libbpf: Replace elf_state->st_ops_* fields with SEC_ST_OPS sec_type

The next patch would add two new section names for struct_ops maps.
To make working with multiple struct_ops sections more convenient:
- remove fields like elf_state->st_ops_{shndx,link_shndx};
- mark section descriptions hosting struct_ops as
  elf_sec_desc->sec_type == SEC_ST_OPS;

After these changes struct_ops sections could be processed uniformly
by iterating bpf_object->efile.secs entries.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-11-eddyz87@gmail.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 595c287d84efc3f12963189c59ad67f05cc7a316..cff72de42bf4b265b2421605b96aad4bb528b1c8 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -612,6 +612,7 @@ enum sec_type {
        SEC_BSS,
        SEC_DATA,
        SEC_RODATA,
+       SEC_ST_OPS,
 };
 
 struct elf_sec_desc {
@@ -627,8 +628,6 @@ struct elf_state {
        Elf *elf;
        Elf64_Ehdr *ehdr;
        Elf_Data *symbols;
-       Elf_Data *st_ops_data;
-       Elf_Data *st_ops_link_data;
        size_t shstrndx; /* section index for section name strings */
        size_t strtabidx;
        struct elf_sec_desc *secs;
@@ -637,8 +636,7 @@ struct elf_state {
        __u32 btf_maps_sec_btf_id;
        int text_shndx;
        int symbols_shndx;
-       int st_ops_shndx;
-       int st_ops_link_shndx;
+       bool has_st_ops;
 };
 
 struct usdt_manager;
@@ -1266,7 +1264,7 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
 }
 
 static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
-                               int shndx, Elf_Data *data, __u32 map_flags)
+                               int shndx, Elf_Data *data)
 {
        const struct btf_type *type, *datasec;
        const struct btf_var_secinfo *vsi;
@@ -1328,7 +1326,7 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
                map->def.key_size = sizeof(int);
                map->def.value_size = type->size;
                map->def.max_entries = 1;
-               map->def.map_flags = map_flags;
+               map->def.map_flags = strcmp(sec_name, STRUCT_OPS_LINK_SEC) == 0 ? BPF_F_LINK : 0;
 
                map->st_ops = calloc(1, sizeof(*map->st_ops));
                if (!map->st_ops)
@@ -1363,15 +1361,25 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
 
 static int bpf_object_init_struct_ops(struct bpf_object *obj)
 {
-       int err;
+       const char *sec_name;
+       int sec_idx, err;
 
-       err = init_struct_ops_maps(obj, STRUCT_OPS_SEC, obj->efile.st_ops_shndx,
-                                  obj->efile.st_ops_data, 0);
-       err = err ?: init_struct_ops_maps(obj, STRUCT_OPS_LINK_SEC,
-                                         obj->efile.st_ops_link_shndx,
-                                         obj->efile.st_ops_link_data,
-                                         BPF_F_LINK);
-       return err;
+       for (sec_idx = 0; sec_idx < obj->efile.sec_cnt; ++sec_idx) {
+               struct elf_sec_desc *desc = &obj->efile.secs[sec_idx];
+
+               if (desc->sec_type != SEC_ST_OPS)
+                       continue;
+
+               sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
+               if (!sec_name)
+                       return -LIBBPF_ERRNO__FORMAT;
+
+               err = init_struct_ops_maps(obj, sec_name, sec_idx, desc->data);
+               if (err)
+                       return err;
+       }
+
+       return 0;
 }
 
 static struct bpf_object *bpf_object__new(const char *path,
@@ -1409,8 +1417,6 @@ static struct bpf_object *bpf_object__new(const char *path,
        obj->efile.obj_buf = obj_buf;
        obj->efile.obj_buf_sz = obj_buf_sz;
        obj->efile.btf_maps_shndx = -1;
-       obj->efile.st_ops_shndx = -1;
-       obj->efile.st_ops_link_shndx = -1;
        obj->kconfig_map_idx = -1;
 
        obj->kern_version = get_kernel_version();
@@ -1427,8 +1433,6 @@ static void bpf_object__elf_finish(struct bpf_object *obj)
        elf_end(obj->efile.elf);
        obj->efile.elf = NULL;
        obj->efile.symbols = NULL;
-       obj->efile.st_ops_data = NULL;
-       obj->efile.st_ops_link_data = NULL;
 
        zfree(&obj->efile.secs);
        obj->efile.sec_cnt = 0;
@@ -2973,14 +2977,13 @@ static int bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 static bool libbpf_needs_btf(const struct bpf_object *obj)
 {
        return obj->efile.btf_maps_shndx >= 0 ||
-              obj->efile.st_ops_shndx >= 0 ||
-              obj->efile.st_ops_link_shndx >= 0 ||
+              obj->efile.has_st_ops ||
               obj->nr_extern > 0;
 }
 
 static bool kernel_needs_btf(const struct bpf_object *obj)
 {
-       return obj->efile.st_ops_shndx >= 0 || obj->efile.st_ops_link_shndx >= 0;
+       return obj->efile.has_st_ops;
 }
 
 static int bpf_object__init_btf(struct bpf_object *obj,
@@ -3681,12 +3684,12 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
                                sec_desc->sec_type = SEC_RODATA;
                                sec_desc->shdr = sh;
                                sec_desc->data = data;
-                       } else if (strcmp(name, STRUCT_OPS_SEC) == 0) {
-                               obj->efile.st_ops_data = data;
-                               obj->efile.st_ops_shndx = idx;
-                       } else if (strcmp(name, STRUCT_OPS_LINK_SEC) == 0) {
-                               obj->efile.st_ops_link_data = data;
-                               obj->efile.st_ops_link_shndx = idx;
+                       } else if (strcmp(name, STRUCT_OPS_SEC) == 0 ||
+                                  strcmp(name, STRUCT_OPS_LINK_SEC) == 0) {
+                               sec_desc->sec_type = SEC_ST_OPS;
+                               sec_desc->shdr = sh;
+                               sec_desc->data = data;
+                               obj->efile.has_st_ops = true;
                        } else {
                                pr_info("elf: skipping unrecognized data section(%d) %s\n",
                                        idx, name);
@@ -6999,12 +7002,12 @@ static int bpf_object__collect_relos(struct bpf_object *obj)
                data = sec_desc->data;
                idx = shdr->sh_info;
 
-               if (shdr->sh_type != SHT_REL) {
+               if (shdr->sh_type != SHT_REL || idx < 0 || idx >= obj->efile.sec_cnt) {
                        pr_warn("internal error at %d\n", __LINE__);
                        return -LIBBPF_ERRNO__INTERNAL;
                }
 
-               if (idx == obj->efile.st_ops_shndx || idx == obj->efile.st_ops_link_shndx)
+               if (obj->efile.secs[idx].sec_type == SEC_ST_OPS)
                        err = bpf_object__collect_st_ops_relos(obj, shdr, data);
                else if (idx == obj->efile.btf_maps_shndx)
                        err = bpf_object__collect_map_relos(obj, shdr, data);