用arm-none-eabi-gcc编译器编译RaspberryPI2和BeableBoneBlack的sqrt函数错误

Question

我是这种编码的新手，我正在尝试做一些测试，为Cortex-A处理器执行裸金属软件。我有使用Cortex-M MCU的经验，我用类似于ARM Keil的IDE和北欧的SDK编译了代码，用于一些BLE工作。现在，我想尝试更好地理解Cortex-A的世界，我将以一种赤裸裸的方式学习编码，从我在网上找到的一些例子开始。我有一些使用Cortex-M的freeRTOS的经验，所以我在网上找到了一些git存储库，它是从一个好家伙那里找到的，他正在为RaspberryPI和BeableBoneBlack移植freeRTOS。从现在开始，我将只为BeableBoneBlack解释我的问题，为RaspberryPI解释我的问题--这是类似的。

我在linux上，我安装了gcc-arm-无eabi编译器，所以我从这个BeagleBone上克隆了freeRTOS存储库的freeRTOS黑。

我通常使用VS代码来编写代码，所以在集成终端中，当我运行命令使正常工作时，我的BBB就会正确地闪烁。所以现在我想改进我的代码，为了进行一些测试，我想使用stdlib.h中的rand()函数。不幸的是，我发现有一些错误：undefined reference to rand。在过去的几个月里，在对BBB进行测试之前，我为RPi2找到了其他的repos，并且我了解到了arm的链接器--无eabi编译器，它需要在过程中添加一些参数来排列链接库文件。现在我有两个文件：makedefs_ti和makefile。打开我在第26-27行中找到的make文件--文件应用程序生成的部分，因此调用链接器。在这一行中，有对makedefs_ti.中定义的LIB_GCC和LIB_C的引用。在第49-50行中，有对安装编译器的目录的引用(我修改了4.7.3，正确地安装在我的linux pc上，即9.2.1)。在makefile中，在-L$(LIB_C)之后，如果添加链接器参数(如-lc或-lg )并尝试重新编译，则会出现类似于arm-none-eabi-ld: cannot find -lc的错误。根据在线资源的一些理解，我对makedefs_ti进行了如下修改：

# Toolchain/library path. LIB_PATH is an exported environmental variable which
# shall point to the installation of toolchain
#
#LIB_GCC=${LIB_PATH}/lib/gcc/arm-none-eabi/4.7.3/
#LIB_C=${LIB_PATH}/arm-none-eabi/lib/
LIB_GCC= /usr/lib/gcc/arm-none-eabi/9.2.1
LIB_C= /usr/lib/arm-none-eabi/lib

以及makefile：

$(LD) -o $@.out $< -T bbb.ld -Map bbb.map $(APP_LIB) $(LDFLAGS) $(RUNTIMELIB) -L $(LPATH) \
   -L $(LIB_GCC) -lgcc -L $(LIB_C) -lc -lg

这样，调用rand()函数的main.c文件就能正确编译。在另一个测试中，我试图编译另一个代码。现在，我编写了一对.c和.h文件(我将它们放在rtos目录中，以便利用当前存在的同一个makefile )，它们在调用sqrt()的函数中。因此，调用main()中的函数并编译，即使我包含了everywhere <math.h>，我也有错误：

undefined reference to `sqrt'

显然编译工作停止了。从此开始，我尝试向链接器添加另一个参数，因此我修改了makefile，如下所示：

$(LD) -o $@.out $< -T bbb.ld -Map bbb.map $(APP_LIB) $(LDFLAGS) $(RUNTIMELIB) -L $(LPATH) \
   -L $(LIB_GCC) -lgcc -L $(LIB_C) -lc -lg -lm

我还发现了其他我无法解决的错误：

arm-none-eabi-ld: /usr/lib/arm-none-eabi/lib/libm.a(lib_a-w_sqrt.o): in function `sqrt':
/build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/math/../../../../../newlib/libm/math/w_sqrt.c:62: undefined reference to `__aeabi_dcmpun'
arm-none-eabi-ld: /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/math/../../../../../newlib/libm/math/w_sqrt.c:63: undefined reference to `__aeabi_dcmplt'
arm-none-eabi-ld: /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/math/../../../../../newlib/libm/math/w_sqrt.c:64: undefined reference to `__errno'
arm-none-eabi-ld: /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/math/../../../../../newlib/libm/math/w_sqrt.c:65: undefined reference to `__aeabi_ddiv'
arm-none-eabi-ld: /usr/lib/arm-none-eabi/lib/libm.a(lib_a-e_sqrt.o): in function `__ieee754_sqrt':
/build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/machine/arm/../../../../../../newlib/libm/machine/arm/../../math/e_sqrt.c:110: undefined reference to `__aeabi_dmul'
arm-none-eabi-ld: /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/machine/arm/../../../../../../newlib/libm/machine/arm/../../math/e_sqrt.c:110: undefined reference to `__aeabi_dadd'
arm-none-eabi-ld: /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/machine/arm/../../../../../../newlib/libm/machine/arm/../../math/e_sqrt.c:117: undefined reference to `__aeabi_dsub'
arm-none-eabi-ld: /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/newlib/libm/machine/arm/../../../../../../newlib/libm/machine/arm/../../math/e_sqrt.c:117: undefined reference to `__aeabi_ddiv'
make: *** [makefile:26: app] Errore 1

我要指出的是，在主工作中正确调用sqrt()时，当我在其他.c文件中调用sqrt()时，问题就会发生。相反，rand()函数在.c附加文件中正确工作。

我不知道如何解决这些错误，有人能帮我吗？

另一天，我尝试的是在项目中编写相同的代码，它可以工作(使用在附加的.c文件中调用sqrt和rand的相同函数)。有什么关系？

如果这是一个很长的解释，我很抱歉，但我没有找到其他方法来解释我的情况。

提前谢谢。

扫射

Answer 1

start.s

.globl _start
_start:
    ;@ enable fpu
    mrc p15, 0, r0, c1, c0, 2
    orr r0,r0,#0x300000 ;@ single precision
    orr r0,r0,#0xC00000 ;@ double precision
    mcr p15, 0, r0, c1, c0, 2
    mov r0,#0x40000000
    fmxr fpexc,r0

    mov sp,#0x8000
    bl notmain
hang: b hang

notmain.c

double notmain ( double a, double b )
{
    return(a+b);
}

(不是一个真正的裸金属应用程序，源自其中之一)

为硬浮子而建

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -mhard-float -mfpu=vfp -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

硬件浮点

00008024 <notmain>:
    8024:   ee300b01    vadd.f64    d0, d0, d1
    8028:   e12fff1e    bx  lr

软浮子建造

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf
arm-none-eabi-ld: notmain.o: in function `notmain':
notmain.c:(.text+0x4): undefined reference to `__aeabi_dadd'
Makefile:33: recipe for target 'notmain.elf' failed
make: *** [notmain.elf] Error 1

它需要gcclib。

用gcc作为链接者(我知道这是多么可怕的想法)。

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf -lgcc
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

..。

00008024 <notmain>:
    8024:   e92d4010    push    {r4, lr}
    8028:   eb000003    bl  803c <__adddf3>
    802c:   e8bd8010    pop {r4, pc}

00008030 <__aeabi_drsub>:
    8030:   e2211102    eor r1, r1, #-2147483648    ; 0x80000000
    8034:   ea000000    b   803c <__adddf3>

00008038 <__aeabi_dsub>:
    8038:   e2233102    eor r3, r3, #-2147483648    ; 0x80000000

0000803c <__adddf3>:
    803c:   e92d4030    push    {r4, r5, lr}

gcc正在把这些东西转交给ld。

[0][/opt/gnuarm/lib/gcc/arm-none-eabi/10.2.0/../../../../arm-none-eabi/bin/ld]
[1][-plugin]
[2][/opt/gnuarm/libexec/gcc/arm-none-eabi/10.2.0/liblto_plugin.so]
[3][-plugin-opt=/opt/gnuarm/libexec/gcc/arm-none-eabi/10.2.0/lto-wrapper]
[4][-plugin-opt=-fresolution=/tmp/ccRiWZtk.res]
[5][-X]
[6][-o]
[7][notmain.elf]
[8][-L/opt/gnuarm/lib/gcc/arm-none-eabi/10.2.0]
[9][-L/opt/gnuarm/lib/gcc/arm-none-eabi/10.2.0/../../../../arm-none-eabi/lib]
[10][start.o]
[11][notmain.o]
[12][-lgcc]
[13][-T]
[14][memmap]

find | grep libgcc
./lib/gcc/arm-none-eabi/10.2.0/libgcc.a
./lib/gcc/arm-none-eabi/10.2.0/thumb/libgcc.a
./lib/gcc/arm-none-eabi/10.2.0/thumb/autofp/v7/fpu/libgcc.a
./lib/gcc/arm-none-eabi/10.2.0/arm/autofp/v5te/fpu/libgcc.a

那就用ld

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf -L/opt/gnuarm/lib/gcc/arm-none-eabi/10.2.0/ -lgcc
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

为什么现在使用addf3？不知道。

00008024 <notmain>:
    8024:   e92d4010    push    {r4, lr}
    8028:   eb000003    bl  803c <__adddf3>
    802c:   e8bd8010    pop {r4, pc}

00008030 <__aeabi_drsub>:
    8030:   e2211102    eor r1, r1, #-2147483648    ; 0x80000000
    8034:   ea000000    b   803c <__adddf3>

00008038 <__aeabi_dsub>:
    8038:   e2233102    eor r3, r3, #-2147483648    ; 0x80000000

0000803c <__adddf3>:
    803c:   e92d4030    push    {r4, r5, lr}
    8040:   e1a04081    lsl r4, r1, #1
    8044:   e1a05083    lsl r5, r3, #1

这就是您处理aeabi的方法，您需要使用硬浮点数，或者包含到gcclib的路径，或者只是将其添加到行中。

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf /opt/gnuarm/lib/gcc/arm-none-eabi/10.2.0/libgcc.a
#arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf -lgcc
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

现在sqrt()是一个C库，而不是gcc库，所以您需要一个C库(看起来您正在尝试使用newlib)，并且您需要构建C库来匹配gcc，所以您需要为硬或软浮动构建它，并且需要包含正确的库。但我不have...well..。

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf /home/so/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1/libgcc.a
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

所以

double sqrt(double x);
double notmain ( double a )
{
    return(sqrt(a));
}

看起来很眼熟

arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf /home/so/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1/libgcc.a /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/libm.a
arm-none-eabi-ld: /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/libm.a(lib_a-w_sqrt.o): in function `sqrt':
w_sqrt.c:(.text.sqrt+0x34): undefined reference to `__aeabi_dcmpun'
arm-none-eabi-ld: w_sqrt.c:(.text.sqrt+0x6c): undefined reference to `__aeabi_dcmplt'
arm-none-eabi-ld: w_sqrt.c:(.text.sqrt+0xc4): undefined reference to `__aeabi_ddiv'
arm-none-eabi-ld: w_sqrt.c:(.text.sqrt+0xd8): undefined reference to `__errno'
arm-none-eabi-ld: w_sqrt.c:(.text.sqrt+0x120): undefined reference to `__errno'
arm-none-eabi-ld: /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/libm.a(lib_a-e_sqrt.o): in function `__ieee754_sqrt':
e_sqrt.c:(.text.__ieee754_sqrt+0x200): undefined reference to `__aeabi_dmul'
arm-none-eabi-ld: e_sqrt.c:(.text.__ieee754_sqrt+0x20c): undefined reference to `__aeabi_dadd'
arm-none-eabi-ld: e_sqrt.c:(.text.__ieee754_sqrt+0x22c): undefined reference to `__aeabi_dsub'
arm-none-eabi-ld: e_sqrt.c:(.text.__ieee754_sqrt+0x238): undefined reference to `__aeabi_ddiv'
Makefile:33: recipe for target 'notmain.elf' failed
make: *** [notmain.elf] Error 1

发现

./arm-none-eabi/lib/libm.a
./arm-none-eabi/lib/thumb/v7e-m/nofp/libm.a
./arm-none-eabi/lib/thumb/v6-m/nofp/libm.a
./arm-none-eabi/lib/thumb/v8-m.base/nofp/libm.a
./arm-none-eabi/lib/thumb/v7/nofp/libm.a
./arm-none-eabi/lib/thumb/v8-m.main+dp/hard/libm.a
./arm-none-eabi/lib/thumb/v8-m.main+dp/softfp/libm.a
./arm-none-eabi/lib/thumb/v7e-m+dp/hard/libm.a
./arm-none-eabi/lib/thumb/v7e-m+dp/softfp/libm.a
./arm-none-eabi/lib/thumb/v7-r+fp.sp/hard/libm.a
./arm-none-eabi/lib/thumb/v7-r+fp.sp/softfp/libm.a
./arm-none-eabi/lib/thumb/v7e-m+fp/hard/libm.a
./arm-none-eabi/lib/thumb/v7e-m+fp/softfp/libm.a
./arm-none-eabi/lib/thumb/v8-m.main+fp/hard/libm.a
./arm-none-eabi/lib/thumb/v8-m.main+fp/softfp/libm.a
./arm-none-eabi/lib/thumb/v7-m/nofp/libm.a
./arm-none-eabi/lib/thumb/nofp/libm.a
./arm-none-eabi/lib/thumb/v7+fp/hard/libm.a
./arm-none-eabi/lib/thumb/v7+fp/softfp/libm.a
./arm-none-eabi/lib/thumb/v8-m.main/nofp/libm.a
./arm-none-eabi/lib/arm/v5te/hard/libm.a
./arm-none-eabi/lib/arm/v5te/softfp/libm.a

armv5te应该适用于armv6

arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf /home/so/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1/libgcc.a /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/arm/v5te/softfp/libm.a
arm-none-eabi-ld: /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/arm/v5te/softfp/libm.a(lib_a-w_sqrt.o): in function `sqrt':
w_sqrt.c:(.text.sqrt+0x94): undefined reference to `__errno'
arm-none-eabi-ld: w_sqrt.c:(.text.sqrt+0xdc): undefined reference to `__errno'
Makefile:33: recipe for target 'notmain.elf' failed
make: *** [notmain.elf] Error 1

errno是一个全局变量。C库可能希望用于软浮动。

int __errno;
double sqrt(double x);
double notmain ( double a )
{
    return(sqrt(a));
}

现在这个工具是快乐的

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf /home/so/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1/libgcc.a /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/arm/v5te/softfp/libm.a
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

但这是硬浮，而不是软。

00008024 <notmain>:
    8024:   eaffffff    b   8028 <sqrt>

00008028 <sqrt>:
    8028:   e52de004    push    {lr}        ; (str lr, [sp, #-4]!)
    802c:   ed2d8b02    vpush   {d8}
    8030:   e1a02000    mov r2, r0
    8034:   e1a03001    mov r3, r1
    8038:   e24dd02c    sub sp, sp, #44 ; 0x2c
    803c:   ec432b18    vmov    d8, r2, r3
    8040:   eb000038    bl  8128 <__ieee754_sqrt>
    8044:   e59f30d4    ldr r3, [pc, #212]  ; 8120 <sqrt+0xf8>
    8048:   eeb48b48    vcmp.f64    d8, d8
    804c:   e1d3c0d0    ldrsb   ip, [r3]
    8050:   eef1fa10    vmrs    APSR_nzcv, fpscr

但是，对于解决这一问题的途径是什么，你会有自己的想法。您需要一个匹配的/构建的库，然后您需要链接它。Keil和其他人只是在工具链中为您做这件事，根据项目进行匹配。和/或与工具链集成的C库。

硬浮子建筑

arm-none-eabi-as --warn --fatal-warnings -mcpu=arm1176jzf-s -march=armv6 -mfpu=vfp start.s -o start.o
arm-none-eabi-gcc -Wall -O2 -ffreestanding -mcpu=arm1176jzf-s -mtune=arm1176jzf-s -mhard-float -mfpu=vfp -c notmain.c -o notmain.o
arm-none-eabi-ld -nostdlib -nostartfiles start.o notmain.o -T memmap -o notmain.elf /home/so/gcc-arm-none-eabi-9-2019-q4-major/lib/gcc/arm-none-eabi/9.2.1/libgcc.a /home/so/gcc-arm-none-eabi-9-2019-q4-major/arm-none-eabi/lib/arm/v5te/hard/libm.a
arm-none-eabi-objdump -D notmain.elf > notmain.list
arm-none-eabi-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
arm-none-eabi-objcopy notmain.elf -O binary kernel.img

工具是快乐的。

00008024 <notmain>:
    8024:   eaffffff    b   8028 <sqrt>

00008028 <sqrt>:
    8028:   e52de004    push    {lr}        ; (str lr, [sp, #-4]!)
    802c:   ed2d8b02    vpush   {d8}
    8030:   eeb08b40    vmov.f64    d8, d0
    8034:   e24dd02c    sub sp, sp, #44 ; 0x2c
    8038:   eb000038    bl  8120 <__ieee754_sqrt>
    803c:   eeb48b48    vcmp.f64    d8, d8
    8040:   e59f30d0    ldr r3, [pc, #208]  ; 8118 <sqrt+0xf0>
    8044:   e1d310d0    ldrsb   

必须使这成为一个真正的应用程序--主调用另一个函数，在其中调用sqrt。然后在硬件和/或检查这些指令上运行它。或者更好地获取sqrt的C库实现，并在项目中构建它，使其与目标和指令集相匹配。(与libgcc调用的情况相同，可以根据需要测试或构建它们)。