When creating multi-split BTF we correctly set the start string offset to be the size of the base string section plus the base BTF start string offset; the latter is needed for multi-split BTF since the offset is non-zero there. Unfortunately the BTF parsing case needed that logic and it was missed. Fixes: 4e29128a9ace ("libbpf/btf: Fix string handling to support multi-split BTF") Signed-off-by: Alan Maguire --- tools/lib/bpf/btf.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 18907f0fcf9f..9f141395c074 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -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) { @@ -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) -- 2.39.3 Write raw BTF to files, parse it and compare to original; this allows us to test parsing of (multi-)split BTF code. Signed-off-by: Alan Maguire --- .../selftests/bpf/prog_tests/btf_split.c | 80 ++++++++++++++++++- 1 file changed, 78 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/btf_split.c b/tools/testing/selftests/bpf/prog_tests/btf_split.c index 3696fb9a05ed..b07a91ff28ff 100644 --- a/tools/testing/selftests/bpf/prog_tests/btf_split.c +++ b/tools/testing/selftests/bpf/prog_tests/btf_split.c @@ -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(); @@ -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); @@ -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) -- 2.39.3