perf build: enable -fno-strict-aliasing

perf pulls in code from kernel headers that assumes it is being built
with -fno-strict-aliasing, namely put_unaligned_*() from
<linux/unaligned.h> which write the data using packed structs that lack
the may_alias attribute.  Enable -fno-strict-aliasing to prevent
miscompilations in sha1.c which would otherwise occur due to this issue.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250625202311.23244-2-ebiggers@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 24736b0bbb302abeae5528cdaa0eb6f0e9a3f005..70a3e771c7c08f62e1b92ff980b00ca998551b6e 100644 (file)
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -19,6 +19,10 @@ detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)
 CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
 HOSTCFLAGS := $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
 
+# This is required because the kernel is built with this and some of the code
+# borrowed from kernel headers depends on it, e.g. put_unaligned_*().
+CFLAGS += -fno-strict-aliasing
+
 # Enabled Wthread-safety analysis for clang builds.
 ifeq ($(CC_NO_CLANG), 0)
   CFLAGS += -Wthread-safety