Skip to content

Multi-split BTF fixes and test #6243

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: bpf-next_base
Choose a base branch
from
+80 −4
Open

Multi-split BTF fixes and test #6243

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
6d6dbac
libbpf: Fix parsing of multi-split BTF
alan-maguire Oct 28, 2025
51ac981
selftests/bpf: Test parsing of (multi-)split BTF
alan-maguire Oct 28, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 2 additions & 2 deletions tools/lib/bpf/btf.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1061,7 +1061,7 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf, b
if (base_btf) {
btf->base_btf = base_btf;
btf->start_id = btf__type_cnt(base_btf);
btf->start_str_off = base_btf->hdr->str_len;
btf->start_str_off = base_btf->hdr->str_len + base_btf->start_str_off;
}

if (is_mmap) {
Expand Down Expand Up @@ -5818,7 +5818,7 @@ void btf_set_base_btf(struct btf *btf, const struct btf *base_btf)
{
btf->base_btf = (struct btf *)base_btf;
btf->start_id = btf__type_cnt(base_btf);
btf->start_str_off = base_btf->hdr->str_len;
btf->start_str_off = base_btf->hdr->str_len + base_btf->start_str_off;
}

int btf__relocate(struct btf *btf, const struct btf *base_btf)
Expand Down
80 changes: 78 additions & 2 deletions tools/testing/selftests/bpf/prog_tests/btf_split.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,11 +12,45 @@ static void btf_dump_printf(void *ctx, const char *fmt, va_list args)
vfprintf(ctx, fmt, args);
}

/* Write raw BTF to file, return number of bytes written or negative errno */
static ssize_t btf_raw_write(struct btf *btf, char *file)
{
ssize_t written = 0;
const void *data;
__u32 size = 0;
int fd, ret;

fd = mkstemp(file);
if (!ASSERT_GE(fd, 0, "create_file"))
return -errno;

data = btf__raw_data(btf, &size);
if (!ASSERT_OK_PTR(data, "btf__raw_data")) {
close(fd);
return -EINVAL;
}
while (written < size) {
ret = write(fd, data + written, size - written);
if (!ASSERT_GE(ret, 0, "write succeeded")) {
close(fd);
return -errno;
}
written += ret;
}
close(fd);
return written;
}

static void __test_btf_split(bool multi)
{
char multisplit_btf_file[] = "/tmp/test_btf_multisplit.XXXXXX";
char split_btf_file[] = "/tmp/test_btf_split.XXXXXX";
char base_btf_file[] = "/tmp/test_btf_base.XXXXXX";
ssize_t multisplit_btf_sz = 0, split_btf_sz = 0, base_btf_sz = 0;
struct btf_dump *d = NULL;
const struct btf_type *t;
struct btf *btf1, *btf2, *btf3 = NULL;
const struct btf_type *t, *ot;
struct btf *btf1 = NULL, *btf2 = NULL, *btf3 = NULL;
struct btf *btf4 = NULL, *btf5 = NULL, *btf6 = NULL;
int str_off, i, err;

btf1 = btf__new_empty();
Expand Down Expand Up @@ -123,6 +157,38 @@ static void __test_btf_split(bool multi)
" int uf2;\n"
"};\n\n", "c_dump");

/* write base, split BTFs to files and ensure parsing succeeds */
base_btf_sz = btf_raw_write(btf1, base_btf_file);
if (base_btf_sz < 0)
goto cleanup;
split_btf_sz = btf_raw_write(btf2, split_btf_file);
if (split_btf_sz < 0)
goto cleanup;
btf4 = btf__parse(base_btf_file, NULL);
if (!ASSERT_OK_PTR(btf4, "parse_base"))
goto cleanup;
btf5 = btf__parse_split(split_btf_file, btf4);
if (!ASSERT_OK_PTR(btf5, "parse_split"))
goto cleanup;
if (multi) {
multisplit_btf_sz = btf_raw_write(btf3, multisplit_btf_file);
if (multisplit_btf_sz < 0)
goto cleanup;
btf6 = btf__parse_split(multisplit_btf_file, btf5);
if (!ASSERT_OK_PTR(btf6, "parse_multisplit"))
goto cleanup;
} else {
btf6 = btf5;
}

/* compare parsed to original BTF */
for (i = 1; i < btf__type_cnt(btf6); i++) {
t = btf__type_by_id(btf6, i);
ot = btf__type_by_id(btf3, i);
if (!ASSERT_EQ(memcmp(t, ot, sizeof(*ot)), 0, "cmp_parsed_orig_btf"))
goto cleanup;
}

cleanup:
if (dump_buf_file)
fclose(dump_buf_file);
Expand All @@ -132,6 +198,16 @@ static void __test_btf_split(bool multi)
btf__free(btf2);
if (btf2 != btf3)
btf__free(btf3);
btf__free(btf4);
btf__free(btf5);
if (btf5 != btf6)
btf__free(btf6);
if (base_btf_sz > 0)
unlink(base_btf_file);
if (split_btf_sz > 0)
unlink(split_btf_file);
if (multisplit_btf_sz > 0)
unlink(multisplit_btf_file);
}

void test_btf_split(void)
Expand Down