From: Andi Kleen <ak@linux.intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
Ingo Molnar <mingo@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Lutomirski <luto@kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH tip-pti 2/2] x86/entry: interleave XOR register clearing with PUSH/MOV instructions
Date: Wed, 7 Feb 2018 07:18:54 -0800 [thread overview]
Message-ID: <20180207151854.GB10945@tassilo.jf.intel.com> (raw)
In-Reply-To: <CA+55aFzRMn6+tFFkAbMT_iDcMphDZFU9+OALEn+ecqa7=RqvUA@mail.gmail.com>
> Plus the fastpath couldn't clear those registers anyway, since it
> didn't even _save_ them - exactly because the whole point of the
> fastpath was that not all registers are clobbered by the calling
> conventions.
Fast path saves more than just register saving. I changed the fast path
to save all registers in my earlier clearregs branches
https://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git/log/?h=spec/clearregs-3
It is still quite a bit faster than all the slow stuff the C do_syscall
code does (e.g. reloading all the arguments, setting up unnecessary
frame pointers etc.).
Just take a look at the disassembly of that function. It's really
not very optimized.
-Andi
next prev parent reply other threads:[~2018-02-07 15:19 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-06 1:18 [PATCH v3 0/3] x86/entry: Clear registers to sanitize speculative usages Dan Williams
2018-02-06 1:18 ` [PATCH v3 1/3] x86/entry: Clear extra registers beyond syscall arguments for 64bit kernels Dan Williams
2018-02-06 11:52 ` [tip:x86/pti] x86/entry/64: Clear extra registers beyond syscall arguments, to reduce speculation attack surface tip-bot for Dan Williams
2018-02-06 1:18 ` [PATCH v3 2/3] x86/entry: Clear registers for 64bit exceptions/interrupts Dan Williams
2018-02-06 9:04 ` Dominik Brodowski
2018-02-06 10:48 ` Ingo Molnar
2018-02-06 9:17 ` Dominik Brodowski
2018-02-06 10:51 ` Ingo Molnar
2018-02-06 10:57 ` Dominik Brodowski
2018-02-06 21:25 ` [PATCH tip-pti 1/2] x86/entry: remove SAVE_C_REGS_EXCEPT_* macros Dominik Brodowski
2018-02-06 22:56 ` Linus Torvalds
2018-02-06 21:32 ` [PATCH tip-pti 2/2] x86/entry: interleave XOR register clearing with PUSH/MOV instructions Dominik Brodowski
2018-02-06 22:30 ` Dan Williams
2018-02-06 22:48 ` Linus Torvalds
2018-02-06 23:05 ` Andy Lutomirski
2018-02-06 23:54 ` Andi Kleen
2018-02-07 1:30 ` Linus Torvalds
2018-02-07 15:18 ` Andi Kleen [this message]
2018-02-07 17:05 ` Linus Torvalds
2018-02-07 17:37 ` Linus Torvalds
2018-02-06 12:00 ` [tip:x86/pti] x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface tip-bot for Dan Williams
2018-02-06 1:18 ` [PATCH v3 3/3] x86/entry: Clear registers for compat syscalls Dan Williams
2018-02-06 7:26 ` Ingo Molnar
2018-02-06 7:53 ` Dan Williams
2018-02-06 12:00 ` [tip:x86/pti] x86/entry/64/compat: Clear registers for compat syscalls, to reduce speculation attack surface tip-bot for Dan Williams
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