From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753852AbcAEAMP (ORCPT ); Mon, 4 Jan 2016 19:12:15 -0500 Received: from mga02.intel.com ([134.134.136.20]:39798 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753332AbcAEAMN (ORCPT ); Mon, 4 Jan 2016 19:12:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,522,1444719600"; d="scan'208";a="886312407" Message-Id: From: Tony Luck Date: Mon, 4 Jan 2016 16:05:51 -0800 Subject: [PATCH v7 0/3] Machine check recovery when kernel accesses poison To: Ingo Molnar Cc: Borislav Petkov , Andrew Morton , Andy Lutomirski , Dan Williams , , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This series is initially targeted at the folks doing filesystems on top of NVDIMMs. They really want to be able to return -EIO when there is a h/w error (just like spinning rust, and SSD does). I plan to use the same infrastructure to write a machine check aware "copy_from_user()" that will SIGBUS the calling application when a syscall touches poison in user space (just like we do when the application touches the poison itself). Changes V6-V7: Boris: Why add/subtract 0x20000000? Added better comment provided by Andy Boris: Churn. Part2 changes things only introduced in part1. Merged parts 1&2 into one patch. Ingo: Missing my sign off on part1. Added. Changes V5-V6 Andy: Provoked massive re-write by providing what is now part1 of this patch series. This frees up two bits in the exception table fixup field that can be used to tag exception table entries as different "classes". This means we don't need my separate exception table fro machine checks. Also avoids duplicating fixup actions for #PF and #MC cases that were in version 5. Andy: Use C99 array initializers to tie the various class fixup functions back to the defintions of each class. Also give the functions meanningful names (not fixup_class0() etc.). Boris: Cleaned up my lousy assembly code removing many spurious 'l' modifiers on instructions. Boris: Provided some helper functions for the machine check severity calculation that make the code more readable. Boris: Have __mcsafe_copy() return a structure with the 'remaining bytes' in a separate field from the fault indicator. Boris had suggested Linux -EFAULT/-EINVAL ... but I thought it made more sense to return the exception number (X86_TRAP_MC, etc.) This finally kills off BIT(63) which has been controversial throughout all the early versions of this patch series. Changes V4-V5 Tony: Extended __mcsafe_copy() to have fixup entries for both machine check and page fault. Changes V3-V4: Andy: Simplify fixup_mcexception() by dropping used-once local variable Andy: "Reviewed-by" tag added to part1 Boris: Moved new functions to memcpy_64.S and declaration to asm/string_64.h Boris: Changed name s/mcsafe_memcpy/__mcsafe_copy/ to make it clear that this is an internal function and that return value doesn't follow memcpy() semantics. Boris: "Reviewed-by" tag added to parts 1&2 Changes V2-V3: Andy: Don't hack "regs->ax = BIT(63) | addr;" in the machine check handler. Now have better fixup code that computes the number of remaining bytes (just like page-fault fixup). Andy: #define for BIT(63). Done, plus couple of extra macros using it. Boris: Don't clutter up generic code (like mm/extable.c) with this. I moved everything under arch/x86 (the asm-generic change is a more generic #define). Boris: Dependencies for CONFIG_MCE_KERNEL_RECOVERY are too generic. I made it a real menu item with default "n". Dan Williams will use "select MCE_KERNEL_RECOVERY" from his persistent filesystem code. Boris: Simplify conditionals in mce.c by moving tolerant/kill_it checks earlier, with a skip to end if they aren't set. Boris: Miscellaneous grammar/punctuation. Fixed. Boris: Don't leak spurious __start_mcextable symbols into kernels that didn't configure MCE_KERNEL_RECOVERY. Done. Tony: New code doesn't belong in user_copy_64.S/uaccess*.h. Moved to new .S/.h files Elliott:Cacheing behavior non-optimal. Could use movntdqa, vmovntdqa or vmovntdqa on source addresses. I didn't fix this yet. Think of the current mcsafe_memcpy() as the first of several functions. This one is useful for small copies (meta-data) where the overhead of saving SSE/AVX state isn't justified. Changes V1->V2: 0-day: Reported build errors and warnings on 32-bit systems. Fixed 0-day: Reported bloat to tinyconfig. Fixed Boris: Suggestions to use extra macros to reduce code duplication in _ASM_*EXTABLE. Done Boris: Re-write "tolerant==3" check to reduce indentation level. See below. Andy: Check IP is valid before searching kernel exception tables. Done. Andy: Explain use of BIT(63) on return value from mcsafe_memcpy(). Done (added decode macros). Andy: Untangle mess of code in tail of do_machine_check() to make it clear what is going on (e.g. that we only enter the ist_begin_non_atomic() if we were called from user code, not from kernel!). Done. Tony Luck (3): x86: Add classes to exception tables x86, mce: Check for faults tagged in EXTABLE_CLASS_FAULT exception table entries x86, mce: Add __mcsafe_copy() arch/x86/Kconfig | 10 +++ arch/x86/include/asm/asm.h | 102 ++++++++++++++++------ arch/x86/include/asm/string_64.h | 10 +++ arch/x86/include/asm/uaccess.h | 17 +++- arch/x86/kernel/cpu/mcheck/mce-severity.c | 32 ++++++- arch/x86/kernel/cpu/mcheck/mce.c | 71 ++++++++-------- arch/x86/kernel/kprobes/core.c | 2 +- arch/x86/kernel/traps.c | 6 +- arch/x86/kernel/x8664_ksyms_64.c | 4 + arch/x86/lib/memcpy_64.S | 136 ++++++++++++++++++++++++++++++ arch/x86/mm/extable.c | 66 ++++++++++----- arch/x86/mm/fault.c | 2 +- 12 files changed, 369 insertions(+), 89 deletions(-) -- 2.1.4