linux-kernel - Re: [PATCH v2 7/7] x86/syscall/32: Add comment to conditional

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Message-ID: <b72d0040-99a3-4f20-9557-099d00b1b3ae@intel.com>
Date: Fri, 14 Mar 2025 10:19:30 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: Brian Gerst <brgerst@...il.com>
CC: Ingo Molnar <mingo@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, "Thomas
 Gleixner" <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, "Andy
 Lutomirski" <luto@...nel.org>, Juergen Gross <jgross@...e.com>, "Boris
 Ostrovsky" <boris.ostrovsky@...cle.com>, X86-kernel <x86@...nel.org>, "LKML
 Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/7] x86/syscall/32: Add comment to conditional

On 3/14/2025 8:12 AM, Brian Gerst wrote:
> Add a CONFIG_X86_FRED comment, since this conditional is nested.
> 
> Signed-off-by: Brian Gerst <brgerst@...il.com>
> Suggested-by: Sohil Mehta <sohil.mehta@...el.com>
> ---
>  arch/x86/entry/syscall_32.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/entry/syscall_32.c b/arch/x86/entry/syscall_32.c
> index 993d72504fc5..2b15ea17bb7c 100644
> --- a/arch/x86/entry/syscall_32.c
> +++ b/arch/x86/entry/syscall_32.c
> @@ -238,7 +238,8 @@ DEFINE_FREDENTRY_RAW(int80_emulation)
>  	instrumentation_end();
>  	syscall_exit_to_user_mode(regs);
>  }
> -#endif
> +#endif /* CONFIG_X86_FRED */
> +
>  #else /* CONFIG_IA32_EMULATION */
>  
>  /* Handles int $0x80 on a 32bit kernel */

Also, there seem to be a couple of adjacent CONFIG_IA32_EMULATION
sections in the file. It might be better to bring them together under
one section in this patch or a follow-up. Something like below:

> diff --git a/arch/x86/entry/syscall_32.c b/arch/x86/entry/syscall_32.c
> index 2b15ea17bb7c..a84f9d3c1695 100644
> --- a/arch/x86/entry/syscall_32.c
> +++ b/arch/x86/entry/syscall_32.c
> @@ -57,16 +57,6 @@ static __always_inline int syscall_32_enter(struct pt_regs *regs)
>         return (int)regs->orig_ax;
>  }
>  
> -#ifdef CONFIG_IA32_EMULATION
> -bool __ia32_enabled __ro_after_init = !IS_ENABLED(CONFIG_IA32_EMULATION_DEFAULT_DISABLED);
> -
> -static int __init ia32_emulation_override_cmdline(char *arg)
> -{
> -       return kstrtobool(arg, &__ia32_enabled);
> -}
> -early_param("ia32_emulation", ia32_emulation_override_cmdline);
> -#endif
> -
>  /*
>   * Invoke a 32-bit syscall.  Called with IRQs on in CT_STATE_KERNEL.
>   */
> @@ -87,6 +77,14 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr)
>  }
>  
>  #ifdef CONFIG_IA32_EMULATION
> +bool __ia32_enabled __ro_after_init = !IS_ENABLED(CONFIG_IA32_EMULATION_DEFAULT_DISABLED);
> +
> +static int __init ia32_emulation_override_cmdline(char *arg)
> +{
> +       return kstrtobool(arg, &__ia32_enabled);
> +}
> +early_param("ia32_emulation", ia32_emulation_override_cmdline);
> +
>  static __always_inline bool int80_is_external(void)
>  {
>         const unsigned int offs = (0x80 / 32) * 0x10;