lesson 13: undefined reference to "_GLOBAL_OFFSET_TABLE"

[littlephone]

when I was using ld to link kernel.o and kernel_entry.o, the error below happens

make \n kernel.o: In function ' dummy_test_entrypoint': \n kernel.c (.text+0x9): undefined reference to '_GLOBAL_OFFSET_TABLE_' \n Any workarounds?

[littlephone]

I tried removing option --oformat binary, it compiles successfully, but I encounters qemu flickering issue like last issue from other user

[iosmanthus]

@littlephone add --ignore-unresolved-symbol _GLOBAL_OFFSET_TABLE_ to ld's args

[TravorLZH]

You need to build a cross compiler from source in order to build this project. The default one in Linux won't work for you. You can see OSDev Wiki

[mpetch]

Do not add --ignore-unresolved-symbol _GLOBAL_OFFSET_TABLE_ to LD. You hid the problem, but didn't solve it. Add -fno-PIC to your C FLAGS for compiling and -no-PIE when you link. On OSDev forum we've seen some questions of kernels not working and this was the root cause. It is preferable to use a cross compiler as Travor suggested.

[ghost]

@mpetch , I tried using -fno-noPIC and -fno-PIE. I did not get any error on compiling but while linking i got this error:-

ld: -f may not be used without -shared

Please help!

[TravorLZH]

@motosoftos, Did you use a cross compiler or the built-in one. Most of the time when the system compiler or linker pops up error, it is preferable to build a cross compiler from source. You may refer the instructions at https://wiki.osdev.org/GCC_Cross-Compiler

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From: motosoftos [email protected] Sent: Wednesday, October 9, 2019 16:28 To: cfenollosa/os-tutorial Cc: Travor Liu; Manual Subject: Re: [cfenollosa/os-tutorial] lesson 13: undefined reference to "_GLOBAL_OFFSET_TABLE" (#16)

@mpetchhttps://github.com/mpetch , I tried using -fno-noPIC and -fno-PIE. I did not get any error on compiling but while linking i got this error:-

ld: -f may not be used without -shared

Please help!

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[ghost]

Sorry, i left that and came back to make it in assembly...

[tai271828]

Today I tried with the flags suggested by @mpetch regarding the flags -fno-PIC (for gcc) and -no-PIE (for ld). https://github.com/cfenollosa/os-tutorial/issues/16#issuecomment-460016961 It works like a charm! Thank you @mpetch .

The following are my commands fwiw. Please note you have to pass -m32 for gcc and -m elf_i386 for the i386 qemu in the lesson13 of the tutorial:

$ gcc -ffreestanding -c kernel.c -m32 -fno-PIC -o kernel.o
$ ld -no-PIE -m elf_i386 -o kernel.bin -Ttext 0x1000 kernel_entry.o kernel.o --oformat binary
ld: warning: cannot find entry symbol _start; defaulting to 0000000000001000

Compiled and linked with my Ubuntu Mate 18.04 x86 laptop.