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

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Date:   Mon, 19 Jun 2023 09:28:22 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.com, jslaby@...e.cz
Subject: Re: [PATCH v3 5/5] x86/entry: Make IA32 syscalls' availability depend
 on ia32_enabled()



On 19.06.23 г. 0:17 ч., Thomas Gleixner wrote:
> 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?

int 0x80 and sysenter make it 2? Which one is the 3rd one - the "native 
64bit syscall" used in for X32 ABI ? This patch specifically deals with 
the first 2?
> 
>>   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