Re: [PATCH v2 bpf-next 12/13] bpf: Add tests for new BPF atomic operations

From: Yonghong Song
Date: Mon Nov 30 2020 - 22:56:08 EST



On 11/27/20 9:57 AM, Brendan Jackman wrote:
This relies on the work done by Yonghong Song in
https://reviews.llvm.org/D72184

Note the hackery in the Makefile that is necessary to avoid breaking
tests for people who haven't yet got a version of Clang supporting
V4. It seems like this hackery ought to be confined to
tools/build/feature - I tried implementing that and found that it
ballooned into an explosion of nightmares at the top of
tools/testing/selftests/bpf/Makefile without actually improving the
clarity of the CLANG_BPF_BUILD_RULE code at all. Hence the simple
$(shell) call...

Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 12 +-
.../selftests/bpf/prog_tests/atomics_test.c | 329 ++++++++++++++++++
.../selftests/bpf/progs/atomics_test.c | 124 +++++++
.../selftests/bpf/verifier/atomic_and.c | 77 ++++
.../selftests/bpf/verifier/atomic_cmpxchg.c | 96 +++++
.../selftests/bpf/verifier/atomic_fetch_add.c | 106 ++++++
.../selftests/bpf/verifier/atomic_or.c | 77 ++++
.../selftests/bpf/verifier/atomic_sub.c | 44 +++
.../selftests/bpf/verifier/atomic_xchg.c | 46 +++
.../selftests/bpf/verifier/atomic_xor.c | 77 ++++
tools/testing/selftests/bpf/verifier/ctx.c | 2 +-
11 files changed, 987 insertions(+), 3 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/atomics_test.c
create mode 100644 tools/testing/selftests/bpf/progs/atomics_test.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_and.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_cmpxchg.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_fetch_add.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_or.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_sub.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_xchg.c
create mode 100644 tools/testing/selftests/bpf/verifier/atomic_xor.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 3d5940cd110d..5eadfd09037d 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -228,6 +228,12 @@ IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
+# Determine if Clang supports BPF arch v4, and therefore atomics.
+CLANG_SUPPORTS_V4=$(if $(findstring v4,$(shell $(CLANG) --target=bpf -mcpu=? 2>&1)),true,)
+ifeq ($(CLANG_SUPPORTS_V4),true)
+ CFLAGS += -DENABLE_ATOMICS_TESTS
+endif
+
CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN) \
-I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR) \
@@ -250,7 +256,9 @@ define CLANG_BPF_BUILD_RULE
$(call msg,CLNG-LLC,$(TRUNNER_BINARY),$2)
$(Q)($(CLANG) $3 -O2 -target bpf -emit-llvm \
-c $1 -o - || echo "BPF obj compilation failed") | \
- $(LLC) -mattr=dwarfris -march=bpf -mcpu=v3 $4 -filetype=obj -o $2
+ $(LLC) -mattr=dwarfris -march=bpf \
+ -mcpu=$(if $(CLANG_SUPPORTS_V4),v4,v3) \
+ $4 -filetype=obj -o $2
endef
# Similar to CLANG_BPF_BUILD_RULE, but with disabled alu32
define CLANG_NOALU32_BPF_BUILD_RULE
@@ -391,7 +399,7 @@ TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c \
TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read \
$(wildcard progs/btf_dump_test_case_*.c)
TRUNNER_BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
-TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(CLANG_CFLAGS)
+TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(CLANG_CFLAGS) $(if $(CLANG_SUPPORTS_V4),-DENABLE_ATOMICS_TESTS,)

If the compiler indeed supports cpu v4 (i.e., atomic insns), -DENABLE_ATOMICS_TESTS will be added to TRUNNER_BPF_FLAGS and
eventually -DENABLE_ATOMICS_TESTS is also available for
no-alu32 test and this will cause compilation error.

I did the following hack to workaround the issue, i.e., only adds
the definition to default (alu32) test run.

index 5eadfd09037d..3d1320fd93eb 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -230,9 +230,6 @@ MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)

# Determine if Clang supports BPF arch v4, and therefore atomics.
CLANG_SUPPORTS_V4=$(if $(findstring v4,$(shell $(CLANG) --target=bpf -mcpu=? 2>&1)),true,)
-ifeq ($(CLANG_SUPPORTS_V4),true)
- CFLAGS += -DENABLE_ATOMICS_TESTS
-endif

CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN) \
@@ -255,6 +252,7 @@ $(OUTPUT)/flow_dissector_load.o: flow_dissector_load.h
define CLANG_BPF_BUILD_RULE
$(call msg,CLNG-LLC,$(TRUNNER_BINARY),$2)
$(Q)($(CLANG) $3 -O2 -target bpf -emit-llvm \
+ $(if $(CLANG_SUPPORTS_V4),-DENABLE_ATOMICS_TESTS,) \
-c $1 -o - || echo "BPF obj compilation failed") | \
$(LLC) -mattr=dwarfris -march=bpf \
-mcpu=$(if $(CLANG_SUPPORTS_V4),v4,v3) \
@@ -399,7 +397,7 @@ TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c \
TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read \
$(wildcard progs/btf_dump_test_case_*.c)
TRUNNER_BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
-TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(CLANG_CFLAGS) $(if $(CLANG_SUPPORTS_V4),-DENABLE_ATOMICS_TESTS,)
+TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(CLANG_CFLAGS)
TRUNNER_BPF_LDFLAGS := -mattr=+alu32
$(eval $(call DEFINE_TEST_RUNNER,test_progs))


TRUNNER_BPF_LDFLAGS := -mattr=+alu32
$(eval $(call DEFINE_TEST_RUNNER,test_progs))
diff --git a/tools/testing/selftests/bpf/prog_tests/atomics_test.c b/tools/testing/selftests/bpf/prog_tests/atomics_test.c
new file mode 100644
index 000000000000..8ecc0392fdf9
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/atomics_test.c
@@ -0,0 +1,329 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+
+#ifdef ENABLE_ATOMICS_TESTS
+
+#include "atomics_test.skel.h"
+
+static void test_add(void)
[...]
+
+#endif /* ENABLE_ATOMICS_TESTS */
diff --git a/tools/testing/selftests/bpf/progs/atomics_test.c b/tools/testing/selftests/bpf/progs/atomics_test.c
new file mode 100644
index 000000000000..3139b00937e5
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/atomics_test.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#ifdef ENABLE_ATOMICS_TESTS
+
+__u64 add64_value = 1;
+__u64 add64_result = 0;
+__u32 add32_value = 1;
+__u32 add32_result = 0;
+__u64 add_stack_value_copy = 0;
+__u64 add_stack_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(add, int a)
+{
+ __u64 add_stack_value = 1;
+
+ add64_result = __sync_fetch_and_add(&add64_value, 2);
+ add32_result = __sync_fetch_and_add(&add32_value, 2);
+ add_stack_result = __sync_fetch_and_add(&add_stack_value, 2);
+ add_stack_value_copy = add_stack_value;
+
+ return 0;
+}
+
+__s64 sub64_value = 1;
+__s64 sub64_result = 0;
+__s32 sub32_value = 1;
+__s32 sub32_result = 0;
+__s64 sub_stack_value_copy = 0;
+__s64 sub_stack_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(sub, int a)
+{
+ __u64 sub_stack_value = 1;
+
+ sub64_result = __sync_fetch_and_sub(&sub64_value, 2);
+ sub32_result = __sync_fetch_and_sub(&sub32_value, 2);
+ sub_stack_result = __sync_fetch_and_sub(&sub_stack_value, 2);
+ sub_stack_value_copy = sub_stack_value;
+
+ return 0;
+}
+
+__u64 and64_value = (0x110ull << 32);
+__u64 and64_result = 0;
+__u32 and32_value = 0x110;
+__u32 and32_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(and, int a)
+{
+
+ and64_result = __sync_fetch_and_and(&and64_value, 0x011ull << 32);
+ and32_result = __sync_fetch_and_and(&and32_value, 0x011);
+
+ return 0;
+}
+
+__u64 or64_value = (0x110ull << 32);
+__u64 or64_result = 0;
+__u32 or32_value = 0x110;
+__u32 or32_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(or, int a)
+{
+ or64_result = __sync_fetch_and_or(&or64_value, 0x011ull << 32);
+ or32_result = __sync_fetch_and_or(&or32_value, 0x011);
+
+ return 0;
+}
+
+__u64 xor64_value = (0x110ull << 32);
+__u64 xor64_result = 0;
+__u32 xor32_value = 0x110;
+__u32 xor32_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(xor, int a)
+{
+ xor64_result = __sync_fetch_and_xor(&xor64_value, 0x011ull << 32);
+ xor32_result = __sync_fetch_and_xor(&xor32_value, 0x011);
+
+ return 0;
+}

All above __sync_fetch_and_{add, sub, and, or, xor} produces a return
value used later. To test atomic_<op> instructions, it will be good if
you can add some tests which ignores the return value.

+
+__u64 cmpxchg64_value = 1;
+__u64 cmpxchg64_result_fail = 0;
+__u64 cmpxchg64_result_succeed = 0;
+__u32 cmpxchg32_value = 1;
+__u32 cmpxchg32_result_fail = 0;
+__u32 cmpxchg32_result_succeed = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(cmpxchg, int a)
+{
+ cmpxchg64_result_fail = __sync_val_compare_and_swap(
+ &cmpxchg64_value, 0, 3);
+ cmpxchg64_result_succeed = __sync_val_compare_and_swap(
+ &cmpxchg64_value, 1, 2);
+
+ cmpxchg32_result_fail = __sync_val_compare_and_swap(
+ &cmpxchg32_value, 0, 3);
+ cmpxchg32_result_succeed = __sync_val_compare_and_swap(
+ &cmpxchg32_value, 1, 2);
+
+ return 0;
+}
+
+__u64 xchg64_value = 1;
+__u64 xchg64_result = 0;
+__u32 xchg32_value = 1;
+__u32 xchg32_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(xchg, int a)
+{
+ __u64 val64 = 2;
+ __u32 val32 = 2;
+
+ __atomic_exchange(&xchg64_value, &val64, &xchg64_result, __ATOMIC_RELAXED);
+ __atomic_exchange(&xchg32_value, &val32, &xchg32_result, __ATOMIC_RELAXED);
+
+ return 0;
+}
+
+#endif /* ENABLE_ATOMICS_TESTS */
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