bpftool: Allow to read btf as raw data

The bpftool interface stays the same, but now it's possible
to run it over BTF raw data, like:

  $ bpftool btf dump file /sys/kernel/btf/vmlinux
  [1] INT '(anon)' size=4 bits_offset=0 nr_bits=32 encoding=(none)
  [2] INT 'long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
  [3] CONST '(anon)' type_id=2

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Link: https://lore.kernel.org/bpf/20191024133025.10691-1-jolsa@kernel.org

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 9a9376d1d3df2aab84609cc0a6e42ce5beb687a7..a7b8bf233cf5756e79c22a00ad33f4f281ff25dc 100644 (file)
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -12,6 +12,9 @@
 #include <libbpf.h>
 #include <linux/btf.h>
 #include <linux/hashtable.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
 
 #include "btf.h"
 #include "json_writer.h"
@@ -388,6 +391,54 @@ done:
        return err;
 }
 
+static struct btf *btf__parse_raw(const char *file)
+{
+       struct btf *btf;
+       struct stat st;
+       __u8 *buf;
+       FILE *f;
+
+       if (stat(file, &st))
+               return NULL;
+
+       f = fopen(file, "rb");
+       if (!f)
+               return NULL;
+
+       buf = malloc(st.st_size);
+       if (!buf) {
+               btf = ERR_PTR(-ENOMEM);
+               goto exit_close;
+       }
+
+       if ((size_t) st.st_size != fread(buf, 1, st.st_size, f)) {
+               btf = ERR_PTR(-EINVAL);
+               goto exit_free;
+       }
+
+       btf = btf__new(buf, st.st_size);
+
+exit_free:
+       free(buf);
+exit_close:
+       fclose(f);
+       return btf;
+}
+
+static bool is_btf_raw(const char *file)
+{
+       __u16 magic = 0;
+       int fd;
+
+       fd = open(file, O_RDONLY);
+       if (fd < 0)
+               return false;
+
+       read(fd, &magic, sizeof(magic));
+       close(fd);
+       return magic == BTF_MAGIC;
+}
+
 static int do_dump(int argc, char **argv)
 {
        struct btf *btf = NULL;
@@ -465,7 +516,11 @@ static int do_dump(int argc, char **argv)
                }
                NEXT_ARG();
        } else if (is_prefix(src, "file")) {
-               btf = btf__parse_elf(*argv, NULL);
+               if (is_btf_raw(*argv))
+                       btf = btf__parse_raw(*argv);
+               else
+                       btf = btf__parse_elf(*argv, NULL);
+
                if (IS_ERR(btf)) {
                        err = PTR_ERR(btf);
                        btf = NULL;