When encoding from a lot of object file sources, it is possible some
will not contain BTF, so if --btf_features=encode_force is set, drive
on as long as at least one _does_ contain a .BTF section.
With this in place, we can test how gcc -gbtf generation across vmlinux
works in a simple manner by doing the following on a kernel build which
specified -gbtf in the KCFLAGS environment variable (tested with gcc 14):
pahole --format_path=btf -J --btf_features=encode_force \
--btf_encode_detached=/tmp/vmlinux.btf $(ar t vmlinux.a)
("ar t vmlinux.a" gives a list of the object files comprising vmlinux)
This is no substitute for link-time BTF deduplication of course, but
it does provide a simple way to see the BTF that gcc generates for vmlinux.
The idea is that we can explore differences in BTF generation across
the various combinations
1. debug info source: DWARF; dedup done via pahole (traditional)
2. debug info source: compiler-generated BTF; dedup done via pahole (above)
3. debug info source: compiler-generated BTF; dedup done via linker (TBD)
Handling 3 - linker-based dedup - will require BTF archives so that is the
next step we need to explore.
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
dwarves.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/dwarves.c b/dwarves.c
index ef93239..8b37b13 100644
--- a/dwarves.c
+++ b/dwarves.c
@@ -2948,17 +2948,27 @@ try_elf:
int cus__load_files(struct cus *cus, struct conf_load *conf,
char *filenames[])
{
- int i = 0;
+ int i = 0, loaded = 0, failed = 0;
while (filenames[i] != NULL) {
int err = cus__load_file(cus, conf, filenames[i]);
if (err) {
errno = -err;
- return -++i;
+ if (conf->btf_encode_force)
+ failed = -(i + 1);
+ else
+ return -++i;
+ } else {
+ loaded++;
}
++i;
}
+ if (conf->btf_encode_force) {
+ /* If no files loaded, error out, otherwise return success */
+ if (loaded == 0)
+ return failed;
+ }
return i ? 0 : cus__load_running_kernel(cus, conf);
}
--
2.43.5
