btf: expose API to work with raw btf_ext data

This patch changes struct btf_ext to retain original data in sequential
block of memory, which makes it possible to expose
btf_ext__get_raw_data() interface similar to btf__get_raw_data(), allowing
users of libbpf to get access to raw representation of .BTF.ext section.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 54 insertions, 48 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 4fba0aa989df..f6b724ed1bdd 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -42,9 +42,8 @@ struct btf {
 
 struct btf_ext_info {
         /*
-         * info points to a deep copy of the individual info section
-         * (e.g. func_info and line_info) from the .BTF.ext.
-         * It does not include the __u32 rec_size.
+         * info points to the individual info section (e.g. func_info and
+         * line_info) from the .BTF.ext. It does not include the __u32 rec_size.
          */
         void *info;
         __u32 rec_size;
@@ -52,8 +51,13 @@ struct btf_ext_info {
 };
 
 struct btf_ext {
+        union {
+                struct btf_ext_header *hdr;
+                void *data;
+        };
         struct btf_ext_info func_info;
         struct btf_ext_info line_info;
+        __u32 data_size;
 };
 
 struct btf_ext_info_sec {
@@ -596,7 +600,7 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
         return 0;
 }
 
-struct btf_ext_sec_copy_param {
+struct btf_ext_sec_setup_param {
         __u32 off;
         __u32 len;
         __u32 min_rec_size;
@@ -604,20 +608,14 @@ struct btf_ext_sec_copy_param {
         const char *desc;
 };
 
-static int btf_ext_copy_info(struct btf_ext *btf_ext,
-                             __u8 *data, __u32 data_size,
-                             struct btf_ext_sec_copy_param *ext_sec)
+static int btf_ext_setup_info(struct btf_ext *btf_ext,
+                              struct btf_ext_sec_setup_param *ext_sec)
 {
-        const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
         const struct btf_ext_info_sec *sinfo;
         struct btf_ext_info *ext_info;
         __u32 info_left, record_size;
         /* The start of the info sec (including the __u32 record_size). */
-        const void *info;
-
-        /* data and data_size do not include btf_ext_header from now on */
-        data = data + hdr->hdr_len;
-        data_size -= hdr->hdr_len;
+        void *info;
 
         if (ext_sec->off & 0x03) {
                 pr_debug(".BTF.ext %s section is not aligned to 4 bytes\n",
@@ -625,16 +623,15 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
                 return -EINVAL;
         }
 
-        if (data_size < ext_sec->off ||
-            ext_sec->len > data_size - ext_sec->off) {
+        info = btf_ext->data + btf_ext->hdr->hdr_len + ext_sec->off;
+        info_left = ext_sec->len;
+
+        if (btf_ext->data + btf_ext->data_size < info + ext_sec->len) {
                 pr_debug("%s section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
-                     ext_sec->desc, ext_sec->off, ext_sec->len);
+                         ext_sec->desc, ext_sec->off, ext_sec->len);
                 return -EINVAL;
         }
 
-        info = data + ext_sec->off;
-        info_left = ext_sec->len;
-
         /* At least a record size */
         if (info_left < sizeof(__u32)) {
                 pr_debug(".BTF.ext %s record size not found\n", ext_sec->desc);
@@ -646,7 +643,7 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
         if (record_size < ext_sec->min_rec_size ||
             record_size & 0x03) {
                 pr_debug("%s section in .BTF.ext has invalid record size %u\n",
-                     ext_sec->desc, record_size);
+                         ext_sec->desc, record_size);
                 return -EINVAL;
         }
 
@@ -692,42 +689,35 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
         ext_info = ext_sec->ext_info;
         ext_info->len = ext_sec->len - sizeof(__u32);
         ext_info->rec_size = record_size;
-        ext_info->info = malloc(ext_info->len);
-        if (!ext_info->info)
-                return -ENOMEM;
-        memcpy(ext_info->info, info + sizeof(__u32), ext_info->len);
+        ext_info->info = info + sizeof(__u32);
 
         return 0;
 }
 
-static int btf_ext_copy_func_info(struct btf_ext *btf_ext,
-                                  __u8 *data, __u32 data_size)
+static int btf_ext_setup_func_info(struct btf_ext *btf_ext)
 {
-        const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
-        struct btf_ext_sec_copy_param param = {
-                .off = hdr->func_info_off,
-                .len = hdr->func_info_len,
+        struct btf_ext_sec_setup_param param = {
+                .off = btf_ext->hdr->func_info_off,
+                .len = btf_ext->hdr->func_info_len,
                 .min_rec_size = sizeof(struct bpf_func_info_min),
                 .ext_info = &btf_ext->func_info,
                 .desc = "func_info"
         };
 
-        return btf_ext_copy_info(btf_ext, data, data_size, &param);
+        return btf_ext_setup_info(btf_ext, &param);
 }
 
-static int btf_ext_copy_line_info(struct btf_ext *btf_ext,
-                                  __u8 *data, __u32 data_size)
+static int btf_ext_setup_line_info(struct btf_ext *btf_ext)
 {
-        const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
-        struct btf_ext_sec_copy_param param = {
-                .off = hdr->line_info_off,
-                .len = hdr->line_info_len,
+        struct btf_ext_sec_setup_param param = {
+                .off = btf_ext->hdr->line_info_off,
+                .len = btf_ext->hdr->line_info_len,
                 .min_rec_size = sizeof(struct bpf_line_info_min),
                 .ext_info = &btf_ext->line_info,
                 .desc = "line_info",
         };
 
-        return btf_ext_copy_info(btf_ext, data, data_size, &param);
+        return btf_ext_setup_info(btf_ext, &param);
 }
 
 static int btf_ext_parse_hdr(__u8 *data, __u32 data_size)
@@ -767,9 +757,7 @@ void btf_ext__free(struct btf_ext *btf_ext)
 {
         if (!btf_ext)
                 return;
-
-        free(btf_ext->func_info.info);
-        free(btf_ext->line_info.info);
+        free(btf_ext->data);
         free(btf_ext);
 }
 
@@ -786,13 +774,23 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
         if (!btf_ext)
                 return ERR_PTR(-ENOMEM);
 
-        err = btf_ext_copy_func_info(btf_ext, data, size);
-        if (err) {
-                btf_ext__free(btf_ext);
-                return ERR_PTR(err);
+        btf_ext->data_size = size;
+        btf_ext->data = malloc(size);
+        if (!btf_ext->data) {
+                err = -ENOMEM;
+                goto done;
         }
+        memcpy(btf_ext->data, data, size);
+
+        err = btf_ext_setup_func_info(btf_ext);
+        if (err)
+                goto done;
 
-        err = btf_ext_copy_line_info(btf_ext, data, size);
+        err = btf_ext_setup_line_info(btf_ext);
+        if (err)
+                goto done;
+
+done:
         if (err) {
                 btf_ext__free(btf_ext);
                 return ERR_PTR(err);
@@ -801,6 +799,12 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
         return btf_ext;
 }
 
+const void *btf_ext__get_raw_data(const struct btf_ext *btf_ext, __u32 *size)
+{
+        *size = btf_ext->data_size;
+        return btf_ext->data;
+}
+
 static int btf_ext_reloc_info(const struct btf *btf,
                               const struct btf_ext_info *ext_info,
                               const char *sec_name, __u32 insns_cnt,
@@ -849,7 +853,8 @@ static int btf_ext_reloc_info(const struct btf *btf,
         return -ENOENT;
 }
 
-int btf_ext__reloc_func_info(const struct btf *btf, const struct btf_ext *btf_ext,
+int btf_ext__reloc_func_info(const struct btf *btf,
+                             const struct btf_ext *btf_ext,
                              const char *sec_name, __u32 insns_cnt,
                              void **func_info, __u32 *cnt)
 {
@@ -857,7 +862,8 @@ int btf_ext__reloc_func_info(const struct btf *btf, const struct btf_ext *btf_ex
                                   insns_cnt, func_info, cnt);
 }
 
-int btf_ext__reloc_line_info(const struct btf *btf, const struct btf_ext *btf_ext,
+int btf_ext__reloc_line_info(const struct btf *btf,
+                             const struct btf_ext *btf_ext,
                              const char *sec_name, __u32 insns_cnt,
                              void **line_info, __u32 *cnt)
 {