564 lines
15 KiB
C
564 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Kernel Probes Jump Optimization (Optprobes)
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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/perf_event.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/extable.h>
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#include <linux/kdebug.h>
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#include <linux/kallsyms.h>
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#include <linux/kgdb.h>
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#include <linux/ftrace.h>
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#include <linux/objtool.h>
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#include <linux/pgtable.h>
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#include <linux/static_call.h>
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#include <asm/text-patching.h>
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#include <asm/cacheflush.h>
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#include <asm/desc.h>
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#include <linux/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 <asm/set_memory.h>
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#include <asm/sections.h>
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#include <asm/nospec-branch.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 < JMP32_INSN_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 is optimized or under unoptimizing */
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if (list_empty(&op->list) || optprobe_queued_unopt(op))
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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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if (copy_from_kernel_nofault(buf, (void *)addr,
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MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
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return 0UL;
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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, DISP32_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, DISP32_SIZE - offs);
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}
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return (unsigned long)buf;
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}
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static void synthesize_clac(kprobe_opcode_t *addr)
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{
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/*
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* Can't be static_cpu_has() due to how objtool treats this feature bit.
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* This isn't a fast path anyway.
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*/
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if (!boot_cpu_has(X86_FEATURE_SMAP))
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return;
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/* Replace the NOP3 with CLAC */
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addr[0] = 0x0f;
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addr[1] = 0x01;
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addr[2] = 0xca;
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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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".pushsection .rodata\n"
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"optprobe_template_func:\n"
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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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" pushq $" __stringify(__KERNEL_DS) "\n"
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/* Save the 'sp - 8', this will be fixed later. */
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" pushq %rsp\n"
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" pushfq\n"
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".global optprobe_template_clac\n"
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"optprobe_template_clac:\n"
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ASM_NOP3
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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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/* Copy 'regs->flags' into 'regs->ss'. */
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" movq 18*8(%rsp), %rdx\n"
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" movq %rdx, 20*8(%rsp)\n"
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RESTORE_REGS_STRING
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/* Skip 'regs->flags' and 'regs->sp'. */
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" addq $16, %rsp\n"
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/* And pop flags register from 'regs->ss'. */
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" popfq\n"
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#else /* CONFIG_X86_32 */
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" pushl %ss\n"
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/* Save the 'sp - 4', this will be fixed later. */
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" pushl %esp\n"
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" pushfl\n"
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".global optprobe_template_clac\n"
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"optprobe_template_clac:\n"
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ASM_NOP3
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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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/* Copy 'regs->flags' into 'regs->ss'. */
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" movl 14*4(%esp), %edx\n"
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" movl %edx, 16*4(%esp)\n"
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RESTORE_REGS_STRING
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/* Skip 'regs->flags' and 'regs->sp'. */
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" addl $8, %esp\n"
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/* And pop flags register from 'regs->ss'. */
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" popfl\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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".popsection\n");
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void optprobe_template_func(void);
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STACK_FRAME_NON_STANDARD(optprobe_template_func);
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#define TMPL_CLAC_IDX \
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((long)optprobe_template_clac - (long)optprobe_template_entry)
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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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/* 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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/* 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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preempt_disable();
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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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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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/* Adjust stack pointer */
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regs->sp += sizeof(long);
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/* Save skipped registers */
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regs->cs = __KERNEL_CS;
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#ifdef CONFIG_X86_32
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regs->gs = 0;
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#endif
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regs->ip = (unsigned long)op->kp.addr + INT3_INSN_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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preempt_enable();
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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, u8 *real)
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{
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struct insn insn;
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int len = 0, ret;
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while (len < JMP32_INSN_SIZE) {
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ret = __copy_instruction(dest + len, src + len, real + len, &insn);
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if (!ret || !can_boost(&insn, src + 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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static_call_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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static int insn_is_indirect_jump(struct insn *insn)
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{
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int ret = __insn_is_indirect_jump(insn);
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#ifdef CONFIG_RETPOLINE
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/*
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* Jump to x86_indirect_thunk_* is treated as an indirect jump.
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* Note that even with CONFIG_RETPOLINE=y, the kernel compiled with
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* older gcc may use indirect jump. So we add this check instead of
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* replace indirect-jump check.
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*/
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if (!ret)
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ret = insn_jump_into_range(insn,
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(unsigned long)__indirect_thunk_start,
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(unsigned long)__indirect_thunk_end -
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(unsigned long)__indirect_thunk_start);
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#endif
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return ret;
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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 and registers setup.
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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 < JMP32_INSN_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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int ret;
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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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ret = insn_decode_kernel(&insn, (void *)recovered_insn);
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if (ret < 0)
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return 0;
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#ifdef CONFIG_KGDB
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/*
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* If there is a dynamically installed kgdb sw breakpoint,
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* this function should not be probed.
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*/
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if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
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kgdb_has_hit_break(addr))
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return 0;
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#endif
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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_INSN_SIZE,
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DISP32_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_disarmed(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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kprobe_opcode_t *addr)
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{
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return (op->kp.addr <= addr &&
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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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u8 *slot = op->optinsn.insn;
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if (slot) {
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int len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE;
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/* Record the perf event before freeing the slot */
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if (dirty)
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perf_event_text_poke(slot, slot, len, NULL, 0);
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free_optinsn_slot(slot, 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 = NULL, *slot;
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int ret, len;
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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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buf = kzalloc(MAX_OPTINSN_SIZE, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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op->optinsn.insn = slot = get_optinsn_slot();
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if (!slot) {
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ret = -ENOMEM;
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goto out;
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}
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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)slot - (long)op->kp.addr + JMP32_INSN_SIZE;
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if (abs(rel) > 0x7fffffff) {
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ret = -ERANGE;
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goto err;
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}
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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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/* 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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slot + TMPL_END_IDX);
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if (ret < 0)
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goto err;
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op->optinsn.size = ret;
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len = TMPL_END_IDX + op->optinsn.size;
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synthesize_clac(buf + TMPL_CLAC_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,
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slot + 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 + len, slot + len,
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(u8 *)op->kp.addr + op->optinsn.size);
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len += JMP32_INSN_SIZE;
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/*
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* Note len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE is also
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* used in __arch_remove_optimized_kprobe().
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*/
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/* We have to use text_poke() for instruction buffer because it is RO */
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perf_event_text_poke(slot, NULL, 0, buf, len);
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text_poke(slot, buf, len);
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ret = 0;
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out:
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kfree(buf);
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return ret;
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err:
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__arch_remove_optimized_kprobe(op, 0);
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goto out;
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}
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/*
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* Replace breakpoints (INT3) with relative jumps (JMP.d32).
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* Caller must call with locking kprobe_mutex and text_mutex.
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*
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* The caller will have installed a regular kprobe and after that issued
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* syncrhonize_rcu_tasks(), this ensures that the instruction(s) that live in
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* the 4 bytes after the INT3 are unused and can now be overwritten.
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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_buff[JMP32_INSN_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 + JMP32_INSN_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_INSN_SIZE,
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DISP32_SIZE);
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insn_buff[0] = JMP32_INSN_OPCODE;
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*(s32 *)(&insn_buff[1]) = rel;
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text_poke_bp(op->kp.addr, insn_buff, JMP32_INSN_SIZE, NULL);
|
|
|
|
list_del_init(&op->list);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Replace a relative jump (JMP.d32) with a breakpoint (INT3).
|
|
*
|
|
* After that, we can restore the 4 bytes after the INT3 to undo what
|
|
* arch_optimize_kprobes() scribbled. This is safe since those bytes will be
|
|
* unused once the INT3 lands.
|
|
*/
|
|
void arch_unoptimize_kprobe(struct optimized_kprobe *op)
|
|
{
|
|
u8 new[JMP32_INSN_SIZE] = { INT3_INSN_OPCODE, };
|
|
u8 old[JMP32_INSN_SIZE];
|
|
u8 *addr = op->kp.addr;
|
|
|
|
memcpy(old, op->kp.addr, JMP32_INSN_SIZE);
|
|
memcpy(new + INT3_INSN_SIZE,
|
|
op->optinsn.copied_insn,
|
|
JMP32_INSN_SIZE - INT3_INSN_SIZE);
|
|
|
|
text_poke(addr, new, INT3_INSN_SIZE);
|
|
text_poke_sync();
|
|
text_poke(addr + INT3_INSN_SIZE,
|
|
new + INT3_INSN_SIZE,
|
|
JMP32_INSN_SIZE - INT3_INSN_SIZE);
|
|
text_poke_sync();
|
|
|
|
perf_event_text_poke(op->kp.addr, old, JMP32_INSN_SIZE, new, JMP32_INSN_SIZE);
|
|
}
|
|
|
|
/*
|
|
* Recover original instructions and breakpoints from relative jumps.
|
|
* Caller must call with locking kprobe_mutex.
|
|
*/
|
|
extern 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 setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
|
|
{
|
|
struct optimized_kprobe *op;
|
|
|
|
if (p->flags & KPROBE_FLAG_OPTIMIZED) {
|
|
/* This kprobe is really able to run optimized path. */
|
|
op = container_of(p, struct optimized_kprobe, kp);
|
|
/* Detour through copied instructions */
|
|
regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
|
|
if (!reenter)
|
|
reset_current_kprobe();
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(setup_detour_execution);
|