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

[Wang Nan <wangnan0@huawei.com>]

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>
---
 tools/lib/bpf/libbpf.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2068f0b..18b221f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -77,6 +77,18 @@ void libbpf_set_print(int (*warn)(const char *format, ...),
 # 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 *path;
 	bool needs_swap;
@@ -86,6 +98,9 @@ struct bpf_object {
 	size_t maps_buf_sz;
 	char *config_str;
 
+	struct bpf_program *programs;
+	size_t nr_programs;
+
 	/*
 	 * Information when doing elf related work. Only valid if fd
 	 * is valid.
@@ -99,6 +114,79 @@ struct bpf_object {
 };
 #define obj_elf_valid(o)	((o)->elf.fd >= 0)
 
+static void bpf_clear_program(struct bpf_program *prog)
+{
+	if (!prog)
+		return;
+	if (prog->section_name) {
+		free(prog->section_name);
+		prog->section_name = NULL;
+	}
+	if (prog->insns) {
+		free(prog->insns);
+		prog->insns = NULL;
+	}
+	prog->insns_cnt = 0;
+	prog->idx = -1;
+}
+
+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));
+	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