Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934026Ab0BEWkQ (ORCPT ); Fri, 5 Feb 2010 17:40:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:23055 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934004Ab0BEWkE (ORCPT ); Fri, 5 Feb 2010 17:40:04 -0500 From: Masami Hiramatsu Subject: [PATCH -tip v9 7/9] x86: Add text_poke_smp for SMP cross modifying code To: Frederic Weisbecker , Ingo Molnar , Ananth N Mavinakayanahalli , lkml Cc: Ananth N Mavinakayanahalli , Ingo Molnar , Jim Keniston , Srikar Dronamraju , Christoph Hellwig , Steven Rostedt , Frederic Weisbecker , "H. Peter Anvin" , Anders Kaseorg , Tim Abbott , Andi Kleen , Jason Baron , Mathieu Desnoyers , systemtap , DLE Date: Fri, 05 Feb 2010 17:47:07 -0500 Message-ID: <20100205224707.31959.95017.stgit@dhcp-100-2-132.bos.redhat.com> In-Reply-To: <20100205224613.31959.59651.stgit@dhcp-100-2-132.bos.redhat.com> References: <20100205224613.31959.59651.stgit@dhcp-100-2-132.bos.redhat.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4758 Lines: 143 Add generic text_poke_smp for SMP which uses stop_machine() to synchronize modifying code. This stop_machine() method is officially described at "7.1.3 Handling Self- and Cross-Modifying Code" on the intel's software developer's manual 3A. Since stop_machine() can't protect code against NMI/MCE, this function can not modify those handlers. And also, this function is basically for modifying multibyte-single-instruction. For modifying multibyte-multi-instructions, we need another special trap & detour code. This code originaly comes from immediate values with stop_machine() version. Thanks Mathieu! Signed-off-by: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Ananth N Mavinakayanahalli Cc: Ingo Molnar Cc: Jim Keniston Cc: Srikar Dronamraju Cc: Christoph Hellwig Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Anders Kaseorg Cc: Tim Abbott Cc: Andi Kleen Cc: Jason Baron --- arch/x86/include/asm/alternative.h | 4 ++ arch/x86/kernel/alternative.c | 60 ++++++++++++++++++++++++++++++++++++ 2 files changed, 63 insertions(+), 1 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index f1e253c..b09ec55 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -165,10 +165,12 @@ static inline void apply_paravirt(struct paravirt_patch_site *start, * invalid instruction possible) or if the instructions are changed from a * consistent state to another consistent state atomically. * More care must be taken when modifying code in the SMP case because of - * Intel's errata. + * Intel's errata. text_poke_smp() takes care that errata, but still + * doesn't support NMI/MCE handler code modifying. * On the local CPU you need to be protected again NMI or MCE handlers seeing an * inconsistent instruction while you patch. */ extern void *text_poke(void *addr, const void *opcode, size_t len); +extern void *text_poke_smp(void *addr, const void *opcode, size_t len); #endif /* _ASM_X86_ALTERNATIVE_H */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index e6ea034..635e4f4 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -572,3 +573,62 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len) local_irq_restore(flags); return addr; } + +/* + * Cross-modifying kernel text with stop_machine(). + * This code originally comes from immediate value. + */ +static atomic_t stop_machine_first; +static int wrote_text; + +struct text_poke_params { + void *addr; + const void *opcode; + size_t len; +}; + +static int __kprobes stop_machine_text_poke(void *data) +{ + struct text_poke_params *tpp = data; + + if (atomic_dec_and_test(&stop_machine_first)) { + text_poke(tpp->addr, tpp->opcode, tpp->len); + smp_wmb(); /* Make sure other cpus see that this has run */ + wrote_text = 1; + } else { + while (!wrote_text) + smp_rmb(); + sync_core(); + } + + flush_icache_range((unsigned long)tpp->addr, + (unsigned long)tpp->addr + tpp->len); + return 0; +} + +/** + * text_poke_smp - Update instructions on a live kernel on SMP + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy + * + * Modify multi-byte instruction by using stop_machine() on SMP. This allows + * user to poke/set multi-byte text on SMP. Only non-NMI/MCE code modifying + * should be allowed, since stop_machine() does _not_ protect code against + * NMI and MCE. + * + * Note: Must be called under get_online_cpus() and text_mutex. + */ +void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len) +{ + struct text_poke_params tpp; + + tpp.addr = addr; + tpp.opcode = opcode; + tpp.len = len; + atomic_set(&stop_machine_first, 1); + wrote_text = 0; + stop_machine(stop_machine_text_poke, (void *)&tpp, NULL); + return addr; +} + -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/