Re: [PATCH v5 bpf-next 9/9] selftests/bpf: Add test for resolve_btfids

Andrii Nakryiko
2020-07-07T01:26:42Z

On Fri, Jul 3, 2020 at 2:54 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding resolve_btfids test under test_progs suite.
>
> It's possible to use btf_ids.h header and its logic in
> user space application, so we can add easy test for it.
>
> The test defines BTF_ID_LIST and checks it gets properly
> resolved.
>
> For this reason the test_progs binary (and other binaries
> that use TRUNNER* macros) is processed with resolve_btfids
> tool, which resolves BTF IDs in .BTF.ids section.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> tools/testing/selftests/bpf/Makefile | 22 ++-
> .../selftests/bpf/prog_tests/resolve_btfids.c | 170 ++++++++++++++++++
> 2 files changed, 190 insertions(+), 2 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 1f9c696b3edf..b47a685d12bd 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -190,6 +190,16 @@ else
> cp "$(VMLINUX_H)" $@
> endif
>
> +$(SCRATCH_DIR)/resolve_btfids: $(BPFOBJ) \
> + $(TOOLSDIR)/bpf/resolve_btfids/main.c \
> + $(TOOLSDIR)/lib/rbtree.c \
> + $(TOOLSDIR)/lib/zalloc.c \
> + $(TOOLSDIR)/lib/string.c \
> + $(TOOLSDIR)/lib/ctype.c \
> + $(TOOLSDIR)/lib/str_error_r.c
> + $(Q)$(MAKE) $(submake_extras) -C $(TOOLSDIR)/bpf/resolve_btfids \
> + OUTPUT=$(SCRATCH_DIR)/ BPFOBJ=$(BPFOBJ)
> +

please indent OUTPUT, so it doesn't look like it's a separate command

> # Get Clang's default includes on this system, as opposed to those seen by
> # '-target bpf'. This fixes "missing" files on some architectures/distros,
> # such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
> @@ -333,7 +343,8 @@ $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o: \
> $(TRUNNER_BPF_SKELS) \
> $$(BPFOBJ) | $(TRUNNER_OUTPUT)
> $$(call msg,TEST-OBJ,$(TRUNNER_BINARY),$$@)
> - cd $$(@D) && $$(CC) -I. $$(CFLAGS) -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
> + cd $$(@D) && $$(CC) -I. $$(CFLAGS) $(TRUNNER_EXTRA_CFLAGS) \
> + -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
>
> $(TRUNNER_EXTRA_OBJS): $(TRUNNER_OUTPUT)/%.o: \
> %.c \
> @@ -355,6 +366,7 @@ $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS) \
> | $(TRUNNER_BINARY)-extras
> $$(call msg,BINARY,,$$@)
> $$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
> + $(TRUNNER_BINARY_EXTRA_CMD)

no need to make this generic, just write out resolve_btfids here explicitly

>
> endef
>
> @@ -365,7 +377,10 @@ TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c \
> network_helpers.c testing_helpers.c \
> flow_dissector_load.h
> TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read \
> - $(wildcard progs/btf_dump_test_case_*.c)
> + $(wildcard progs/btf_dump_test_case_*.c) \
> + $(SCRATCH_DIR)/resolve_btfids
> +TRUNNER_EXTRA_CFLAGS := -D"BUILD_STR(s)=\#s" -DVMLINUX_BTF="BUILD_STR($(VMLINUX_BTF))"
> +TRUNNER_BINARY_EXTRA_CMD := $(SCRATCH_DIR)/resolve_btfids --btf $(VMLINUX_BTF) test_progs

I hope we can get rid of this, see suggestion below.

> TRUNNER_BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
> TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(CLANG_CFLAGS)
> TRUNNER_BPF_LDFLAGS := -mattr=+alu32
> @@ -373,6 +388,7 @@ $(eval $(call DEFINE_TEST_RUNNER,test_progs))
>

[...]

> +
> +static int duration;
> +
> +static struct btf *btf__parse_raw(const char *file)

another copy here...

> +{
> + struct btf *btf;
> + struct stat st;
> + __u8 *buf;
> + FILE *f;
> +

[...]

> +
> +BTF_ID_LIST(test_list)
> +BTF_ID_UNUSED
> +BTF_ID(typedef, pid_t)
> +BTF_ID(struct, sk_buff)
> +BTF_ID(union, thread_union)
> +BTF_ID(func, memcpy)
> +
> +struct symbol {
> + const char *name;
> + int type;
> + int id;
> +};
> +
> +struct symbol test_symbols[] = {
> + { "unused", -1, 0 },

could use BTF_KIND_UNKN here instead of -1

> + { "pid_t", BTF_KIND_TYPEDEF, -1 },
> + { "sk_buff", BTF_KIND_STRUCT, -1 },
> + { "thread_union", BTF_KIND_UNION, -1 },
> + { "memcpy", BTF_KIND_FUNC, -1 },
> +};
> +

[...]

> +
> +static int resolve_symbols(void)
> +{
> + const char *path = VMLINUX_BTF;

This build-time parameter passing to find the original VMLINUX_BTF
really sucks, IMO.

Why not use the btf_dump tests approach and have our own small
"vmlinux BTF", which resolve_btfids would use to resolve these IDs?
See how btf_dump_xxx.c files define BTFs that are used in tests. You
can do something similar here, and use a well-known BPF object file as
a source of BTF, both here in a test and in Makefile for --btf param
to resolve_btfids?

> + struct btf *btf;
> + int type_id;
> + __u32 nr;
> + …