On Wed, Mar 25, 2020 at 9:20 AM Stanislav Fomichev <sdf@xxxxxxxxxx> wrote:
>
> For each prog/btf load we allocate and free 16 megs of verifier buffer.
> On production systems it doesn't really make sense because the
> programs/btf have gone through extensive testing and (mostly) guaranteed
> to successfully load.
>
> Let's assume successful case by default and skip buffer allocation
> on the first try. If there is an error, start with BPF_LOG_BUF_SIZE
> and double it on each ENOSPC iteration.
>
> v2:
> * Don't allocate the buffer at all on the first try (Andrii Nakryiko)
>
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
> ---
> tools/lib/bpf/btf.c | 20 +++++++++++++++-----
> tools/lib/bpf/libbpf.c | 22 ++++++++++++++--------
> 2 files changed, 29 insertions(+), 13 deletions(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index 3d1c25fc97ae..bfef3d606b54 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -657,22 +657,32 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf)
>
> int btf__load(struct btf *btf)
> {
> - __u32 log_buf_size = BPF_LOG_BUF_SIZE;
> + __u32 log_buf_size = 0;
> char *log_buf = NULL;
> int err = 0;
>
> if (btf->fd >= 0)
> return -EEXIST;
>
> - log_buf = malloc(log_buf_size);
> - if (!log_buf)
> - return -ENOMEM;
> +retry_load:
> + if (log_buf_size) {
> + log_buf = malloc(log_buf_size);
> + if (!log_buf)
> + return -ENOMEM;
>
> - *log_buf = 0;
> + *log_buf = 0;
> + }
>
> btf->fd = bpf_load_btf(btf->data, btf->data_size,
> log_buf, log_buf_size, false);
> if (btf->fd < 0) {
> + if (!log_buf || errno == ENOSPC) {
> + log_buf_size = max((__u32)BPF_LOG_BUF_SIZE,
> + log_buf_size << 1);
> + free(log_buf);
> + goto retry_load;
> + }
> +
> err = -errno;
> pr_warn("Error loading BTF: %s(%d)\n", strerror(errno), errno);
> if (*log_buf)
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 085e41f9b68e..b2fd43a03708 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4855,8 +4855,8 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
> {
> struct bpf_load_program_attr load_attr;
> char *cp, errmsg[STRERR_BUFSIZE];
> - int log_buf_size = BPF_LOG_BUF_SIZE;
> - char *log_buf;
> + size_t log_buf_size = 0;
> + char *log_buf = NULL;
> int btf_fd, ret;
>
> if (!insns || !insns_cnt)
> @@ -4896,22 +4896,28 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
> load_attr.prog_flags = prog->prog_flags;
>
> retry_load:
> - log_buf = malloc(log_buf_size);
> - if (!log_buf)
> - pr_warn("Alloc log buffer for bpf loader error, continue without log\n");
> + if (log_buf_size) {
> + log_buf = malloc(log_buf_size);
> + if (!log_buf)
> + pr_warn("Alloc log buffer for bpf loader error, continue without log\n");
> +
considering that log_buf is not allocated first time, if it fails to
allocate on retry then it should be an error, no?
Otherwise looks good, please add my ack after fixing this:
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
> + *log_buf = 0;
> + }
>
> ret = bpf_load_program_xattr(&load_attr, log_buf, log_buf_size);
>
> if (ret >= 0) {
> - if (load_attr.log_level)
> + if (log_buf && load_attr.log_level)
> pr_debug("verifier log:\n%s", log_buf);
> *pfd = ret;
> ret = 0;
> goto out;
> }
>
> - if (errno == ENOSPC) {
> - log_buf_size <<= 1;
> + if (!log_buf || errno == ENOSPC) {
> + log_buf_size = max((size_t)BPF_LOG_BUF_SIZE,
> + log_buf_size << 1);
> +
> free(log_buf);
> goto retry_load;
> }
> --
> 2.25.1.696.g5e7596f4ac-goog
>
