From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757887AbcAKAZn (ORCPT ); Sun, 10 Jan 2016 19:25:43 -0500 Received: from mga03.intel.com ([134.134.136.65]:20685 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757663AbcAKAZj (ORCPT ); Sun, 10 Jan 2016 19:25:39 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,550,1444719600"; d="scan'208";a="27025772" Date: Sun, 10 Jan 2016 16:25:38 -0800 From: "Luck, Tony" To: Andy Lutomirski Cc: Ingo Molnar , Borislav Petkov , Andrew Morton , Andy Lutomirski , Dan Williams , Robert , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , linux-nvdimm , X86 ML , Brian Gerst Subject: Re: [PATCH v8 1/3] x86: Expand exception table to allow new handling options Message-ID: <20160111002538.GA23027@agluck-desk.sc.intel.com> References: <3a259f1cce4a3c309c2f81df715f8c2c9bb80015.1452297867.git.tony.luck@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 08, 2016 at 05:52:54PM -0800, Andy Lutomirski wrote: > I think I preferred the relative function pointer approach. > > Also, I think it would be nicer if the machine check code would invoke > the handler regardless of which handler (or class) is selected. Then > the handlers that don't want to handle #MC can just reject them. > > Also, can you make the handlers return bool instead of int? This patch is currently on top of the 3 patches ... just to check direction. Obviously it needs to be folded into parts 1 & 2. [and my Documentation changes updated] So function pointers and bool returns are here. Only bit that I think Andy won't be "happy" with is ex_has_fault_handler(). But perhaps I've worn him down so he can be resigned to this as a necessary evil until the machine check handler gets a major overhaul. Brian: You started to say you wanted the int fields, but then looked like you took it back at you'd only need a half dozen or so functions to cover all the possible "mov -FAULT,reg" cases that you'd like to optimize. -Tony diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index 0280f5c5d160..f5063b6659eb 100644 --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -42,28 +42,24 @@ #define _ASM_SI __ASM_REG(si) #define _ASM_DI __ASM_REG(di) -#define EXTABLE_CLASS_DEFAULT 0 /* standard uaccess fixup */ -#define EXTABLE_CLASS_FAULT 1 /* provide trap number in %ax */ -#define EXTABLE_CLASS_EX 2 /* uaccess + set uaccess_err */ - /* Exception table entry */ #ifdef __ASSEMBLY__ -# define _ASM_EXTABLE_CLASS(from, to, class) \ +# define _ASM_EXTABLE_HANDLE(from, to, handler) \ .pushsection "__ex_table","a" ; \ .balign 4 ; \ .long (from) - . ; \ .long (to) - . ; \ - .long (class) ; \ + .long (handler) - . ; \ .popsection # define _ASM_EXTABLE(from, to) \ - _ASM_EXTABLE_CLASS(from, to, EXTABLE_CLASS_DEFAULT) + _ASM_EXTABLE_HANDLE(from, to, ex_handler_default) # define _ASM_EXTABLE_FAULT(from, to) \ - _ASM_EXTABLE_CLASS(from, to, EXTABLE_CLASS_FAULT) + _ASM_EXTABLE_HANDLE(from, to, ex_handler_fault) # define _ASM_EXTABLE_EX(from, to) \ - _ASM_EXTABLE_CLASS(from, to, EXTABLE_CLASS_EX) + _ASM_EXTABLE_HANDLE(from, to, ex_handler_ext) # define _ASM_NOKPROBE(entry) \ .pushsection "_kprobe_blacklist","aw" ; \ @@ -96,23 +92,23 @@ .endm #else -# define _EXPAND_EXTABLE_CLASS(x) #x -# define _ASM_EXTABLE_CLASS(from, to, class) \ +# define _EXPAND_EXTABLE_HANDLE(x) #x +# define _ASM_EXTABLE_HANDLE(from, to, handler) \ " .pushsection \"__ex_table\",\"a\"\n" \ " .balign 4\n" \ " .long (" #from ") - .\n" \ " .long (" #to ") - .\n" \ - " .long (" _EXPAND_EXTABLE_CLASS(class) ")\n" \ + " .long (" _EXPAND_EXTABLE_HANDLE(handler) ") - .\n" \ " .popsection\n" # define _ASM_EXTABLE(from, to) \ - _ASM_EXTABLE_CLASS(from, to, EXTABLE_CLASS_DEFAULT) + _ASM_EXTABLE_HANDLE(from, to, ex_handler_default) # define _ASM_EXTABLE_FAULT(from, to) \ - _ASM_EXTABLE_CLASS(from, to, EXTABLE_CLASS_FAULT) + _ASM_EXTABLE_HANDLE(from, to, ex_handler_fault) # define _ASM_EXTABLE_EX(from, to) \ - _ASM_EXTABLE_CLASS(from, to, EXTABLE_CLASS_EX) + _ASM_EXTABLE_HANDLE(from, to, ex_handler_ext) /* For C file, we already have NOKPROBE_SYMBOL macro */ #endif diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 315d1423377c..565b382b2f35 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -104,14 +104,14 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un */ struct exception_table_entry { - int insn, fixup; - u32 handler; + int insn, fixup, handler; }; /* This is not the generic standard exception_table_entry format */ #define ARCH_HAS_SORT_EXTABLE #define ARCH_HAS_SEARCH_EXTABLE extern int fixup_exception(struct pt_regs *regs, int trapnr); +extern bool ex_has_fault_handler(unsigned long ip); extern int early_fixup_exception(unsigned long *ip); /* diff --git a/arch/x86/kernel/cpu/mcheck/mce-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c index e87aa060977c..bca8b3936740 100644 --- a/arch/x86/kernel/cpu/mcheck/mce-severity.c +++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c @@ -185,15 +185,6 @@ static struct severity { #define mc_recoverable(mcg) (((mcg) & (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) == \ (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) -static inline bool mce_in_kernel_recov(unsigned long addr) -{ - const struct exception_table_entry *fixup; - - fixup = search_exception_tables(addr); - - return fixup && fixup->handler == EXTABLE_CLASS_FAULT; -} - /* * If mcgstatus indicated that ip/cs on the stack were * no good, then "m->cs" will be zero and we will have @@ -209,7 +200,7 @@ static int error_context(struct mce *m) { if ((m->cs & 3) == 3) return IN_USER; - if (mc_recoverable(m->mcgstatus) && mce_in_kernel_recov(m->ip)) + if (mc_recoverable(m->mcgstatus) && ex_has_fault_handler(m->ip)) return IN_KERNEL_RECOV; return IN_KERNEL; } diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index cfaf5feace36..e1a996bc84e3 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -3,7 +3,7 @@ #include #include -typedef int (*ex_handler_t)(const struct exception_table_entry *, +typedef bool (*ex_handler_t)(const struct exception_table_entry *, struct pt_regs *, int); static inline unsigned long @@ -16,23 +16,30 @@ ex_fixup_addr(const struct exception_table_entry *x) { return (unsigned long)&x->fixup + x->fixup; } +static inline ex_handler_t +ex_fixup_handler(const struct exception_table_entry *x) +{ + return (ex_handler_t)((unsigned long)&x->handler + x->handler); +} -static int ex_handler_default(const struct exception_table_entry *fixup, +bool ex_handler_default(const struct exception_table_entry *fixup, struct pt_regs *regs, int trapnr) { regs->ip = ex_fixup_addr(fixup); return 1; } +EXPORT_SYMBOL(ex_handler_default); -static int ex_handler_fault(const struct exception_table_entry *fixup, +bool ex_handler_fault(const struct exception_table_entry *fixup, struct pt_regs *regs, int trapnr) { regs->ip = ex_fixup_addr(fixup); regs->ax = trapnr; return 1; } +EXPORT_SYMBOL_GPL(ex_handler_fault); -static int ex_handler_ext(const struct exception_table_entry *fixup, +bool ex_handler_ext(const struct exception_table_entry *fixup, struct pt_regs *regs, int trapnr) { /* Special hack for uaccess_err */ @@ -40,16 +47,25 @@ static int ex_handler_ext(const struct exception_table_entry *fixup, regs->ip = ex_fixup_addr(fixup); return 1; } +EXPORT_SYMBOL(ex_handler_ext); + +bool ex_has_fault_handler(unsigned long ip) +{ + const struct exception_table_entry *e; + ex_handler_t handler; -static ex_handler_t allhandlers[] = { - [EXTABLE_CLASS_DEFAULT] = ex_handler_default, - [EXTABLE_CLASS_FAULT] = ex_handler_fault, - [EXTABLE_CLASS_EX] = ex_handler_ext, -}; + e = search_exception_tables(ip); + if (!e) + return 0; + handler = ex_fixup_handler(e); + + return handler == ex_handler_fault; +} int fixup_exception(struct pt_regs *regs, int trapnr) { const struct exception_table_entry *e; + ex_handler_t handler; #ifdef CONFIG_PNPBIOS if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) { @@ -69,10 +85,8 @@ int fixup_exception(struct pt_regs *regs, int trapnr) if (!e) return 0; - /* if exception table corrupted die here rather than jump into space */ - BUG_ON(e->handler >= ARRAY_SIZE(allhandlers)); - - return allhandlers[e->handler](e, regs, trapnr); + handler = ex_fixup_handler(e); + return handler(e, regs, trapnr); } /* Restricted version used during very early boot */ @@ -80,15 +94,17 @@ int __init early_fixup_exception(unsigned long *ip) { const struct exception_table_entry *e; unsigned long new_ip; + ex_handler_t handler; e = search_exception_tables(*ip); if (!e) return 0; new_ip = ex_fixup_addr(e); + handler = ex_fixup_handler(e); /* special handling not supported during early boot */ - if (e->handler != EXTABLE_CLASS_DEFAULT) + if (handler != ex_handler_default) return 0; *ip = new_ip; @@ -157,7 +173,7 @@ void sort_extable(struct exception_table_entry *start, i += 4; p->fixup += i; i += 4; - /* p->handler doesn't need noodling */ + p->handler += i; i += 4; } @@ -171,7 +187,7 @@ void sort_extable(struct exception_table_entry *start, i += 4; p->fixup -= i; i += 4; - /* p->handler doesn't need unnoodling */ + p->handler -= i; i += 4; } } diff --git a/scripts/sortextable.c b/scripts/sortextable.c index b17b716959a4..7b29fb14f870 100644 --- a/scripts/sortextable.c +++ b/scripts/sortextable.c @@ -219,6 +219,7 @@ static void x86_sort_relative_table(char *extab_image, int image_size) w(r(loc) + i, loc); w(r(loc + 1) + i + 4, loc + 1); + w(r(loc + 2) + i + 8, loc + 2); i += sizeof(uint32_t) * 3; } @@ -231,6 +232,7 @@ static void x86_sort_relative_table(char *extab_image, int image_size) w(r(loc) - i, loc); w(r(loc + 1) - (i + 4), loc + 1); + w(r(loc + 2) - (i + 8), loc + 2); i += sizeof(uint32_t) * 3; }