我终于在 Ubuntu Xenial x86_64 主机上交叉编译并链接了一个二进制文件，以便在 Raspberry Pi 4 的 armhf 上运行。
我的工具链来自 ARM 并放置在 $TOOLCHAIN 中。
我的 sysroot 是一个循环安装的 Raspberry OS 镜像，位于 $RASPBIAN_ROOT 中。
这是一个示例编译行:
$TOOLCHAIN/gcc-arm-8.3-2019.03/bin/arm-linux-gnueabihf-g++ -std=c++11 --sysroot=$RASPBIAN_ROOT \
-D_ARM_ -DOTHER_DEFINES \
-v -w -fexceptions -fpermissive -pipe \
-mcpu=cortex-a72 -mfpu=neon-vfpv4 -mfloat-abi=hard \
-Wabi-tag -D_GLIBCXX_USE_CXX11_ABI=0 \
-fno-use-cxa-atexit \
-g \
-I . -I .. -I extlib1/include -I extlib2/include -I $RASPBIAN_ROOT/usr/include/libxml2 \
-I $TOOLCHAIN/gcc-arm-8.3-2019.03/arm-none-linux-gnueabihf/libc/usr/include \
-I $RASPBIAN_ROOT/usr/include/arm-linux-gnueabihf \
-I $RASPBIAN_ROOT/usr/include \
-c File.cpp -o obj/linux/armhf/debug/File.o
还有一些.c文件。这是链接行:
$TOOLCHAIN/gcc-arm-8.3-2019.03/bin/arm-linux-gnueabihf-ld.gold \
-L ../localdependency \
-L $RASPBIAN_ROOT/opt/vc/lib \
-L $RASPBIAN_ROOT/usr/lib/arm-linux-gnueabihf \
-L $RASPBIAN_ROOT/lib \
-L$RASPBIAN_ROOT/usr/lib \
-L $RASPBIAN_ROOT/usr/lib/gcc/arm-linux-gnueabihf/8 -o bin/linux/armhf/debug/executable obj/linux/armhf/debug/File.o ... \
$RASPBIAN_ROOT/usr/lib/gcc/arm-linux-gnueabihf/8/crtbegin.o \
$RASPBIAN_ROOT/usr/lib/gcc/arm-linux-gnueabihf/8/crtend.o \
$RASPBIAN_ROOT/usr/lib/gcc/arm-linux-gnueabihf/8/libgcc_eh.a \
--verbose --sysroot=$RASPBIAN_ROOT \
-lbcm_host -lvcos -lvchiq_arm -lcurl -lxml2 \
-lpthread -lz -lm -ldl -lstdc++ -lc -lgcc -lgcc_s
...这似乎产生了一个可执行文件。 (为了便于阅读，对这两行进行了编辑。)
但是，在 pi 上运行时，出现段错误:
$ ./executable param1 param2
Segmentation fault
如果我尝试调试，它甚至不会到达 main():
$ gdb executable
GNU gdb (Raspbian 8.2.1-2) 8.2.1
...
(gdb) b main
Breakpoint 1 at 0x2c7c74: file main.cpp, line 7029.
(gdb) r param1 param2
Starting program: /home/user/executable param1 param2
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.
Program received signal SIGSEGV, Segmentation fault.
0xb6f97420 in __libc_enable_asynccancel () at ../nptl/cancellation.c:33
33 ../nptl/cancellation.c: No such file or directory.
(gdb) bt
#0 0xb6f97420 in __libc_enable_asynccancel () at ../nptl/cancellation.c:33
#1 0xb6f77968 in __GI___libc_write (nbytes=407, buf=0xb6fdc838 <banner>, fd=1) at ../sysdeps/unix/sysv/linux/write.c:26
#2 __GI___libc_write (fd=fd@entry=1, buf=0xb6fdc838 <banner>, nbytes=nbytes@entry=407) at ../sysdeps/unix/sysv/linux/write.c:24
#3 0xb6ec98d8 in __libc_print_version () at version.c:71
#4 __libc_main () at version.c:71
#5 0x00000000 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)
虽然我看到“警告:无法找到动态链接器断点函数。” (并且我试图弄清楚 ld.so 从哪里来)我更倾向于相信我的工具链/sysroot/libs 没有正确配置。
一个简单的 helloWorld 可以很好地交叉编译和执行:
#include <iostream>
int main(int argc, char* argv[]) {
int i = 1;
std::cout << "hello world " << i << std::endl;
return 0;
}
$ ./rpihello
hello world 1
$ ldd rpihello
linux-vdso.so.1 (0xbef33000)
/usr/lib/arm-linux-gnueabihf/libarmmem-${PLATFORM}.so => /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so (0xb6f90000)
libstdc++.so.6 => /usr/lib/arm-linux-gnueabihf/libstdc++.so.6 (0xb6e30000)
libm.so.6 => /lib/arm-linux-gnueabihf/libm.so.6 (0xb6dae000)
libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0xb6d81000)
libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0xb6c33000)
/lib/ld-linux-armhf.so.3 (0xb6fa5000)
编辑 1
因为 nptl/cancellation.c 似乎来自 libc，我仔细检查了我是否拥有所有必要的包，我相信我有(否则我会遇到广泛的 Pi 问题):
pi$ cat /etc/ld.so.conf.d/\*
/opt/vc/lib
# Multiarch support
/usr/local/lib/arm-linux-gnueabihf
/lib/arm-linux-gnueabihf
/usr/lib/arm-linux-gnueabihf
/usr/lib/arm-linux-gnueabihf/libfakeroot
# libc default configuration
/usr/local/lib
pi$ apt list --installed | grep ^libc
libc-ares2/now 1.14.0-1 armhf [installed,upgradable to: 1.14.0-1+deb10u1]
libc-bin/stable,now 2.28-10+rpi1 armhf [installed]
libc-dev-bin/stable,now 2.28-10+rpi1 armhf [installed,automatic]
libc-l10n/stable,now 2.28-10+rpi1 all [installed,automatic]
libc6-dbg/stable,now 2.28-10+rpi1 armhf [installed]
libc6-dev/stable,now 2.28-10+rpi1 armhf [installed]
libc6-pic/stable,now 2.28-10+rpi1 armhf [installed]
libc6/stable,now 2.28-10+rpi1 armhf [installed]
libcc1-0/stable,now 8.3.0-6+rpi1 armhf [installed,automatic]
pi$ apt list --installed | grep ^libgcc
libgcc-6-dev/stable,now 6.5.0-1+rpi1+b1 armhf [installed,automatic]
libgcc-8-dev/stable,now 8.3.0-6+rpi1 armhf [installed,automatic]
libgcc1-dbg/stable,now 1:8.3.0-6+rpi1 armhf [installed,automatic]
libgcc1/stable,now 1:8.3.0-6+rpi1 armhf [installed]
所以我仍然认为我以某种方式搞砸了交叉编译/链接。
编辑2
我已经成功地在树莓派上编译了我的代码库，并且生成的二进制文件显示出与交叉编译的结果相同的结果。因此，要么我编译错误，要么我的 sysroot 和 pi 的系统都有些乏味。
编辑3
rpi $ readelf -dW myexecutable
Dynamic section at offset 0x664e58 contains 48 entries:
Tag Type Name/Value
0x00000003 (PLTGOT) 0x6716d4
0x00000002 (PLTRELSZ) 5856 (bytes)
0x00000017 (JMPREL) 0x2d940
0x00000014 (PLTREL) REL
0x00000011 (REL) 0x2d2e0
0x00000012 (RELSZ) 1632 (bytes)
0x00000013 (RELENT) 8 (bytes)
0x00000015 (DEBUG) 0x0
0x00000006 (SYMTAB) 0x8148
0x0000000b (SYMENT) 16 (bytes)
0x00000005 (STRTAB) 0xfb48
0x0000000a (STRSZ) 94185 (bytes)
0x6ffffef5 (GNU_HASH) 0x26b34
0x00000004 (HASH) 0x2930c
0x00000001 (NEEDED) Shared library: [libbcm_host.so]
0x00000001 (NEEDED) Shared library: [libvcos.so]
0x00000001 (NEEDED) Shared library: [libvchiq_arm.so]
0x00000001 (NEEDED) Shared library: [libjson.so]
0x00000001 (NEEDED) Shared library: [libmylocallib.so]
...
0x00000001 (NEEDED) Shared library: [libpthread.so.0]
0x00000001 (NEEDED) Shared library: [libz.so.1]
0x00000001 (NEEDED) Shared library: [libm.so.6]
0x00000001 (NEEDED) Shared library: [libdl.so.2]
0x00000001 (NEEDED) Shared library: [libstdc++.so.6]
0x00000001 (NEEDED) Shared library: [libc.so.6]
0x00000019 (INIT_ARRAY) 0x66dd60
0x0000001b (INIT_ARRAYSZ) 244 (bytes)
0x0000001a (FINI_ARRAY) 0x66de54
0x0000001c (FINI_ARRAYSZ) 4 (bytes)
0x6ffffff0 (VERSYM) 0x2c1b0
0x6ffffffe (VERNEED) 0x2d0f0
0x6fffffff (VERNEEDNUM) 9
0x00000000 (NULL) 0x0
我发现这很有趣:
rpi $ file myexecutable
myexecutable: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /usr/lib/libc.so.1, with debug_info, not stripped
rpi $ file `which ls`
/bin/ls: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 3.2.0, BuildID[sha1]=67a394390830ea3ab4e83b5811c66fea9784ee69, stripped
我的可执行文件不应该使用 ld 作为解释器吗？
编辑4
我将 added [2] --dynamic-linker=/lib/ld-linux-armhf.so.3 添加到我的链接器行，但现在我没有堆栈:
Program received signal SIGSEGV, Segmentation fault.
0x00000000 in ?? ()
(gdb) bt
#0 0x00000000 in ?? ()
(gdb)
运行 strace executable 最后几行是这些:
rt_sigprocmask(SIG_BLOCK, NULL, ~[ILL TRAP BUS FPE KILL SEGV STOP RTMIN RT_1], 8) = 0
rt_sigaction(SIGILL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=SA_RESTORER, sa_restorer=0xb5e55120}, NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
clock_gettime(CLOCK_MONOTONIC_COARSE, {tv_sec=6336, tv_nsec=768744979}) = 0
gettimeofday({tv_sec=1631533208, tv_usec=497816}, NULL) = 0
openat(AT_FDCWD, "/dev/urandom", O_RDONLY) = 3
read(3, "\314\4bJn\36\16\240f\203\216I\257\306\251r\202\v\232\263\210\374\222\276TN\33,[\3A\233", 32) = 32
close(3) = 0
openat(AT_FDCWD, "/dev/urandom", O_RDONLY) = 3
read(3, "\301\231\203~G6Ey_\262Y\241\34\216F\2448w\2365Z\213\376\223\260\322zwo\334+e", 32) = 32
close(3) = 0
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=NULL} ---
+++ killed by SIGSEGV +++
Segmentation fault
/dev/urandom 确实存在。
编辑5
$ readelf -h executable
ELF Header:
Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: ARM
Version: 0x1
Entry point address: 0x0
Start of program headers: 52 (bytes into file)
Start of section headers: 40514564 (bytes into file)
Flags: 0x5000400, Version5 EABI, hard-float ABI
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 8
Size of section headers: 40 (bytes)
Number of section headers: 37
Section header string table index: 36
我认为入口点地址不应该是 0x0。
编辑6
我在 pi3 和 arm-qemu chroot 上编译了代码——结果相同。
最佳答案
我找到的解决方案是使用 toolchain 交叉编译来自 raspberrypi.org 并将 --sysroot= 设置为 Raspbian 图像。他们的releases或多或少地遵循 Debian 的并始终支持所有现有的 Raspberry Pies。
CXX 和 LD 都指向它们的 g++，这意味着由 GCC 决定链接标志。如有必要，我可以使用 -Wl,..
除了 -Wabi-tag -D_GLIBCXX_USE_CXX11_ABI=0，CFLAGS 是非常标准的。
Raspbian 在 Buster 10.3 之间更改了他们的下载 URL 格式(2020-02-13) 和 10.4 (2020-05-28) 并开始提供完整版和精简版。我用的是后者。
由于这些图像通常几乎没有可用空间，因此我首先 extend图像文件、分区 (p2) 和底层文件系统，因此我可以通过 quemu-arm chroot 到 sysroot 来安装满足我项目依赖关系的 -dev 包。
关于gcc - 在交叉编译的 armhf 中调用 main() 之前的段错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/69131713/