Re: [RFC PATCH v3 16/37] bpf tools: Collect eBPF programs from their own sections

Namhyung Kim
2015-05-18T12:31:00Z

Hi,

On Sun, May 17, 2015 at 10:56:41AM +0000, Wang Nan wrote:
> This patch collects all programs in an object file into an array of
> 'struct bpf_program' for further processing. That structure is for
> representing each eBPF program. 'bpf_prog' should be a better name, but
> it has been used by linux/filter.h. Although it is a kernel space name,
> I still prefer to call it 'bpf_program' to prevent possible confusion.
>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> ---

[SNIP]

> +static struct bpf_program *
> +bpf_program_alloc(struct bpf_object *obj, void *data, size_t size,
> + char *name, int idx)
> +{
> + struct bpf_program *prog, *progs;
> + int nr_progs;
> +
> + if (size < sizeof(struct bpf_insn)) {
> + pr_warning("corrupted section '%s'\n", name);
> + return NULL;
> + }
> +
> + progs = obj->programs;
> + nr_progs = obj->nr_programs;
> +
> + progs = realloc(progs, sizeof(*prog) * (nr_progs + 1));
> + if (!progs) {
> + /*
> + * In this case the original obj->programs
> + * is still valid, so don't need special treat for
> + * bpf_close_object().
> + */
> + pr_warning("failed to alloc a new program '%s'\n",
> + name);
> + return NULL;
> + }
> +
> + obj->programs = progs;
> +
> + prog = &progs[nr_progs];
> + bzero(prog, sizeof(*prog));
> +
> + obj->nr_programs = nr_progs + 1;
> +
> + prog->section_name = strdup(name);
> + if (!prog->section_name) {
> + pr_warning("failed to alloc name for prog %s\n",
> + name);
> + goto out;
> + }
> +
> + prog->insns = malloc(size);
> + if (!prog->insns) {
> + pr_warning("failed to alloc insns for %s\n", name);
> + goto out;
> + }
> + prog->insns_cnt = size / sizeof(struct bpf_insn);
> + memcpy(prog->insns, data,
> + prog->insns_cnt * sizeof(struct bpf_insn));

Doesn't the data need to be swapped?

Thanks,
Namhyung

> + prog->idx = idx;
> +
> + return prog;
> +out:
> + bpf_clear_program(prog);
> + return NULL;
> +}
> +
> static struct bpf_object *__bpf_obj_alloc(const char *path)
> {
> struct bpf_object *obj;
> @@ -380,6 +468,22 @@ static int bpf_obj_elf_collect(struct bpf_object *obj)
> err = -EEXIST;
> } else
> obj->elf.symbols = data;
> + } else if ((sh.sh_type == SHT_PROGBITS) &&
> + (sh.sh_flags & SHF_EXECINSTR) &&
> + (data->d_size > 0)) {
> + struct bpf_program *prog;
> +
> + prog = bpf_program_alloc(obj, data->d_buf,
> + data->d_size, name,
> + idx);
> + if (!prog) {
> + pr_warning("failed to alloc "
> + "program %s (%s)", name,
> + obj->path);
> + err = -ENOMEM;
> + } else
> + pr_debug("found program %s\n",
> + prog->section_name);
> }
> if (err)
> goto out;
> @@ -446,5 +550,12 @@ void bpf_close_object(struct bpf_object *obj)
> free(obj->maps_buf);
> if (obj->config_str)
> free(obj->config_str);
> + if (obj->programs) {
> + size_t i;
> +
> + for (i = 0; i < obj->nr_programs; i++)
> + bpf_clear_program(&obj->programs[i]);
> + free(obj->programs);
> + }
> free(obj);
> }
> --
> 1.8.3.4
>