linux-kernel - [tip:x86/urgent] Revert "x86/boot: Fail the boot if !M486 and CPUID is missing"

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-426d1aff3138cf38da14e912df3c75e312f96e9e@git.kernel.org>
Date:   Mon, 19 Dec 2016 03:04:30 -0800
From:   tip-bot for Andy Lutomirski <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jpoimboe@...hat.com, tglx@...utronix.de, tedheadster@...il.com,
        luto@...nel.org, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, brgerst@...il.com, hpa@...or.com,
        Xen-devel@...ts.xen.org, hmh@....eng.br, jgross@...e.com,
        gnomes@...rguk.ukuu.org.uk, andrew.cooper3@...rix.com,
        dvlasenk@...hat.com, peterz@...radead.org, mingo@...nel.org,
        boris.ostrovsky@...cle.com, bp@...en8.de
Subject: [tip:x86/urgent] Revert "x86/boot: Fail the boot if !M486 and CPUID
 is missing"

Commit-ID:  426d1aff3138cf38da14e912df3c75e312f96e9e
Gitweb:     http://git.kernel.org/tip/426d1aff3138cf38da14e912df3c75e312f96e9e
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Fri, 9 Dec 2016 10:24:06 -0800
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 19 Dec 2016 11:54:20 +0100

Revert "x86/boot: Fail the boot if !M486 and CPUID is missing"

This reverts commit ed68d7e9b9cfb64f3045ffbcb108df03c09a0f98.

The patch wasn't quite correct -- there are non-Intel (and hence
non-486) CPUs that we support that don't have CPUID.  Since we no
longer require CPUID for sync_core(), just revert the patch.

I think the relevant CPUs are Geode and Elan, but I'm not sure.

In principle, we should try to do better at identifying CPUID-less
CPUs in early boot, but that's more complicated.

Reported-by: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Juergen Gross <jgross@...e.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Matthew Whitehead <tedheadster@...il.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Henrique de Moraes Holschuh <hmh@....eng.br>
Cc: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: xen-devel <Xen-devel@...ts.xen.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: http://lkml.kernel.org/r/82acde18a108b8e353180dd6febcc2876df33f24.1481307769.git.luto@kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/boot/cpu.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/x86/boot/cpu.c b/arch/x86/boot/cpu.c
index 4224ede..26240dd 100644
--- a/arch/x86/boot/cpu.c
+++ b/arch/x86/boot/cpu.c
@@ -87,12 +87,6 @@ int validate_cpu(void)
 		return -1;
 	}
 
-	if (CONFIG_X86_MINIMUM_CPU_FAMILY <= 4 && !IS_ENABLED(CONFIG_M486) &&
-	    !has_eflag(X86_EFLAGS_ID)) {
-		printf("This kernel requires a CPU with the CPUID instruction.  Build with CONFIG_M486=y to run on this CPU.\n");
-		return -1;
-	}
-
 	if (err_flags) {
 		puts("This kernel requires the following features "
 		     "not present on the CPU:\n");