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Date: Fri, 26 Jan 2018 11:02:54 -0800
From: Andy Lutomirski <luto@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>, Al Viro <viro@...iv.linux.org.uk>,
Alan Cox <alan@...ux.intel.com>, David Laight <David.Laight@...lab.com>,
"the arch/x86 maintainers" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jann Horn <jannh@...gle.com>,
Samuel Neves <samuel.c.p.neves@...il.com>, Dan Williams <dan.j.williams@...el.com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast
path with retpolines on
On Fri, Jan 26, 2018 at 10:54 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, Jan 26, 2018 at 10:23 AM, Andy Lutomirski <luto@...nel.org> wrote:
>>
>> The issue is that doing it this way gives us, effectively:
>>
>> long sys_foo(int a, int b)
>> {
>> body here;
>> }
>>
>> long SyS_foo(const struct pt_regs *regs)
>> {
>> return sys_foo(regs->di, regs->si);
>> }
>>
>> whereas what we want is *static* long sys_foo(...).
>
> How about just marking 'sys_foo()' as being always_inline (but still
> not static)? Because the case that _matters_ is that SyS_foo(), thing
> when this is enabled.
>
> Sure, you'll get two copies of the code (one in SyS_foo(), the other
> being the callable-from C 'sys_foo()' that is exported and almost
> never used). But that seems a fairly small price to pay. We could
> leave it for later to try to get rid of the unused copies entirely.
>
I could do that, but Josh Triplett will yell at me.
Anyway, I'll fiddle with it. This isn't exactly high priority.
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