From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934599AbaH0NPy (ORCPT ); Wed, 27 Aug 2014 09:15:54 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:63434 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934491AbaH0NPt (ORCPT ); Wed, 27 Aug 2014 09:15:49 -0400 From: Wang Nan To: Russell King , "David A. Long" , Jon Medhurst , Taras Kondratiuk , Ben Dooks , "Ananth N Mavinakayanahalli" , Anil S Keshavamurthy , "David S. Miller" , Masami Hiramatsu , Will Deacon CC: Wang Nan , Pei Feiyue , , Subject: [PATCH v5 3/3] kprobes: arm: enable OPTPROBES for ARM 32 Date: Wed, 27 Aug 2014 21:02:32 +0800 Message-ID: <1409144552-12751-4-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.4 In-Reply-To: <1409144552-12751-1-git-send-email-wangnan0@huawei.com> References: <1409144552-12751-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.197.247] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020205.53FDD9B1.01A0,ss=1,re=0.000,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2011-05-27 18:58:46 X-Mirapoint-Loop-Id: da61be36005aa4deae7e32b9f3f76ede Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch introduce kprobeopt for ARM 32. Limitations: - Currently only kernel compiled with ARM ISA is supported. - Offset between probe point and optinsn slot must not larger than 32MiB. Masami Hiramatsu suggests replacing 2 words, it will make things complex. Futher patch can make such optimization. Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because ARM instruction is always 4 bytes aligned and 4 bytes long. This patch replace probed instruction by a 'b', branch to trampoline code and then calls optimized_callback(). optimized_callback() calls opt_pre_handler() to execute kprobe handler. It also emulate/simulate replaced instruction. When unregistering kprobe, the deferred manner of unoptimizer may leave branch instruction before optimizer is called. Different from x86_64, which only copy the probed insn after optprobe_template_end and reexecute them, this patch call singlestep to emulate/simulate the insn directly. Futher patch can optimize this behavior. v1 -> v2: - Improvement: if replaced instruction is conditional, generate a conditional branch instruction for it; - Introduces RELATIVEJUMP_OPCODES due to ARM kprobe_opcode_t is 4 bytes; - Removes size field in struct arch_optimized_insn; - Use arm_gen_branch() to generate branch instruction; - Remove all recover logic: ARM doesn't use tail buffer, no need recover replaced instructions like x86; - Remove incorrect CONFIG_THUMB checking; - can_optimize() always returns true if address is well aligned; - Improve optimized_callback: using opt_pre_handler(); - Bugfix: correct range checking code and improve comments; - Fix commit message. v2 -> v3: - Rename RELATIVEJUMP_OPCODES to MAX_COPIED_INSNS; - Remove unneeded checking: arch_check_optimized_kprobe(), can_optimize(); - Add missing flush_icache_range() in arch_prepare_optimized_kprobe(); - Remove unneeded 'return;'. v3 -> v4: - Use __mem_to_opcode_arm() to translate copied_insn to ensure it works in big endian kernel; - Replace 'nop' placeholder in trampoline code template with '.long 0' to avoid confusion: reader may regard 'nop' as an instruction, but it is value in fact. v4 -> v5: - Don't optimize stack store operations. - Introduce prepared field to arch_optimized_insn to indicate whether it is prepared. Similar to size field with x86. See v1 -> v2. Signed-off-by: Wang Nan Acked-by: Masami Hiramatsu Cc: Russell King Cc: "David A. Long" Cc: Jon Medhurst Cc: Taras Kondratiuk Cc: Ben Dooks Cc: Ananth N Mavinakayanahalli Cc: Anil S Keshavamurthy Cc: "David S. Miller" Cc: Will Deacon --- arch/arm/Kconfig | 1 + arch/arm/include/asm/kprobes.h | 28 +++++ arch/arm/kernel/Makefile | 3 +- arch/arm/kernel/kprobes-opt.c | 259 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 290 insertions(+), 1 deletion(-) create mode 100644 arch/arm/kernel/kprobes-opt.c diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index c49a775..7106fba 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -57,6 +57,7 @@ config ARM select HAVE_MEMBLOCK select HAVE_MOD_ARCH_SPECIFIC if ARM_UNWIND select HAVE_OPROFILE if (HAVE_PERF_EVENTS) + select HAVE_OPTPROBES if (!THUMB2_KERNEL) select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h index 49fa0df..88a0345 100644 --- a/arch/arm/include/asm/kprobes.h +++ b/arch/arm/include/asm/kprobes.h @@ -51,5 +51,33 @@ int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr); int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data); +/* optinsn template addresses */ +extern __visible kprobe_opcode_t optprobe_template_entry; +extern __visible kprobe_opcode_t optprobe_template_val; +extern __visible kprobe_opcode_t optprobe_template_call; +extern __visible kprobe_opcode_t optprobe_template_end; + +#define MAX_OPTIMIZED_LENGTH (4) +#define MAX_OPTINSN_SIZE \ + (((unsigned long)&optprobe_template_end - \ + (unsigned long)&optprobe_template_entry)) +#define RELATIVEJUMP_SIZE (4) + +struct arch_optimized_insn { + /* + * copy of the original instructions. + * Different from x86, ARM kprobe_opcode_t is u32. + */ +#define MAX_COPIED_INSN ((RELATIVEJUMP_SIZE) / sizeof(kprobe_opcode_t)) + kprobe_opcode_t copied_insn[MAX_COPIED_INSN]; + /* detour code buffer */ + kprobe_opcode_t *insn; + /* + * we always copies one instruction on arm32, + * size always be 4, so no size field. + */ + /* indicate whether this optimization is prepared */ + bool prepared; +}; #endif /* _ARM_KPROBES_H */ diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 38ddd9f..6a38ec1 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -52,11 +52,12 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o obj-$(CONFIG_UPROBES) += probes.o probes-arm.o uprobes.o uprobes-arm.o -obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o +obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o insn.o ifdef CONFIG_THUMB2_KERNEL obj-$(CONFIG_KPROBES) += kprobes-thumb.o probes-thumb.o else obj-$(CONFIG_KPROBES) += kprobes-arm.o probes-arm.o +obj-$(CONFIG_OPTPROBES) += kprobes-opt.o endif obj-$(CONFIG_ARM_KPROBES_TEST) += test-kprobes.o test-kprobes-objs := kprobes-test.o diff --git a/arch/arm/kernel/kprobes-opt.c b/arch/arm/kernel/kprobes-opt.c new file mode 100644 index 0000000..8407858 --- /dev/null +++ b/arch/arm/kernel/kprobes-opt.c @@ -0,0 +1,259 @@ +/* + * Kernel Probes Jump Optimization (Optprobes) + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright (C) IBM Corporation, 2002, 2004 + * Copyright (C) Hitachi Ltd., 2012 + * Copyright (C) Huawei Inc., 2014 + */ + +#include +#include +#include +#include +/* for arm_gen_branch */ +#include "insn.h" +/* for patch_text */ +#include "patch.h" + +asm ( + ".global optprobe_template_entry\n" + "optprobe_template_entry:\n" + " sub sp, sp, #80\n" + " stmia sp, {r0 - r14} \n" + " add r3, sp, #80\n" + " str r3, [sp, #52]\n" + " mrs r4, cpsr\n" + " str r4, [sp, #64]\n" + " mov r1, sp\n" + " ldr r0, 1f\n" + " ldr r2, 2f\n" + " blx r2\n" + " ldr r1, [sp, #64]\n" + " msr cpsr_fs, r1\n" + " ldmia sp, {r0 - r15}\n" + ".global optprobe_template_val\n" + "optprobe_template_val:\n" + "1: .long 0\n" + ".global optprobe_template_call\n" + "optprobe_template_call:\n" + "2: .long 0\n" + ".global optprobe_template_end\n" + "optprobe_template_end:\n"); + +#define TMPL_VAL_IDX \ + ((long)&optprobe_template_val - (long)&optprobe_template_entry) +#define TMPL_CALL_IDX \ + ((long)&optprobe_template_call - (long)&optprobe_template_entry) +#define TMPL_END_IDX \ + ((long)&optprobe_template_end - (long)&optprobe_template_entry) + +/* + * ARM can always optimize an instruction when using ARM ISA. + */ +int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) +{ + return optinsn->prepared; +} + +/* + * In ARM ISA, kprobe opt always replace one instruction (4 bytes + * aligned and 4 bytes long). It is impossiable to encounter another + * kprobe in the address range. So always return 0. + */ +int arch_check_optimized_kprobe(struct optimized_kprobe *op) +{ + return 0; +} + +/* Caller must ensure addr & 3 == 0 */ +static int can_optimize(struct optimized_kprobe *op) +{ + if (op->kp.ainsn.is_stack_operation) + return 0; + return 1; +} + +/* Free optimized instruction slot */ +static void +__arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty) +{ + if (op->optinsn.insn) { + free_optinsn_slot(op->optinsn.insn, dirty); + op->optinsn.insn = NULL; + } +} + +extern void kprobe_handler(struct pt_regs *regs); + +static void +optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) +{ + unsigned long flags; + struct kprobe *p = &op->kp; + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + /* Save skipped registers */ + regs->ARM_pc = (unsigned long)op->kp.addr; + regs->ARM_ORIG_r0 = ~0UL; + + local_irq_save(flags); + + if (kprobe_running()) { + kprobes_inc_nmissed_count(&op->kp); + } else { + __this_cpu_write(current_kprobe, &op->kp); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + opt_pre_handler(&op->kp, regs); + __this_cpu_write(current_kprobe, NULL); + } + + /* In each case, we must singlestep the replaced instruction. */ + op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); + + local_irq_restore(flags); +} + +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op) +{ + u8 *buf; + unsigned long rel_chk; + unsigned long val; + + if (!can_optimize(op)) + return -EILSEQ; + + op->optinsn.insn = get_optinsn_slot(); + if (!op->optinsn.insn) + return -ENOMEM; + + /* + * Verify if the address gap is in 32MiB range, because this uses + * a relative jump. + * + * kprobe opt use a 'b' instruction to branch to optinsn.insn. + * According to ARM manual, branch instruction is: + * + * 31 28 27 24 23 0 + * +------+---+---+---+---+----------------+ + * | cond | 1 | 0 | 1 | 0 | imm24 | + * +------+---+---+---+---+----------------+ + * + * imm24 is a signed 24 bits integer. The real branch offset is computed + * by: imm32 = SignExtend(imm24:'00', 32); + * + * So the maximum forward branch should be: + * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc + * The maximum backword branch should be: + * (0xff800000 << 2) = 0xfe000000 = -0x2000000 + * + * We can simply check (rel & 0xfe000003): + * if rel is positive, (rel & 0xfe000000) shoule be 0 + * if rel is negitive, (rel & 0xfe000000) should be 0xfe000000 + * the last '3' is used for alignment checking. + */ + rel_chk = (unsigned long)((long)op->optinsn.insn - + (long)op->kp.addr + 8) & 0xfe000003; + + if ((rel_chk != 0) && (rel_chk != 0xfe000000)) { + __arch_remove_optimized_kprobe(op, 0); + return -ERANGE; + } + + buf = (u8 *)op->optinsn.insn; + + /* Copy arch-dep-instance from template */ + memcpy(buf, &optprobe_template_entry, TMPL_END_IDX); + + /* Set probe information */ + val = (unsigned long)op; + memcpy(buf + TMPL_VAL_IDX, &val, sizeof(val)); + + /* Set probe function call */ + val = (unsigned long)optimized_callback; + memcpy(buf + TMPL_CALL_IDX, &val, sizeof(val)); + + flush_icache_range((unsigned long)buf, + (unsigned long)buf + TMPL_END_IDX); + + op->optinsn.prepared = true; + return 0; +} + +void arch_optimize_kprobes(struct list_head *oplist) +{ + struct optimized_kprobe *op, *tmp; + + list_for_each_entry_safe(op, tmp, oplist, list) { + unsigned long insn; + WARN_ON(kprobe_disabled(&op->kp)); + + /* + * Backup instructions which will be replaced + * by jump address + */ + memcpy(op->optinsn.copied_insn, op->kp.addr, + RELATIVEJUMP_SIZE); + + insn = arm_gen_branch((unsigned long)op->kp.addr, + (unsigned long)op->optinsn.insn); + BUG_ON(insn == 0); + + /* + * Make it a conditional branch if replaced insn + * is consitional + */ + insn = (__mem_to_opcode_arm( + op->optinsn.copied_insn[0]) & 0xf0000000) | + (insn & 0x0fffffff); + + patch_text(op->kp.addr, insn); + + list_del_init(&op->list); + } +} + +void arch_unoptimize_kprobe(struct optimized_kprobe *op) +{ + arch_arm_kprobe(&op->kp); +} + +/* + * Recover original instructions and breakpoints from relative jumps. + * Caller must call with locking kprobe_mutex. + */ +void arch_unoptimize_kprobes(struct list_head *oplist, + struct list_head *done_list) +{ + struct optimized_kprobe *op, *tmp; + + list_for_each_entry_safe(op, tmp, oplist, list) { + arch_unoptimize_kprobe(op); + list_move(&op->list, done_list); + } +} + +int arch_within_optimized_kprobe(struct optimized_kprobe *op, + unsigned long addr) +{ + return ((unsigned long)op->kp.addr <= addr && + (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr); +} + +void arch_remove_optimized_kprobe(struct optimized_kprobe *op) +{ + __arch_remove_optimized_kprobe(op, 1); +} -- 1.8.4