parse 'arr[[10]]'Failed to parse global variable presets: arr[[10]]=0
^^^^^^^^^ ^^^ ^^^
Can't ? dot or comma missing dot
./veristat -q -G "struct1[0] = 0" set_global_vars.bpf.o
Setting value for type Struct is not supported
^^^^^^^^^
report full_name here?
I applied a diff as in the attachment, to see what offsets are being assigned.
Looks like this shows a bug:
./veristat -q -G "struct1[0].filler = 42" set_global_vars.bpf.o > /dev/null
setting struct1[0].filler: offset 54, kind int, value 42
Shouldn't offset be 2 in this case?
(maybe print such info in debug (-d) mode?)
Unrelated to this patch, but still a bug:
# Catches range error:
./veristat -q -G "struct1[0].filler2 = 100500" set_global_vars.bpf.o
Variable unsigned short value 100500 is out of range [0; 65535]
# Does not range error:
./veristat -q -G "struct1[0].filler2 = -1" set_global_vars.bpf.o
... success ...
[...]
diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index bc9ebf5a2985..7f3e8ba75acc 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -1725,6 +1725,8 @@ static int adjust_var_secinfo(struct btf *btf, const struct btf_type *t,
return 0;
}
+const char *btf_kind_str(const struct btf_type *t);
+
static int set_global_var(struct bpf_object *obj, struct btf *btf,
struct bpf_map *map, struct btf_var_secinfo *sinfo,
struct var_preset *preset)
@@ -1761,6 +1763,9 @@ static int set_global_var(struct bpf_object *obj, struct btf *btf,
}
}
+ fprintf(stderr, "setting %s: offset %d, kind %s, value %lld\n",
+ preset->full_name, sinfo->offset, btf_kind_str(base_type), value);
+
/* Check if value fits into the target variable size */
if (sinfo->size < sizeof(value)) {
bool is_signed = is_signed_type(base_type);
