2021-07-16 22:49:19

by Alan Maguire

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

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

Suggested-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Alan Maguire <[email protected]>
---
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);

@@ -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);
-
return libbpf_err(ret);
}
--
1.8.3.1

2021-07-17 00:34:32

by Andrii Nakryiko

Subject: 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 <[email protected]> wrote:
>
> By using the stack for this small structure, we avoid the need
> for freeing memory in error paths.
>
> Suggested-by: Andrii Nakryiko <[email protected]>
> Signed-off-by: Alan Maguire <[email protected]>
> ---
> 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
>