linux-kernel - Re: [RFC/INCOMPLETE 08/13] x86/entry/64: Migrate 64-bit syscalls to new exit hooks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALCETrUzQw=78_3i6=nmLbzw+hW7WtYo2iAaj+7+hH1RD_EaAw@mail.gmail.com>
Date:	Wed, 17 Jun 2015 07:12:13 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC/INCOMPLETE 08/13] x86/entry/64: Migrate 64-bit syscalls to
 new exit hooks

On Wed, Jun 17, 2015 at 3:02 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Ingo Molnar <mingo@...nel.org> wrote:
>
>>
>> * Andy Lutomirski <luto@...nel.org> wrote:
>>
>> > This is separate for ease of bisection.
>> >
>> > Signed-off-by: Andy Lutomirski <luto@...nel.org>
>> > ---
>> >  arch/x86/entry/entry_64.S | 68 +++++------------------------------------------
>> >  1 file changed, 7 insertions(+), 61 deletions(-)
>> >
>> > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
>> > index 33acc3dcc281..a5044d7a9d43 100644
>> > --- a/arch/x86/entry/entry_64.S
>> > +++ b/arch/x86/entry/entry_64.S
>> > @@ -229,6 +229,11 @@ entry_SYSCALL_64_fastpath:
>> >      */
>> >     USERGS_SYSRET64
>> >
>> > +GLOBAL(int_ret_from_sys_call_irqs_off)
>> > +   TRACE_IRQS_ON
>> > +   ENABLE_INTERRUPTS(CLBR_NONE)
>> > +   jmp int_ret_from_sys_call
>>
>> Any reason why irq state tracking cannot be done in C as well, like the rest of
>> the irq state tracking code?
>
> Never mind, I see you've done exactly that in patch #12.
>

There are still some TRACE_IRQS_ON, LOCKDEP_SYS_EXIT, and such
scattered throughout the asm.  it's plausible that even more of that
could be moved to C.

We could also benchmark and find out how bad it would be if we just
always filled pt_regs in completely in syscalls.  If the performance
hit isn't enough to matter, then we could potentially move the entire
syscall path except pt_regs setup and sysret/iret into three C
functions.

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/