[PATCH bpf-next] scripts/bpf: Print an error when known types list needs updating

[Jakub Sitnicki]

Don't generate a broken bpf_helper_defs.h header if the helper script needs
updating because it doesn't recognize a newly added type. Instead print an
error that explains why the build is failing and stop.

Fixes: 456a513bb5d4 ("scripts/bpf: Emit an #error directive known types list 
needs updating")
Suggested-by: Andrii Nakryiko <andr...@fb.com>
Signed-off-by: Jakub Sitnicki <ja...@cloudflare.com>
---
 scripts/bpf_helpers_doc.py | 4 ++--
 tools/lib/bpf/Makefile     | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 08300bc024da..7548569e8076 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -488,8 +488,8 @@ class PrinterHelpers(Printer):
             return t
         if t in self.mapped_types:
             return self.mapped_types[t]
-        print("")
-        print("#error \"Unrecognized type '%s', please add it to known 
types!\"" % t)
+        print("Unrecognized type '%s', please add it to known types!" % t,
+              file=sys.stderr)
         sys.exit(1)
 
     seen_helpers = set()
diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 75b538577c17..26c202261c5f 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -169,7 +169,8 @@ $(BPF_IN): force elfdep bpfdep bpf_helper_defs.h
 
 bpf_helper_defs.h: $(srctree)/include/uapi/linux/bpf.h
        $(Q)$(srctree)/scripts/bpf_helpers_doc.py --header              \
-               --file $(srctree)/include/uapi/linux/bpf.h > bpf_helper_defs.h
+               --file $(srctree)/include/uapi/linux/bpf.h > $@.tmp
+       @mv $@.tmp $@
 
 $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
 
-- 
2.20.1