From: Andy Lutomirski <luto@kernel.org>
To: David Laight <David.Laight@aculab.com>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
Borislav Petkov <bpetkov@suse.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Dave Hansen <dave.hansen@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH v3 14/19] x86/entry/64: Create a percpu SYSCALL entry trampoline
Date: Thu, 30 Nov 2017 21:56:41 -0800 [thread overview]
Message-ID: <CALCETrVzZE3EBYD9WetSjtQ6EQO2S7GvfqFtLhbtBzLoOxtujQ@mail.gmail.com> (raw)
In-Reply-To: <60410e99331c454caeaa787e372c8f37@AcuMS.aculab.com>
On Fri, Nov 24, 2017 at 3:39 AM, David Laight <David.Laight@aculab.com> wrote:
> From: Andy Lutomirski
>> Sent: 24 November 2017 04:33
> ...
>> + /*
>> + * x86 lacks a near absolute jump, and we can't jump to the real
>> + * entry text with a relative jump, so we fake it using retq.
>> + */
>> + pushq $entry_SYSCALL_64_after_hwframe
>> + retq
>
> Don't some of the cpus have hardware logic that follows call and return?
> The above will break that logic and slow things down (unless it is an
> expected sequence).
Indeed, and it makes a *huge* difference.
>
> Is there a scratch register that can be used for an indirect jump?
No, but I can fudge it.
>
> David
>
next prev parent reply other threads:[~2017-12-01 5:57 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-24 4:32 [PATCH v3 00/19] Entry stack switching Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 01/19] x86/asm/64: Allocate and enable the SYSENTER stack Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 02/19] x86/dumpstack: Add get_stack_info() support for " Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 03/19] x86/gdt: Put per-cpu GDT remaps in ascending order Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 04/19] x86/fixmap: Generalize the GDT fixmap mechanism Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 05/19] x86/kasan/64: Teach KASAN about the cpu_entry_area Andy Lutomirski
2017-11-24 13:16 ` Andrey Ryabinin
2017-11-24 16:27 ` Andy Lutomirski
2017-11-24 17:21 ` [PATCH v4] x86/mm/kasan: " Andrey Ryabinin
2017-11-24 19:26 ` Andy Lutomirski
2017-11-24 17:26 ` [PATCH v3 05/19] x86/kasan/64: " Andrey Ryabinin
2017-11-24 4:32 ` [PATCH v3 06/19] x86/asm: Fix assumptions that the HW TSS is at the beginning of cpu_tss Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 07/19] x86/dumpstack: Handle stack overflow on all stacks Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 08/19] x86/asm: Move SYSENTER_stack to the beginning of struct tss_struct Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 09/19] x86/asm: Remap the TSS into the cpu entry area Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 10/19] x86/asm/64: Separate cpu_current_top_of_stack from TSS.sp0 Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 11/19] x86/espfix/64: Stop assuming that pt_regs is on the entry stack Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 12/19] x86/asm/64: Use a percpu trampoline stack for IDT entries Andy Lutomirski
2017-11-24 4:32 ` [PATCH v3 13/19] x86/asm/64: Return to userspace from the trampoline stack Andy Lutomirski
2017-11-24 4:33 ` [PATCH v3 14/19] x86/entry/64: Create a percpu SYSCALL entry trampoline Andy Lutomirski
2017-11-24 11:39 ` David Laight
2017-12-01 5:56 ` Andy Lutomirski [this message]
2017-11-24 4:33 ` [PATCH v3 15/19] x86/irq: Remove an old outdated comment about context tracking races Andy Lutomirski
2017-11-24 4:33 ` [PATCH v3 16/19] x86/irq/64: In the stack overflow warning, print the offending IP Andy Lutomirski
2017-11-24 4:33 ` [PATCH v3 17/19] x86/entry/64: Move the IST stacks into cpu_entry_area Andy Lutomirski
2017-11-24 4:33 ` [PATCH v3 18/19] x86/entry/64: Remove the SYSENTER stack canary Andy Lutomirski
2017-11-24 4:33 ` [PATCH v3 19/19] x86/entry: Clean up SYSENTER_stack code Andy Lutomirski
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