When BPF selftests are built in RELEASE=1 mode with -O2 optimization
level, uprobe_multi binary, called from multi-uprobe tests is optimized
to the point that all the thousands of target uprobe_multi_func_XXX
functions are eliminated, breaking tests.
So ensure they are preserved through noinline + asm volatile trick.
But, actually, compiling uprobe_multi binary with -O2 takes a really
long time, and is quite useless (it's not a benchmark). So in addition
to ensuring that uprobe_multi_func_XXX functions are preserved, opt-out
of -O2 explicitly in Makefile and stick to -O0. This saves a lot of
compilation time.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 2 +-
tools/testing/selftests/bpf/uprobe_multi.c | 4 +++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 3b9eb40d6343..b0ac3dd80acf 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -759,7 +759,7 @@ $(OUTPUT)/veristat: $(OUTPUT)/veristat.o
$(OUTPUT)/uprobe_multi: uprobe_multi.c
$(call msg,BINARY,,$@)
- $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $^ $(LDLIBS) -o $@
+ $(Q)$(CC) $(CFLAGS) -O0 $(LDFLAGS) $^ $(LDLIBS) -o $@
EXTRA_CLEAN := $(SCRATCH_DIR) $(HOST_SCRATCH_DIR) \
prog_tests/tests.h map_tests/tests.h verifier/tests.h \
diff --git a/tools/testing/selftests/bpf/uprobe_multi.c b/tools/testing/selftests/bpf/uprobe_multi.c
index a61ceab60b68..e38228563766 100644
--- a/tools/testing/selftests/bpf/uprobe_multi.c
+++ b/tools/testing/selftests/bpf/uprobe_multi.c
@@ -9,7 +9,9 @@
#define NAME(name, idx) PASTE(name, idx)
-#define DEF(name, idx) int NAME(name, idx)(void) { return 0; }
+#define DEF(name, idx) \
+ int __attribute__((noinline)) \
+ NAME(name, idx)(void) { asm volatile (""); return 0; }
#define CALL(name, idx) NAME(name, idx)();
#define F(body, name, idx) body(name, idx)
--
2.43.0
