On Tue, Jun 3, 2025 at 8:39 AM Blake Jones blakejones@google.com wrote:
On Tue, Jun 3, 2025 at 6:18 AM Jiri Olsa olsajiri@gmail.com wrote:
+static int btf_dump_string_data(struct btf_dump *d,
const struct btf_type *t,__u32 id,const void *data)+{
const struct btf_array *array = btf_array(t);__u32 i;btf_dump_data_pfx(d);btf_dump_printf(d, "\"");for (i = 0; i < array->nelems; i++, data++) {char c;if (data >= d->typed_dump->data_end)return -E2BIG;curious, is this just string array without null terminating byte? should we just print " and return 0 instead of E2BIG error ?
Good question. That E2BIG error would happen, for example, if we tried to print the array "{ 'a', 'b', 'c' }" when the type was "char[4]".
Exactly, data is truncated, we have to return E2BIG. But I think that is checked earlier with btf_dump_type_data_check_overflow(), so we probably don't need to do this here?
Please add tests with truncated data so we know for sure?
I'd say your proposed behavior would be consistent with the semantic of ".emit_strings should display strings in an intuitively useful way",
It still should follow the overall contract, so I think E2BIG is justified for truncated data.
But there is also a bit of a quirk. If a string is not zero-terminated, we actually don't distinguish it in any way. Would it make sense to detect this and still print it as an array of individual characters? It's clearly not a valid C string at that point, so emit_strings doesn't have to apply. WDYT? The implementation would be simple -- find zero in an array, if found - emit everything up to that point as string, if not - emit character array?
and I'd be in favor of doing that (replacing "return -E2BIG" with "break"). If others agree (specifically Andrii, who had comments about the semantics yesterday), I'll make that change.
Blake