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__jited_x86 test tag to check x86 assembly after jit

PATCH Superseded Eduard Zingerman 2 participants 9 messages Aug 15, 2024

Subsystems (3)
Kselftest BPF BPF selftests

v2 of 3 Superseded Latest is v3 →

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Eduard Zingerman

author maintainer
#0 lore raw

v2 cover __jited_x86 test tag to check x86 assembly after jit

Some of the logic in the BPF jits might be non-trivial. It might be useful to allow testing this logic by comparing generated native code with expected code template. This patch set adds a macro __jit_x86() that could be used for test_loader based tests in a following manner:

    __success
    __jit_x86("endbr64")
    __jit_x86("nopl	(%rax,%rax)")
    __jit_x86("xorq	%rax, %rax")
    __jit_x86("pushq %rbp")
    ...
    SEC("tc")
    __naked int main(void) { ... }

The last patch in a set adds a test for jit code generated for tail calls handling to demonstrate the feature.

The feature uses LLVM libraries to do the disassembly.
At selftests compilation time Makefile detects if these libraries are available. When libraries are not available tests using __jit_x86() are skipped.
Current CI environment does not include llvm development libraries, but changes to add these are trivial.

This was previously discussed here:
https://lore.kernel.org/bpf/[email protected]/

Changes v1->v2:
- stylistic changes suggested by Yonghong;
- fix for -Wformat-truncation related warning when compiled with llvm15 (Yonghong).

v1: https://lore.kernel.org/bpf/[email protected]/

Eduard Zingerman (4):
selftests/bpf: less spam in the log for message matching selftests/bpf: utility function to get program disassembly after jit selftests/bpf: __jited_x86 test tag to check x86 assembly after jit selftests/bpf: validate jit behaviour for tail calls

 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 +
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 tools/testing/selftests/bpf/progs/bpf_misc.h  |   2 +
 .../bpf/progs/verifier_tailcall_jit.c         | 103 ++++++++
 tools/testing/selftests/bpf/test_loader.c     | 159 ++++++++----
 8 files changed, 513 insertions(+), 49 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/jit_disasm_helpers.c
 create mode 100644 tools/testing/selftests/bpf/jit_disasm_helpers.h
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_tailcall_jit.c
Signature · 1 line
2.45.2
author maintainer
#1 lore raw

PATCH v2 1/4 selftests/bpf: less spam in the log for message matching

When running test_loader based tests in the verbose mode each matched message leaves a trace in the stderr, e.g.:

./test_progs -vvv -t ...
validate_msgs:PASS:expect_msg 0 nsec
validate_msgs:PASS:expect_msg 0 nsec
validate_msgs:PASS:expect_msg 0 nsec
validate_msgs:PASS:expect_msg 0 nsec
validate_msgs:PASS:expect_msg 0 nsec

This is not very helpful when debugging such tests and clobbers the log a lot.

Signed-off-by Eduard Zingerman <[email protected]>
---
 tools/testing/selftests/bpf/test_loader.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
tools/testing/selftests/bpf/test_loader.c +2 -1
index 12b0c41e8d64..1b1290e090e7 100644
@@ -531,7 +531,8 @@ static void validate_msgs(char *log_buf, struct expected_msgs *msgs,
 			}
 		}
 
-		if (!ASSERT_OK_PTR(match, "expect_msg")) {
+		if (!match) {
+			PRINT_FAIL("expect_msg\n");
 			if (env.verbosity == VERBOSE_NONE)
 				emit_fn(log_buf, true /*force*/);
 			for (j = 0; j <= i; j++) {
Signature · 1 line
2.45.2
author maintainer
#2 lore raw

PATCH v2 2/4 selftests/bpf: utility function to get program disassembly after jit

In reply to Eduard Zingerman

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 <[email protected]>
Signed-off-by Eduard Zingerman <[email protected]>
---
 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
tools/testing/selftests/bpf/.gitignore +1 -0
index 8f14d8faeb0b..7de4108771a0 100644
@@ -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
tools/testing/selftests/bpf/Makefile +49 -2

105 lines not on this page · raw message

tools/testing/selftests/bpf/jit_disasm_helpers.c new file +234 -0

234 lines not on this page · raw message

tools/testing/selftests/bpf/jit_disasm_helpers.h new file +10 -0
new file mode 100644
index 000000000000..e6924fd65ecf
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+
+#ifndef __JIT_DISASM_HELPERS_H
+#define __JIT_DISASM_HELPERS_H
+
+#include <stddef.h>
+
+int get_jited_program_text(int fd, char *text, size_t text_sz);
+
+#endif /* __JIT_DISASM_HELPERS_H */
Signature · 1 line
2.45.2
#3 lore raw

Re: [PATCH bpf-next v2 2/4] selftests/bpf: utility function to get program disassembly after jit

Quoted 92 lines · Eduard Zingerman

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 <[email protected]>
Signed-off-by Eduard Zingerman <[email protected]>
---
 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
tools/testing/selftests/bpf/.gitignore +1 -0
index 8f14d8faeb0b..7de4108771a0 100644
@@ -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
tools/testing/selftests/bpf/Makefile +27 -0
index f54185e96a95..b1a52739d9e7 100644
@@ -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

tools/testing/selftests/bpf/Makefile endef · line 203

Quoted 10 lines
tools/testing/selftests/bpf/Makefile +10 -0
+  # 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?

Quoted 8 lines
tools/testing/selftests/bpf/Makefile +1 -0
 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

[...]

author maintainer
#4 lore raw

Re: [PATCH bpf-next v2 2/4] selftests/bpf: utility function to get program disassembly after jit

On Thu, 2024-08-15 at 14:17 -0700, Andrii Nakryiko wrote:

[...]

Quoted 23 lines
Quoted 23 lines
tools/testing/selftests/bpf/Makefile +19 -0
@@ -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)
Quoted 8 lines

tools/testing/selftests/bpf/Makefile endef · line 203

Quoted 6 lines
tools/testing/selftests/bpf/Makefile +6 -0
+    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 :(

Yes, I should have waited a bit more, sorry.

Quoted 2 lines

But I just noticed that formatting seems off here. Can you please check space vs tabs issues?

For the block above the lines are indented using two spaces and four spaces. This is not a rule body, so should not be a problem afaik. What's not working on your side?

Quoted 3 lines
Quoted 3 lines
tools/testing/selftests/bpf/Makefile +0 -0
 SCRATCH_DIR := $(OUTPUT)/tools
 BUILD_DIR := $(SCRATCH_DIR)/build
 INCLUDE_DIR := $(SCRATCH_DIR)/include

[...]

#5 lore raw

Re: [PATCH bpf-next v2 2/4] selftests/bpf: utility function to get program disassembly after jit

Quoted 37 lines · Eduard Zingerman

On Thu, 2024-08-15 at 14:17 -0700, Andrii Nakryiko wrote:

[...]

Quoted 23 lines
Quoted 23 lines
tools/testing/selftests/bpf/Makefile +19 -0
@@ -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)
Quoted 8 lines

tools/testing/selftests/bpf/Makefile endef · line 203

Quoted 6 lines
tools/testing/selftests/bpf/Makefile +6 -0
+    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 :(

Quoted 2 lines

Yes, I should have waited a bit more, sorry.

no worries

Quoted 7 lines
Quoted 2 lines

But I just noticed that formatting seems off here. Can you please check space vs tabs issues?

For the block above the lines are indented using two spaces and four spaces. This is not a rule body, so should not be a problem afaik. What's not working on your side?

oh, it's just for consistency with the rest of Makefile. We use tabs for indentation, so let's stay consistent.

Quoted 6 lines
Quoted 3 lines
Quoted 3 lines
tools/testing/selftests/bpf/Makefile +0 -0
 SCRATCH_DIR := $(OUTPUT)/tools
 BUILD_DIR := $(SCRATCH_DIR)/build
 INCLUDE_DIR := $(SCRATCH_DIR)/include

[...]

author maintainer
#6 lore raw

Re: [PATCH bpf-next v2 2/4] selftests/bpf: utility function to get program disassembly after jit

On Thu, 2024-08-15 at 15:10 -0700, Andrii Nakryiko wrote:

[...]

Quoted 7 lines
Quoted 4 lines

For the block above the lines are indented using two spaces and four spaces. This is not a rule body, so should not be a problem afaik. What's not working on your side?

oh, it's just for consistency with the rest of Makefile. We use tabs for indentation, so let's stay consistent.

Ok, will change

[...]

author maintainer
#7 lore raw

PATCH v2 3/4 selftests/bpf: __jited_x86 test tag to check x86 assembly after jit

In reply to Eduard Zingerman

Allow to verify jit behaviour by writing tests as below:

    SEC("tp")
    __jit_x86("endbr64")
    __jit_x86("movabs $0x.*,%r9")
    __jit_x86("add    %gs:0x.*,%r9")
    __jit_x86("mov    $0x1,%edi")
    __jit_x86("mov    %rdi,-0x8(%r9)")
    __jit_x86("mov    -0x8(%r9),%rdi")
    __jit_x86("xor    %eax,%eax")
    __jit_x86("lock xchg %rax,-0x8(%r9)")
    __jit_x86("lock xadd %rax,-0x8(%r9)")
    __naked void stack_access_insns(void)
    {
    	asm volatile (... ::: __clobber_all);
    }

Use regular expressions by default, use basic regular expressions class in order to avoid escaping symbols like $(), often used in AT&T disassembly syntax.

Signed-off-by Eduard Zingerman <[email protected]>
---
 tools/testing/selftests/bpf/progs/bpf_misc.h |   2 +
 tools/testing/selftests/bpf/test_loader.c    | 156 +++++++++++++------
 2 files changed, 112 insertions(+), 46 deletions(-)
tools/testing/selftests/bpf/progs/bpf_misc.h +2 -0
index a225cd87897c..06e353a0a5b1 100644
@@ -90,6 +90,8 @@
 #define __arch_x86_64		__arch("X86_64")
 #define __arch_arm64		__arch("ARM64")
 #define __arch_riscv64		__arch("RISCV64")
+#define __jit_x86(basic_regex)	__attribute__((btf_decl_tag("comment:test_jit_x86=" basic_regex)))
+#define __jit_x86_unpriv(basic_regex)	__attribute__((btf_decl_tag("comment:test_jit_x86_unpriv=" basic_regex)))
 
 /* Convenience macro for use with 'asm volatile' blocks */
 #define __naked __attribute__((naked))
tools/testing/selftests/bpf/test_loader.c +110 -46

303 lines not on this page · raw message

Signature · 1 line
2.45.2
author maintainer
#8 lore raw

PATCH v2 4/4 selftests/bpf: validate jit behaviour for tail calls

In reply to Eduard Zingerman

A program calling sub-program which does a tail call. The idea is to verify instructions generated by jit for tail calls:
- in program and sub-program prologues;
- for subprogram call instruction;
- for tail call itself.

Signed-off-by Eduard Zingerman <[email protected]>
---
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../bpf/progs/verifier_tailcall_jit.c         | 103 ++++++++++++++++++
 2 files changed, 105 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_tailcall_jit.c
tools/testing/selftests/bpf/prog_tests/verifier.c +2 -0
index f8f546eba488..cf3662dbd24f 100644
@@ -75,6 +75,7 @@
 #include "verifier_stack_ptr.skel.h"
 #include "verifier_subprog_precision.skel.h"
 #include "verifier_subreg.skel.h"
+#include "verifier_tailcall_jit.skel.h"
 #include "verifier_typedef.skel.h"
 #include "verifier_uninit.skel.h"
 #include "verifier_unpriv.skel.h"

@@ -198,6 +199,7 @@ void test_verifier_spin_lock(void)            { RUN(verifier_spin_lock); }
 void test_verifier_stack_ptr(void)            { RUN(verifier_stack_ptr); }
 void test_verifier_subprog_precision(void)    { RUN(verifier_subprog_precision); }
 void test_verifier_subreg(void)               { RUN(verifier_subreg); }
+void test_verifier_tailcall_jit(void)         { RUN(verifier_tailcall_jit); }
 void test_verifier_typedef(void)              { RUN(verifier_typedef); }
 void test_verifier_uninit(void)               { RUN(verifier_uninit); }
 void test_verifier_unpriv(void)               { RUN(verifier_unpriv); }
tools/testing/selftests/bpf/progs/verifier_tailcall_jit.c new file +103 -0

103 lines not on this page · raw message

Signature · 1 line
2.45.2