From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
"H.J. Lu" <hjl.tools@gmail.com>, Borislav Petkov <bp@alien8.de>,
Jan Beulich <JBeulich@suse.com>,
Binutils <binutils@sourceware.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] x86: Stop relying on magic jmp behavior for early_idt_handlers
Date: Fri, 22 May 2015 13:59:32 -0700 [thread overview]
Message-ID: <555F98B4.3030308@zytor.com> (raw)
In-Reply-To: <CALCETrXja3FHMT9WSZQ86ozyi8KsFKmFeR_JDDrt6GtRSLa8OA@mail.gmail.com>
On 05/21/2015 11:51 PM, Andy Lutomirski wrote:
>>>
>>> #ifdef __KERNEL__
>>> +
>>> +/*
>>> + * early_idt_handlers is an array of entry points. For simplicity, it's
>>> + * a real array. We allocate nine bytes for each entry: two one-byte
>>> + * push instructions and a five-byte jump in the worst case.
>>> + */
>>> +#define EARLY_IDT_HANDLER_STRIDE 9
>>
>> So how come that two plus five equals nine? ;-)
>
> A "one-byte push" would be pretty impressive :)
>
Well, non-REX register pushes are just one byte. However, these take an
immediate constant.
>>
>> Ditto for the 64-bit side.
>
> Sounds good. I'll do all this tomorrow and resend.
>
Thank you! Since I trust you, I'll send you this in advance:
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
prev parent reply other threads:[~2015-05-22 21:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-22 1:27 [PATCH v2] x86: Stop relying on magic jmp behavior for early_idt_handlers Andy Lutomirski
2015-05-22 6:22 ` Ingo Molnar
2015-05-22 6:51 ` Andy Lutomirski
2015-05-22 20:59 ` H. Peter Anvin
2015-05-22 20:59 ` H. Peter Anvin [this message]
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