linux-kernel - Re: [PATCH v3 5/5] x86/entry: Make IA32 syscalls' availability depend on ia32

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Date:   Sun, 18 Jun 2023 23:17:54 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Nikolay Borisov <nik.borisov@...e.com>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.com, jslaby@...e.cz,
        Nikolay Borisov <nik.borisov@...e.com>
Subject: Re: [PATCH v3 5/5] x86/entry: Make IA32 syscalls' availability
 depend on ia32_enabled()

On Fri, Jun 16 2023 at 15:57, Nikolay Borisov wrote:
> Another major aspect of supporting running of 32bit processes is the
> ability to access 32bit syscalls. Such syscalls are invoked either by
> using the legacy int 0x80 call gate interface or via the newer sysenter
> instruction.
>
> Ensure that if ia32 emulation is disabled (either at compile time or
> runtime) then those 2 syscall mechanisms are also disabled.

AFAICT there are _three_ mechanisms for 32bit syscalls, no?

>  void __init idt_setup_traps(void)
>  {
>  	idt_setup_from_table(idt_table, def_idts, ARRAY_SIZE(def_idts), true);
> +
> +	if (ia32_enabled()) {
> +		idt_setup_from_table(idt_table, ia32_idt, ARRAY_SIZE(ia32_idt),
> +				     true);

Just let it stick out. The 80 character limit is history.

Thanks,

        tglx