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Date:   Sun, 28 Feb 2021 12:15:16 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Fangrui Song <maskray@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "H . J . Lu" <hjl.tools@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Brian Gerst <brgerst@...il.com>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Chao Yu <chao@...nel.org>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Ingo Molnar <mingo@...hat.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jethro Beekman <jethro@...tanix.com>,
        Kees Cook <keescook@...omium.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sasha Levin <sashal@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Takashi Iwai <tiwai@...e.com>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>
Subject: Re: [PATCH RFC] x86: remove toolchain check for X32 ABI capability

On Sun, Feb 28, 2021 at 3:41 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> This commit reverts 0bf6276392e9 ("x32: Warn and disable rather than
> error if binutils too old").
>
> The help text in arch/x86/Kconfig says enabling the X32 ABI support
> needs binutils 2.22 or later. This is met because the minimal binutils
> version is 2.23 according to Documentation/process/changes.rst.
>
> I would not say I am not familiar with toolchain configuration, but

I mean:
I would not say I am familiar ...
That is why I added RFC.

I appreciate comments from people who are familiar
with toolchains (binutils, llvm).

If this change is not safe,
we can move this check to Kconfig at least.









> I checked the configure.tgt code in binutils. The elf32_x86_64
> emulation mode seems to be included when it is configured for the
> x86_64-*-linux-* target.
>
> I also tried lld and llvm-objcopy, and succeeded in building x32 VDSO.
>
> I removed the compile-time check in arch/x86/Makefile, in the hope of
> elf32_x86_64 being always supported.
>
> With this, CONFIG_X86_X32 and CONFIG_X86_X32_ABI will be equivalent.
> Rename the former to the latter.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  arch/x86/Kconfig                       |  8 ++------
>  arch/x86/Makefile                      | 16 ----------------
>  arch/x86/include/asm/syscall_wrapper.h |  6 +++---
>  arch/x86/include/asm/vdso.h            |  2 +-
>  arch/x86/kernel/process_64.c           |  2 +-
>  fs/fuse/file.c                         |  2 +-
>  fs/xfs/xfs_ioctl32.c                   |  2 +-
>  sound/core/control_compat.c            | 16 ++++++++--------
>  sound/core/pcm_compat.c                | 20 ++++++++++----------
>  9 files changed, 27 insertions(+), 47 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 2792879d398e..7272cba2744c 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2865,7 +2865,7 @@ config IA32_AOUT
>         help
>           Support old a.out binaries in the 32bit emulation.
>
> -config X86_X32
> +config X86_X32_ABI
>         bool "x32 ABI for 64-bit mode"
>         depends on X86_64
>         help
> @@ -2874,10 +2874,6 @@ config X86_X32
>           full 64-bit register file and wide data path while leaving
>           pointers at 32 bits for smaller memory footprint.
>
> -         You will need a recent binutils (2.22 or later) with
> -         elf32_x86_64 support enabled to compile a kernel with this
> -         option set.
> -
>  config COMPAT_32
>         def_bool y
>         depends on IA32_EMULATION || X86_32
> @@ -2886,7 +2882,7 @@ config COMPAT_32
>
>  config COMPAT
>         def_bool y
> -       depends on IA32_EMULATION || X86_X32
> +       depends on IA32_EMULATION || X86_X32_ABI
>
>  if COMPAT
>  config COMPAT_FOR_U64_ALIGNMENT
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 2d6d5a28c3bf..e163549f5be7 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -125,22 +125,6 @@ else
>          KBUILD_CFLAGS += -mcmodel=kernel
>  endif
>
> -ifdef CONFIG_X86_X32
> -       x32_ld_ok := $(call try-run,\
> -                       /bin/echo -e '1: .quad 1b' | \
> -                       $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
> -                       $(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMPO" && \
> -                       $(LD) -m elf32_x86_64 "$$TMPO" -o "$$TMP",y,n)
> -        ifeq ($(x32_ld_ok),y)
> -                CONFIG_X86_X32_ABI := y
> -                KBUILD_AFLAGS += -DCONFIG_X86_X32_ABI
> -                KBUILD_CFLAGS += -DCONFIG_X86_X32_ABI
> -        else
> -                $(warning CONFIG_X86_X32 enabled but no binutils support)
> -        endif
> -endif
> -export CONFIG_X86_X32_ABI
> -
>  #
>  # If the function graph tracer is used with mcount instead of fentry,
>  # '-maccumulate-outgoing-args' is needed to prevent a GCC bug
> diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h
> index a84333adeef2..69bf87c41a0b 100644
> --- a/arch/x86/include/asm/syscall_wrapper.h
> +++ b/arch/x86/include/asm/syscall_wrapper.h
> @@ -158,7 +158,7 @@ extern long __ia32_sys_ni_syscall(const struct pt_regs *regs);
>  #endif /* CONFIG_IA32_EMULATION */
>
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>  /*
>   * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
>   * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
> @@ -176,12 +176,12 @@ extern long __ia32_sys_ni_syscall(const struct pt_regs *regs);
>
>  #define __X32_COMPAT_SYS_NI(name)                                      \
>         __SYS_NI(x32, compat_sys_##name)
> -#else /* CONFIG_X86_X32 */
> +#else /* CONFIG_X86_X32_ABI */
>  #define __X32_COMPAT_SYS_STUB0(name)
>  #define __X32_COMPAT_SYS_STUBx(x, name, ...)
>  #define __X32_COMPAT_COND_SYSCALL(name)
>  #define __X32_COMPAT_SYS_NI(name)
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>
>
>  #ifdef CONFIG_COMPAT
> diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
> index 98aa103eb4ab..2963a2f5dbc4 100644
> --- a/arch/x86/include/asm/vdso.h
> +++ b/arch/x86/include/asm/vdso.h
> @@ -37,7 +37,7 @@ struct vdso_image {
>  extern const struct vdso_image vdso_image_64;
>  #endif
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>  extern const struct vdso_image vdso_image_x32;
>  #endif
>
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index d08307df69ad..a93b6f4296fc 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -656,7 +656,7 @@ void set_personality_64bit(void)
>
>  static void __set_personality_x32(void)
>  {
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>         if (current->mm)
>                 current->mm->context.flags = 0;
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 8cccecb55fb8..c53c620d1a7a 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2797,7 +2797,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
>  #else
>         if (flags & FUSE_IOCTL_COMPAT) {
>                 inarg.flags |= FUSE_IOCTL_32BIT;
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>                 if (in_x32_syscall())
>                         inarg.flags |= FUSE_IOCTL_COMPAT_X32;
>  #endif
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index 33c09ec8e6c0..e8038bc966e7 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -233,7 +233,7 @@ xfs_compat_ioc_fsbulkstat(
>         inumbers_fmt_pf         inumbers_func = xfs_fsinumbers_fmt_compat;
>         bulkstat_one_fmt_pf     bs_one_func = xfs_fsbulkstat_one_fmt_compat;
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>         if (in_x32_syscall()) {
>                 /*
>                  * ... but on x32 the input xfs_fsop_bulkreq has pointers
> diff --git a/sound/core/control_compat.c b/sound/core/control_compat.c
> index 1d708aab9c98..5d1b94bda2cd 100644
> --- a/sound/core/control_compat.c
> +++ b/sound/core/control_compat.c
> @@ -153,7 +153,7 @@ struct snd_ctl_elem_value32 {
>          unsigned char reserved[128];
>  };
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>  /* x32 has a different alignment for 64bit values from ia32 */
>  struct snd_ctl_elem_value_x32 {
>         struct snd_ctl_elem_id id;
> @@ -165,7 +165,7 @@ struct snd_ctl_elem_value_x32 {
>         } value;
>         unsigned char reserved[128];
>  };
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>
>  /* get the value type and count of the control */
>  static int get_ctl_type(struct snd_card *card, struct snd_ctl_elem_id *id,
> @@ -350,7 +350,7 @@ static int snd_ctl_elem_write_user_compat(struct snd_ctl_file *file,
>         return ctl_elem_write_user(file, data32, &data32->value);
>  }
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>  static int snd_ctl_elem_read_user_x32(struct snd_card *card,
>                                       struct snd_ctl_elem_value_x32 __user *data32)
>  {
> @@ -362,7 +362,7 @@ static int snd_ctl_elem_write_user_x32(struct snd_ctl_file *file,
>  {
>         return ctl_elem_write_user(file, data32, &data32->value);
>  }
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>
>  /* add or replace a user control */
>  static int snd_ctl_elem_add_compat(struct snd_ctl_file *file,
> @@ -421,10 +421,10 @@ enum {
>         SNDRV_CTL_IOCTL_ELEM_WRITE32 = _IOWR('U', 0x13, struct snd_ctl_elem_value32),
>         SNDRV_CTL_IOCTL_ELEM_ADD32 = _IOWR('U', 0x17, struct snd_ctl_elem_info32),
>         SNDRV_CTL_IOCTL_ELEM_REPLACE32 = _IOWR('U', 0x18, struct snd_ctl_elem_info32),
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>         SNDRV_CTL_IOCTL_ELEM_READ_X32 = _IOWR('U', 0x12, struct snd_ctl_elem_value_x32),
>         SNDRV_CTL_IOCTL_ELEM_WRITE_X32 = _IOWR('U', 0x13, struct snd_ctl_elem_value_x32),
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>  };
>
>  static inline long snd_ctl_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg)
> @@ -463,12 +463,12 @@ static inline long snd_ctl_ioctl_compat(struct file *file, unsigned int cmd, uns
>                 return snd_ctl_elem_add_compat(ctl, argp, 0);
>         case SNDRV_CTL_IOCTL_ELEM_REPLACE32:
>                 return snd_ctl_elem_add_compat(ctl, argp, 1);
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>         case SNDRV_CTL_IOCTL_ELEM_READ_X32:
>                 return snd_ctl_elem_read_user_x32(ctl->card, argp);
>         case SNDRV_CTL_IOCTL_ELEM_WRITE_X32:
>                 return snd_ctl_elem_write_user_x32(ctl, argp);
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>         }
>
>         down_read(&snd_ioctl_rwsem);
> diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c
> index 590a46a9e78d..937f5117a81f 100644
> --- a/sound/core/pcm_compat.c
> +++ b/sound/core/pcm_compat.c
> @@ -147,13 +147,13 @@ static int snd_pcm_ioctl_channel_info_compat(struct snd_pcm_substream *substream
>         return err;
>  }
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>  /* X32 ABI has the same struct as x86-64 for snd_pcm_channel_info */
>  static int snd_pcm_channel_info_user(struct snd_pcm_substream *substream,
>                                      struct snd_pcm_channel_info __user *src);
>  #define snd_pcm_ioctl_channel_info_x32(s, p)   \
>         snd_pcm_channel_info_user(s, p)
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>
>  struct compat_snd_pcm_status64 {
>         snd_pcm_state_t state;
> @@ -373,7 +373,7 @@ static int snd_pcm_ioctl_xfern_compat(struct snd_pcm_substream *substream,
>         return err;
>  }
>
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>  /* X32 ABI has 64bit timespec and 64bit alignment */
>  struct snd_pcm_mmap_status_x32 {
>         snd_pcm_state_t state;
> @@ -464,7 +464,7 @@ static int snd_pcm_ioctl_sync_ptr_x32(struct snd_pcm_substream *substream,
>
>         return 0;
>  }
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>
>  /*
>   */
> @@ -484,10 +484,10 @@ enum {
>         SNDRV_PCM_IOCTL_READN_FRAMES32 = _IOR('A', 0x53, struct snd_xfern32),
>         SNDRV_PCM_IOCTL_STATUS_COMPAT64 = _IOR('A', 0x20, struct compat_snd_pcm_status64),
>         SNDRV_PCM_IOCTL_STATUS_EXT_COMPAT64 = _IOWR('A', 0x24, struct compat_snd_pcm_status64),
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>         SNDRV_PCM_IOCTL_CHANNEL_INFO_X32 = _IOR('A', 0x32, struct snd_pcm_channel_info),
>         SNDRV_PCM_IOCTL_SYNC_PTR_X32 = _IOWR('A', 0x23, struct snd_pcm_sync_ptr_x32),
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>  };
>
>  static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg)
> @@ -531,10 +531,10 @@ static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned l
>         case __SNDRV_PCM_IOCTL_SYNC_PTR32:
>                 return snd_pcm_common_ioctl(file, substream, cmd, argp);
>         case __SNDRV_PCM_IOCTL_SYNC_PTR64:
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>                 if (in_x32_syscall())
>                         return snd_pcm_ioctl_sync_ptr_x32(substream, argp);
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>                 return snd_pcm_common_ioctl(file, substream, cmd, argp);
>         case SNDRV_PCM_IOCTL_HW_REFINE32:
>                 return snd_pcm_ioctl_hw_params_compat(substream, 1, argp);
> @@ -566,10 +566,10 @@ static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned l
>                 return snd_pcm_status_user_compat64(substream, argp, false);
>         case SNDRV_PCM_IOCTL_STATUS_EXT_COMPAT64:
>                 return snd_pcm_status_user_compat64(substream, argp, true);
> -#ifdef CONFIG_X86_X32
> +#ifdef CONFIG_X86_X32_ABI
>         case SNDRV_PCM_IOCTL_CHANNEL_INFO_X32:
>                 return snd_pcm_ioctl_channel_info_x32(substream, argp);
> -#endif /* CONFIG_X86_X32 */
> +#endif /* CONFIG_X86_X32_ABI */
>         }
>
>         return -ENOIOCTLCMD;
> --
> 2.27.0
>
> --
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--
Best Regards
Masahiro Yamada

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