Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753585AbcCEOGa (ORCPT ); Sat, 5 Mar 2016 09:06:30 -0500 Received: from torg.zytor.com ([198.137.202.12]:36558 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752105AbcCEOGV (ORCPT ); Sat, 5 Mar 2016 09:06:21 -0500 Date: Sat, 5 Mar 2016 06:03:35 -0800 From: tip-bot for Dave Hansen Message-ID: Cc: hpa@zytor.com, deller@gmx.de, dave@sr71.net, peterz@infradead.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, sfr@canb.auug.org.au, akpm@linux-foundation.org, mingo@kernel.org, tglx@linutronix.de, dave.hansen@linux.intel.com Reply-To: hpa@zytor.com, deller@gmx.de, linux-kernel@vger.kernel.org, peterz@infradead.org, dave@sr71.net, torvalds@linux-foundation.org, sfr@canb.auug.org.au, akpm@linux-foundation.org, mingo@kernel.org, dave.hansen@linux.intel.com, tglx@linutronix.de In-Reply-To: <20160301125451.02C7426D@viggo.jf.intel.com> References: <20160301125451.02C7426D@viggo.jf.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:mm/pkeys] mm/pkeys: Fix siginfo ABI breakage caused by new u64 field Git-Commit-ID: 49cd53bf14aeb471c4a2682300dfc05ef2fd09f2 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3850 Lines: 106 Commit-ID: 49cd53bf14aeb471c4a2682300dfc05ef2fd09f2 Gitweb: http://git.kernel.org/tip/49cd53bf14aeb471c4a2682300dfc05ef2fd09f2 Author: Dave Hansen AuthorDate: Tue, 1 Mar 2016 04:54:51 -0800 Committer: Ingo Molnar CommitDate: Sat, 5 Mar 2016 15:00:06 +0100 mm/pkeys: Fix siginfo ABI breakage caused by new u64 field Stephen Rothwell reported this linux-next build failure: http://lkml.kernel.org/r/20160226164406.065a1ffc@canb.auug.org.au ... caused by the Memory Protection Keys patches from the tip tree triggering a newly introduced build-time sanity check on an ARM build, because they changed the ABI of siginfo in an unexpected way. If u64 has a natural alignment of 8 bytes (which is the case on most mainstream platforms, with the notable exception of x86-32), then the leadup to the _sifields union matters: typedef struct siginfo { int si_signo; int si_errno; int si_code; union { ... } _sifields; } __ARCH_SI_ATTRIBUTES siginfo_t; Note how the first 3 fields give us 12 bytes, so _sifields is not 8 naturally bytes aligned. Before the _pkey field addition the largest element of _sifields (on 32-bit platforms) was 32 bits. With the u64 added, the minimum alignment requirement increased to 8 bytes on those (rare) 32-bit platforms. Thus GCC padded the space after si_code with 4 extra bytes, and shifted all _sifields offsets by 4 bytes - breaking the ABI of all of those remaining fields. On 64-bit platforms this problem was hidden due to _sifields already having numerous fields with natural 8 bytes alignment (pointers). To fix this, we replace the u64 with an '__u32'. The __u32 does not increase the minimum alignment requirement of the union, and it is also large enough to store the 16-bit pkey we have today on x86. Reported-by: Stehen Rothwell Signed-off-by: Dave Hansen Acked-by: Stehen Rothwell Cc: Andrew Morton Cc: Dave Hansen Cc: Helge Deller Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-next@vger.kernel.org Fixes: cd0ea35ff551 ("signals, pkeys: Notify userspace about protection key faults") Link: http://lkml.kernel.org/r/20160301125451.02C7426D@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/ia64/include/uapi/asm/siginfo.h | 2 +- arch/mips/include/uapi/asm/siginfo.h | 2 +- include/uapi/asm-generic/siginfo.h | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/ia64/include/uapi/asm/siginfo.h b/arch/ia64/include/uapi/asm/siginfo.h index 0151cfa..f72bf01 100644 --- a/arch/ia64/include/uapi/asm/siginfo.h +++ b/arch/ia64/include/uapi/asm/siginfo.h @@ -70,7 +70,7 @@ typedef struct siginfo { void __user *_upper; } _addr_bnd; /* used when si_code=SEGV_PKUERR */ - u64 _pkey; + __u32 _pkey; }; } _sigfault; diff --git a/arch/mips/include/uapi/asm/siginfo.h b/arch/mips/include/uapi/asm/siginfo.h index 6f4edf0..cc49dc2 100644 --- a/arch/mips/include/uapi/asm/siginfo.h +++ b/arch/mips/include/uapi/asm/siginfo.h @@ -93,7 +93,7 @@ typedef struct siginfo { void __user *_upper; } _addr_bnd; /* used when si_code=SEGV_PKUERR */ - u64 _pkey; + __u32 _pkey; }; } _sigfault; diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index 90384d5..1abaf62 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -98,7 +98,7 @@ typedef struct siginfo { void __user *_upper; } _addr_bnd; /* used when si_code=SEGV_PKUERR */ - u64 _pkey; + __u32 _pkey; }; } _sigfault;