エラーLinuxカーネルにQEMUでコマンドを実行する時、 "` cprintf '' に未定義参照"

Question

（1）これは、主な機能（runproctest.c）である：

#include "defs.h" 

void 
runproctest(void) 
{ 
cprintf("testing runnable: test1\n"); 
} 

（2）defs.h。

// console.c 
void   cprintf(char*, ...); 

（3）console.cの

#include "defs.h" 

void 
cprintf(char *fmt, ...) 
{ 
    int i, c, locking; 
    uint *argp; 
    char *s; 

    locking = cons.locking; 
    if(locking) 
    acquire(&cons.lock); 

    if (fmt == 0) 
... 
} 

（4）のmain.c

#include "types.h" 
#include "defs.h" 
#include "param.h" 
#include "memlayout.h" 
#include "mmu.h" 
#include "proc.h" 
#include "x86.h" 

static void startothers(void); 
static void mpmain(void) __attribute__((noreturn)); 
extern pde_t *kpgdir; 
extern char end[]; // first address after kernel loaded from ELF file 

// Bootstrap processor starts running C code here. 
// Allocate a real stack and switch to it, first 
// doing some setup required for memory allocator to work. 
int 
main(void) 
{ 
    kinit1(end, P2V(4*1024*1024)); // phys page allocator 
    kvmalloc();  // kernel page table 
    mpinit();  // detect other processors 
    lapicinit();  // interrupt controller 
    seginit();  // segment descriptors 
    cprintf("\ncpu%d: starting xv6\n\n", cpunum()); 
    picinit();  // another interrupt controller 
    ioapicinit(); // another interrupt controller 
    consoleinit(); // console hardware 
    uartinit();  // serial port 
    pinit();   // process table 
    tvinit();  // trap vectors 
    binit();   // buffer cache 
    fileinit();  // file table 
    ideinit();  // disk 
    if(!ismp) 
    timerinit(); // uniprocessor timer 
    startothers(); // start other processors 
    kinit2(P2V(4*1024*1024), P2V(PHYSTOP)); // must come after startothers() 
    userinit();  // first user process 
    mpmain();  // finish this processor's setup 
} 

// Other CPUs jump here from entryother.S. 
static void 
mpenter(void) 
{ 
    switchkvm(); 
    seginit(); 
    lapicinit(); 
    mpmain(); 
} 

// Common CPU setup code. 
static void 
mpmain(void) 
{ 
    cprintf("cpu%d: starting\n", cpunum()); 
    idtinit();  // load idt register 
    xchg(&cpu->started, 1); // tell startothers() we're up 
    scheduler();  // start running processes 
} 

pde_t entrypgdir[]; // For entry.S 

// Start the non-boot (AP) processors. 
static void 
startothers(void) 
{ 
    extern uchar _binary_entryother_start[], _binary_entryother_size[]; 
    uchar *code; 
    struct cpu *c; 
    char *stack; 

    // Write entry code to unused memory at 0x7000. 
    // The linker has placed the image of entryother.S in 
    // _binary_entryother_start. 
    code = P2V(0x7000); 
    memmove(code, _binary_entryother_start, (uint)_binary_entryother_size); 

    for(c = cpus; c < cpus+ncpu; c++){ 
    if(c == cpus+cpunum()) // We've started already. 
     continue; 

    // Tell entryother.S what stack to use, where to enter, and what 
    // pgdir to use. We cannot use kpgdir yet, because the AP processor 
    // is running in low memory, so we use entrypgdir for the APs too. 
    stack = kalloc(); 
    *(void**)(code-4) = stack + KSTACKSIZE; 
    *(void**)(code-8) = mpenter; 
    *(int**)(code-12) = (void *) V2P(entrypgdir); 

    lapicstartap(c->apicid, V2P(code)); 

    // wait for cpu to finish mpmain() 
    while(c->started == 0) 
     ; 
    } 
} 

// The boot page table used in entry.S and entryother.S. 
// Page directories (and page tables) must start on page boundaries, 
// hence the __aligned__ attribute. 
// PTE_PS in a page directory entry enables 4Mbyte pages. 

__attribute__((__aligned__(PGSIZE))) 
pde_t entrypgdir[NPDENTRIES] = { 
    // Map VA's [0, 4MB) to PA's [0, 4MB) 
    [0] = (0) | PTE_P | PTE_W | PTE_PS, 
    // Map VA's [KERNBASE, KERNBASE+4MB) to PA's [0, 4MB) 
    [KERNBASE>>PDXSHIFT] = (0) | PTE_P | PTE_W | PTE_PS, 
}; 

（5）ここに私のMakefileです：

OBJS = \ 
    bio.o\ 
    console.o\ 
    exec.o\ 
    file.o\ 
    fs.o\ 
    ide.o\ 
    ioapic.o\ 
    kalloc.o\ 
    kbd.o\ 
    lapic.o\ 
    log.o\ 
    main.o\ 
    mp.o\ 
    picirq.o\ 
    pipe.o\ 
    proc.o\ 
    spinlock.o\ 
    string.o\ 
    swtch.o\ 
    syscall.o\ 
    sysfile.o\ 
    sysproc.o\ 
    timer.o\ 
    trapasm.o\ 
    trap.o\ 
    uart.o\ 
    vectors.o\ 
    vm.o\ 
     runproctest.o\ 

# Cross-compiling (e.g., on Mac OS X) 
# TOOLPREFIX = i386-jos-elf 

# Using native tools (e.g., on X86 Linux) 
#TOOLPREFIX = 

# Try to infer the correct TOOLPREFIX if not set 
ifndef TOOLPREFIX 
TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \ 
    then echo 'i386-jos-elf-'; \ 
    elif objdump -i 2>&1 | grep 'elf32-i386' >/dev/null 2>&1; \ 
    then echo ''; \ 
    else echo "***" 1>&2; \ 
    echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1>&2; \ 
    echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2; \ 
    echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2; \ 
    echo "*** prefix other than 'i386-jos-elf-', set your TOOLPREFIX" 1>&2; \ 
    echo "*** environment variable to that prefix and run 'make' again." 1>&2; \ 
    echo "*** To turn off this error, run 'gmake TOOLPREFIX= ...'." 1>&2; \ 
    echo "***" 1>&2; exit 1; fi) 
endif 

# If the makefile can't find QEMU, specify its path here 
QEMU = /home/yuanzheng/Qemu_installed/bin/qemu-system-i386 

# Try to infer the correct QEMU 
ifndef QEMU 
QEMU = $(shell if which qemu > /dev/null; \ 
    then echo qemu; exit; \ 
    elif which qemu-system-i386 > /dev/null; \ 
    then echo qemu-system-i386; exit; \ 
    else \ 
    qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \ 
    if test -x $$qemu; then echo $$qemu; exit; fi; fi; \ 
    echo "***" 1>&2; \ 
    echo "*** Error: Couldn't find a working QEMU executable." 1>&2; \ 
    echo "*** Is the directory containing the qemu binary in your PATH" 1>&2; \ 
    echo "*** or have you tried setting the QEMU variable in Makefile?" 1>&2; \ 
    echo "***" 1>&2; exit 1) 
endif 

CC = $(TOOLPREFIX)gcc 
AS = $(TOOLPREFIX)gas 
LD = $(TOOLPREFIX)ld 
OBJCOPY = $(TOOLPREFIX)objcopy 
OBJDUMP = $(TOOLPREFIX)objdump 
CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer 
#CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -fvar-tracking -fvar-tracking-assignments -O0 -g -Wall -MD -gdwarf-2 -m32 -Werror -fno-omit-frame-pointer 
CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector) 
ASFLAGS = -m32 -gdwarf-2 -Wa,-divide 
# FreeBSD ld wants ``elf_i386_fbsd'' 
LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2>/dev/null) 

xv6.img: bootblock kernel fs.img 
    dd if=/dev/zero of=xv6.img count=10000 
    dd if=bootblock of=xv6.img conv=notrunc 
    dd if=kernel of=xv6.img seek=1 conv=notrunc 

xv6memfs.img: bootblock kernelmemfs 
    dd if=/dev/zero of=xv6memfs.img count=10000 
    dd if=bootblock of=xv6memfs.img conv=notrunc 
    dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc 

bootblock: bootasm.S bootmain.c 
    $(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c 
    $(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S 
    $(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o 
    $(OBJDUMP) -S bootblock.o > bootblock.asm 
    $(OBJCOPY) -S -O binary -j .text bootblock.o bootblock 
    ./sign.pl bootblock 

entryother: entryother.S 
    $(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S 
    $(LD) $(LDFLAGS) -N -e start -Ttext 0x7000 -o bootblockother.o entryother.o 
    $(OBJCOPY) -S -O binary -j .text bootblockother.o entryother 
    $(OBJDUMP) -S bootblockother.o > entryother.asm 

initcode: initcode.S 
    $(CC) $(CFLAGS) -nostdinc -I. -c initcode.S 
    $(LD) $(LDFLAGS) -N -e start -Ttext 0 -o initcode.out initcode.o 
    $(OBJCOPY) -S -O binary initcode.out initcode 
    $(OBJDUMP) -S initcode.o > initcode.asm 

kernel: $(OBJS) entry.o entryother initcode kernel.ld 
    $(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother 
    $(OBJDUMP) -S kernel > kernel.asm 
    $(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .*//; /^$$/d' > kernel.sym 

# kernelmemfs is a copy of kernel that maintains the 
# disk image in memory instead of writing to a disk. 
# This is not so useful for testing persistent storage or 
# exploring disk buffering implementations, but it is 
# great for testing the kernel on real hardware without 
# needing a scratch disk. 
MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o 
kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode kernel.ld fs.img 
    $(LD) $(LDFLAGS) -T kernel.ld -o kernelmemfs entry.o $(MEMFSOBJS) -b binary initcode entryother fs.img 
    $(OBJDUMP) -S kernelmemfs > kernelmemfs.asm 
    $(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .*//; /^$$/d' > kernelmemfs.sym 

tags: $(OBJS) entryother.S _init 
    etags *.S *.c 

vectors.S: vectors.pl 
    perl vectors.pl > vectors.S 

ULIB = ulib.o usys.o printf.o umalloc.o 

_%: %.o $(ULIB) 
    $(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^ 
    $(OBJDUMP) -S $@ > $*.asm 
    $(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .*//; /^$$/d' > $*.sym 

_forktest: forktest.o $(ULIB) 
    # forktest has less library code linked in - needs to be small 
    # in order to be able to max out the proc table. 
    $(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o 
    $(OBJDUMP) -S _forktest > forktest.asm 

mkfs: mkfs.c fs.h 
    gcc -Werror -Wall -o mkfs mkfs.c 

# Prevent deletion of intermediate files, e.g. cat.o, after first build, so 
# that disk image changes after first build are persistent until clean. More 
# details: 
# http://www.gnu.org/software/make/manual/html_node/Chained-Rules.html 
.PRECIOUS: %.o 

UPROGS=\ 
    _cat\ 
    _echo\ 
    _forktest\ 
    _grep\ 
    _init\ 
    _kill\ 
    _ln\ 
    _ls\ 
    _mkdir\ 
    _rm\ 
    _sh\ 
    _stressfs\ 
    _usertests\ 
    _wc\ 
    _zombie\ 
     _runnable\ 
     _runnabletest\ 
     _runproctest\ 

fs.img: mkfs README $(UPROGS) 
    ./mkfs fs.img README $(UPROGS) 

-include *.d 

clean: 
    rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \ 
    *.o *.d *.asm *.sym vectors.S bootblock entryother \ 
    initcode initcode.out kernel xv6.img fs.img kernelmemfs mkfs \ 
    .gdbinit \ 
    $(UPROGS) 

# make a printout 
FILES = $(shell grep -v '^\#' runoff.list) 
PRINT = runoff.list runoff.spec README toc.hdr toc.ftr $(FILES) 

xv6.pdf: $(PRINT) 
    ./runoff 
    ls -l xv6.pdf 

print: xv6.pdf 

# run in emulators 

bochs : fs.img xv6.img 
    if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi 
    bochs -q 

# try to generate a unique GDB port 
GDBPORT = $(shell expr `id -u` % 5000 + 25000) 
# QEMU's gdb stub command line changed in 0.11 
QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \ 
    then echo "-gdb tcp::$(GDBPORT)"; \ 
    else echo "-s -p $(GDBPORT)"; fi) 
ifndef CPUS 
CPUS := 2 
endif 
QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA) 

qemu: fs.img xv6.img 
    $(QEMU) -serial mon:stdio $(QEMUOPTS) 

qemu-memfs: xv6memfs.img 
    $(QEMU) -drive file=xv6memfs.img,index=0,media=disk,format=raw -smp $(CPUS) -m 256 

qemu-nox: fs.img xv6.img 
    $(QEMU) -nographic $(QEMUOPTS) 

.gdbinit: .gdbinit.tmpl 
    sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@ 

qemu-gdb: fs.img xv6.img .gdbinit 
    @echo "*** Now run 'gdb'." 1>&2 
    $(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB) 

qemu-nox-gdb: fs.img xv6.img .gdbinit 
    @echo "*** Now run 'gdb'." 1>&2 
    $(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB) 

# CUT HERE 
# prepare dist for students 
# after running make dist, probably want to 
# rename it to rev0 or rev1 or so on and then 
# check in that version. 

EXTRA=\ 
    mkfs.c ulib.c user.h cat.c echo.c forktest.c grep.c kill.c\ 
    ln.c ls.c mkdir.c rm.c stressfs.c usertests.c wc.c zombie.c\ 
    printf.c umalloc.c runnable.c printf.h runnabletest.c runproctest.c\ 
    README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\ 
    .gdbinit.tmpl gdbutil\ 

dist: 
    rm -rf dist 
    mkdir dist 
    for i in $(FILES); \ 
    do \ 
     grep -v PAGEBREAK $$i >dist/$$i; \ 
    done 
    sed '/CUT HERE/,$$d' Makefile >dist/Makefile 
    echo >dist/runoff.spec 
    cp $(EXTRA) dist 

dist-test: 
    rm -rf dist 
    make dist 
    rm -rf dist-test 
    mkdir dist-test 
    cp dist/* dist-test 
    cd dist-test; $(MAKE) print 
    cd dist-test; $(MAKE) bochs || true 
    cd dist-test; $(MAKE) qemu 

# update this rule (change rev#) when it is time to 
# make a new revision. 
tar: 
    rm -rf /tmp/xv6 
    mkdir -p /tmp/xv6 
    cp dist/* dist/.gdbinit.tmpl /tmp/xv6 
    (cd /tmp; tar cf - xv6) | gzip >xv6-rev9.tar.gz # the next one will be 9 (6/27/15) 

.PHONY: dist-test dist 

と私はmake qemuを入力したときに問題があります：

yuanzheng@ubuntu:~/Operating_System/xv6_sourcecode/xv6-public$ make qemu 
ld -m elf_i386 -N -e main -Ttext 0 -o _runproctest runproctest.o ulib.o usys.o printf.o umalloc.o 
ld: warning: cannot find entry symbol main; defaulting to 0000000000000000 
runproctest.o: In function `runproctest': 
/home/yuanzheng/Operating_System/xv6_sourcecode/xv6-public/runproctest.c:26: undefined reference to `cprintf' 
Makefile:141: recipe for target '_runproctest' failed 
make: *** [_runproctest] Error 1 

これがなぜ起こるか私にはわからない...

Answer 1

メイクファイル内の

、この行：

ld -m elf_i386 -N -e main -Ttext 0 -o _runproctest runproctest.o ulib.o usys.o printf.o umalloc.o 

は次のようになります。

ld -m elf_i386 -N -e main -Ttext 0 -o _runproctest runproctest.o ulib.o usys.o printf.o umalloc.o console.o 

同様の問題を持つmakeファイル内の他のldコマンドがあるかもしれません。

また、エラーメッセージごとに、実行可能ファイル_runproctestの作成に使用されるファイルのどこにでもmain()関数がありません。それは（通常）コードが正しく実行されないことを強く示しています。余談として

：大文字が続く__または_で始まる

名は、環境のために予約されています。

大文字のアンダースコア（おそらく）を使用して自分のアイテムに名前を付けると動作しますが、環境名スペースが乱雑です。あなたの名前の先頭に_を使用しないことを強くお勧めします。