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Date: Tue, 7 Jul 2015 12:17:56 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Wang Nan <wangnan0@...wei.com>
Cc: ast@...mgrid.com, brendan.d.gregg@...il.com, daniel@...earbox.net,
namhyung@...nel.org, masami.hiramatsu.pt@...achi.com,
paulus@...ba.org, a.p.zijlstra@...llo.nl, mingo@...hat.com,
jolsa@...nel.org, dsahern@...il.com, linux-kernel@...r.kernel.org,
lizefan@...wei.com, hekuang@...wei.com, xiakaixu@...wei.com,
pi3orama@....com
Subject: Re: [RFC PATCH v10 12/50] bpf tools: Collect eBPF programs from
their own sections
Em Wed, Jul 01, 2015 at 02:14:00AM +0000, Wang Nan escreveu:
> 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@...wei.com>
> Acked-by: Alexei Starovoitov <ast@...mgrid.com>
> ---
> tools/lib/bpf/libbpf.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 107 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 9b016c0..9c01b55f 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -78,12 +78,27 @@ void libbpf_set_print(libbpf_print_fn_t warn,
> # define LIBBPF_ELF_C_READ_MMAP ELF_C_READ
> #endif
>
> +/*
> + * bpf_prog should be a better name but it has been used in
> + * linux/filter.h.
> + */
> +struct bpf_program {
> + /* Index in elf obj file, for relocation use. */
> + int idx;
> + char *section_name;
> + struct bpf_insn *insns;
> + size_t insns_cnt;
> +};
> +
> struct bpf_object {
> char license[64];
> u32 kern_version;
> void *maps_buf;
> size_t maps_buf_sz;
>
> + struct bpf_program *programs;
> + size_t nr_programs;
> +
> /*
> * Information when doing elf related work. Only valid if fd
> * is valid.
> @@ -100,6 +115,74 @@ struct bpf_object {
> };
> #define obj_elf_valid(o) ((o)->efile.elf)
>
> +static void bpf_program__clear(struct bpf_program *prog)
> +{
> + if (!prog)
> + return;
> +
> + zfree(&prog->section_name);
> + zfree(&prog->insns);
> + prog->insns_cnt = 0;
> + prog->idx = -1;
> +}
> +
> +static struct bpf_program *
> +bpf_program__new(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;
So here you basically commited your allocator, i.e. obj->nr_programs
now includes one extra program, but...
> + prog->section_name = strdup(name);
> + if (!prog->section_name) {
> + pr_warning("failed to alloc name for prog %s\n",
> + name);
> + goto out;
Here, that BTW could be better named "goto out_clear", you bail out
by calling...
> + }
> +
> + 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));
> + prog->idx = idx;
> +
> + return prog;
> +out:
... bpf_program__clear(), that will not reduce the number of entries in
obj->nr_programs, how will you garbage collect the unused entries?
Why not decouple bpf_program__new() from bpf_object?
I.e. you call it it will allocate space for a new bpf_program, if all
goes well, you then insert it into that bpf_object instance, no?
Even with this problem, I am applying it to my local tree to continue
looking at the other patches and to test the end result.
- Arnaldo
> + bpf_program__clear(prog);
> + return NULL;
> +}
> +
> static struct bpf_object *bpf_object__new(const char *path,
> void *obj_buf,
> size_t obj_buf_sz)
> @@ -342,6 +425,21 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
> err = -EEXIST;
> } else
> obj->efile.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__new(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;
> @@ -415,11 +513,20 @@ struct bpf_object *bpf_object__open_buffer(void *obj_buf,
>
> void bpf_object__close(struct bpf_object *obj)
> {
> + size_t i;
> +
> if (!obj)
> return;
>
> bpf_object__elf_finish(obj);
>
> zfree(&obj->maps_buf);
> +
> + if (obj->programs && obj->nr_programs) {
> + for (i = 0; i < obj->nr_programs; i++)
> + bpf_program__clear(&obj->programs[i]);
> + }
> + zfree(&obj->programs);
> +
> free(obj);
> }
> --
> 1.8.3.4
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