linux-kernel - Re: [PATCH v1 05/14] x86/boot: call puts() from within die()

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Message-ID: <CAFULd4Ynf7SqhidfDurgW5LcQ3jTNgGEVexmdGMpkznjd84CUg@mail.gmail.com>
Date: Wed, 21 Jan 2026 11:07:36 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Petr Mladek <pmladek@...e.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <kees@...nel.org>, 
	"Peter Zijlstra (Intel)" <peterz@...radead.org>, Nathan Chancellor <nathan@...nel.org>, 
	Kiryl Shutsemau <kas@...nel.org>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev, x86@...nel.org
Subject: Re: [PATCH v1 05/14] x86/boot: call puts() from within die()

On Tue, Jan 20, 2026 at 8:54 PM H. Peter Anvin <hpa@...or.com> wrote:
>
> Every call to die() has a call to puts() in front of it, which adds
> unnecessary code bloat. Move the puts() into die() which, being a
> noreturn function, is terminal and allows the compiler to not generate
> unnecessary code around it.
>
> Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>

Reviewed-by: Uros Bizjak <ubizjak@...il.com>

> ---
>  arch/x86/boot/boot.h   | 2 +-
>  arch/x86/boot/header.S | 5 +++--
>  arch/x86/boot/main.c   | 6 ++----
>  arch/x86/boot/pm.c     | 6 ++----
>  4 files changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
> index 1f2b7252e387..b4eb8405ba55 100644
> --- a/arch/x86/boot/boot.h
> +++ b/arch/x86/boot/boot.h
> @@ -280,7 +280,7 @@ void console_init(void);
>  void query_edd(void);
>
>  /* header.S */
> -void __noreturn die(void);
> +void __noreturn die(const char *msg);
>
>  /* memory.c */
>  void detect_memory(void);
> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
> index 85a21d576f5b..5a54d33e51c2 100644
> --- a/arch/x86/boot/header.S
> +++ b/arch/x86/boot/header.S
> @@ -611,14 +611,15 @@ SETUP_SIGNATURE = 0x5a5aaa55
>  # Setup corrupt somehow...
>  setup_bad:
>         movl    $setup_corrupt, %eax
> -       calll   puts
>         # Fall through...
>
>         .globl  die
>         .type   die, @function
>  die:
> +       calll   puts
> +1:
>         hlt
> -       jmp     die
> +       jmp     1b
>
>         .size   die, .-die
>
> diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
> index da01ade4959e..ad8869aad6db 100644
> --- a/arch/x86/boot/main.c
> +++ b/arch/x86/boot/main.c
> @@ -143,10 +143,8 @@ void main(void)
>         init_heap();
>
>         /* Make sure we have all the proper CPU support */
> -       if (validate_cpu()) {
> -               puts("Unable to boot - please use a kernel appropriate for your CPU.\n");
> -               die();
> -       }
> +       if (validate_cpu())
> +               die("Unable to boot - please use a kernel appropriate for your CPU.\n");
>
>         /* Tell the BIOS what CPU mode we intend to run in */
>         set_bios_mode();
> diff --git a/arch/x86/boot/pm.c b/arch/x86/boot/pm.c
> index 5941f930f6c5..3be89ba4b1b3 100644
> --- a/arch/x86/boot/pm.c
> +++ b/arch/x86/boot/pm.c
> @@ -106,10 +106,8 @@ void go_to_protected_mode(void)
>         realmode_switch_hook();
>
>         /* Enable the A20 gate */
> -       if (enable_a20()) {
> -               puts("A20 gate not responding, unable to boot...\n");
> -               die();
> -       }
> +       if (enable_a20())
> +               die("A20 gate not responding, unable to boot...\n");
>
>         /* Reset coprocessor (IGNNE#) */
>         reset_coprocessor();
> --
> 2.52.0
>