[PATCH 1/3] tracing: Fix empty symbol names in simple_ring_buffer undef check

[Vincent Donnefort]

Sparc64 emits empty symmbol names. Skips them when establishing the
allowlist and when extracing undefined symbols.

Fixes: 1211907ac0b5 ("tracing: Generate undef symbols allowlist for simple_ring_buffer")
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/5574c9e6-9ed2-4ee6-a2b2-fb6ee81e83a1@xxxxxxxxxxxx/
Signed-off-by: Vincent Donnefort <vdonnefort@xxxxxxxxxx>
---
 kernel/trace/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index f934ff586bd4..0e1846f7dda3 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -146,11 +146,11 @@ KASAN_SANITIZE_undefsyms_base.o := y
 
 UNDEFINED_ALLOWLIST = __asan __gcov __kasan __kcsan __hwasan __sancov __sanitizer __tsan __ubsan __msan \
 		      __aeabi_unwind_cpp __s390_indirect_jump __x86_indirect_thunk simple_ring_buffer \
-		      $(shell $(NM) -u $(obj)/undefsyms_base.o 2>/dev/null | awk '{print $$2}')
+		      $(shell $(NM) -u $(obj)/undefsyms_base.o 2>/dev/null | awk '$$2 {print $$2}')
 
 quiet_cmd_check_undefined = NM      $<
       cmd_check_undefined = \
-          undefsyms=$$($(NM) -u $< | grep -v $(addprefix -e , $(UNDEFINED_ALLOWLIST)) || true); \
+          undefsyms=$$($(NM) -u $< | awk '$$2 {print $$2}' | grep -v $(addprefix -e , $(UNDEFINED_ALLOWLIST)) || true); \
           if [ -n "$$undefsyms" ]; then \
               echo "Unexpected symbols in $<:" >&2; \
               echo "$$undefsyms" >&2; \
-- 
2.55.0.1082.g2b9226bbc0-goog