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From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>,
	Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
	"kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>, X86 ML <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Borislav Petkov <bp@alien8.de>, Nadav Amit <nadav.amit@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Brian Gerst <brgerst@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>, Jann Horn <jann@thejh.net>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [kernel-hardening] [PATCH v5 03/32] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated
Date: Fri, 22 Jul 2016 22:11:05 +0200	[thread overview]
Message-ID: <20160722201104.GA6613@gmail.com> (raw)
In-Reply-To: <CALCETrVKzUh_RYBoogWsEjYMe89en-NeNQhnWomy4LD=DaKfWQ@mail.gmail.com>


* Andy Lutomirski <luto@amacapital.net> wrote:

> This garbage (as evidenced by my bug and my failed attempt to fix it)
> only works if you never have a low-level page table that isn't linked
> into a higher-level page table, and it mostly requires you to do
> everything exactly the way it was originally done so all the horrible
> inline helpers don't get confused.
> 
> And AFAICT all of this was done to manually unroll a loop, and I bet
> it never sped anything up measurably even on 386 or PPro.
> 
> Whenever some vendor releases a 5 level page table CPU, can we
> *please* clean this up first?  We should have a type that points to a
> table, a different type that points to an entry (or maybe not have
> pointers to entries at all), and the levels should be referred to by
> *number*.  When you need to traverse all the way down, you write a
> *loop* instead of four bloody helper functions, some of which are
> incomprehensibly no-ops on some kernels.  And if this means that, on
> Intel, we have a silly branch in the inner loop because the bottom
> level entry format is special, who cares?
> </rant>

I'd welcome (and help out!) any effort to clean it up gradually.

Thanks,

	Ingo

  parent reply	other threads:[~2016-07-22 20:11 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-11 20:53 [PATCH v5 00/32] virtually mapped stacks and thread_info cleanup Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 01/32] bluetooth: Switch SMP to crypto_cipher_encrypt_one() Andy Lutomirski
2016-07-14 19:10   ` Andy Lutomirski
2016-07-14 20:30     ` Marcel Holtmann
2016-07-14 20:41     ` David Miller
2016-07-11 20:53 ` [PATCH v5 02/32] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 03/32] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski
2016-07-22  4:43   ` [kernel-hardening] " Valdis.Kletnieks
2016-07-22  5:34     ` Andy Lutomirski
2016-07-22 10:21       ` Ingo Molnar
2016-07-22 18:21         ` Andy Lutomirski
2016-07-22 18:31           ` Andy Lutomirski
2016-07-22 20:11           ` Ingo Molnar [this message]
2016-07-23  5:21       ` Valdis.Kletnieks
2016-07-23 14:58         ` Nicolai Stange
2016-07-28  9:26           ` Valdis.Kletnieks
2016-07-11 20:53 ` [PATCH v5 04/32] x86/mm: Remove kernel_unmap_pages_in_pgd() and efi_cleanup_page_tables() Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 05/32] mm: Track NR_KERNEL_STACK in KiB instead of number of stacks Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 06/32] mm: Fix memcg stack accounting for sub-page stacks Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 07/32] fork: Add generic vmalloced stack support Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 08/32] dma-api: Teach the "DMA-from-stack" check about vmapped stacks Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 09/32] x86/dumpstack: When OOPSing, rewind the stack before do_exit() Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 10/32] x86/dumpstack: Honor supplied @regs arg Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 11/32] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 12/32] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 13/32] x86/mm/64: In vmalloc_fault(), use CR3 instead of current->active_mm Andy Lutomirski
2016-07-12 17:51   ` [kernel-hardening] " Dave Hansen
2016-07-12 18:03     ` Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 14/32] x86/mm/64: Enable vmapped stacks Andy Lutomirski
2016-07-13  7:53   ` Ingo Molnar
2016-07-13 18:42     ` Andy Lutomirski
2016-07-14  8:34       ` Ingo Molnar
2016-07-14 16:51         ` Andy Lutomirski
2016-07-14 18:45           ` Ingo Molnar
2016-07-11 20:53 ` [PATCH v5 15/32] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 16/32] x86: Move uaccess_err and sig_on_uaccess_err to thread_struct Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 17/32] x86: Move addr_limit " Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 18/32] signal: Consolidate {TS,TLF}_RESTORE_SIGMASK code Andy Lutomirski
2016-07-12 11:57   ` Brian Gerst
2016-07-12 23:01     ` Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 19/32] x86/smp: Remove stack_smp_processor_id() Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 20/32] x86/smp: Remove unnecessary initialization of thread_info::cpu Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 21/32] x86/asm: Move 'status' from struct thread_info to struct thread_struct Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 22/32] kdb: Use task_cpu() instead of task_thread_info()->cpu Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 23/32] printk: When dumping regs, show the stack, not thread_info Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 24/32] x86/entry: Get rid of pt_regs_to_thread_info() Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 25/32] um: Stop conflating task_struct::stack with thread_info Andy Lutomirski
2016-07-11 20:53 ` [PATCH v5 26/32] sched: Allow putting thread_info into task_struct Andy Lutomirski
2016-07-11 20:54 ` [PATCH v5 27/32] x86: Move " Andy Lutomirski
2016-07-11 20:54 ` [PATCH v5 28/32] sched: Add try_get_task_stack() and put_task_stack() Andy Lutomirski
2016-07-11 20:54 ` [PATCH v5 29/32] kthread: to_live_kthread() needs try_get_task_stack() Andy Lutomirski
2016-07-11 20:54 ` [PATCH v5 30/32] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski
2016-07-11 20:54 ` [PATCH v5 31/32] sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK Andy Lutomirski
2016-07-11 20:54 ` [PATCH v5 32/32] fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set Andy Lutomirski
2016-07-12  8:56 ` [PATCH v5 00/32] virtually mapped stacks and thread_info cleanup Herbert Xu
2016-07-13  8:54 ` Christian Borntraeger
2016-07-13 18:36   ` Andy Lutomirski
2016-07-13 18:53     ` Christian Borntraeger

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