[RFC PATCH v7 11/37] bpf tools: Collect eBPF programs from their own sections

Wang Nan
2015-06-12T05:45:29Z

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>
Acked-by: Alexei Starovoitov <ast@plumgrid.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 77ad7d3..91b2490 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;
+
+ 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));
+ prog->idx = idx;
+
+ return prog;
+out:
+ bpf_program__clear(prog);
+ return NULL;
+}
+
static struct bpf_object *bpf_object__new(const char *path,
void *obj_buf,
size_t obj_buf_sz)
@@ -341,6 +424,21 @@ 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;
@@ -414,11 +512,20 @@ 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