From nobody Fri Feb 20 15:29:20 2026 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4fHZ0x0hN8z6SVj0 for ; Fri, 20 Feb 2026 15:29:21 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R12" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4fHZ0w74q5z3cfR for ; Fri, 20 Feb 2026 15:29:20 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1771601361; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=DMU8dfTKhz+KtpEMdox0fDKV6mcMkODjdUAoR36QYWU=; b=rsYZ/rWXQGumNDyODKYQXmjB0HdJ1VY6ZLBY8qyZ2X7/+fJEPeLLfbEAfQYJks6yzw0meo znc9RTUUF+qtukhXJ2tF6SWqCrNAkBMdUJ95rv49TIe/b5tP2FzmpXhmenKdErA1b9TQmC AwCXEVRUIqOQPeBh60C++YterhiOub0/qIBP9XqDNI71C/6ySE4F/D9gKPH/CP/F2CvYSD Y0Zalsegf8xdaCCteqQ3/Q9ckSbxgrtC+FisXJW72+8Gdgivky3xl3i0i/EuDHjh40SYVi BLXan/o4/4OJ2xqTust8ugZDXyV3dfk+XXPMmpXXoMPcvnPj7HuIWv1yC6G2kg== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1771601361; a=rsa-sha256; cv=none; b=M79wcFMDdK2YnYEwB4diWS5ePL7g4dKvPNVExazuWvFT9n9MyVyp8U1DkWSq0A9FcUL0xz dE5SFw7bDeqjlYk9toQm6OTqc1y5wLB65LGc/n4rJ+CrsbHkAKzlflkTXnGs7Eby62oy8n bTmpWE4pYXoL34U5qENfOLTA9etP3hVKxBq5M1AuZyluu8qvDx2rcXH/yrfQY5rtmZUn2z 1bDi209IIsbICqlfT+d1g1q2hG9DeYRfrCbb9ADorFQZ7eMREV81bYVViR3fjiRAcFGOtl Q4jmfVf/ErRoGZCUJB4pTE2+Zmu6+JFhdl8SDQ39t0mCuXBN777rER5HAEbP3Q== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1771601361; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=DMU8dfTKhz+KtpEMdox0fDKV6mcMkODjdUAoR36QYWU=; b=enWE4kvW0iNSK/jjSwDmMB5Go0mrb8ES08Nj0o0rHZLZs6SJBZzmFrWb0rVCI2YR1TKClW W3LPbxGKQZZ5p4emI83F4uwLEIOd4LQ7qlmcHkEenWT3Aez11wdGJ9h+kUCpGO0d1vrquj 716EX3B7vc5n19mZ8qy0VbdbIpuqlInCVJI11PUqtTqO8dYQ9lnZrahiqPrgLVsH7BDUgF YQher0KxoJ5qDeuUD0igNGeqjkdadAwBejvxgr1boXeqvYXhupFrQa9VjJmLWefEvm0Xi8 qB3DIF+Mh40mjCSrErkq90aeN9Pi+acVFF04lmfJKGTsVKKZYlyRJRXHNxaIFA== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4fHZ0w60dlzZHj for ; Fri, 20 Feb 2026 15:29:20 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 25700 by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Fri, 20 Feb 2026 15:29:20 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Cc: Aaron LI From: Ed Maste Subject: git: 89d7b30c652c - main - i386,amd64: Explicitly set ECX=0 in do_cpuid() to be future-proof List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: emaste X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 89d7b30c652c98ea12abc5eb9424464cbfb45953 Auto-Submitted: auto-generated Date: Fri, 20 Feb 2026 15:29:20 +0000 Message-Id: <69987dd0.25700.5b173030@gitrepo.freebsd.org> The branch main has been updated by emaste: URL: https://cgit.FreeBSD.org/src/commit/?id=89d7b30c652c98ea12abc5eb9424464cbfb45953 commit 89d7b30c652c98ea12abc5eb9424464cbfb45953 Author: Aaron LI AuthorDate: 2026-02-16 04:00:12 +0000 Commit: Ed Maste CommitDate: 2026-02-20 15:26:20 +0000 i386,amd64: Explicitly set ECX=0 in do_cpuid() to be future-proof In principle, do_cpuid() should only be used for CPUID leaves without sub-leaves. Even accessing sub-leaf zero (ECX=0), one must use cpuid_count(ax, 0) rather than cpuid(ax). However, one might assume do_cpuid(ax) is equivalent to cpuid_count(ax, 0), but the old do_cpuid() did not initialize ECX before executing the CPUID instruction. If ECX contained a non-zero value, the instruction could return unexpected results, potentially leading to subtle and hard-to-debug issues, especially in ported code. To be future-proof and to help port code, adjust do_cpuid(ax) to be cpuid_count(ax, 0) to explicitly set ECX=0. It's believed that this change does not fix any real bugs in FreeBSD. See also the DragonFly commit: https://github.com/DragonFlyBSD/DragonFlyBSD/commit/0087a1d163488a57787a9a6431dd94070b1988d4 Signed-off-by: Aaron LI Reviewed by: kib Pull Request: https://github.com/freebsd/freebsd-src/pull/2027 --- sys/amd64/include/cpufunc.h | 10 ++++------ sys/i386/include/cpufunc.h | 24 +++++------------------- 2 files changed, 9 insertions(+), 25 deletions(-) diff --git a/sys/amd64/include/cpufunc.h b/sys/amd64/include/cpufunc.h index 9a4c82275a99..e52c55dc80f0 100644 --- a/sys/amd64/include/cpufunc.h +++ b/sys/amd64/include/cpufunc.h @@ -100,19 +100,17 @@ disable_intr(void) } static __inline void -do_cpuid(u_int ax, u_int *p) +cpuid_count(u_int ax, u_int cx, u_int *p) { __asm __volatile("cpuid" : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3]) - : "0" (ax)); + : "0" (ax), "c" (cx)); } static __inline void -cpuid_count(u_int ax, u_int cx, u_int *p) +do_cpuid(u_int ax, u_int *p) { - __asm __volatile("cpuid" - : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3]) - : "0" (ax), "c" (cx)); + cpuid_count(ax, 0, p); } static __inline void diff --git a/sys/i386/include/cpufunc.h b/sys/i386/include/cpufunc.h index b200588b0739..5ee516656d72 100644 --- a/sys/i386/include/cpufunc.h +++ b/sys/i386/include/cpufunc.h @@ -91,14 +91,6 @@ disable_intr(void) } #ifdef _KERNEL -static __inline void -do_cpuid(u_int ax, u_int *p) -{ - __asm __volatile("cpuid" - : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3]) - : "0" (ax)); -} - static __inline void cpuid_count(u_int ax, u_int cx, u_int *p) { @@ -108,7 +100,7 @@ cpuid_count(u_int ax, u_int cx, u_int *p) } #else static __inline void -do_cpuid(u_int ax, u_int *p) +cpuid_count(u_int ax, u_int cx, u_int *p) { __asm __volatile( "pushl\t%%ebx\n\t" @@ -116,21 +108,15 @@ do_cpuid(u_int ax, u_int *p) "movl\t%%ebx,%1\n\t" "popl\t%%ebx" : "=a" (p[0]), "=DS" (p[1]), "=c" (p[2]), "=d" (p[3]) - : "0" (ax)); + : "0" (ax), "c" (cx)); } +#endif static __inline void -cpuid_count(u_int ax, u_int cx, u_int *p) +do_cpuid(u_int ax, u_int *p) { - __asm __volatile( - "pushl\t%%ebx\n\t" - "cpuid\n\t" - "movl\t%%ebx,%1\n\t" - "popl\t%%ebx" - : "=a" (p[0]), "=DS" (p[1]), "=c" (p[2]), "=d" (p[3]) - : "0" (ax), "c" (cx)); + cpuid_count(ax, 0, p); } -#endif static __inline void enable_intr(void)