Re: [PATCH v2 bpf-next 3/3] libbpf: btf typed dump does not need to allocate dump data

On Fri, Jul 16, 2021 at 3:47 PM Alan Maguire alan.maguire@oracle.com wrote:

By using the stack for this small structure, we avoid the need for freeing memory in error paths.

Suggested-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Alan Maguire alan.maguire@oracle.com

---

tools/lib/bpf/btf_dump.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index e5fbfb8..bd8e005 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -2240,6 +2240,7 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, const void *data, size_t data_sz, const struct btf_dump_type_data_opts *opts) {

•   struct btf_dump_data typed_dump = {};
    const struct btf_type *t;
    int ret;
  
  

@@ -2250,7 +2251,7 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, if (!t) return libbpf_err(-ENOENT);

•   d->typed_dump = calloc(1, sizeof(struct btf_dump_data));
  

•   d->typed_dump = &typed_dump;
    if (!d->typed_dump)
            return libbpf_err(-ENOMEM);
  

can't happen, removed, please pay attention to the surrounding code

@@ -2269,7 +2270,5 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,

    ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0);

•   free(d->typed_dump);
  

added resetting to NULL here, so that we don't have an accidental dangling pointers

    return libbpf_err(ret);

}

-- 1.8.3.1