无法在内核树之外编译 bindsnoop eBPF c 代码

【问题标题】：Failed to compile bindsnoop eBPF c code outside of kernel tree无法在内核树之外编译 bindsnoop eBPF c 代码
【发布时间】：2021-10-03 22:27:39
【问题描述】：

我正在尝试将用 C 编写的 BPF 程序构建到 bpf 字节码中。程序 C 代码取自 https://github.com/iovisor/bcc/blob/master/tools/bindsnoop.py（我使用了来自 bpf_text 的 C 代码并进行了一些自定义）。 我不想使用 bcc python 工具，我的目的是用 C 编写内核和用户空间代码，我想在内核树之外构建一个内核程序。

我使用的是 Ubuntu 20.10，这里是 uname -a 输出： Linux bb-VirtualBox 5.8.0-63-generic #71-Ubuntu SMP Tue Jul 13 15:59:12 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Linux 头文件已安装，但由于某种原因，我有两个目录包含 5.8.0-63 的 linux 头文件： /usr/src/linux-headers-5.8.0-63 和 /usr/src/linux-headers-5.8.0-63-generic

我使用这篇文章为我的程序创建了一个 makefile：https://blogs.oracle.com/linux/post/bpf-in-depth-building-bpf-programs 所以makefile如下所示：

OBJS = kprobe_bindsnoop_kern.o

LLC ?= llc
CLANG ?= clang
INC_FLAGS = -nostdinc -isystem `$(CLANG) -print-file-name=include`
EXTRA_CFLAGS ?= -O2 -emit-llvm

linuxhdrsgen ?= /usr/src/linux-headers-5.8.0-63-generic

LINUXINCLUDE =  -I$(linuxhdrsgen)/arch/x86/include \
                -I$(linuxhdrsgen)/arch/x86/include/generated/uapi \
                -I$(linuxhdrsgen)/arch/x86/include/generated \
                -I$(linuxhdrsgen)/arch/x86/include/uapi \
                -I$(linuxhdrsgen)/arch/x86/include/generated/uapi \
                -I$(linuxhdrsgen)/include/uapi \
                -I$(linuxhdrsgen)/include/generated/uapi \
                -I$(linuxhdrsgen)/include \
                -include ${linuxhdrsgen}/include/linux/kconfig.h

all: $(OBJS)

.PHONY: clean

clean:
    rm -f $(OBJS)

INC_FLAGS = -nostdinc -isystem `$(CLANG) -print-file-name=include`

$(OBJS):  %.o:%.c
    $(CLANG) $(INC_FLAGS) \
        -D__KERNEL__ -D__ASM_SYSREG_H \
        -Wno-unused-value -Wno-pointer-sign \
        -Wno-compare-distinct-pointer-types \
        -Wno-gnu-variable-sized-type-not-at-end \
        -Wno-address-of-packed-member -Wno-tautological-compare \
        -Wno-unknown-warning-option \
        -I../include $(LINUXINCLUDE) \
        $(EXTRA_CFLAGS) -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@

而 kprobe_bindsnoop_kern.c 从以下一组包含文件开始：

#include <uapi/linux/ptrace.h>
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wtautological-compare"
#include <net/sock.h>
#pragma clang diagnostic pop
#include <net/inet_sock.h>
#include <net/net_namespace.h>
#include <bcc/proto.h>

下面可以看到编译输出：

clang -nostdinc -isystem `clang -print-file-name=include` \
    -D__KERNEL__ -D__ASM_SYSREG_H \
    -Wno-unused-value -Wno-pointer-sign \
    -Wno-compare-distinct-pointer-types \
    -Wno-gnu-variable-sized-type-not-at-end \
    -Wno-address-of-packed-member -Wno-tautological-compare \
    -Wno-unknown-warning-option \
    -I../include -I/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/ -I/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/generated/uapi -I/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/generated/ -I/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/uapi -I/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/generated/uapi -I/usr/src/linux-headers-5.8.0-63-generic/include/uapi -I/usr/src/linux-headers-5.8.0-63-generic/include/generated/uapi -I/usr/src/linux-headers-5.8.0-63-generic/include -include /usr/src/linux-headers-5.8.0-63-generic/include/linux/kconfig.h \
    -O2 -emit-llvm -c kprobe_bindsnoop_kern.c -o -| llc -march=bpf -filetype=obj -o kprobe_bindsnoop_kern.o
In file included from kprobe_bindsnoop_kern.c:22:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/uapi/linux/ptrace.h:143:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/ptrace.h:5:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/segment.h:6:
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:59:2: error: unknown type name 's32'
        s32 instr_offset;       /* original instruction */
        ^
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:60:2: error: unknown type name 's32'
        s32 repl_offset;        /* offset to replacement instruction */
        ^
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:61:2: error: unknown type name 'u16'
        u16 cpuid;              /* cpuid bit set for replacement */
        ^
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:62:2: error: unknown type name 'u8'
        u8  instrlen;           /* length of original instruction */
        ^
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:63:2: error: unknown type name 'u8'
        u8  replacementlen;     /* length of new instruction */
        ^
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:64:2: error: unknown type name 'u8'
        u8  padlen;             /* length of build-time padding */
        ^
/usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/alternative.h:85:8: error: unknown type name 'bool'
extern bool skip_smp_alternatives;
       ^
In file included from kprobe_bindsnoop_kern.c:22:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/uapi/linux/ptrace.h:143:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/ptrace.h:5:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/segment.h:169:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/cache.h:5:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/linkage.h:7:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/export.h:43:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/compiler.h:266:
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:16:15: error: unknown type name 'bool'
static inline bool __kasan_check_read(const volatile void *p, unsigned int size)
              ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:18:9: error: use of undeclared identifier 'true'
        return true;
               ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:20:15: error: unknown type name 'bool'
static inline bool __kasan_check_write(const volatile void *p, unsigned int size)
              ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:22:9: error: use of undeclared identifier 'true'
        return true;
               ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:34:15: error: unknown type name 'bool'
static inline bool kasan_check_read(const volatile void *p, unsigned int size)
              ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:36:9: error: use of undeclared identifier 'true'
        return true;
               ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:38:15: error: unknown type name 'bool'
static inline bool kasan_check_write(const volatile void *p, unsigned int size)
              ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kasan-checks.h:40:9: error: use of undeclared identifier 'true'
        return true;
               ^
In file included from kprobe_bindsnoop_kern.c:22:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/uapi/linux/ptrace.h:143:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/ptrace.h:5:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/segment.h:169:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/cache.h:5:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/linkage.h:7:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/export.h:43:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/compiler.h:267:
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kcsan-checks.h:148:67: error: unknown type name 'size_t'
static inline void __kcsan_check_access(const volatile void *ptr, size_t size,
                                                                  ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kcsan-checks.h:164:53: error: unknown type name 'size_t'
kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
                                                    ^
/usr/src/linux-headers-5.8.0-63-generic/include/linux/kcsan-checks.h:184:65: error: unknown type name 'size_t'
static inline void kcsan_check_access(const volatile void *ptr, size_t size,
                                                                ^
In file included from kprobe_bindsnoop_kern.c:22:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/uapi/linux/ptrace.h:143:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/ptrace.h:6:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/page_types.h:7:
In file included from /usr/src/linux-headers-5.8.0-63-generic/include/linux/mem_encrypt.h:17:
In file included from /usr/src/linux-headers-5.8.0-63-generic/arch/x86/include/asm/mem_encrypt.h:15:
/usr/src/linux-headers-5.8.0-63-generic/include/linux/init.h:155:8: error: unknown type name 'bool'
extern bool rodata_enabled;
       ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

我尝试添加 #include 或 #include 但这无济于事。 我查了很多帖子，像这样 Error compiling eBPF C code out of kernel tree 和这个 how to build BPF program out of the kernel tree 但仍然没有得到答案。 我错过了什么？ 任何帮助将不胜感激))

【问题讨论】：

  • What am I missing? 一些 typedef。
  • 这些s32 和u8 等可能在某些密件抄送标头中定义。您可以将它们替换为 __s32、__u8 等，您可能会从已包含的标题中提取它们。
  • @wildplasser 谢谢！你的意思是我需要为 bool、size_t、u8、u16 等手动添加所有 typedef？我认为这不是一个好主意
  • @Qeole 我添加了 typdefs 但它没有帮助 - 看起来我需要重写来自 linux/types.h 的所有 typedefs 等等。它现在抱怨 atomic_t、phys_addr_t、bool、true/false 等等。似乎是一个永无止境的故事......
  • 您可能缺少包含文件。也许是有条件的。如果你真的找不到并修复它，唯一的方法就是自己写一个。 （这不是太难）

标签： c linux ebpf


【解决方案1】：

感谢所有试图帮助我的人！ 最后，问题非常简单——只需要更改 makefile 中指定的包含目录的顺序即可。

刚刚将“-I$(linuxhdrsgen)/include”移到列表中的第一个，它解决了这个问题。 意思是，现在包含目录的列表如下所示：

LINUXINCLUDE = -I$(linuxhdrsgen)/include
-I$(linuxhdrsgen)/arch/x86/include
-I$(linuxhdrsgen)/arch/x86/include/generated/uapi
-I$(linuxhdrsgen)/arch/x86/include/生成
-I$(linuxhdrsgen)/arch/x86/include/uapi
-I$(linuxhdrsgen)/arch/x86/include/generated/uapi
-I$(linuxhdrsgen)/include/uapi
-I$(linuxhdrsgen)/include/生成/uapi
-include ${linuxhdrsgen}/include/linux/kconfig.h

【讨论】：

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