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452 lines
12 KiB
452 lines
12 KiB
/*
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* Kernel Probes Jump Optimization (Optprobes)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2002, 2004
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* Copyright (C) Hitachi Ltd., 2012
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*/
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/hardirq.h>
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#include <linux/preempt.h>
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#include <linux/module.h>
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#include <linux/kdebug.h>
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#include <linux/kallsyms.h>
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#include <linux/ftrace.h>
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#include <asm/cacheflush.h>
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#include <asm/desc.h>
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#include <asm/pgtable.h>
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#include <asm/uaccess.h>
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#include <asm/alternative.h>
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#include <asm/insn.h>
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#include <asm/debugreg.h>
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#include "common.h"
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unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
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{
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struct optimized_kprobe *op;
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struct kprobe *kp;
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long offs;
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int i;
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for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
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kp = get_kprobe((void *)addr - i);
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/* This function only handles jump-optimized kprobe */
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if (kp && kprobe_optimized(kp)) {
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op = container_of(kp, struct optimized_kprobe, kp);
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/* If op->list is not empty, op is under optimizing */
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if (list_empty(&op->list))
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goto found;
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}
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}
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return addr;
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found:
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/*
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* If the kprobe can be optimized, original bytes which can be
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* overwritten by jump destination address. In this case, original
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* bytes must be recovered from op->optinsn.copied_insn buffer.
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*/
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memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
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if (addr == (unsigned long)kp->addr) {
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buf[0] = kp->opcode;
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memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
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} else {
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offs = addr - (unsigned long)kp->addr - 1;
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memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
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}
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return (unsigned long)buf;
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}
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/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
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static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
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{
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#ifdef CONFIG_X86_64
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*addr++ = 0x48;
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*addr++ = 0xbf;
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#else
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*addr++ = 0xb8;
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#endif
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*(unsigned long *)addr = val;
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}
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asm (
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".global optprobe_template_entry\n"
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"optprobe_template_entry:\n"
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#ifdef CONFIG_X86_64
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/* We don't bother saving the ss register */
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" pushq %rsp\n"
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" pushfq\n"
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SAVE_REGS_STRING
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" movq %rsp, %rsi\n"
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".global optprobe_template_val\n"
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"optprobe_template_val:\n"
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ASM_NOP5
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ASM_NOP5
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".global optprobe_template_call\n"
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"optprobe_template_call:\n"
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ASM_NOP5
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/* Move flags to rsp */
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" movq 144(%rsp), %rdx\n"
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" movq %rdx, 152(%rsp)\n"
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RESTORE_REGS_STRING
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/* Skip flags entry */
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" addq $8, %rsp\n"
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" popfq\n"
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#else /* CONFIG_X86_32 */
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" pushf\n"
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SAVE_REGS_STRING
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" movl %esp, %edx\n"
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".global optprobe_template_val\n"
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"optprobe_template_val:\n"
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ASM_NOP5
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".global optprobe_template_call\n"
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"optprobe_template_call:\n"
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ASM_NOP5
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RESTORE_REGS_STRING
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" addl $4, %esp\n" /* skip cs */
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" popf\n"
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#endif
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".global optprobe_template_end\n"
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"optprobe_template_end:\n");
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#define TMPL_MOVE_IDX \
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((long)&optprobe_template_val - (long)&optprobe_template_entry)
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#define TMPL_CALL_IDX \
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((long)&optprobe_template_call - (long)&optprobe_template_entry)
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#define TMPL_END_IDX \
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((long)&optprobe_template_end - (long)&optprobe_template_entry)
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#define INT3_SIZE sizeof(kprobe_opcode_t)
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/* Optimized kprobe call back function: called from optinsn */
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static void
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optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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unsigned long flags;
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/* This is possible if op is under delayed unoptimizing */
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if (kprobe_disabled(&op->kp))
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return;
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local_irq_save(flags);
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if (kprobe_running()) {
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kprobes_inc_nmissed_count(&op->kp);
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} else {
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/* Save skipped registers */
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#ifdef CONFIG_X86_64
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regs->cs = __KERNEL_CS;
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#else
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regs->cs = __KERNEL_CS | get_kernel_rpl();
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regs->gs = 0;
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#endif
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regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
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regs->orig_ax = ~0UL;
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__this_cpu_write(current_kprobe, &op->kp);
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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opt_pre_handler(&op->kp, regs);
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__this_cpu_write(current_kprobe, NULL);
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}
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local_irq_restore(flags);
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}
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NOKPROBE_SYMBOL(optimized_callback);
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static int copy_optimized_instructions(u8 *dest, u8 *src)
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{
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int len = 0, ret;
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while (len < RELATIVEJUMP_SIZE) {
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ret = __copy_instruction(dest + len, src + len);
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if (!ret || !can_boost(dest + len))
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return -EINVAL;
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len += ret;
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}
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/* Check whether the address range is reserved */
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if (ftrace_text_reserved(src, src + len - 1) ||
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alternatives_text_reserved(src, src + len - 1) ||
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jump_label_text_reserved(src, src + len - 1))
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return -EBUSY;
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return len;
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}
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/* Check whether insn is indirect jump */
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static int insn_is_indirect_jump(struct insn *insn)
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{
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return ((insn->opcode.bytes[0] == 0xff &&
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(X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
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insn->opcode.bytes[0] == 0xea); /* Segment based jump */
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}
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/* Check whether insn jumps into specified address range */
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static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
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{
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unsigned long target = 0;
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switch (insn->opcode.bytes[0]) {
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case 0xe0: /* loopne */
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case 0xe1: /* loope */
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case 0xe2: /* loop */
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case 0xe3: /* jcxz */
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case 0xe9: /* near relative jump */
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case 0xeb: /* short relative jump */
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break;
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case 0x0f:
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if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
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break;
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return 0;
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default:
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if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
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break;
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return 0;
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}
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target = (unsigned long)insn->next_byte + insn->immediate.value;
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return (start <= target && target <= start + len);
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}
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/* Decode whole function to ensure any instructions don't jump into target */
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static int can_optimize(unsigned long paddr)
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{
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unsigned long addr, size = 0, offset = 0;
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struct insn insn;
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kprobe_opcode_t buf[MAX_INSN_SIZE];
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/* Lookup symbol including addr */
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if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
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return 0;
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/*
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* Do not optimize in the entry code due to the unstable
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* stack handling.
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*/
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if ((paddr >= (unsigned long)__entry_text_start) &&
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(paddr < (unsigned long)__entry_text_end))
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return 0;
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/* Check there is enough space for a relative jump. */
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if (size - offset < RELATIVEJUMP_SIZE)
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return 0;
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/* Decode instructions */
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addr = paddr - offset;
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while (addr < paddr - offset + size) { /* Decode until function end */
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unsigned long recovered_insn;
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if (search_exception_tables(addr))
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/*
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* Since some fixup code will jumps into this function,
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* we can't optimize kprobe in this function.
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*/
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return 0;
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recovered_insn = recover_probed_instruction(buf, addr);
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if (!recovered_insn)
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return 0;
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kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
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insn_get_length(&insn);
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/* Another subsystem puts a breakpoint */
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if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
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return 0;
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/* Recover address */
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insn.kaddr = (void *)addr;
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insn.next_byte = (void *)(addr + insn.length);
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/* Check any instructions don't jump into target */
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if (insn_is_indirect_jump(&insn) ||
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insn_jump_into_range(&insn, paddr + INT3_SIZE,
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RELATIVE_ADDR_SIZE))
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return 0;
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addr += insn.length;
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}
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return 1;
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}
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/* Check optimized_kprobe can actually be optimized. */
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int arch_check_optimized_kprobe(struct optimized_kprobe *op)
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{
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int i;
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struct kprobe *p;
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for (i = 1; i < op->optinsn.size; i++) {
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p = get_kprobe(op->kp.addr + i);
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if (p && !kprobe_disabled(p))
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return -EEXIST;
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}
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return 0;
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}
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/* Check the addr is within the optimized instructions. */
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int arch_within_optimized_kprobe(struct optimized_kprobe *op,
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unsigned long addr)
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{
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return ((unsigned long)op->kp.addr <= addr &&
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(unsigned long)op->kp.addr + op->optinsn.size > addr);
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}
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/* Free optimized instruction slot */
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static
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void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
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{
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if (op->optinsn.insn) {
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free_optinsn_slot(op->optinsn.insn, dirty);
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op->optinsn.insn = NULL;
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op->optinsn.size = 0;
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}
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}
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void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
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{
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__arch_remove_optimized_kprobe(op, 1);
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}
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/*
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* Copy replacing target instructions
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* Target instructions MUST be relocatable (checked inside)
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* This is called when new aggr(opt)probe is allocated or reused.
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*/
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int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
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struct kprobe *__unused)
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{
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u8 *buf;
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int ret;
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long rel;
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if (!can_optimize((unsigned long)op->kp.addr))
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return -EILSEQ;
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op->optinsn.insn = get_optinsn_slot();
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if (!op->optinsn.insn)
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return -ENOMEM;
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/*
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* Verify if the address gap is in 2GB range, because this uses
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* a relative jump.
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*/
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rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
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if (abs(rel) > 0x7fffffff) {
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__arch_remove_optimized_kprobe(op, 0);
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return -ERANGE;
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}
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buf = (u8 *)op->optinsn.insn;
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/* Copy instructions into the out-of-line buffer */
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ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
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if (ret < 0) {
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__arch_remove_optimized_kprobe(op, 0);
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return ret;
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}
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op->optinsn.size = ret;
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/* Copy arch-dep-instance from template */
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memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
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/* Set probe information */
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synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
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/* Set probe function call */
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synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
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/* Set returning jmp instruction at the tail of out-of-line buffer */
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synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
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(u8 *)op->kp.addr + op->optinsn.size);
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flush_icache_range((unsigned long) buf,
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(unsigned long) buf + TMPL_END_IDX +
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op->optinsn.size + RELATIVEJUMP_SIZE);
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return 0;
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}
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/*
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* Replace breakpoints (int3) with relative jumps.
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* Caller must call with locking kprobe_mutex and text_mutex.
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*/
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void arch_optimize_kprobes(struct list_head *oplist)
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{
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struct optimized_kprobe *op, *tmp;
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u8 insn_buf[RELATIVEJUMP_SIZE];
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list_for_each_entry_safe(op, tmp, oplist, list) {
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s32 rel = (s32)((long)op->optinsn.insn -
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((long)op->kp.addr + RELATIVEJUMP_SIZE));
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WARN_ON(kprobe_disabled(&op->kp));
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/* Backup instructions which will be replaced by jump address */
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memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
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RELATIVE_ADDR_SIZE);
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insn_buf[0] = RELATIVEJUMP_OPCODE;
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*(s32 *)(&insn_buf[1]) = rel;
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text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
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op->optinsn.insn);
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list_del_init(&op->list);
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}
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}
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/* Replace a relative jump with a breakpoint (int3). */
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void arch_unoptimize_kprobe(struct optimized_kprobe *op)
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{
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u8 insn_buf[RELATIVEJUMP_SIZE];
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/* Set int3 to first byte for kprobes */
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insn_buf[0] = BREAKPOINT_INSTRUCTION;
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memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
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text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
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op->optinsn.insn);
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}
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/*
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* Recover original instructions and breakpoints from relative jumps.
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* Caller must call with locking kprobe_mutex.
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*/
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extern void arch_unoptimize_kprobes(struct list_head *oplist,
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struct list_head *done_list)
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{
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struct optimized_kprobe *op, *tmp;
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list_for_each_entry_safe(op, tmp, oplist, list) {
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arch_unoptimize_kprobe(op);
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list_move(&op->list, done_list);
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}
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}
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int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
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{
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struct optimized_kprobe *op;
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if (p->flags & KPROBE_FLAG_OPTIMIZED) {
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/* This kprobe is really able to run optimized path. */
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op = container_of(p, struct optimized_kprobe, kp);
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/* Detour through copied instructions */
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regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
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if (!reenter)
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reset_current_kprobe();
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preempt_enable_no_resched();
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return 1;
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}
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return 0;
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}
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NOKPROBE_SYMBOL(setup_detour_execution);
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