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Date: Mon, 30 Nov 2020 19:55:02 -0800
From: Yonghong Song <yhs@...com>
To: Brendan Jackman <jackmanb@...gle.com>, <bpf@...r.kernel.org>
CC: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
KP Singh <kpsingh@...omium.org>,
Florent Revest <revest@...omium.org>,
<linux-kernel@...r.kernel.org>, Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH v2 bpf-next 12/13] bpf: Add tests for new BPF atomic
operations
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@...gle.com>
> ---
> 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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