linux-kernel - Re: BUG: mips: errors when compiling kernel with a large initramfs

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Date:   Tue, 7 Apr 2020 21:24:56 +0800
From:   "Xu, Yanfei" <yanfei.xu@...driver.com>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: BUG: mips: errors when compiling kernel with a large initramfs


On 4/7/20 8:25 PM, Jiaxun Yang wrote:
> On Tue, 7 Apr 2020 17:58:23 +0800
> "Xu, Yanfei" <yanfei.xu@...driver.com> wrote:
>
>> Hi,
>>
>>
>> It fails to compile mips kernel with large initramfs (at link time).
>>
>> kernel version: 5.6.0
>>
>>
>> Steps to reproduce:
>>
>> 1. git clone mainline kernel
>>
>> 2. set ARCH=mips and CROSS_COMPILE=mips-linux-gnu-
>>
>> 3. make defconfig
>>
>> 4.enable initramfs support and set the path about initramfs source
>> file
>>
>> 5.make -j24
>>
>> [KEY] when your initramfs files is too large, and cause
>> usr/initramfs_data.cpio.gz
>>
>> compiled is larger than 225M, you will get the following error. BTW,
>> x86 doesn't
>>
>> have this issue that I have tested.
>>
>> ------------------------------error
>> messages-----------------------------------------
>>
>>     CHK     include/generated/compile.h
>>     LD      vmlinux.o
>>     MODPOST vmlinux.o
>>     MODINFO modules.builtin.modinfo
>>     GEN     modules.builtin
>>     LD      .tmp_vmlinux.kallsyms1
>> kernel/configs.o: In function `ikconfig_cleanup':
>> /home/wrsadmin/work/linux/kernel/linux-master/kernel/configs.c:72:(.exit.text+0x8):
>> relocation truncated to fit: R_MIPS_26 against `remove_proc_entry'
>> fs/binfmt_script.o: In function `exit_script_binfmt':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/binfmt_script.c:165:(.exit.text+0x4):
>> relocation truncated to fit: R_MIPS_26 against `unregister_binfmt'
>> fs/binfmt_elf.o: In function `exit_elf_binfmt':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/binfmt_elf.c:2393:(.exit.text+0x4):
>> relocation truncated to fit: R_MIPS_26 against `unregister_binfmt'
>> fs/mbcache.o: In function `mbcache_exit':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/mbcache.c:429:(.exit.text+0x4):
>> relocation truncated to fit: R_MIPS_26 against `kmem_cache_destroy'
>> fs/nfs_common/grace.o: In function `exit_grace':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/nfs_common/grace.c:133:(.exit.text+0x4):
>> relocation truncated to fit: R_MIPS_26 against
>> `unregister_pernet_subsys' fs/ext4/super.o: In function
>> `ext4_destroy_lazyinit_thread':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/ext4/super.c:3456:(.exit.text+0x24):
>> relocation truncated to fit: R_MIPS_26 against `kthread_stop'
>> fs/ext4/super.o: In function `unregister_as_ext2':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/ext4/super.c:6126:(.exit.text+0x30):
>> relocation truncated to fit: R_MIPS_26 against
>> `unregister_filesystem' fs/ext4/super.o: In function
>> `unregister_as_ext3':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/ext4/super.c:6155:(.exit.text+0x3c):
>> relocation truncated to fit: R_MIPS_26 against
>> `unregister_filesystem' fs/ext4/super.o: In function `ext4_exit_fs':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/ext4/super.c:6261:(.exit.text+0x48):
>> relocation truncated to fit: R_MIPS_26 against
>> `unregister_filesystem' fs/ext4/super.o: In function
>> `destroy_inodecache':
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/ext4/super.c:1218:(.exit.text+0x50):
>> relocation truncated to fit: R_MIPS_26 against `rcu_barrier'
>> /home/wrsadmin/work/linux/kernel/linux-master/fs/ext4/super.c:1219:(.exit.text+0x5c):
>> additional relocation overflows omitted from the output
>> Makefile:1086: recipe for target 'vmlinux' failed make[1]: ***
>> [vmlinux] Error 1 Makefile:1058: recipe for target
>> 'autoksyms_recursive' failed make: *** [autoksyms_recursive] Error 2
>>
>>
>> Any comment will be appreciated.
> Actually I think that won't work even if you managed to workaround
> reloc issue.
>
> MIPS have limited LOW MEM range accessible via KSEG0 (512M, but can be
> less if your system place some MMIO register in that range). Kernel
> image will be placed here together with built-in initramfs, and a
> lot of memory like Page Table can only be allocated from here.
>
> Such a huge initrd will occupy the whole LOW MEM range leaving no space
> for others.

As you said, it is really a problem about a huge initramfs. I'll pay 
attention

about this point.

> It seems like your system is 32bit, we have no solution for that
> hardware limitaion. For 64bit system you may try to move your kernel
> into XKPHYS instead of KSEG0.

Yes, it is a 32bit system. And thanks for your workaround about 64bit.

: )

Thanks,

Yanfei

>
> Thanks
>
> --
> Jiaxun Yang
>
>> Thanks,
>>
>> Yanfei
>>
>