linux-kernel - [tip:x86/urgent] x86/cpu: Use indirect call to measure performance in init_amd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-429ed86b5c99b388543f6f7f6983b1230326f2bb@git.kernel.org>
Date:   Wed, 12 Jul 2017 06:09:57 -0700
From:   tip-bot for Mikulas Patocka <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     brgerst@...il.com, dvlasenk@...hat.com, peterz@...radead.org,
        mpatocka@...hat.com, hpa@...or.com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, luto@...nel.org, jpoimboe@...hat.com,
        torvalds@...ux-foundation.org, mingo@...nel.org, bp@...en8.de
Subject: [tip:x86/urgent] x86/cpu: Use indirect call to measure performance
 in init_amd_k6()

Commit-ID:  429ed86b5c99b388543f6f7f6983b1230326f2bb
Gitweb:     http://git.kernel.org/tip/429ed86b5c99b388543f6f7f6983b1230326f2bb
Author:     Mikulas Patocka <mpatocka@...hat.com>
AuthorDate: Tue, 11 Jul 2017 07:44:05 -0400
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 12 Jul 2017 10:42:32 +0200

x86/cpu: Use indirect call to measure performance in init_amd_k6()

This old piece of code is supposed to measure the performance of indirect
calls to determine if the processor is buggy or not, however the compiler
optimizer turns it into a direct call.

Use the OPTIMIZER_HIDE_VAR() macro to thwart the optimization, so that a real
indirect call is generated.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1707110737530.8746@file01.intranet.prod.int.rdu2.redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/amd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index bb5abe8..3b9e220 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -134,6 +134,7 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
 
 		n = K6_BUG_LOOP;
 		f_vide = vide;
+		OPTIMIZER_HIDE_VAR(f_vide);
 		d = rdtsc();
 		while (n--)
 			f_vide();