linux-kernel - Re: [PATCHv2 2/6] x86/vdso: introduce do_map_vdso() and vdso

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Date:	Thu, 7 Jul 2016 14:04:35 +0300
From:	Dmitry Safonov <dsafonov@...tuozzo.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Dmitry Safonov" <0x7f454c46@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Ingo Molnar <mingo@...hat.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>, <xemul@...tuozzo.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCHv2 2/6] x86/vdso: introduce do_map_vdso() and vdso_type
 enum

On 07/06/2016 05:21 PM, Andy Lutomirski wrote:
> On Wed, Jun 29, 2016 at 3:57 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
>> Make in-kernel API to map vDSO blobs on x86.
>
> I think the addr calculation was already confusing and is now even
> worse.  How about simplifying it?  Get rid of calculate_addr entirely
> and push the vdso_addr calls into arch_setup_additional_pages, etc.
> Then just use addr directly in the map_vdso code.

Thanks, will do.

>> +int do_map_vdso(vdso_type type, unsigned long addr, bool randomize_addr)
>>  {
>> -       if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
>> -               return 0;
>> -
>> -       return map_vdso(&vdso_image_32, false);
>> -}
>> +       switch (type) {
>> +#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
>> +       case VDSO_32:
>> +               if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
>> +                       return 0;
>> +               /* vDSO aslr turned off for i386 vDSO */
>> +               return map_vdso(&vdso_image_32, addr, false);
>> +#endif
>> +#ifdef CONFIG_X86_64
>> +       case VDSO_64:
>> +               if (!vdso64_enabled)
>> +                       return 0;
>> +               return map_vdso(&vdso_image_64, addr, randomize_addr);
>> +#endif
>> +#ifdef CONFIG_X86_X32_ABI
>> +       case VDSO_X32:
>> +               if (!vdso64_enabled)
>> +                       return 0;
>> +               return map_vdso(&vdso_image_x32, addr, randomize_addr);
>>  #endif
>> +       default:
>> +               return -EINVAL;
>> +       }
>> +}
>
> Why is this better than just passing the vdso_image pointer in?

Hmm, then all callers should be under the same ifdefs as vdso_image
blobs. Ok, will do.