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From: Dominik Brodowski <linux@dominikbrodowski.net>
To: Dan Williams <dan.j.williams@intel.com>
Cc: tglx@linutronix.de, mingo@kernel.org,
	Andi Kleen <ak@linux.intel.com>,
	torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
	luto@kernel.org
Subject: Re: [PATCH v3 2/3] x86/entry: Clear registers for 64bit exceptions/interrupts
Date: Tue, 6 Feb 2018 10:04:55 +0100	[thread overview]
Message-ID: <20180206090455.GA15925@isilmar-4.linta.de> (raw)
In-Reply-To: <151787989146.7847.15749181712358213254.stgit@dwillia2-desk3.amr.corp.intel.com>

On Mon, Feb 05, 2018 at 05:18:11PM -0800, Dan Williams wrote:
> @@ -1178,6 +1180,7 @@ ENTRY(paranoid_entry)
>  	cld
>  	SAVE_C_REGS 8
>  	SAVE_EXTRA_REGS 8
> +	CLEAR_REGS_NOSPEC
>  	ENCODE_FRAME_POINTER 8
>  	movl	$1, %ebx
>  	movl	$MSR_GS_BASE, %ecx
> @@ -1185,7 +1188,6 @@ ENTRY(paranoid_entry)
>  	testl	%edx, %edx
>  	js	1f				/* negative -> in kernel */
>  	SWAPGS
> -	xorl	%ebx, %ebx

Here, %ebx will be filled with $1 (see code snipped above) *after* the
call to CLEAR_REGS_NOSPEC. That's what this line has been clearing in the
past. So I'm not sure whether this line should be removed.

Thanks,
	Dominik

  reply	other threads:[~2018-02-06  9:05 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 [this message]
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
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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