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From: Peter Zijlstra <peterz@infradead.org>
To: Jarkko Sakkinen <jarkko@kernel.org>
Cc: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Borislav Petkov <bp@alien8.de>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>,
	Haitao Huang <haitao.huang@intel.com>
Subject: Re: [PATCH v22 8/8] x86/vdso: Add ENDBR64 to __vdso_sgx_enter_enclave
Date: Thu, 11 Mar 2021 09:42:05 +0100	[thread overview]
Message-ID: <YEnX3Zn0FXPt7pcM@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YEmQJjwjs8UCEO2F@kernel.org>

On Thu, Mar 11, 2021 at 05:36:06AM +0200, Jarkko Sakkinen wrote:
> Does it do any harm to put it there unconditionally?

Blows up your text footprint and I$ pressure. These instructions are 4
bytes each.

Aside from that, they're a NOP, so only consume front-end resources
(hopefully) on older CPUs and when IBT is disabled.

  reply	other threads:[~2021-03-11  8:43 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-10 22:05 [PATCH v22 0/8] Control-flow Enforcement: Indirect Branch Tracking Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 1/8] x86/cet/ibt: Update Kconfig for user-mode " Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 2/8] x86/cet/ibt: User-mode Indirect Branch Tracking support Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 3/8] x86/cet/ibt: Handle signals for Indirect Branch Tracking Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 4/8] x86/cet/ibt: Update ELF header parsing " Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 5/8] x86/cet/ibt: Update arch_prctl functions " Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 6/8] x86/vdso/32: Add ENDBR32 to __kernel_vsyscall entry point Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 7/8] x86/vdso: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2021-03-10 22:05 ` [PATCH v22 8/8] x86/vdso: Add ENDBR64 to __vdso_sgx_enter_enclave Yu-cheng Yu
2021-03-10 22:39   ` Jarkko Sakkinen
2021-03-10 22:55     ` Yu, Yu-cheng
2021-03-10 23:17       ` Borislav Petkov
2021-03-10 23:20       ` Dave Hansen
2021-03-10 23:22         ` Yu, Yu-cheng
2021-03-12 16:55         ` Jarkko Sakkinen
2021-03-12 16:57           ` Jarkko Sakkinen
2021-03-12 16:59           ` Dave Hansen
2021-03-11  3:36       ` Jarkko Sakkinen
2021-03-11  8:42         ` Peter Zijlstra [this message]
2021-03-11 15:44           ` Yu, Yu-cheng
2021-03-12 16:56           ` Jarkko Sakkinen

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