Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753883AbbFAQd0 (ORCPT ); Mon, 1 Jun 2015 12:33:26 -0400 Received: from collab.rosalab.ru ([195.19.76.181]:38410 "EHLO collab.rosalab.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753854AbbFAQdL (ORCPT ); Mon, 1 Jun 2015 12:33:11 -0400 From: Eugene Shatokhin To: Masami Hiramatsu , Ingo Molnar Cc: Andy Lutomirski , Ingo Molnar , LKML , Eugene Shatokhin Subject: [PATCH 2/2] kprobes/x86: Use 16 bytes for each instruction slot again Date: Mon, 1 Jun 2015 19:32:11 +0300 Message-Id: <1433176331-479-3-git-send-email-eugene.shatokhin@rosalab.ru> X-Mailer: git-send-email 2.3.2 In-Reply-To: <1433176331-479-1-git-send-email-eugene.shatokhin@rosalab.ru> References: <1433176331-479-1-git-send-email-eugene.shatokhin@rosalab.ru> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3160 Lines: 90 Commit 91e5ed49fca0 ("x86/asm/decoder: Fix and enforce max instruction size in the insn decoder") has changed MAX_INSN_SIZE from 16 to 15 bytes on x86. As a side effect, the slots Kprobes use to store the instructions became 1 byte shorter. This is unfortunate because, for example, the Kprobes' "boost" feature can not be used now for the instructions of length 11, like a quite common kind of MOV: * movq $0xffffffffffffffff,-0x3fe8(%rax) (48 c7 80 18 c0 ff ff ff ff ff ff) * movq $0x0,0x88(%rdi) (48 c7 87 88 00 00 00 00 00 00 00) and so on. This patch makes the insn slots 16 bytes long, like they were before while keeping MAX_INSN_SIZE intact. Other tools may benefit from this change as well. Signed-off-by: Eugene Shatokhin --- arch/x86/include/asm/kprobes.h | 1 + arch/x86/kernel/kprobes/core.c | 2 +- kernel/kprobes.c | 8 ++++++-- 3 files changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h index 4421b5d..f3f0b4e 100644 --- a/arch/x86/include/asm/kprobes.h +++ b/arch/x86/include/asm/kprobes.h @@ -27,6 +27,7 @@ #include #define __ARCH_WANT_KPROBES_INSN_SLOT +#define KPROBE_INSN_SLOT_SIZE 16 struct pt_regs; struct kprobe; diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 0a42b76..1067f90 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -881,7 +881,7 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs, if (p->ainsn.boostable == 0) { if ((regs->ip > copy_ip) && - (regs->ip - copy_ip) + 5 <= MAX_INSN_SIZE) { + (regs->ip - copy_ip) + 5 <= KPROBE_INSN_SLOT_SIZE) { /* * These instructions can be executed directly if it * jumps back to correct address. diff --git a/kernel/kprobes.c b/kernel/kprobes.c index c90e417..1dc074d 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -57,7 +57,6 @@ #define KPROBE_HASH_BITS 6 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) - /* * Some oddball architectures like 64bit powerpc have function descriptors * so this must be overridable. @@ -90,6 +89,11 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash) static LIST_HEAD(kprobe_blacklist); #ifdef __ARCH_WANT_KPROBES_INSN_SLOT + +#ifndef KPROBE_INSN_SLOT_SIZE +#define KPROBE_INSN_SLOT_SIZE MAX_INSN_SIZE +#endif + /* * kprobe->ainsn.insn points to the copy of the instruction to be * single-stepped. x86_64, POWER4 and above have no-exec support and @@ -135,7 +139,7 @@ struct kprobe_insn_cache kprobe_insn_slots = { .alloc = alloc_insn_page, .free = free_insn_page, .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages), - .insn_size = MAX_INSN_SIZE, + .insn_size = KPROBE_INSN_SLOT_SIZE, .nr_garbage = 0, }; static int collect_garbage_slots(struct kprobe_insn_cache *c); -- 2.3.2 -- 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/