From: "H. Peter Anvin" <hpa@zytor.com>
To: Thomas Garnier <thgarnie@google.com>
Cc: "Andy Lutomirski" <luto@amacapital.net>,
"Ingo Molnar" <mingo@kernel.org>,
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Subject: [kernel-hardening] Re: [PATCH v3 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state
Date: Wed, 22 Mar 2017 13:49:17 -0700 [thread overview]
Message-ID: <679d163f-2927-ed56-71dc-976fcf5e213f@zytor.com> (raw)
In-Reply-To: <CAJcbSZHhHjJ4h-4D4r7ocZxj2ys1rgNuq6iG_Q-q0kxfcitDQw@mail.gmail.com>
On 03/22/17 13:41, Thomas Garnier wrote:
>>> with the change below for additional feedback.
>>
>> Can you specify what that means?
>
> If I set inline by default, the compiler chose not to inline it on
> x86. If I force inline the size impact was actually bigger (without
> the architecture specific code).
>
That's utterly bizarre. Something strange is going on there. I suspect
the right thing to do is to out-of-line the error case only, but even
that seems strange. It should be something like four instructions inline.
>>
>> On x86, where there is only one caller of this, it really seems like it
>> ought to reduce the overhead to almost zero (since it most likely is
>> hidden in the pipeline.)
>>
>> I would like to suggest defining it inline if
>> CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE is set; I really don't
>> care about an architecture which doesn't have it.
>
> But if there is only one caller, does the compiler is not suppose to
> inline the function based on options?
If it is marked static in the same file, yes, but you have it in a
different file from what I can tell.
> The assembly will call it too, so I would need an inline and a
> non-inline based on the caller.
Where? I don't see that anywhere, at least for x86.
-hpa
next prev parent reply other threads:[~2017-03-22 20:49 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-11 0:04 [kernel-hardening] [PATCH v3 1/4] syscalls: Restore address limit after a syscall Thomas Garnier
2017-03-11 0:04 ` [kernel-hardening] [PATCH v3 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state Thomas Garnier
2017-03-11 9:42 ` [kernel-hardening] " Ingo Molnar
2017-03-13 15:53 ` Thomas Garnier
2017-03-14 0:04 ` H. Peter Anvin
2017-03-14 9:40 ` H. Peter Anvin
2017-03-14 15:17 ` Thomas Garnier
2017-03-14 15:39 ` Andy Lutomirski
2017-03-14 16:29 ` Thomas Garnier
2017-03-14 16:44 ` H. Peter Anvin
2017-03-14 16:51 ` Thomas Garnier
2017-03-14 17:53 ` H. Peter Anvin
2017-03-15 17:43 ` Thomas Garnier
2017-03-22 19:15 ` Thomas Garnier
2017-03-22 20:21 ` H. Peter Anvin
2017-03-22 20:41 ` Thomas Garnier
2017-03-22 20:49 ` H. Peter Anvin [this message]
2017-03-22 21:11 ` Thomas Garnier
2017-03-14 16:30 ` H. Peter Anvin
2017-03-11 0:05 ` [kernel-hardening] [PATCH v3 3/4] arm/syscalls: " Thomas Garnier
2017-03-11 0:05 ` [kernel-hardening] [PATCH v3 4/4] arm64/syscalls: " Thomas Garnier
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