(2014/08/09 11:12), Wang Nan wrote: > 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;'. > > Signed-off-by: Wang Nan <[email protected]>
Thank you for the great work! :) This looks enough simple and fine. Acked-by: Masami Hiramatsu <[email protected]> > Cc: Masami Hiramatsu <[email protected]> > Cc: Jon Medhurst (Tixy) <[email protected]> > Cc: Russell King - ARM Linux <[email protected]> > --- > arch/arm/Kconfig | 1 + > arch/arm/include/asm/kprobes.h | 26 +++++ > arch/arm/kernel/Makefile | 3 +- > arch/arm/kernel/kprobes-opt.c | 254 > +++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 283 insertions(+), 1 deletion(-) > create mode 100644 arch/arm/kernel/kprobes-opt.c > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 290f02ee..2106918 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..a05297f 100644 > --- a/arch/arm/include/asm/kprobes.h > +++ b/arch/arm/include/asm/kprobes.h > @@ -51,5 +51,31 @@ 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. > + */ > +}; > > #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..d38f5ab > --- /dev/null > +++ b/arch/arm/kernel/kprobes-opt.c > @@ -0,0 +1,254 @@ > +/* > + * 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 <linux/kprobes.h> > +#include <linux/jump_label.h> > +#include <asm/kprobes.h> > +#include <asm/cacheflush.h> > +/* 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: nop\n" > + ".global optprobe_template_call\n" > + "optprobe_template_call:\n" > + "2: nop\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 1; > +} > + > +/* > + * 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(unsigned long paddr) > +{ > + 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((unsigned long)op->kp.addr)) > + 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); > + 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 = (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); > +} > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
