On Thu, Aug 15, 2024 at 1:56 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> This commit adds a utility function to get disassembled text for jited
> representation of a BPF program designated by file descriptor.
> Function prototype looks as follows:
>
> int get_jited_program_text(int fd, char *text, size_t text_sz)
>
> Where 'fd' is a file descriptor for the program, 'text' and 'text_sz'
> refer to a destination buffer for disassembled text.
>
> The code and makefile changes are inspired by jit_disasm.c from bpftool.
> Use llvm libraries to disassemble BPF program instead of libbfd to avoid
> issues with disassembly output stability pointed out in [1].
>
> Selftests makefile uses Makefile.feature to detect if LLVM libraries
> are available. If that is not the case selftests build proceeds but
> the function returns -ENOTSUP at runtime.
>
> [1] commit eb9d1acf634b ("bpftool: Add LLVM as default library for disassembling JIT-ed programs")
>
> Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
> Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
> tools/testing/selftests/bpf/.gitignore | 1 +
> tools/testing/selftests/bpf/Makefile | 51 +++-
> .../selftests/bpf/jit_disasm_helpers.c | 234 ++++++++++++++++++
> .../selftests/bpf/jit_disasm_helpers.h | 10 +
> 4 files changed, 294 insertions(+), 2 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/jit_disasm_helpers.c
> create mode 100644 tools/testing/selftests/bpf/jit_disasm_helpers.h
>
> diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
> index 8f14d8faeb0b..7de4108771a0 100644
> --- a/tools/testing/selftests/bpf/.gitignore
> +++ b/tools/testing/selftests/bpf/.gitignore
> @@ -8,6 +8,7 @@ test_lru_map
> test_lpm_map
> test_tag
> FEATURE-DUMP.libbpf
> +FEATURE-DUMP.selftests
> fixdep
> /test_progs
> /test_progs-no_alu32
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index f54185e96a95..b1a52739d9e7 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -33,6 +33,13 @@ OPT_FLAGS ?= $(if $(RELEASE),-O2,-O0)
> LIBELF_CFLAGS := $(shell $(PKG_CONFIG) libelf --cflags 2>/dev/null)
> LIBELF_LIBS := $(shell $(PKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
>
> +ifeq ($(srctree),)
> +srctree := $(patsubst %/,%,$(dir $(CURDIR)))
> +srctree := $(patsubst %/,%,$(dir $(srctree)))
> +srctree := $(patsubst %/,%,$(dir $(srctree)))
> +srctree := $(patsubst %/,%,$(dir $(srctree)))
> +endif
> +
> CFLAGS += -g $(OPT_FLAGS) -rdynamic \
> -Wall -Werror -fno-omit-frame-pointer \
> $(GENFLAGS) $(SAN_CFLAGS) $(LIBELF_CFLAGS) \
> @@ -55,6 +62,11 @@ progs/test_sk_lookup.c-CFLAGS := -fno-strict-aliasing
> progs/timer_crash.c-CFLAGS := -fno-strict-aliasing
> progs/test_global_func9.c-CFLAGS := -fno-strict-aliasing
>
> +# Some utility functions use LLVM libraries
> +jit_disasm_helpers.c-CFLAGS = $(LLVM_CFLAGS)
> +test_progs-LDLIBS = $(LLVM_LDLIBS)
> +test_progs-LDFLAGS = $(LLVM_LDFLAGS)
> +
> ifneq ($(LLVM),)
> # Silence some warnings when compiled with clang
> CFLAGS += -Wno-unused-command-line-argument
> @@ -164,6 +176,31 @@ endef
>
> include ../lib.mk
>
> +NON_CHECK_FEAT_TARGETS := clean docs-clean
> +CHECK_FEAT := $(filter-out $(NON_CHECK_FEAT_TARGETS),$(or $(MAKECMDGOALS), "none"))
> +ifneq ($(CHECK_FEAT),)
> +FEATURE_USER := .selftests
> +FEATURE_TESTS := llvm
> +FEATURE_DISPLAY := $(FEATURE_TESTS)
> +
> +# Makefile.feature expects OUTPUT to end with a slash
> +$(let OUTPUT,$(OUTPUT)/,\
> + $(eval include ../../../build/Makefile.feature))
> +endif
> +
> +ifeq ($(feature-llvm),1)
> + LLVM_CFLAGS += -DHAVE_LLVM_SUPPORT
> + LLVM_CONFIG_LIB_COMPONENTS := mcdisassembler all-targets
> + # both llvm-config and lib.mk add -D_GNU_SOURCE, which ends up as conflict
> + LLVM_CFLAGS += $(filter-out -D_GNU_SOURCE,$(shell $(LLVM_CONFIG) --cflags))
> + LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --libs $(LLVM_CONFIG_LIB_COMPONENTS))
> + ifeq ($(shell $(LLVM_CONFIG) --shared-mode),static)
> + LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
> + LLVM_LDLIBS += -lstdc++
> + endif
> + LLVM_LDFLAGS += $(shell $(LLVM_CONFIG) --ldflags)
> +endif
> +
Seems like we raced between me commenting on v1 and you posting v2 :(
But I just noticed that formatting seems off here. Can you please
check space vs tabs issues?
> SCRATCH_DIR := $(OUTPUT)/tools
> BUILD_DIR := $(SCRATCH_DIR)/build
> INCLUDE_DIR := $(SCRATCH_DIR)/include
> @@ -488,6 +525,7 @@ define DEFINE_TEST_RUNNER
>
> TRUNNER_OUTPUT := $(OUTPUT)$(if $2,/)$2
> TRUNNER_BINARY := $1$(if $2,-)$2
> +TRUNNER_BASE_NAME := $1
[...]
