[PATCH] bpftool: Try to read btf as raw data if elf read fails

Jiri Olsa
2019-10-18T10:34:08Z

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
libbpf: failed to get EHDR from /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

I'm also adding err init to 0 because I was getting uninitialized
warnings from gcc.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/bpf/bpftool/btf.c | 47 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 42 insertions(+), 5 deletions(-)

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 9a9376d1d3df..100fb7e02329 100644
--- 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 +391,35 @@ static int dump_btf_c(const struct btf *btf,
return err;
}

+static struct btf *btf__parse_raw(const char *file)
+{
+ struct btf *btf = ERR_PTR(-EINVAL);
+ __u8 *buf = NULL;
+ struct stat st;
+ FILE *f;
+
+ if (stat(file, &st))
+ return btf;
+
+ f = fopen(file, "rb");
+ if (!f)
+ return btf;
+
+ buf = malloc(st.st_size);
+ if (!buf)
+ goto err;
+
+ if ((size_t) st.st_size != fread(buf, 1, st.st_size, f))
+ goto err;
+
+ btf = btf__new(buf, st.st_size);
+
+err:
+ free(buf);
+ fclose(f);
+ return btf;
+}
+
static int do_dump(int argc, char **argv)
{
struct btf *btf = NULL;
@@ -397,7 +429,7 @@ static int do_dump(int argc, char **argv)
__u32 btf_id = -1;
const char *src;
int fd = -1;
- int err;
+ int err = 0;

if (!REQ_ARGS(2)) {
usage();
@@ -468,10 +500,15 @@ static int do_dump(int argc, char **argv)
btf = btf__parse_elf(*argv, NULL);
if (IS_ERR(btf)) {
err = PTR_ERR(btf);
- btf = NULL;
- p_err("failed to load BTF from %s: %s",
- *argv, strerror(err));
- goto done;
+ if (err == -LIBBPF_ERRNO__FORMAT)
+ btf = btf__parse_raw(*argv);
+ if (IS_ERR(btf)) {
+ btf = NULL;
+ /* Display the original error value. */
+ p_err("failed to load BTF from %s: %s",
+ *argv, strerror(err));
+ goto done;
+ }
}
NEXT_ARG();
} else {
--
2.21.0