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selftests/bpf: utility function to get program disassembly after jit
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.
Output format looks as follows:
18: 77 06 ja L0
1a: 50 pushq %rax
1b: 48 89 e0 movq %rsp, %rax
1e: eb 01 jmp L1
20: 50 L0: pushq %rax
21: 50 L1: pushq %rax
^ ^^^^^^^^ ^ ^^^^^^^^^^^^^^^^^^
| binary insn | textual insn
| representation | representation
| |
instruction offset inferred local label name
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 -EOPNOTSUPP at runtime.
[1] commit eb9d1acf63 ("bpftool: Add LLVM as default library for disassembling JIT-ed programs")
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240820102357.3372779-6-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman
Alexei Starovoitov
parent
f8d161756d
commit
b991fc5207
1
tools/testing/selftests/bpf/.gitignore
vendored
1
tools/testing/selftests/bpf/.gitignore
vendored
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@ -8,6 +8,7 @@ test_lru_map
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test_lpm_map
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test_tag
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FEATURE-DUMP.libbpf
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FEATURE-DUMP.selftests
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fixdep
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/test_progs
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/test_progs-no_alu32
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@ -33,6 +33,13 @@ OPT_FLAGS ?= $(if $(RELEASE),-O2,-O0)
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LIBELF_CFLAGS := $(shell $(PKG_CONFIG) libelf --cflags 2>/dev/null)
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LIBELF_LIBS := $(shell $(PKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
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ifeq ($(srctree),)
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srctree := $(patsubst %/,%,$(dir $(CURDIR)))
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srctree := $(patsubst %/,%,$(dir $(srctree)))
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srctree := $(patsubst %/,%,$(dir $(srctree)))
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srctree := $(patsubst %/,%,$(dir $(srctree)))
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endif
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CFLAGS += -g $(OPT_FLAGS) -rdynamic \
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-Wall -Werror -fno-omit-frame-pointer \
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$(GENFLAGS) $(SAN_CFLAGS) $(LIBELF_CFLAGS) \
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@ -60,6 +67,9 @@ progs/timer_crash.c-CFLAGS := -fno-strict-aliasing
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progs/test_global_func9.c-CFLAGS := -fno-strict-aliasing
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progs/verifier_nocsr.c-CFLAGS := -fno-strict-aliasing
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# Some utility functions use LLVM libraries
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jit_disasm_helpers.c-CFLAGS = $(LLVM_CFLAGS)
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ifneq ($(LLVM),)
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# Silence some warnings when compiled with clang
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CFLAGS += -Wno-unused-command-line-argument
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@ -168,6 +178,31 @@ endef
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include ../lib.mk
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NON_CHECK_FEAT_TARGETS := clean docs-clean
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CHECK_FEAT := $(filter-out $(NON_CHECK_FEAT_TARGETS),$(or $(MAKECMDGOALS), "none"))
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ifneq ($(CHECK_FEAT),)
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FEATURE_USER := .selftests
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FEATURE_TESTS := llvm
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FEATURE_DISPLAY := $(FEATURE_TESTS)
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# Makefile.feature expects OUTPUT to end with a slash
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$(let OUTPUT,$(OUTPUT)/,\
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$(eval include ../../../build/Makefile.feature))
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endif
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ifeq ($(feature-llvm),1)
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LLVM_CFLAGS += -DHAVE_LLVM_SUPPORT
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LLVM_CONFIG_LIB_COMPONENTS := mcdisassembler all-targets
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# both llvm-config and lib.mk add -D_GNU_SOURCE, which ends up as conflict
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LLVM_CFLAGS += $(filter-out -D_GNU_SOURCE,$(shell $(LLVM_CONFIG) --cflags))
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LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --libs $(LLVM_CONFIG_LIB_COMPONENTS))
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ifeq ($(shell $(LLVM_CONFIG) --shared-mode),static)
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LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
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LLVM_LDLIBS += -lstdc++
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endif
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LLVM_LDFLAGS += $(shell $(LLVM_CONFIG) --ldflags)
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endif
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SCRATCH_DIR := $(OUTPUT)/tools
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BUILD_DIR := $(SCRATCH_DIR)/build
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INCLUDE_DIR := $(SCRATCH_DIR)/include
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@ -612,6 +647,10 @@ ifeq ($(filter clean docs-clean,$(MAKECMDGOALS)),)
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include $(wildcard $(TRUNNER_TEST_OBJS:.o=.d))
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endif
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# add per extra obj CFGLAGS definitions
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$(foreach N,$(patsubst $(TRUNNER_OUTPUT)/%.o,%,$(TRUNNER_EXTRA_OBJS)), \
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$(eval $(TRUNNER_OUTPUT)/$(N).o: CFLAGS += $($(N).c-CFLAGS)))
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$(TRUNNER_EXTRA_OBJS): $(TRUNNER_OUTPUT)/%.o: \
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%.c \
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$(TRUNNER_EXTRA_HDRS) \
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@ -628,6 +667,9 @@ ifneq ($2:$(OUTPUT),:$(shell pwd))
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$(Q)rsync -aq $$^ $(TRUNNER_OUTPUT)/
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endif
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$(OUTPUT)/$(TRUNNER_BINARY): LDLIBS += $$(LLVM_LDLIBS)
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$(OUTPUT)/$(TRUNNER_BINARY): LDFLAGS += $$(LLVM_LDFLAGS)
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# some X.test.o files have runtime dependencies on Y.bpf.o files
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$(OUTPUT)/$(TRUNNER_BINARY): | $(TRUNNER_BPF_OBJS)
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@ -637,7 +679,7 @@ $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS) \
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$(TRUNNER_BPFTOOL) \
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| $(TRUNNER_BINARY)-extras
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$$(call msg,BINARY,,$$@)
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$(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
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$(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) $$(LDFLAGS) -o $$@
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$(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@
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$(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)bpftool \
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$(OUTPUT)/$(if $2,$2/)bpftool
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@ -656,6 +698,7 @@ TRUNNER_EXTRA_SOURCES := test_progs.c \
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cap_helpers.c \
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unpriv_helpers.c \
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netlink_helpers.c \
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jit_disasm_helpers.c \
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test_loader.c \
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xsk.c \
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disasm.c \
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@ -798,7 +841,8 @@ EXTRA_CLEAN := $(SCRATCH_DIR) $(HOST_SCRATCH_DIR) \
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$(addprefix $(OUTPUT)/,*.o *.d *.skel.h *.lskel.h *.subskel.h \
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no_alu32 cpuv4 bpf_gcc bpf_testmod.ko \
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bpf_test_no_cfi.ko \
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liburandom_read.so)
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liburandom_read.so) \
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$(OUTPUT)/FEATURE-DUMP.selftests
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.PHONY: docs docs-clean
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234
tools/testing/selftests/bpf/jit_disasm_helpers.c
Normal file
234
tools/testing/selftests/bpf/jit_disasm_helpers.c
Normal file
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@ -0,0 +1,234 @@
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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
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#include <bpf/bpf.h>
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#include <bpf/libbpf.h>
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#include <test_progs.h>
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#ifdef HAVE_LLVM_SUPPORT
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#include <llvm-c/Core.h>
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#include <llvm-c/Disassembler.h>
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#include <llvm-c/Target.h>
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#include <llvm-c/TargetMachine.h>
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/* The intent is to use get_jited_program_text() for small test
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* programs written in BPF assembly, thus assume that 32 local labels
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* would be sufficient.
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*/
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#define MAX_LOCAL_LABELS 32
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static bool llvm_initialized;
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struct local_labels {
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bool print_phase;
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__u32 prog_len;
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__u32 cnt;
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__u32 pcs[MAX_LOCAL_LABELS];
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char names[MAX_LOCAL_LABELS][4];
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};
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static const char *lookup_symbol(void *data, uint64_t ref_value, uint64_t *ref_type,
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uint64_t ref_pc, const char **ref_name)
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{
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struct local_labels *labels = data;
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uint64_t type = *ref_type;
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int i;
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*ref_type = LLVMDisassembler_ReferenceType_InOut_None;
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*ref_name = NULL;
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if (type != LLVMDisassembler_ReferenceType_In_Branch)
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return NULL;
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/* Depending on labels->print_phase either discover local labels or
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* return a name assigned with local jump target:
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* - if print_phase is true and ref_value is in labels->pcs,
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* return corresponding labels->name.
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* - if print_phase is false, save program-local jump targets
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* in labels->pcs;
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*/
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if (labels->print_phase) {
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for (i = 0; i < labels->cnt; ++i)
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if (labels->pcs[i] == ref_value)
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return labels->names[i];
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} else {
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if (labels->cnt < MAX_LOCAL_LABELS && ref_value < labels->prog_len)
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labels->pcs[labels->cnt++] = ref_value;
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}
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return NULL;
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}
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static int disasm_insn(LLVMDisasmContextRef ctx, uint8_t *image, __u32 len, __u32 pc,
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char *buf, __u32 buf_sz)
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{
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int i, cnt;
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cnt = LLVMDisasmInstruction(ctx, image + pc, len - pc, pc,
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buf, buf_sz);
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if (cnt > 0)
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return cnt;
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PRINT_FAIL("Can't disasm instruction at offset %d:", pc);
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for (i = 0; i < 16 && pc + i < len; ++i)
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printf(" %02x", image[pc + i]);
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printf("\n");
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return -EINVAL;
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}
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static int cmp_u32(const void *_a, const void *_b)
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{
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__u32 a = *(__u32 *)_a;
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__u32 b = *(__u32 *)_b;
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if (a < b)
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return -1;
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if (a > b)
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return 1;
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return 0;
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}
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static int disasm_one_func(FILE *text_out, uint8_t *image, __u32 len)
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{
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char *label, *colon, *triple = NULL;
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LLVMDisasmContextRef ctx = NULL;
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struct local_labels labels = {};
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__u32 *label_pc, pc;
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int i, cnt, err = 0;
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char buf[64];
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triple = LLVMGetDefaultTargetTriple();
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ctx = LLVMCreateDisasm(triple, &labels, 0, NULL, lookup_symbol);
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if (!ASSERT_OK_PTR(ctx, "LLVMCreateDisasm")) {
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err = -EINVAL;
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goto out;
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}
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cnt = LLVMSetDisasmOptions(ctx, LLVMDisassembler_Option_PrintImmHex);
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if (!ASSERT_EQ(cnt, 1, "LLVMSetDisasmOptions")) {
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err = -EINVAL;
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goto out;
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}
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/* discover labels */
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labels.prog_len = len;
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pc = 0;
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while (pc < len) {
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cnt = disasm_insn(ctx, image, len, pc, buf, 1);
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if (cnt < 0) {
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err = cnt;
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goto out;
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}
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pc += cnt;
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}
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qsort(labels.pcs, labels.cnt, sizeof(*labels.pcs), cmp_u32);
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for (i = 0; i < labels.cnt; ++i)
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/* use (i % 100) to avoid format truncation warning */
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snprintf(labels.names[i], sizeof(labels.names[i]), "L%d", i % 100);
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/* now print with labels */
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labels.print_phase = true;
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pc = 0;
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while (pc < len) {
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cnt = disasm_insn(ctx, image, len, pc, buf, sizeof(buf));
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if (cnt < 0) {
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err = cnt;
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goto out;
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}
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label_pc = bsearch(&pc, labels.pcs, labels.cnt, sizeof(*labels.pcs), cmp_u32);
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label = "";
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colon = "";
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if (label_pc) {
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label = labels.names[label_pc - labels.pcs];
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colon = ":";
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}
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fprintf(text_out, "%x:\t", pc);
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for (i = 0; i < cnt; ++i)
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fprintf(text_out, "%02x ", image[pc + i]);
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for (i = cnt * 3; i < 12 * 3; ++i)
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fputc(' ', text_out);
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fprintf(text_out, "%s%s%s\n", label, colon, buf);
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pc += cnt;
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}
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out:
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if (triple)
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LLVMDisposeMessage(triple);
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if (ctx)
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LLVMDisasmDispose(ctx);
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return err;
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}
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int get_jited_program_text(int fd, char *text, size_t text_sz)
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{
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struct bpf_prog_info info = {};
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__u32 info_len = sizeof(info);
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__u32 jited_funcs, len, pc;
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__u32 *func_lens = NULL;
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FILE *text_out = NULL;
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uint8_t *image = NULL;
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int i, err = 0;
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if (!llvm_initialized) {
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LLVMInitializeAllTargetInfos();
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LLVMInitializeAllTargetMCs();
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LLVMInitializeAllDisassemblers();
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llvm_initialized = 1;
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}
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text_out = fmemopen(text, text_sz, "w");
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if (!ASSERT_OK_PTR(text_out, "open_memstream")) {
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err = -errno;
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goto out;
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}
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/* first call is to find out jited program len */
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err = bpf_prog_get_info_by_fd(fd, &info, &info_len);
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if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd #1"))
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goto out;
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len = info.jited_prog_len;
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image = malloc(len);
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if (!ASSERT_OK_PTR(image, "malloc(info.jited_prog_len)")) {
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err = -ENOMEM;
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goto out;
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}
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jited_funcs = info.nr_jited_func_lens;
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func_lens = malloc(jited_funcs * sizeof(__u32));
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if (!ASSERT_OK_PTR(func_lens, "malloc(info.nr_jited_func_lens)")) {
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err = -ENOMEM;
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goto out;
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}
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memset(&info, 0, sizeof(info));
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info.jited_prog_insns = (__u64)image;
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info.jited_prog_len = len;
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info.jited_func_lens = (__u64)func_lens;
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info.nr_jited_func_lens = jited_funcs;
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err = bpf_prog_get_info_by_fd(fd, &info, &info_len);
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if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd #2"))
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goto out;
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for (pc = 0, i = 0; i < jited_funcs; ++i) {
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fprintf(text_out, "func #%d:\n", i);
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disasm_one_func(text_out, image + pc, func_lens[i]);
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fprintf(text_out, "\n");
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pc += func_lens[i];
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}
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out:
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if (text_out)
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fclose(text_out);
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if (image)
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free(image);
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if (func_lens)
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free(func_lens);
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return err;
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}
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#else /* HAVE_LLVM_SUPPORT */
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int get_jited_program_text(int fd, char *text, size_t text_sz)
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{
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if (env.verbosity >= VERBOSE_VERY)
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printf("compiled w/o llvm development libraries, can't dis-assembly binary code");
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return -EOPNOTSUPP;
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}
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#endif /* HAVE_LLVM_SUPPORT */
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10
tools/testing/selftests/bpf/jit_disasm_helpers.h
Normal file
10
tools/testing/selftests/bpf/jit_disasm_helpers.h
Normal file
|
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@ -0,0 +1,10 @@
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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#ifndef __JIT_DISASM_HELPERS_H
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#define __JIT_DISASM_HELPERS_H
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#include <stddef.h>
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int get_jited_program_text(int fd, char *text, size_t text_sz);
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#endif /* __JIT_DISASM_HELPERS_H */
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