bpf tools: Collect eBPF programs from their own sections

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.

bpf_object__add_program() creates a new 'struct bpf_program' object.
It first init a variable in stack using bpf_program__init(), then if
success, enlarges obj->programs array and copy the new object in.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-13-git-send-email-wangnan0@huawei.com
[ Made bpf_object__add_program() propagate the error (-EINVAL or -ENOMEM) ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9b016c0868677aa6e458dddc0545859280d370c5..102156f322b6f2ae14eaac803c761ee02c59375a 100644 (file)
--- 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 +115,85 @@ struct bpf_object {
 };
 #define obj_elf_valid(o)       ((o)->efile.elf)
 
+static void bpf_program__exit(struct bpf_program *prog)
+{
+       if (!prog)
+               return;
+
+       zfree(&prog->section_name);
+       zfree(&prog->insns);
+       prog->insns_cnt = 0;
+       prog->idx = -1;
+}
+
+static int
+bpf_program__init(void *data, size_t size, char *name, int idx,
+                   struct bpf_program *prog)
+{
+       if (size < sizeof(struct bpf_insn)) {
+               pr_warning("corrupted section '%s'\n", name);
+               return -EINVAL;
+       }
+
+       bzero(prog, sizeof(*prog));
+
+       prog->section_name = strdup(name);
+       if (!prog->section_name) {
+               pr_warning("failed to alloc name for prog %s\n",
+                          name);
+               goto errout;
+       }
+
+       prog->insns = malloc(size);
+       if (!prog->insns) {
+               pr_warning("failed to alloc insns for %s\n", name);
+               goto errout;
+       }
+       prog->insns_cnt = size / sizeof(struct bpf_insn);
+       memcpy(prog->insns, data,
+              prog->insns_cnt * sizeof(struct bpf_insn));
+       prog->idx = idx;
+
+       return 0;
+errout:
+       bpf_program__exit(prog);
+       return -ENOMEM;
+}
+
+static int
+bpf_object__add_program(struct bpf_object *obj, void *data, size_t size,
+                       char *name, int idx)
+{
+       struct bpf_program prog, *progs;
+       int nr_progs, err;
+
+       err = bpf_program__init(data, size, name, idx, &prog);
+       if (err)
+               return err;
+
+       progs = obj->programs;
+       nr_progs = obj->nr_programs;
+
+       progs = realloc(progs, sizeof(progs[0]) * (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);
+               bpf_program__exit(&prog);
+               return -ENOMEM;
+       }
+
+       pr_debug("found program %s\n", prog.section_name);
+       obj->programs = progs;
+       obj->nr_programs = nr_progs + 1;
+       progs[nr_progs] = prog;
+       return 0;
+}
+
 static struct bpf_object *bpf_object__new(const char *path,
                                          void *obj_buf,
                                          size_t obj_buf_sz)
@@ -342,6 +436,17 @@ 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)) {
+                       err = bpf_object__add_program(obj, data->d_buf,
+                                                     data->d_size, name, idx);
+                       if (err) {
+                               char errmsg[128];
+                               strerror_r(-err, errmsg, sizeof(errmsg));
+                               pr_warning("failed to alloc program %s (%s): %s",
+                                          name, obj->path, errmsg);
+                       }
                }
                if (err)
                        goto out;
@@ -415,11 +520,20 @@ 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__exit(&obj->programs[i]);
+       }
+       zfree(&obj->programs);
+
        free(obj);
 }