linux-kernel - Re: [BUG Report] undefined reference to `convert_to

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Date:   Tue, 3 Jan 2023 11:05:01 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "x86@...nel.org" <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, <hpa@...or.com>
Subject: Re: [BUG Report] undefined reference to `convert_to_fxsr'

On 2022/12/30 19:16, Borislav Petkov wrote:
> On Fri, Dec 30, 2022 at 09:49:50AM +0800, Miaohe Lin wrote:
>> Many thanks for doing this. :) But it seems it's not the matter of gcc
>> version. Somewhat confused...
> 
> Put your .config somewhere outside your git repo, clean all build
> artifacts and reset it properly by doing:
> 
> git reset --hard
> git clean -dqfx
> 
> and then copy back the .config and see if you can still repro.
> 

Yes, it still reproduces in my working server. It might be the problem of gcc version.
Does the below origin analysis looks sane to you?

"""
I think it's because convert_to_fxsr() is only defined when CONFIG_X86_32 or CONFIG_IA32_EMULATION is enabled. But it can be
call from __fpu_restore_sig() via below path:

bool fpu__restore_sig(void __user *buf, int ia32_frame):

        if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) {
                success = !fpregs_soft_set(current, NULL, 0,
                                           sizeof(struct user_i387_ia32_struct),
                                           NULL, buf);
        } else {
                success = __fpu_restore_sig(buf, buf_fx, ia32_fxstate); /* Will call convert_to_fxsr() later. */
        }

__fpu_restore_sig() will call convert_to_fxsr() even if neither CONFIG_X86_32 nor CONFIG_IA32_EMULATION is enabled. So the link error occurs.
"""

Below is the reproduce log:

linux-rtfsc:/home/linmiaohe/linux # git reset --hard
HEAD is now at 69b41ac87e4a Merge tag 'for-6.2-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
linux-rtfsc:/home/linmiaohe/linux # git clean -dqfx
linux-rtfsc:/home/linmiaohe/linux # cp ../virt/hmm_config .config
linux-rtfsc:/home/linmiaohe/linux # make menuconfig -j384
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/kconfig/confdata.o
  HOSTCC  scripts/kconfig/expr.o
  YACC    scripts/kconfig/parser.tab.[ch]
  HOSTCC  scripts/kconfig/menu.o
  LEX     scripts/kconfig/lexer.lex.c
  HOSTCC  scripts/kconfig/preprocess.o
  HOSTCC  scripts/kconfig/symbol.o
  HOSTCC  scripts/kconfig/util.o
  HOSTCC  scripts/kconfig/mconf.o
  HOSTCC  scripts/kconfig/lxdialog/checklist.o
  HOSTCC  scripts/kconfig/lxdialog/inputbox.o
  HOSTCC  scripts/kconfig/lxdialog/textbox.o
  HOSTCC  scripts/kconfig/lxdialog/menubox.o
  HOSTCC  scripts/kconfig/lxdialog/util.o
  HOSTCC  scripts/kconfig/lxdialog/yesno.o
  HOSTCC  scripts/kconfig/lexer.lex.o
  HOSTCC  scripts/kconfig/parser.tab.o
  HOSTLD  scripts/kconfig/mconf
.config:5767:warning: symbol value 'm' invalid for VFIO_VIRQFD

*** End of the configuration.
*** Execute 'make' to start the build or try 'make help'.

linux-rtfsc:/home/linmiaohe/linux # make -j384
...
  DESCEND objtool
  CALL    scripts/checksyscalls.sh
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  LD      .tmp_vmlinux.kallsyms1
ld: arch/x86/kernel/fpu/signal.o: in function `__fpu_restore_sig':
/home/linmiaohe/linux/arch/x86/kernel/fpu/signal.c:421: undefined reference to `convert_to_fxsr'
make[1]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
make: *** [Makefile:1252: vmlinux] Error 2
make: *** Waiting for unfinished jobs....
linux-rtfsc:/home/linmiaohe/linux #

Many thanks for your time. :)

Thanks,
Miaohe Lin