From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H . Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 30/43] x86/mm/kaiser: Map espfix structures
Date: Mon, 27 Nov 2017 10:14:24 +0100 [thread overview]
Message-ID: <20171127091424.zvfg7fsr7v2kfxnl@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CALCETrVyBC=kk4zLLYyQ_YTg5gaMpOGzpr9p7u_mBOGff=PuUA@mail.gmail.com>
On Fri, Nov 24, 2017 at 08:17:06AM -0800, Andy Lutomirski wrote:
> On Fri, Nov 24, 2017 at 5:47 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Fri, Nov 24, 2017 at 10:14:35AM +0100, Ingo Molnar wrote:
> >> From: Dave Hansen <dave.hansen@linux.intel.com>
> >>
> >> There is some rather arcane code to help when an IRET returns
> >> to 16-bit segments. It is referred to as the "espfix" code.
> >> This consists of a few per-cpu variables:
> >>
> >> espfix_stack: tells us where the stack is allocated
> >> (the bottom)
> >> espfix_waddr: tells us to where %rsp may be pointed
> >> (the top)
> >>
> >> These are in addition to the stack itself. All three things must
> >> be mapped for the espfix code to function.
> >>
> >> Note: the espfix code runs with a kernel GSBASE, but user
> >> (shadow) page tables. A switch to the kernel page tables could
> >> be performed instead of mapping these structures, but mapping
> >> them is simpler and less likely to break the assembly. To switch
> >> over to the kernel copy, additional temporary storage would be
> >> required which is in short supply in this context.
> >
> > With Andy's patches that should actually be doable, no?
>
> I don't think it has much to do with my patches. We can freely spill
> to the stack in the espfix64 code, though.
Ah, I was thinking of how you made scratch space easier for the SYSENTER
stuff.
But if we can freely spill here, should we not do the kernel switch
instead of doing this user mapping? The way I understand things, the
less of these magic mappings we have the better.
next prev parent reply other threads:[~2017-11-27 9:14 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-24 9:14 [PATCH 00/43] x86 entry-stack and Kaiser series, 2017/11/24 version Ingo Molnar
2017-11-24 9:14 ` [PATCH 01/43] x86/decoder: Add new TEST instruction pattern Ingo Molnar
2017-11-24 10:38 ` Borislav Petkov
2017-12-02 7:39 ` Robert Elliott (Persistent Memory)
2017-11-24 9:14 ` [PATCH 02/43] x86/entry/64: Allocate and enable the SYSENTER stack Ingo Molnar
2017-11-24 9:14 ` [PATCH 03/43] x86/dumpstack: Add get_stack_info() support for " Ingo Molnar
2017-11-24 9:14 ` [PATCH 04/43] x86/gdt: Put per-cpu GDT remaps in ascending order Ingo Molnar
2017-11-24 9:14 ` [PATCH 05/43] x86/fixmap: Generalize the GDT fixmap mechanism Ingo Molnar
2017-11-24 11:00 ` Borislav Petkov
2017-11-24 9:14 ` [PATCH 06/43] x86/kasan/64: Teach KASAN about the cpu_entry_area Ingo Molnar
2017-11-24 9:14 ` [PATCH 07/43] x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu_tss Ingo Molnar
2017-11-24 9:14 ` [PATCH 08/43] x86/dumpstack: Handle stack overflow on all stacks Ingo Molnar
2017-11-24 9:14 ` [PATCH 09/43] x86/entry: Move SYSENTER_stack to the beginning of struct tss_struct Ingo Molnar
2017-11-24 11:44 ` Borislav Petkov
2017-11-24 9:14 ` [PATCH 10/43] x86/entry: Remap the TSS into the cpu entry area Ingo Molnar
2017-11-24 9:14 ` [PATCH 11/43] x86/entry/64: Separate cpu_current_top_of_stack from TSS.sp0 Ingo Molnar
2017-11-24 14:19 ` Borislav Petkov
2017-11-24 9:14 ` [PATCH 12/43] x86/espfix/64: Stop assuming that pt_regs is on the entry stack Ingo Molnar
2017-11-24 9:14 ` [PATCH 13/43] x86/entry/64: Use a percpu trampoline stack for IDT entries Ingo Molnar
2017-11-24 11:27 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 14/43] x86/entry/64: Return to userspace from the trampoline stack Ingo Molnar
2017-11-24 13:46 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 15/43] x86/entry/64: Create a percpu SYSCALL entry trampoline Ingo Molnar
2017-11-24 13:52 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 16/43] x86/irq: Remove an old outdated comment about context tracking races Ingo Molnar
2017-11-24 13:53 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 17/43] x86/irq/64: Print the offending IP in the stack overflow warning Ingo Molnar
2017-11-24 14:22 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 18/43] x86/entry/64: Move the IST stacks into cpu_entry_area Ingo Molnar
2017-11-24 14:23 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 19/43] x86/entry/64: Remove the SYSENTER stack canary Ingo Molnar
2017-11-24 14:23 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 20/43] x86/entry: Clean up SYSENTER_stack code Ingo Molnar
2017-11-24 14:24 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 21/43] x86/mm/kaiser: Disable global pages by default with KAISER Ingo Molnar
2017-11-24 9:14 ` [PATCH 22/43] x86/mm/kaiser: Prepare assembly for entry/exit CR3 switching Ingo Molnar
2017-11-24 12:05 ` Peter Zijlstra
2017-11-24 12:17 ` Ingo Molnar
2017-11-24 12:45 ` Peter Zijlstra
2017-11-24 13:04 ` Thomas Gleixner
2017-11-24 9:14 ` [PATCH 23/43] x86/mm/kaiser: Introduce user-mapped per-cpu areas Ingo Molnar
2017-11-24 9:14 ` [PATCH 24/43] x86/mm/kaiser: Mark per-cpu data structures required for entry/exit Ingo Molnar
2017-11-24 9:14 ` [PATCH 25/43] x86/mm/kaiser: Unmap kernel from userspace page tables (core patch) Ingo Molnar
2017-11-24 12:13 ` Peter Zijlstra
2017-11-24 13:46 ` Ingo Molnar
2017-11-24 12:16 ` Peter Zijlstra
2017-11-24 16:33 ` Dave Hansen
2017-11-26 15:13 ` Ingo Molnar
2017-11-24 13:30 ` Peter Zijlstra
2017-11-26 15:15 ` Ingo Molnar
2017-11-27 8:59 ` [PATCH] x86/mm/kaiser: Use the other page_table_lock pattern Peter Zijlstra
2017-11-27 8:59 ` [PATCH] mm: Unify page_table_lock allocation pattern Peter Zijlstra
2017-11-24 9:14 ` [PATCH 26/43] x86/mm/kaiser: Allow NX poison to be set in p4d/pgd Ingo Molnar
2017-11-24 9:14 ` [PATCH 27/43] x86/mm/kaiser: Make sure static PGDs are 8k in size Ingo Molnar
2017-11-24 9:14 ` [PATCH 28/43] x86/mm/kaiser: Map CPU entry area Ingo Molnar
2017-11-24 13:43 ` Peter Zijlstra
2017-11-24 9:14 ` [PATCH 29/43] x86/mm/kaiser: Map dynamically-allocated LDTs Ingo Molnar
2017-11-24 9:14 ` [PATCH 30/43] x86/mm/kaiser: Map espfix structures Ingo Molnar
2017-11-24 13:47 ` Peter Zijlstra
2017-11-24 16:17 ` Andy Lutomirski
2017-11-27 9:14 ` Peter Zijlstra [this message]
2017-11-27 15:35 ` Peter Zijlstra
2017-11-24 9:14 ` [PATCH 31/43] x86/mm/kaiser: Map entry stack variable Ingo Molnar
2017-11-24 9:14 ` [PATCH 32/43] x86/mm/kaiser: Map virtually-addressed performance monitoring buffers Ingo Molnar
2017-11-24 9:14 ` [PATCH 33/43] x86/mm: Move CR3 construction functions Ingo Molnar
2017-11-24 9:14 ` [PATCH 34/43] x86/mm: Remove hard-coded ASID limit checks Ingo Molnar
2017-11-24 9:14 ` [PATCH 35/43] x86/mm: Put mmu-to-h/w ASID translation in one place Ingo Molnar
2017-11-24 9:14 ` [PATCH 36/43] x86/mm: Allow flushing for future ASID switches Ingo Molnar
2017-11-24 9:14 ` [PATCH 37/43] x86/mm/kaiser: Use PCID feature to make user and kernel switches faster Ingo Molnar
2017-11-24 9:14 ` [PATCH 38/43] x86/mm/kaiser: Disable native VSYSCALL Ingo Molnar
2017-11-24 9:14 ` [PATCH 39/43] x86/mm/kaiser: Add debugfs file to turn KAISER on/off at runtime Ingo Molnar
2017-11-24 9:14 ` [PATCH 40/43] x86/mm/kaiser: Add a function to check for KAISER being enabled Ingo Molnar
2017-11-24 9:14 ` [PATCH 41/43] x86/mm/kaiser: Un-poison PGDs at runtime Ingo Molnar
2017-11-24 9:14 ` [PATCH 42/43] x86/mm/kaiser: Allow KAISER to be enabled/disabled " Ingo Molnar
2017-11-24 9:14 ` [PATCH 43/43] x86/mm/kaiser: Add Kconfig Ingo Molnar
2017-11-24 13:55 ` [PATCH 00/43] x86 entry-stack and Kaiser series, 2017/11/24 version Ingo Molnar
2017-11-24 15:23 ` Thomas Gleixner
2017-11-24 17:19 ` Ingo Molnar
2017-11-24 17:23 [PATCH 00/43] x86 entry-stack and Kaiser series, 2017/11/24, v2 version Ingo Molnar
2017-11-24 17:23 ` [PATCH 30/43] x86/mm/kaiser: Map espfix structures Ingo Molnar
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